identifier	taxonID	type	CVterm	format	language	title	description	additionalInformationURL	UsageTerms	rights	Owner	contributor	creator	bibliographicCitation
03AD87B1DD00426F31209C8F9399FB6A.text	03AD87B1DD00426F31209C8F9399FB6A.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Tarphyceratida Flower 1950	<div><p>Order  Tarphyceratida Flower, 1950</p><p>Diagnosis (compiled after Furnish &amp; Glenister 1964; Frey 1995; emended)</p><p>Multiceratoid cephalopods with coiled to gyroconic conchs of various whorl profile and simple transverse or slightly curved suture lines. Coiling planispiral, rarely torticonic; body chambers usually long, extending from a half to more than one complete whorl in length. Last whorl commonly slightly to greatly divergent from preceding coiled portions; terminal aperture commonly modified. Siphuncle varies in position; siphuncular segments more or less tubular, nautilosiphonate, with orthochoanitic or loxochoanitic septal necks and thick connecting rings in stratigraphically earlier forms, and cyrtochoanitic septal necks and thin homogeneous rings in stratigraphically later forms. Muscle attachment scars ventromyarian or sometimes pleuromyarian. Thin cameral deposits present in some taxa. Shell surface smooth or ornamented with transverse lirae, ribs or annuli, or spiral ornament elements.</p><p>Families included</p><p>Barrandeoceratidae Foerste, 1925;  Estonioceratidae Hyatt in Zittel, 1900;  Ophioceratidae Hyatt, 1894;  Plectoceratidae Hyatt in Zittel, 1900;  Tarphyceratidae Hyatt, 1894;  Trocholitidae Chapman, 1857 .</p><p>Remarks</p><p>The combined diagnosis of Furnish &amp; Glenister (1964) and Frey (1995) is expanded here to include the presence of pleuromyarian muscle attachment scars (e.g., Dzik 1984; King &amp; Evans 2019) and cameral deposits (Ulrich et al. 1942; Manda &amp; Turek 2018) and the character of shell ornament.</p></div>	https://treatment.plazi.org/id/03AD87B1DD00426F31209C8F9399FB6A	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Aubrechtová, Martina;Korn, Dieter	Aubrechtová, Martina, Korn, Dieter (2025): The coiled Middle Ordovician cephalopod genera Trocholites and Curtoceras (Tarphyceratida) from Baltoscandia and north-central Europe. European Journal of Taxonomy 982: 1-78, DOI: 10.5852/ejt.2025.982.2843, URL: https://europeanjournaloftaxonomy.eu/index.php/ejt/article/download/2843/12943
03AD87B1DD00426C315899949238FD9A.text	03AD87B1DD00426C315899949238FD9A.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Trocholitidae Chapman 1857	<div><p>Family  Trocholitidae Chapman, 1857</p><p>Diagnosis (after Furnish &amp; Glenister 1964; Frey 1995; emended)</p><p>Family of the order  Tarphyceratida with subglobular to discoidal conchs consisting of three to five or more gradually expanding volutions; body chamber may uncoil from preceding volution. Terminal aperture of body chamber with flares in some taxa, aperture often modified with ventral sinus and lateral projections. Whorl profile usually impressed dorsally; usually depressed except for the adult growth stage that may have an equidimensional or compressed whorl profile; flanks and venter broadly rounded or flattened. Shell ornament varies during ontogeny, usually consisting of imbricating and / or frilled lirae, ribs or annuli, but taxa with smooth shell surface exist; ornament elements form ventral sinus. Conch in some taxa with periodic constrictions. Phragmocone chambers short (on average six phragmocone chambers relative to whorl height). Suture line simple with shallow ventral lobe or rarely saddle. Siphuncle subcentral, subdorsal or marginodorsal in position, ventral to central in initial volution; siphuncle segments tubular, weakly convex or weakly concavo-convex, narrow in diameter (usually less than 0.25 of apertural height); septal necks short (less than 0.20 of segment length), orthochoanitic or loxochoanitic; connecting rings usually thick, layered, but becoming thin and homogeneous in some taxa.</p><p>Genera included</p><p>Arkoceras Ulrich, Foerste, Miller &amp; Furnish, 1942;  Crenuloceras Flower, 1968;  Curtoceras Ulrich, Foerste, Miller &amp; Furnish 1942;  Discoceras Barrande, 1867;  Hardmanoceras Teichert &amp; Glenister, 1952;  Jasperoceras Ulrich, Foerste, Miller &amp; Furnish, 1942;  Litoceras Hyatt, 1884;  Paradiscoceras Barskov, 1972;  Plectolites Flower, 1968;  Trocholites Conrad, 1838;  Trocholitoceras Hyatt, 1894;  Weberoceras Barskov, 1972;  Wichitoceras Ulrich, Foerste, Miller &amp; Furnish, 1942;  Yushanoceras Chen &amp; Liu, 1976 .</p><p>Remarks</p><p>Chapman (1857) must be regarded as the correct author of the family name.  Trocholitidae Schröder, 1891 is an objective junior synonym.</p><p>The diagnosis compiled from Furnish &amp; Glenister (1964) and Frey (1995) is rephrased and modified to reflect results of the revision of  Trocholites and  Curtoceras performed herein. The added details concern the shape of the terminal aperture, whorl profile, shape of connecting rings and shape of septal necks.</p></div>	https://treatment.plazi.org/id/03AD87B1DD00426C315899949238FD9A	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Aubrechtová, Martina;Korn, Dieter	Aubrechtová, Martina, Korn, Dieter (2025): The coiled Middle Ordovician cephalopod genera Trocholites and Curtoceras (Tarphyceratida) from Baltoscandia and north-central Europe. European Journal of Taxonomy 982: 1-78, DOI: 10.5852/ejt.2025.982.2843, URL: https://europeanjournaloftaxonomy.eu/index.php/ejt/article/download/2843/12943
03AD87B1DD03426A31389FA594CAF929.text	03AD87B1DD03426A31389FA594CAF929.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Trocholites Conrad 1838	<div><p>Genus  Trocholites Conrad, 1838</p><p>Type species</p><p>Trocholites ammonius Conrad, 1838; by original designation.</p><p>Diagnosis (after Frey 1995; Kröger &amp; Aubrechtová 2018; emended)</p><p>Genus of the family  Trocholitidae with adult conch diameters of generally less than 100 mm, five or more volutions. Conch discoidal or pachyconic (CWI = 0.30–0.80) with moderately wide to very wide umbilicus (UWI = 0.30–0.60) and low or moderate whorl expansion (WER = 1.50–2.00). Body chamber 0.50–0.75 of a volution in length; not uncoiling from the preceding whorl. Whorl profile weakly to strongly depressed (WWI = 1.20–2.20), broadly reniform, weakly to strongly impressed dorsally (IZR up to 0.45), broadly rounded across venter and flanks. Aperture commonly flared with ventral sinus and ventrolateral extensions. Siphuncular diameter 0.16–0.30 of the whorl height, marginodorsal or subdorsal in position in all growth stages; septal necks short (&lt;0.20 of chamber height), orthochoanitic and / or loxochoanitic in shape. Ornament composed of growth lines and lirae, less commonly of narrow annuli or ribs; ornament elements extended into ventral sinus. Suture line straight or with shallow lobes.</p><p>Species included</p><p>North America (Conrad 1838; Miller &amp; Dyer 1878; Hyatt 1894; Ruedemann 1926; Foerste 1930; Flower 1943):  Trocholites ammonius Conrad, 1838;  T. canadensis Hyatt, 1894;  T. circularis Miller &amp; Dyer, 1878;  T. dyeri Hyatt, 1894;  T. faberi Foerste, 1930;  T. gracilis Flower, 1943;  T. major Ruedemann, 1926;  T. minusculus Miller &amp; Dyer, 1878;  T. planorbiformis Conrad, 1838;  T. ruedemanni Flower, 1943 .</p><p>Great Britain (Hyatt 1894):  Trocholites blakei Hyatt, 1894 .</p><p>North Europe and St Petersburg Region of Russia (Eichwald 1840; Kjerulf 1865; Remelé 1880; Schröder 1882, 1891; Foerste 1932; Kröger &amp; Aubrechtová 2018; this paper):  Trocholites baldri sp. nov.;  Palaeonautilus broeggeri Foerste, 1932;  T. contractus Schröder, 1891;  Nautilus depressus Eichwald, 1840;  T. freyjae sp. nov.;  T. gennadii Kröger &amp; Aubrechtová, 2018;  T. glacialis sp. nov.;  P. hospes Remelé, 1880;  T. kadakaensis sp. nov.;  T. luna sp. nov.;  T. macrostoma Schröder, 1882;  Lituites nakholmensis Kjerulf, 1865;  T. remélei Schröder, 1891;  T. splendor sp. nov.;  T. tureki sp. nov.;  T. triangulus sp. nov.;  T. vodickai sp. nov.;  T. vortex sp. nov.;  T. zaryensis sp. nov.</p><p>South and Central Europe (Babin &amp; Gutiérrez-Marco 1992; Aubrechtová et al. 2023):  Trocholites fugax Babin &amp; Gutiérrez Marco, 1992;  T. chaloupkai Aubrechtová et al., 2023 .</p><p>South Korea (Kobayashi 1934):  Trocholites ammonioides Kobayashi, 1934 . China (Frech 1911; Chen &amp; Liu 1974, 1976; Lai 1981; Lai &amp; Wang 1981; Gao et al. 1982; Chen &amp; Zou 1984; Guo 1998):  Palaeonautilus hubeiensis Chen &amp; Liu, 1974;  Trocholites huanxianese Chen in Gao, Lai &amp; Wen, 1982;  T. jiangxiense Lai, 1981;  T. lativentrosus Lai &amp; Wang, 1981;  T. mirabilis Lai &amp; Wang, 1981;  T. wuhaiensis Chen in Chen &amp; Zou, 1984;  T. xiazhenensis Chen &amp; Liu, 1976;  T. yushanensis Lai, 1981;  T. yunnanensis Reed, 1917;  T. zhejiangense Lai, 1981 .</p><p>Australia (Stait et al. 1985):  Trocholites costatum Stait et al.1985 .</p><p>Remarks</p><p>Representatives of the genus  Trocholites are usually rather small with only 20 to 60 mm conch diameter in the terminal growth stage. They possess evolute or subevolute conchs and have a distinctly depressed whorl profile; the whorl profile possesses a small dorsal imprint zone. The terminal body chamber does not deviate from the preceding whorl, but often has an aperture with ventral and lateral flares.</p><p>Trocholites is similar to  Curtoceras and both genera may be confused under certain circumstances. The conch in  Curtoceras is more discoidal (CWI = 0.30–0.40) and the whorl profile is weakly depressed or nearly equidimensional (WWI = 1.00–1.50). The terminal body chamber uncoils from the preceding whorl at least in some species of  Curtoceras . However, there are species with transitional morphology that are difficult to assign to one genus or the other, especially if the adult growth stage is not known.</p><p>Discoceras is distinguished from  Trocholites by the much greater adult conch size (usually exceeding 100 mm) and coarser shell ornament with elements that are characteristically frilled and imbricate; the siphuncle in the species of  Discoceras is usually not marginal in position. In adult growth stages of  Discoceras, the conch is more discoidal (CWI &lt;0.35) and the whorls are usually only weakly embracing. The whorl profile in  Discoceras is very variable between species and during ontogeny. It is usually weakly depressed in earlier stages of growth (WWI = 1.00–1.50), but becomes equidimensional or compressed during ontogeny (WWI = 0.50–1.00). In some species of  Discoceras, the whorl profile is oval or circular, while in others it is subrectangular, subquadratic, trapezoidal or heart-shaped. In many species of  Discoceras, the last volution uncoils from the preceding whorl to varying degrees.</p><p>Schröder (1882, 1891) discussed or established several species of  Trocholites, most of which could be reliably identified in the collection currently studied. Only three species remain problematic:  T. orbis,  T. macromphalus and  T. soraviensis .</p><p>Trocholites orbis, according to its original description, is very similar to  T. depressus and differs from this species only in being somewhat more discoidal and lacking strong ribs on the shell surface. Unfortunately,  T. orbis is only known from the original description and illustration of the holotype (Schröder 1891: pl. 1(24) fig. 3; see also Fig. 1C herein). This specimen originated from an Ordovician erratic boulder at “Nasser Garten bei Königsberg” (present day Portowoje, south of Kaliningrad, Russia) and belonged to the collection of the “Provinzial-Museum zu Königsberg i. Pr.” (Regional Museum of Königsberg in Prussia), which was most probably destroyed during World War II (pers. com. D. Weyer, Berlin, 2022). The species has never been revised and the only two other specimens assigned to it by Neben &amp; Krueger (1971) and Dzik (1984) probably belong to  T. depressus . From the collection at hand, we could not unequivocally assign any specimens to the species  T. orbis . The available information on the (probably lost) type material do not permit further comparison of  T. orbis with  T. depressus or any other species of the genus.</p><p>Trocholites macromphalus is known only from the holotype (Schröder 1891: pl. 1(24) fig. 5; see also Fig. 1E herein). It originated from Darriwilian strata of the Estonian island of Osmussaar and was said to be deposited at the “Museum der Akademie der Wissenschaften zu St. Petersburg ” (Museum of the Academy of Sciences of St Petersburg). The holotype was never re-examined and its current location and status could not be confirmed. In the currently examined collection, some specimens of  Curtoceras teres are most similar based on the original description and illustration. However, since Schröder (1891) noted that the holotype had a dorsal siphuncle and ribs on internal whorls, the species is transferred to  Curtoceras but not synonymised with  C. teres .</p><p>The holotype of  Trocholites soraviensis originated from an Ordovician erratic boulder at Żory (Poland) and was included in the “Sammlung der Kgl. geologischen Landesanstalt und Bergakademie zu Berlin“ (Collection of the Royal Geological Survey and Mining Academy of Berlin). After its description by Schröder (1891), it has never been restudied and remains the only unequivocal representative of the species. The holotype (Schröder 1891: pl. 2 fig. 1; see also Fig. 1F herein) is most similar to specimens herein assigned to  Trocholites freyjae sp. nov.,  T. baldri sp. nov. and  T. glacialis sp. nov. However, reliable comparison is not possible based on the available information. The present location of the holotype is unknown and it is possible that it was destroyed during World War II. This cannot be confirmed, though, and thus, neotype designation and comparison to representatives of other species of  Trocholites is avoided.</p><p>Some species of  Trocholites recorded from various regions of China, especially  T. huanxianese,  T. yunnanensis and  T. xiazhenensis, may in fact belong to  Curtoceras or  Discoceras, but the currently available data do not allow a reliable taxonomic assignment.</p><p>The holotype of the Ordovician species  Trocholites zhuozishanensis described by Guo (1998) from Inner Mongolia (northern China) has ventrally shifted siphuncle and thus should not be assigned to  Trocholites or any other genus of the family  Trocholitidae .</p><p>Trocholites lativentrosus from the Sandbian Kanling Formation of the Tarim Basin of north-west China appears to resemble some species studied here ( Trocholites freyjae sp. nov.,  T. baldri sp. nov. and  T. glacialis sp. nov.) in conch geometry, especially whorl profile shape and impression rate, but information available on the type material is not sufficient to make reliable comparisons and draw conclusions regarding possible synonymy.</p><p>Myagkova (1955) reported the occurrence of the type species  Trocholites ammonius from Middle Ordovician strata of the Middle Urals of Russia. However, the illustration and description suggest that the specimen should rather be assigned to a species of  Curtoceras or possibly  Discoceras; the type species is thus only unequivocally known from North America.</p><p>The late Darriwilian species  Trocholites scoticus from Great Britain is transferred to  Curtoceras because the two type specimens of Blake (1882) reportedly have only weakly depressed whorl profile and the body chamber in the holotype is adaperturally uncoiled.</p><p>Geographic and stratigraphic occurrence</p><p>North America, Europe, St Petersburg Region of Russia, China, South Korea, Australia, Middle–Late Ordovician; Great Britain, Llandovery Series (early Silurian).</p></div>	https://treatment.plazi.org/id/03AD87B1DD03426A31389FA594CAF929	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Aubrechtová, Martina;Korn, Dieter	Aubrechtová, Martina, Korn, Dieter (2025): The coiled Middle Ordovician cephalopod genera Trocholites and Curtoceras (Tarphyceratida) from Baltoscandia and north-central Europe. European Journal of Taxonomy 982: 1-78, DOI: 10.5852/ejt.2025.982.2843, URL: https://europeanjournaloftaxonomy.eu/index.php/ejt/article/download/2843/12943
03AD87B1DD054273314F9BD596FCFCEA.text	03AD87B1DD054273314F9BD596FCFCEA.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Trocholites depressus (Eichwald 1840)	<div><p>Trocholites depressus (Eichwald, 1840)</p><p>Figs 1D, I, 5–7; Table 3</p><p>Nautilus depressus Eichwald, 1840: 106 .</p><p>Clymenia incongrua Eichwald, 1840: 108 .</p><p>Clymenia Odini Eichwald, 1840: 107 .</p><p>Clymenia depressa – Eichwald 1860: 1305, pl. 50 fig. 5.</p><p>Clymenia incongrua – Eichwald 1860: 1306, pl. 50 fig. 7.</p><p>Clymenia Odini – Eichwald 1860: 1304, pl. 51 fig. 27.</p><p>Palaeonautilus depressus – Remelé 1880: 246; 1890: 37.</p><p>Palaeonautilus incongruus – Remelé 1880: 247.</p><p>?  Trocholites depressus – Rüdiger 1889: 48. — Sweet 1958: 93, pl. 7 figs 3–7, text-fig. 12. — Chen 1987: 173, pl. 7 figs 7–9, text-fig. 35.</p><p>Trocholites depressus – Schröder 1891: 13 (151), pl. 1(24) figs 4, 7. — Balashov 1953: 242, pl. 7 fig. 2. — Kröger &amp; Keupp 2004: text-fig. 1.</p><p>?  Trocholites incongruus – Schröder 1891: 154, pl. 2(25) figs 3–4.</p><p>Trocholites incongruus – Schröder 1891: 153, pl. 2(25) fig. 2. — Balashov 1953: 240, pl. 7 fig. 1; 1962: pl. 9 fig. 6; 1974: pl. 9 fig. 6.</p><p>Trocholites cf. orbis – Schröder 1891: 13 (151), pl. 1(24) fig. 6.</p><p>Trocholites Odini – Foord 1891: 50. — Schröder 1891: 13 (151). — Balashov 1953: 243, pl. 7 fig. 3.</p><p>Trocholites orbis – Neben &amp; Krueger 1971: pl. 32 figs 10–11. — Dzik 1984: pl. 6 fig. 3.</p><p>?  Trocholites cf. incongruus – Neben &amp; Krueger 1971: pl. 32 figs 8–9.</p><p>?  Trocholites soraviensis – Neben &amp; Krueger 1973: pl. 81 figs 10–11.</p><p>?  Trocholites orbis – Dzik 1984: pl. 6 fig. 2.</p><p>?  Trocholites cf. depressus – Babin &amp; Gutiérrez-Marco 1992: 524, 534, text-fig. 4g.</p><p>non  Trocholites incongruus – Angelin 1880: 11, pl. 9 figs 15–18.</p><p>non  Trocholites cf. incongruus – Rüdiger 1889: 48.</p><p>Diagnosis</p><p>Species of the genus  Trocholites with an adult conch diameter of 30–40 mm. Conch in the last whorl thinly discoidal (CWI = 0.35–0.40) and evolute (UWI ~ 0.50) with low coiling rate (WER ~ 1.65). Whorl profile weakly to moderately depressed (WWI = 1.25–1.60) with rounded flanks and slightly flattened venter in the adult stage. Whorl width slightly increasing, whorl height slightly decreasing in last quarter volution. Phragmocone chambers moderately long (RCL = 0.30–0.40). Suture line nearly straight. Ornament on inner whorls with lirae and narrow or distinct ribs, and on outer whorl with raised lirae, sometimes with annular ridges visible on the internal mould.</p><p>Type material</p><p>Neotype (designated here)</p><p>ESTONIA • Odinsholm (=  Osmussaar);  Lasnamägi Regional Stage, late Darriwilian; Eichwald Coll.; illustrated by Eichwald (1860: pl. 50 fig. 5), Schröder (1891: pl. 1(24) fig. 4) and Balashov (1953: pl. 7 fig. 2), re-illustrated here in Fig. 5A; PMSPU 1-1128.</p><p>Additional material</p><p>ESTONIA • 1 spec.; Osmussaar; Darriwilian Stage; 1876; Dames Coll.; illustrated by Schröder (1891: pl. 1 fig. 7), re-illustrated here in Fig. 6F; MB.C. 9719  • 1 spec.;  Osmussaar 1;  Lasnamägi Regional Stage; illustrated in Fig. 5B; TUG 1351-14   • 1 spec.;  Osmussaar;  Lasnamägi Regional Stage; Schmidt Coll.; illustrated in Fig. 6G; GIT 225-1074   • 1 spec.;  Osmussaar 1;  Uhaku Regional Stage; illustrated in Fig. 6A; GIT 697-129   • 2 specs;  Osmussaar 2;  Uhaku Regional Stage; Männil Coll.; illustrated in Fig. 6C; GIT 697-410   • 1 spec.;  Osmussaar 2;  Uhaku Regional Stage; Männil Coll.; GIT 697-404-1   • 1 spec.;  Osmussaar; probably Darriwilian Stage; TAM G432:787   • 1 spec.;  Osmussaar cliff; probably Darriwilian Stage; 1985; Männil Coll.; illustrated in Fig. 6B; GIT 697-535   • 1 spec.; Väike-Pakri Island;  Lasnamägi Regional Stage; Orviku Coll.; illustrated in Fig. 5C; GIT 145-1   • 1 spec.; Tallinn;  Lasnamägi Regional Stage; TUG 2-721   • 1 spec.; Odinsholm (=  Osmussaar);  Lasnamägi Regional Stage, late Darriwilian; Eichwald Coll.; illustrated by Eichwald (1860: pl. 51 fig. 27), Schröder (1891: pl. 1(24) fig. 6) and Balashov (1953: pl. 7 fig. 3), re-illustrated here in Fig. 5D; PMSPU 1-1127   • 1 spec.; Odinsholm (=  Osmussaar);  Lasnamägi Regional Stage, late Darriwilian; Eichwald Coll.; illustrated by Eichwald (1860: pl. 50 fig. 7a), Schröder (1891: pl. 2(25) fig. 2) and Balashov (1953: pl. 7 fig. 1a, c); PMSPU 1-1129   • 1 spec.; Odinsholm (=  Osmussaar);  Lasnamägi Regional Stage, late Darriwilian; Eichwald Coll.; illustrated by Balashov (1953: pl. 7 fig. 1b); PMSPU 1-2622.</p><p>GERMANY – Brandenburg • 1 spec.; Niederfinow; Ordovician;  Neben and Krueger Coll .; illustrated in Fig. 6D; MB.C. 32160  . –   Mecklenburg-Vorpommern • 1 spec.;  Lebbin;  Lasnamägi Regional Stage; Neben and Krueger Coll.; illustrated by Neben &amp; Krueger (1971: pl. 32 figs 10–11), re-illustrated here in Fig. 6E; MB.C. 32161  .</p><p>Description</p><p>Neotype PMSPU 1-1128 (Fig. 5A) is a nearly complete conch with 3.5 volutions preserved. The diameter of the conch is 36 mm; the body chamber is 240 degrees long and the aperture has a ventral sinus, ventrolateral extension and dorsolateral sinus. In the last 90 degrees, the conch is discoidal (CWI ~ 0.40) and widely umbilicate (UWI increases slightly from 0.46 to 0.48); the whorl profile is evenly convex from the venter to the flanks and increasingly depressed (WWI increases from 1.36 to 1.48). Ornament is only locally preserved; it consists of fine lirae, which are accompanied by narrow but distinct ribs on inner whorls. The phragmocone chambers are moderately long (RCL = 0.31); the suture line is straight.</p><p>Specimen MB.C.32160 (Fig. 6D) is an almost complete adult specimen with a conch diameter of 29 mm. The length of the body chamber is half a volution; its terminal apertural end has a ventral extension and thus produces a pronounced ventral sinus. Within the last half volution, the conch becomes progressively discoidal (CWI decreases from 0.44 to 0.38) and remains evolute (UWI rises weakly from 0.50 to 0.52) with a low coiling rate (WER = 1.64). The largest whorl is moderately depressed (WWI = 1.58) and weakly embracing (IZR = 0.09). The shell is only preserved in inner whorls, where there are distinct, smooth ribs and lirae; the internal mould of the adult body chamber has annular grooves that extend with a ventral sinus and a single more prominent impression near the beginning of the body chamber. The phragmocone chambers are moderately long (RCL = 0.30); the suture line is more or less straight.</p><p>Specimen MB.C.32161 (Fig. 6E) is an almost complete, well-preserved conch of an adult individual with 29 mm conch diameter. The length of the body chamber is half a volution; the terminal aperture extends into a ventral sinus. In the last half volution, the conch is increasingly discoidal (CWI decreases from 0.41 to 0.33), increasingly evolute (UWI increases slightly from 0.44 to 0.48) and moderately expanding (WER = 1.77). The whorl profile is weakly depressed (WWI decreases from 1.31 to 1.21) and weakly impressed dorsally (IZR = 0.10) with a broadly rounded venter and rounded flanks. The shell wall of the inner whorls is ornamented with unevenly spaced thin ribs and lirae; in the outer whorl, the ribs fade out and are replaced by raised lirae. There are annular impressions present on the internal mould of the terminal body chamber. The ornament elements extend straight across the flank and turn to form a deep ventral sinus. In the outer whorl, the phragmocone chambers are short or moderately long (RCL varies between 0.17 and 0.23). The suture line is nearly straight.</p><p>Specimen PMSPU 1-1127 (Fig. 5D) is a conch of 31 mm diameter, consisting of nearly five whorls; the last ~ 35 degrees of the conch belong to the body chamber. The initial volution of the phragmocone is preserved, the initial chamber is present, the umbilical window is ~ 0.25 mm across. In the last 90 degrees of the last whorl, the conch is widely umbilicate (UWI ~ 0.46). Ornament is poorly preserved but transverse elements are indicated locally on the surface. Phragmocone chambers are moderately long (RCL up to ~ 0.40); suture line is almost straight.</p><p>Specimen GIT 697-129 (Fig. 6A) has a conch diameter of 34 mm; the specimen possesses 5.25 whorls and is nearly complete. Only the aperture of the body chamber is missing. At a diameter of 30 mm, the conch is thinly discoidal (CWI = 0.39) and evolute (UWI = 0.49). The whorl profile is weakly depressed in the last whorl (WWI decreases from 1.43 to 1.35) with broadly rounded flanks and venter. The ornament consists of evenly spaced lirae, which are irregularly raised and form groups of more widely spaced, rib-like elements (0.5–1.0 mm apart in inner whorls). The phragmocone chambers are rather long (RCL = 0.40 at wh = 7 mm); the suture line is almost straight.</p><p>Specimen GIT 145-1 (Fig. 5C) is a median longitudinal section of an essentially complete conch with a maximum diameter of 40 mm, consisting of six volutions. During ontogeny, the coiling rate generally decreases from WER = 2.70 to WER = 1.70. The siphuncle remains marginodorsal (RSP = 1.00) and is relatively wide (RSH between 0.26 and 0.32). The septal necks are short and loxochoanitic, sometimes the brims are thickened. The connecting rings are thin with a deposit-like structure on the side facing the chamber, which extends also on the adapical side of septum. The phragmocone chambers are rather long especially in the early volutions (RCL 0.70–0.30); the suture line is straight. Ornament is preserved in small area on penultimate whorl and consists from lirae and low ribs; two annular ridges are present on the internal mould at about the beginning of the body chamber.</p><p>Specimen PMSPU 1-1129 represents a juvenile growth stage of a conch in which four whorls are preserved; traces of at least one more volution are visible. The maximum diameter of the conch is 22 mm; at this size the conch has UWI of 0.41 and RCL of ~ 0.25. The suture line is straight. Fine transverse ornament is visible on the shell surface.</p><p>Specimen PMSPU 1-2622 is a median transverse section of a conch in the juvenile growth stage, consisting of four volutions and 22 mm in diameter. In the last 1.5 volutions, the conch changes from thickly to thinly discoidal (CWI = 0.52–0.45) and is evolute (UWI = 0.48–0.50); coiling rate is moderate to low (WER = 1.82–1.70). Whorl profile of the outer volution is rounded from ventral and lateral sides but inner whorl profiles appear to be slightly ventrally flattened; the whorls are moderately depressed (WWI = 1.64–1.67) and moderately to weakly impressed (IZR = 0.19–0.14). The siphuncle is marginodorsal (RSP = 1.00) and rather wide (RSH ~ 0.30).</p><p>Specimen MB.C.9719 (Fig. 6F) is a subadult phragmocone with 26 mm diameter; the body chamber is missing. At this diameter, the conch is thinly discoidal (CWI = 0.41) and evolute (UWI = 0.45). In the last three quarters volution, the whorl profile has broadly rounded flanks and venter and changes from moderately to weakly depressed (WWI decreases from 1.67 to 1.38). The shell wall is ornamented with fine lirae with symmetric crests, but low ribs are locally visible on one side of the specimen. The phragmocone chambers increase in length in the last three quarters of the terminal volution (RCL changes from 0.24 to 0.37); the suture line is almost straight.</p><p>The other specimens are in a subadult or adult growth stage and range from 31 to 43 mm in conch diameter. In the last whorl, these conchs become more discoidal (CWI decreases from 0.45 to 0.36) and more widely umbilicate (UWI increases from 0.44 to 0.50) (Fig. 7A–B). The whorl profile in the last whorl is rounded, moderately to weakly impressed and becomes less depressed (WWI decreases from 1.61 to 1.20) during ontogeny (Fig. 7C). In some specimens, the WWI increases in the last half of the body chamber (e.g., GIT 697-535). The siphuncle has a marginodorsal position (RSP = 1.00) and the RSH decreases from 0.35 to 0.26 (n = 5). The complete body chamber is preserved in GIT 697-410 (Fig. 6C), where it is about half a volution long and the aperture extends into a ventral sinus. In the specimens TUG 2-271 and TUG 1351-14 (Fig. 5B), the latest phragmocone chambers are significantly shortened (down to RCL = 0.10).</p><p>Remarks</p><p>Three late Darriwilian species of  Trocholites have been described from the Estonian islet of Osmussaar (formerly Odinsholm or Odensholm):  T. depressus,  T. incongruus and  T. odini . These species were established by Eichwald (1840), who gave short descriptions but no illustrations of any type material. One specimen of each species was illustrated later by him (Eichwald 1860), but he did not explicitly state that these belonged to the respective type collections. The originals of Eichwald (1860) were studied and re-illustrated by Schröder (1891) and Balashov (1953); the latter author regarded them as holotypes (see discussion below).  Trocholites incongruus and  T. odini were not properly revised and are unequivocally known only from the probable type material. New material was assigned only to  Trocholites depressus by Kröger &amp; Keupp (2004). Other assignments to  T. depressus are more or less questionable (e.g., Sweet 1958; Chen 1987).</p><p>High-resolution photographs of the originals of Eichwald (1860) are accessible for our study. These, along with the historical descriptions and illustrations, suggest that these specimens differ only slightly in conch geometry and shell ornament. Furthermore, the original specimens of  T. incongruus appear to only represent an earlier ontogenetic stage of representatives of the other two species.</p><p>Among the material currently examined from northern Germany and Estonia, there are over a dozen specimens that appear to closely resemble the probable types of the three species discussed above. These specimens are all discoidal, slowly expanding with a wide umbilicus and weakly depressed, weakly impressed and laterally broadly rounded whorl profile. The siphuncle is marginodorsal (RSP = 1.00) and rather wide; the shell ornament consists of lirae raised at irregular intervals. The variation concerns the ww / wh ratio (WWI = 1.58 in specimen MB.C.32160 but 1.21 in specimen MB.C. 32161 in the adult growth stage; Fig. 7C) and the dorsal impression (IZR = 0.09 in specimen MB.C.32160 and 0.16 in specimen GIT 697-404-1). At least some of these differences may be due to the variation in adult conch size (between 30 mm and 40 mm) resulting in the comparison of non-corresponding growth stages. Ribs are developed on the shell surface in most specimens but these ribs are of variable thickness (GIT 697- 129 and MB.C.32160). Therefore, the results of our investigation conclude that the differences between  Trocholites depressus,  T. incongruus and  T. odini are likely attributable to intraspecific variation and based on ontogenetic differences. The three taxa are consequently synonymized herein; the species name  depressus has priority.</p><p>Eichwald (1840) did not figure any specimens and later (Eichwald 1860) he did not indicate whether the illustrated specimen was part of the type collection. Therefore, the specimen of Eichwald (1860), later re-illustrated by Balashov (1953: pl. 7 fig. 2), cannot be considered the holotype of “  Nautilus depressus ”. Nevertheless, we refer to it here as a neotype. This is justified by the following reasons: Eichwald (1860) clearly regarded the specimen as a representative of his earlier described species  Nautilus depressus Eichwald, 1840; Balashov (1953) physically examined and re-photographed the specimen; photographs of the specimen were available for the present study, confirming that it corresponds to the original as well as to the currently understood range of the species. The neotype is deposited in the Natural History Collections of St Petersburg State University under collection number PMSP-1-1128.</p><p>It is important to note that there is some inconsistency in the scientific literature regarding the use of the species name  odini . The confusion occurred after Verneuil (1845: 360, pl. 25 fig. 8) included a specimen with a nearly circular whorl profile and an uncoiled terminal body chamber in the species and used for this the combination  Lituites odini . This contradicts the original description by Eichwald (1840). Consequently, Eichwald (1860) and others (Remelé 1890; Foord 1891) correctly assigned that specimen to  Curtoceras teres . However, many authors confused the two species and used the names  odini and  teres as synonyms; both Eichwald and Verneuil were sometimes stated as authors of the name  odini . The fact that the probable holotype of  T. odini was first figured by Eichwald as late as in 1860 possibly contributed to this ambiguity. Nevertheless, the material examined by us confirms that they are clearly two separate species but also represent two different genera,  Trocholites and  Curtoceras (see under  C. teres below).</p><p>Specimen GIT 145-1 (Fig. 5C) is extraordinary as it has a healed perforation of the phragmocone, which was previously discussed in detail by Kröger &amp; Keupp (2004). This specimen is shortly re-described and re-figured here for completeness.</p><p>Representatives of  Trocholites depressus are similar to specimen MB.C.32182 of T. sp. 4 and the type specimens NRM Mo 152354 and GIT 362-721-2 of  T. tureki sp. nov. in conch width and whorl profile shape. However, specimen MB.C.32182 has a narrower siphuncle shifted from the dorsal shell wall and its inner volutions are not flattened ventrally; both specimens NRM Mo 152354 and GIT 362-721-2 have a more regularly developed ornament with low ribs / annuli present also on the surface of the outer whorl.</p><p>The subadult holotype of  Trocholites chaloupkai from the early Katian part of the Zahořany Formation of the Prague Basin is also similar to the representatives of  T. depressus, particularly in conch geometry and siphuncular position and diameter (Aubrechtová et al. 2023). However, the Bohemian specimen differs by a more significant ventral flattening of the conch, presence of deep ventral lobe of suture line and a unique, web-like shell ornament.</p><p>Compared to the species of  Curtoceras,  T. depressus is most similar to  C. teres; the similarities concern especially the umbilical width (UWI) and conch width (CWI). The specimens of  C. teres differ from the specimens of  T. depressus, however, in the much higher and much more rapidly decreasing coiling rate (particularly in early and mid-ontogeny; WER = 9.9–1.9 vs 2.7–1.6), the whorl profile is less depressed, equidimensional or even slightly compressed (WWI = 1.66–0.82 vs 1.67– 1.2 in ontogeny) and the siphuncle is much narrower (RSH ~ 0.16 vs 0.30) with some distance from the dorsal shell wall; also, the shell ornament in  C. teres lacks strong ribs on inner whorls.</p><p>Geographic and stratigraphic occurrence</p><p>Northern Estonia, northern Germany, north-west Poland, Sweden,? Norway and?Tibet; Darriwilian, Middle Ordovician.</p></div>	https://treatment.plazi.org/id/03AD87B1DD054273314F9BD596FCFCEA	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Aubrechtová, Martina;Korn, Dieter	Aubrechtová, Martina, Korn, Dieter (2025): The coiled Middle Ordovician cephalopod genera Trocholites and Curtoceras (Tarphyceratida) from Baltoscandia and north-central Europe. European Journal of Taxonomy 982: 1-78, DOI: 10.5852/ejt.2025.982.2843, URL: https://europeanjournaloftaxonomy.eu/index.php/ejt/article/download/2843/12943
03AD87B1DD1C427A312B9E14951CF91B.text	03AD87B1DD1C427A312B9E14951CF91B.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Trocholites hospes (Remele 1880)	<div><p>Trocholites hospes (Remelé, 1880)</p><p>Figs 1G–H, 8–12; Table 4</p><p>Palaeonautilus hospes Remelé, 1880: 249, pl. 2 fig. 3.?  Palaeonautilus hospes Remelé, 1880: 249, pl. 2 fig. 4.</p><p>Palaeonautilus hospes – Remelé 1881: 2, 13, text-fig.1. — Foerste 1930: 286, pl. 43 fig. 2, pl. 44 figs 4–5. — Balashov 1962: pl. 9 fig. 5.</p><p>Palaeonautilus (Trocholites) hospes – Remelé 1890: 40, pl. 2 fig. 3.</p><p>?  Palaeonautilus (Trocholites) hospes – Remelé 1890: pl. 2 fig. 4, pl. 5 fig. 8.</p><p>?  Trocholites hospes – Schröder 1891: 17 (155), pl. 1(24) figs 8–9.</p><p>?  Palaeonautilus hospes – Schindewolf 1939: 60, text-fig. 14, pl. 4 fig. 7.</p><p>Trocholites hospes – Balashov 1953: 244, pl. 5 fig. 3. — Sweet 1958: 96, pl. 8 figs 3, 5. — Neben &amp; Krueger 1971: pl. 32 figs 12–14.</p><p>Diagnosis</p><p>Species of the genus  Trocholites with an adult conch diameter of 43–60 mm. Conch in the last whorl thickly discoidal (CWI = 0.52–0.60) and subevolute (UWI = 0.30–0.40) with moderately high coiling rate (WER = 1.75–1.90). Whorl profile weakly to moderately depressed (WWI = 1.40–1.80), rounded, venter sometimes slightly flattened, usually moderately embracing (IZR = 0.20–0.30). Whorl width and whorl height stagnant or slightly increasing in last quarter volution. Terminal aperture with ventral and lateral flares. Shell ornament with fine lirae extending with rather deep, rounded ventral sinus. Phragmocone chambers moderately long (RCL = 0.20–0.24). Suture line straight.</p><p>Material examined</p><p>BALTIC REGION • 1 spec.; locality unknown;  Aseri or Lasnamägi or Uhaku regional stages; Deubel Coll.; illustrated in Fig. 10A; MB.C. 7638.</p><p>GERMANY – Brandenburg • 1 spec.; Herzsprung (Uckermark); upper Lasnamägi Regional Stage; illustrated by Foerste (1930: pl. 44 fig. 4), re-illustrated here in Fig. 8A; MB.C. 11557 •   1 spec.; Oderberg;  Lasnamägi or Uhaku Regional Stage; Neben Coll.; illustrated by Neben &amp; Krueger (1971: pl. 32 fig. 14), re-illustrated here in Fig. 8C; MB.C. 32162  •  1 spec.; Karlstein (Neumark); probably Darriwilian; Neben and Krueger Coll.; illustrated in Fig. 9A; MB.C. 32163 •  1 spec.; Oderberg; upper Lasnamägi Regional Stage; 1936: Neben Coll.; illustrated by Neben &amp; Krueger (1971: pl. 32 figs 12–13), re-illustrated here in Fig. 9B; MB.C. 11556 •   1 spec.; Eberswalde;  Lasnamägi or Uhaku Regional Stage; Remelé Coll.; illustrated by Neben &amp; Krueger (1971: pl. 32 figs 1–2), re-illustrated here in Fig. 8D; MB.C. 11555.2  •  1 spec.; Oderberg; upper Lasnamägi Regional Stage; Neben and Krueger Coll.; illustrated in Fig. 9C; MB.C. 32164 .</p><p>POLAND – West Pomerania • 1 spec.; Cieszeniewo; upper Lasnamägi Regional Stage; 1890; Dorow Coll.; illustrated by Foerste (1930: pl. 43 fig. 2, pl. 44 fig. 5), re-illustrated here in Fig. 8B; MB.C. 11558 •   1 spec.; Ustronie Morskie (West Pomerania);  Lasnamägi or Uhaku Regional Stage; Müldner Coll.; illustrated in Fig. 9D; MB.C. 32165  •   1 spec.; Ustronie Morskie (West Pomerania);  Lasnamägi or Uhaku Regional Stage; Neben and Krueger Coll.; MB.C. 32166  .</p><p>Description</p><p>Specimen MB.C.11557 (Fig. 8A) is a conch in the terminal stage of growth and has a diameter of about 56 mm. The conch is thickly discoidal (CWI = 0.56) and subevolute (UWI = 0.38). The last whorl is moderately depressed; the WWI decreases from 1.64 to 1.58 during the last quarter volution of the conch. The length of the terminal body chamber is 270 degrees; its venter is slightly flattened. Its aperture possesses ventral and lateral flares producing a deep ventral sinus and prominent ventrolateral lappets. The shell ornament is preserved only in the penultimate whorl and in a very small area at the ventral margin of the aperture; it consists of irregularly spaced, coarse lirae. The internal mould has very low annuli on the venter and in the ventrolateral area. The phragmocone chambers are rather long (RCL = 0.40). The suture line is almost straight and extends with a very broad and shallow external lobe.</p><p>Specimen MB.C.11558 (Fig. 8B) is an almost complete conch of a fully grown individual with a conch diameter of 51 mm. The conch is thickly discoidal (CWI = 0.58) and subevolute (UWI = 0.37). The whorl profile is moderately depressed; the WWI increases from 1.73 to 1.83 in the last 90 degrees of the volutions. The body chamber has a length of about 220 degrees and possesses ventral and ventrolateral flares; a ventral sinus is developed at the aperture. Small remains of the shell ornament are preserved only in the ventrolateral area near the aperture and in the inner volutions; they consist of fine and irregularly developed lirae. The phragmocone chambers are moderately long (RCL = 0.23). The suture line is almost straight with the exception of a very shallow and broad external lobe. At the beginning of the last whorl, the moderately wide siphuncle has a subdorsal position (RSH = 0.24; RSP = 0.84).</p><p>Specimen MB.C.32162 (Fig. 8C) is an almost complete adult conch with a conch diameter of 51 mm and has nearly five whorls preserved. The conch is thickly discoidal (CWI = 0.57) and subevolute (UWI = 0.42); the coiling rate is moderate (WER = 1.77). The whorl profile is moderately depressed (WWI = 1.75) and moderately embracing (IZR = 0.24). The specimen is almost completely exfoliated; small remains of the shell ornament are preserved only in the inner whorls, where fine and regularly spaced lirae are present. The phragmocone chambers are moderately long (RCL = 0.22). The suture line is almost straight, but extends with a very shallow and broad external lobe. At about half of the last whorl, the rather thin siphuncle has a subdorsal position (RSH = 0.18; RSP = 0.80). At the base of the body chamber, traces of muscle scar imprints are preserved.</p><p>Specimen MB.C.32163 (Fig. 9A) is an almost complete, well-preserved adult conch with a diameter of 50 mm. The conch is thickly discoidal (CWI = 0.58) and subevolute (UWI = 0.33) with a moderately high coiling rate (WER = 1.82). The whorl profile is weakly depressed (WWI = 1.50) and strongly impressed dorsally (IZR = 0.33) in the terminal half volution of the conch. The terminal body chamber is slightly longer than half of a volution; its aperture possesses ventral and lateral flares; a ventral sinus is indicated. Remain of the shell are preserved only in small areas; the ornament consists of rather regular, fine lirae.</p><p>Specimen MB.C.11556 (Fig. 9B) is a well-preserved, almost complete conch, which already represents the final stage of growth with a diameter of 43 mm. In this stage of growth, the conch is thickly discoidal (CWI = 0.56), subevolute (UWI = 0.37) and moderately expanding (WER = 1.83); the whorl profile in the last half volution is rounded, moderately depressed (WWI = 1.59) and moderately impressed dorsally (IZR = 0.27). The length of the terminal body chamber is 250 degrees; its aperture possesses ventral and lateral flares. The shell ornament is preserved only near the aperture and consists of irregularly thick lirae, which turn back already from the umbilical seam and form a rather deep, blunt V-shaped ventral sinus. The phragmocone chambers are moderately long (RCL = 0.24). The suture line extends almost straight across the flank and form a very broad and shallow external lobe. Faint traces of muscle scar imprints are preserved in the rear part of the body chamber.</p><p>Specimen MB.C.32164 (Fig. 9C) is a well-preserved, subadult individual with 47 mm conch diameter; the conch is thinly discoidal (CWI = 0.52) and subevolute (UWI = 0.35) and the profile of the last whorl is moderately depressed (WWI = 1.53). The whorl profile is crescent-shaped with broadly rounded venter and flanks; an umbilical margin is not discernible. The shell ornament is well-preserved in large areas; it consists of irregularly spaced, fine and slightly thickened lirae. They are directed backwardly right from the umbilical seam and form a deep, blunt V-shaped ventral sinus.</p><p>Specimen MB.C.32165 (Fig. 9D) is, with a conch diameter of 64 mm, the largest specimen of  Trocholites in our collection. The last ~ 0.50 a whorl corresponds to the body chamber. The specimen has a well-preserved shell ornament that consists of fine and almost equally spaced lirae. On the body chamber, the lirae are fine on the flanks, but on the venter they become more prominent and form a rounded, nearly rectangular sinus.</p><p>Specimen MB.C.7638 (Fig, 10A) is an incomplete conch in the early growth stage with 26.5 mm diameter and was sectioned. During ontogeny (between 4.0 mm and 26.5 mm conch diameter), the conch changes from thickly pachyconic to thinly pachyconic (CWI decreases from 0.82 to 0.71) and from involute to subinvolute (UWI increases from 0.15 to 0.29); the coiling rate decreases markedly (WER drops from 2.60 to 1.67). The whorl profile changes only slightly and remains moderately depressed (WWI = 1.98–1.84), but changes from moderately to strongly impressed (IZR increases from 0.18 to 0.42) (Fig. 10B–D). The shell ornament is not well-discernible; it appears to consist of thin ribs or raised lirae in the internal whorl and only lirae in the outer whorl. The phragmocone chambers are rather long (RCL = 0.39 in the external volution). The siphuncle remains close or in contact with the dorsal shell wall and changes from RSH 0.15 to 0.20 in ontogeny.</p><p>Remarks</p><p>Remelé (1880) described and figured two specimens of “  Palaeonautilus hospes ” from late Darriwilian erratics near Heegermühle (Brandenburg, Germany); subsequently these specimens were re-described and re-figured by him (Remelé 1881, 1890). Only one of these two specimens (MB.C.11555.2) is available for study; it was also illustrated by Neben &amp; Krueger (1971: pl. 32 figs 1–2) and is re-illustrated here in Fig. 8D. However, this syntype was assigned to  Trocholites remelei by Neben &amp; Krueger (1971). Its internal mould shows some annular ridges in the outermost preserved whorl, but the shell surface is ornamented only with fine lirae, not clusters of raised lirae as in the lectotype of  T. remelei (see below).</p><p>Alternatively, it is possible that the specimen MB.C.11555.2 (Fig. 8D) belongs to  T. contractus, but the corresponding growth stage (dm = 26 mm) of that species has a wider conch (CWI ~ 0.65 in the neotype of  T. contractus, but only ~ 0.55 in specimen MB.C.11555.2) with a more depressed whorl profile (WWI ~ 2.12 vs ~ 2.00). The unprofessional preparation of specimen MB.C.11555.2 by previous researchers makes it difficult to decide whether this syntype belongs to  T. hospes or another species of  Trocholites such as  T. contractus . For this reason, this syntype is not considered here.</p><p>The other syntype presented by Remelé (1880, 1881, 1890) was not available for study, but according to original descriptions, as well as figures, it can be reliably assigned to  T. hospes .</p><p>Some specimens of  Trocholites hospes have a more depressed whorl profile (WWI = 1.83 at 52 mm diameter in MB.C.11558; WWI = 1.75 at 51 mm diameter in MB.C.32162) than others (WWI = 1.50 at dm at 50 mm diameter in MB.C.32163) in the terminal growth stage (Fig. 12). These differences probably result from size variations of fully adult conchs, which range in their diameters between 43 mm and 60 mm.</p><p>Trocholites hospes is easily recognised among the species of  Trocholites by its rather large and stout conch, the deep and moderately wide umbilicus, the fine lirae on the shell surface and the terminal body chamber with apertural flares. Most similar to  T. hospes is  T. splendor sp. nov., which differs by its more slender conch (CWI = 0.50 at dm = 49 mm), a less strongly depressed whorl profile (WWI = 1.34 at dm = 49 mm) (Fig. 12) and the presence of thin ribs or raised lirae on the shell surface of the inner whorls.</p><p>The lectotype of the Darriwilian  Trocholites remelei from Sweden also resembles specimens of  T. hospes, but the shell in  T. remelei possesses annuli or groups of raised lirae, which are visible not only on the internal mould but also on the shell surface. Furthermore,  T. remelei, which is known only from a single specimen, has more strongly expanding, less depressed and narrower whorl than corresponding growth stages of  T. hospes (Fig. 12).</p><p>Another species that could be confused with juvenile growth stages of  Trocholites hospes is  T. contractus (Fig. 12); specimens of both species have similarly stout conchs (CWI ~ 0.60) with a deep umbilicus, distinctly depressed whorl profiles (WWI ~ 2.00), similar whorl overlap (IZR ~ 0.30) and lirae on the shell surface. However,  T. contractus reaches a much smaller terminal conch diameter (about 33 mm) and its body chamber markedly decreases in height, width and imprint zone rate toward the aperture.</p><p>Among the non-Baltic trocholitid species, the specimens of  Trocholites hospes resemble the holotype of  T. hubeiensis (Kuniutan (Guniutan) Formation, Darriwilian, Hubei Province of China). It is difficult to make an accurate measurement of the holotype from the only figure and description available, but it appears that the holotype has a similar conch geometry, including a high expansion rate, a narrow umbilicus, a moderately depressed and continuously rounded whorl profile and a subdorsal, comparatively thin siphuncle. On the other hand, the phragmocone chambers appear to be shorter in the holotype of  T. hubeiensis . Nothing is known of the adult conch size. However, the similarity is rather high and it may thus be possible that  T. hubeiensis is a junior synonym of  T. hospes . This would be another species of coiled cephalopods that occurs in both Baltica and South China; the other species include the tarphyceratid  Discoceras rarospira (Eichwald, 1860) from Middle–Late Ordovician strata of Baltoscandia and the Kuniutan (Guniutan) Formation (Middle Ordovician) of Yunnan (Zhang &amp; Chen 2002), and the lituitid  Cyclolituites lynnensis Kjerulf, 1865 that is known from the late Darriwilian / early Sandbian boundary strata of Norway (Kjerulf 1865; Sweet 1958) and the Sandbian of the Hunan Province of China (Fang et al. 2017, 2021). Chen (1987) also reported an occurrence of  T. depressus in Ordovician strata of northern Tibet.</p><p>Similar in conch geometry to the specimens of  Trocholites hospes is also the holotype of  T. ruedemanni (Fig. 12) from early Sandbian (?) strata of New York (USA), except that the adult conch size in the latter is considerably smaller (29 mm vs 43–60 mm), the terminal body chamber is slightly uncoiled and the shell ornament on the umbilical wall in the last two whorls has nodes and fine costae (Flower 1943).</p><p>Geographic and stratigraphic occurrence</p><p>Norway, Sweden (Island of Öland), northern Germany, northern Poland, St Petersburg Region of Russia; Darriwilian (Middle Ordovician).</p></div>	https://treatment.plazi.org/id/03AD87B1DD1C427A312B9E14951CF91B	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Aubrechtová, Martina;Korn, Dieter	Aubrechtová, Martina, Korn, Dieter (2025): The coiled Middle Ordovician cephalopod genera Trocholites and Curtoceras (Tarphyceratida) from Baltoscandia and north-central Europe. European Journal of Taxonomy 982: 1-78, DOI: 10.5852/ejt.2025.982.2843, URL: https://europeanjournaloftaxonomy.eu/index.php/ejt/article/download/2843/12943
03AD87B1DD154279314A9A2A9319FA8D.text	03AD87B1DD154279314A9A2A9319FA8D.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Trocholites macrostoma Schroder 1882	<div><p>Trocholites macrostoma Schröder, 1882</p><p>Figs 1A, 13–14; Table 5</p><p>Trocholites macrostoma Schröder, 1882: 99 .</p><p>Trocholites macrostoma – Schröder 1891: 149, pl. 1(24) fig. 1. — Neben &amp; Krueger 1971: pl. 32 figs 15–16.</p><p>Diagnosis</p><p>Species of the genus  Trocholites with an adult conch diameter of about 42 mm. Conch in the last whorl thinly discoidal (CWI ~ 0.43) and evolute (UWI ~ 0.53) with very low coiling rate (WER ~ 1.52). Whorl profile moderately depressed (WWI ~ 1.73) with rounded venter and flanks, moderately embracing (IZR = 0.18–0.28). Aperture with ventral flares. Shell ornament with irregularly thick, rursiradiate lirae, accumulations of lirae and growth lines, with shallow but relatively sharp ventral sinus; surface of internal mould with low and wide annular ridges.</p><p>Type material</p><p>Neotype (designated here)</p><p>GERMANY – Brandenburg • Oderberg; Darriwilian; Neben and Krueger Coll.; figured by Neben &amp; Krueger (1971: pl. 32 figs 15–16), re-illustrated here in Fig. 13; MB.C. 32167.</p><p>Additional material</p><p>GERMANY – Brandenburg • 1 spec.;  Niederfinow;  Lasnamägi Regional Stage; Neben and Krueger Coll.; illustrated in Fig. 14A; MB.C. 32168  .</p><p>Description</p><p>Neotype MB.C.32167 (Fig. 13) is a well-preserved, nearly complete adult specimen with a conch diameter of 40 mm. The terminal body chamber is slightly longer than half a volution and possesses a ventral flare at the aperture. In the last half volution, the conch becomes more discoidal (CWI decreases from 0.48 to 0.43) and more evolute (UWI increases from 0.46 to 0.53); the terminal whorl is moderately depressed (WWI decreases from 1.81 to 1.72) and moderately embracing (IZR = 0.28). The coiling rate of the conch is very low (WER = 1.48). Shell ornament is well-preserved in the inner whorls and part of the last whorl; it consists of distinct and irregularly thick lirae or clusters of lirae; the internal mould has very low and widely spaced annular ridges. The elements of the ornament are rursiradiate in their direction and form a shallow, subangular ventral sinus.</p><p>Specimen MB.C.32168 (Fig. 14A) is a conch with 35 mm diameter; the specimen was sectioned and displays five whorls. Conch width and coiling rate generally decrease during ontogeny between 3.4 mm and 35 mm conch diameter (CWI changes from 0.96 to 0.43 and the WER from 2.66 to 1.56), while the umbilicus becomes wider (UWI increases significantly from 0.18 to 0.53). The whorl profile shows rounded flanks and a slightly flattened venter only in some inner whorls; it is always weakly impressed and strongly or moderately depressed (WWI decreases from 2.65 to 1.74). Whorl height and whorl width increase during growth but in the last half volution, the width appears to decrease slightly (ww changes from 15.4 to 15.1 mm). The siphuncle has a subdorsal position and a relative diameter (RSH) of about 0.20, however, both distance and diameter cannot be accurately measured due to the insufficient preservation of the specimen.</p><p>Remarks</p><p>A single specimen of  Trocholites macrostoma was described by Schröder (1882) and subsequently illustrated by him (Schröder 1891: pl. 1(24) fig. 1; see also Fig. 1A herein). This holotype originated from the  Echinosphaerites Limestone (Darriwilian Stage, Middle Ordovician) of an unspecified locality in “Ostpreussen” (present day Kaliningrad Region of Russia). Schröder (1891) stated that the holotype was kept in the Mineralogical Museum of the University of Königsberg (now Kaliningrad). However, this collection was most probably destroyed in World War II (pers. com. D. Weyer, Berlin, 2022). Therefore, we propose here specimen MB.C.32167 as the neotype for  T. macrostoma . This specimen is nearly identical in size and dimensions to the holotype. The only difference is that the last whorl in the holotype is slightly less impressed (IZR ~ 0.23 vs ~ 0.28) and that the last whorl of the holotype appears to have had an even lower coiling rate than that calculated for neotype MB.C.32167. However, the precise value cannot be determined reliably from the illustration of the holotype. The two specimens come probably from the same stratigraphic horizon (Darriwilian, Middle Ordovician).</p><p>The neotype of  Trocholites macrostoma closely resembles the specimens of  T. vodickai sp. nov., but it is separated from these by the slowly expanding, moderately impressed and moderately depressed last whorl and by the presence of distinct, rursiradiate lirae on the shell surface.</p><p>The other specimen (MB.C.32168) assigned here to  T. macrostoma differs from the neotype only by the small decrease in absolute whorl width in the latest ontogeny. Specimen MB.C.32168 additionally differs from  T. freyjae sp. nov.,  T. baldri sp. nov.,  T. glacialis sp. nov., T. sp. 1, T. sp. 2 and T. sp. 3 in the ontogenetic trajectories of several characters between conch diameters of 5 to 25 mm. In this growth interval, the CWI decreases and UWI increases significantly in MB.C.32168; the WWI is higher than in the other species (Fig. 11). In addition, the whorl width (but not whorl height) of the terminal body chamber appears to decrease close to the aperture.</p><p>In  Trocholites depressus, the last whorl tends to be more discoidal (CWI as low as 0.33 vs over 0.40 in  T. macrostoma) and more rapidly expanding (WER ~ 1.65 vs 1.52) with a less depressed (WWI = 1.25– 1.60 vs ~1.73) whorl profile; the shell ornament has ribs (vs irregularly thick lirae in  T. macrostoma). The specimens of  Trocholites macrostoma differ from the holotype of  T. luna sp. nov. in that the last whorl of the conch is less expanded (WER ~ 1.52 vs 1.60), the whorl profile is more depressed (WWI ~ 1.73 vs 1.55; the venter of body chamber lacks annuli, only lirae are present.</p></div>	https://treatment.plazi.org/id/03AD87B1DD154279314A9A2A9319FA8D	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Aubrechtová, Martina;Korn, Dieter	Aubrechtová, Martina, Korn, Dieter (2025): The coiled Middle Ordovician cephalopod genera Trocholites and Curtoceras (Tarphyceratida) from Baltoscandia and north-central Europe. European Journal of Taxonomy 982: 1-78, DOI: 10.5852/ejt.2025.982.2843, URL: https://europeanjournaloftaxonomy.eu/index.php/ejt/article/download/2843/12943
03AD87B1DD164247315798B09610FD15.text	03AD87B1DD164247315798B09610FD15.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Trocholites contractus Schroder 1891	<div><p>Trocholites contractus Schröder, 1891</p><p>Figs 1B, 15; Table 6</p><p>Trocholites contractus Schröder, 1891: 19 (157), pl. 1(24) fig. 2.</p><p>Trocholites contractus – Sweet 1958: 95, pl. 7, figs 1–2. — Neben &amp; Krueger 1971: pl. 32 figs 6–7. — Dzik 1984: 43, text-figs 11, 12.52, pl. 5 fig. 4, pl. 6 fig. 1.</p><p>?  Trocholites contractus – Dzik 1984: pl. 5 fig. 4, pl. 6 fig. 1.</p><p>Diagnosis</p><p>Species of the genus  Trocholites with an adult conch diameter of about 33 mm. Conch in the last whorl thickly discoidal (CWI ~ 0.46) and evolute (UWI ~ 0.53) with low coiling rate (WER ~ 1.60). Whorl profile moderately depressed (WWI ~ 1.95) with rounded venter and flanks. Whorl width and whorl height decreasing in last half volution (CWI ~ 0.70–0.50; wh / dm ~ 0.30–0.20). Siphuncle marginodorsal in position.</p><p>Type material</p><p>Neotype (designated here)</p><p>GERMANY – Berlin • Lübars;  Lasnamägi Regional Stage; Neben and Krueger Coll.; figured by Neben and Krueger (1971: pl. 32 figs 6–7), re-illustrated here in Fig. 15; MB.C. 32169.</p><p>Description</p><p>Neotype MB.C.32169 (Fig. 15) is an adult, well-preserved internal mould with a conch diameter of 33 mm; almost 3 whorls are preserved. The last half volution shows conspicuous changes in the shape of the conch morphology, where the terminal body chamber undergoes a significant reduction of width and height. During the last half whorl, in which the conch diameter increases from 26 mm to 33 mm, the general morphology changes from thinly pachyconic to discoidal (CWI decreases from 0.65 to 0.46) and from subevolute to evolute (umbilicus widens, UWI increases from 0.43 to 0.53); the last half whorl becomes less strongly depressed (WWI decreases from 2.12 to 1.99), the coiling rate is low (WER = 1.61) and the last whorl is weakly embracing (IZR = 0.08) at the mature aperture. The body chamber clearly decreases in width starting from its beginning (from about 17 mm to 15 mm), and also in height starting at about its mid-length (from 8.8 mm to 7.5 mm; wh /dm = 0.30–0.23). The phragmocone chambers are moderately long (RCL = 0.23).</p><p>Remarks</p><p>Trocholites contractus was described by Schröder (1891: 19 (157), pl. 1(24) fig. 2; see also Fig. 1B herein) on the basis of a single specimen from the locality “Rosehnen in Samlande”, present day Priboi on the Samland Peninsula, Kaliningrad Region of Russia. The specimen came from a block of the  Echinosphaerites Limestone (Darriwilian, Middle Ordovician) and Schröder (1891) stated that it had been kept in the “Regional Museum of Königsberg” (Kaliningrad). Since that collection was most probably destroyed during World War II (pers. com. D. Weyer, Berlin, 2022), a neotype has been selected and described here. The proposed neotype corresponds stratigraphically to the holotype. Both specimens do not differ significantly from each other morphologically.</p><p>Trocholites contractus differs from other species of the genus in the whorl profile; its whorls are wider, more depressed and more strongly embracing. In these aspects, the neotype of  T. contractus resembles the preadult growth stage of  T. hospes (Fig. 12). However, individuals of  T. hospes attain a much larger adult size (up to 60 mm in diameter), while in  T. contractus the size of the conch in the terminal stage is only about 33 mm. Furthermore, a characteristic feature that readily distinguishes  T. contractus from  T. hospes and any other trocholitid species is the marked and rapid decrease in whorl width, whorl height and impression rate of the terminal body chamber.</p><p>Geographic and stratigraphic occurrence</p><p>Kaliningrad Region of Russia, northern Germany, Poland, Norway, Estonia; Darriwilian, Middle Ordovician.</p></div>	https://treatment.plazi.org/id/03AD87B1DD164247315798B09610FD15	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Aubrechtová, Martina;Korn, Dieter	Aubrechtová, Martina, Korn, Dieter (2025): The coiled Middle Ordovician cephalopod genera Trocholites and Curtoceras (Tarphyceratida) from Baltoscandia and north-central Europe. European Journal of Taxonomy 982: 1-78, DOI: 10.5852/ejt.2025.982.2843, URL: https://europeanjournaloftaxonomy.eu/index.php/ejt/article/download/2843/12943
03AD87B1DD28424431289E399549F970.text	03AD87B1DD28424431289E399549F970.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Trocholites remelei Schroder 1891	<div><p>Trocholites remelei Schröder, 1891</p><p>Fig. 16; Table 7</p><p>Trocholites Remeléi Schröder, 1891: 18 (156).</p><p>Trocholites remeléi – Neben &amp; Krueger 1971: pl. 32 figs 4–5.</p><p>non  Trocholites incongruus – Angelin 1880: 11, pl. 9 figs 15–18.</p><p>non  Trocholites remeléi – Neben &amp; Krueger 1971: pl. 32 figs 1–3.</p><p>Diagnosis</p><p>Species of the genus  Trocholites with conch at dm 22 mm thinly pachyconic (CWI ~ 0.60) and subevolute (UWI ~ 0.30). Whorl profile weakly depressed (WWI ~ 1.43) and moderately impressed (IZR ~ 0.34), rounded from lateral sides and slightly flattened from ventral side. Coiling rate is moderate (WER ~ 1.88). Shell ornament with low, regularly spaced clusters of raised lirae manifested on internal mould as annular ridges.</p><p>Type material</p><p>Lectotype</p><p>SWEDEN –  Öland • 1 spec.;  Lerkaka;  Lasnamägi or Uhaku regional stages; 1881; Dames Coll.; illustrated by Neben &amp; Krueger (1971: pl. 32 figs 4–5), re-illustrated here in Fig. 16; MB.C. 11562.</p><p>Description</p><p>Lectotype MB.C.11562 (Fig. 16) is a conch with 22 mm diameter. At least three whorls are visible; the last half whorl belongs to the body chamber. In the last half volution, the conch becomes slightly more slender (CWI decreases from 0.63 to 0.59) and remains subevolute (UWI ~ 0.32) with a moderate coiling rate (WER = 1.88). The body chamber is moderately embracing the preceding whorl (IZR = 0.34) and less depressed (WWI decreases from 1.61 to 1.43). The shell is ornamented with low, regularly spaced clusters of raised lirae, which are visible on the internal mould as annular ridges; the lirae extend with a sinus across the venter.</p><p>Remarks</p><p>Angelin (1880: pl. 9 figs 15–18) illustrated two specimens of  Trocholites incongruus from Darriwilian strata of Sweden. Remelé (1880) stated that these specimens do not belong to  T. incongruus and subsequently Schröder (1891) established the new species  Trocholites remelei based on these specimens. Schröder also assigned a small late Darriwilian trocholitid (MB.C.11562; Fig. 16) from the Island of Öland (Sweden) to  T. remelei . This was illustrated by Neben &amp; Krueger (1971) and is chosen here as lectotype. Examination of the two specimens NRM Mo 152355 and NRM Mo 152354 of Angelin (1880) revealed that they are more discoidal (CWI = 0.50 and 0.41 vs 0.59), with a wider umbilicus and less impressed whorls. They possess a different type of ornament than the lectotype and each is assigned to a different species below ( Trocholites tureki sp. nov. and  T. freyjae sp. nov.).</p><p>It has to be noted that Neben &amp; Krueger (1971) also included syntype MB.C.11555.2 of  T. hospes (Remelé 1890: pl. 2 fig. 4) in  T. remelei; however, this is not accepted here since no annular ornament elements are present on the shell surface or internal mould surface of this specimen (Fig. 8D).</p><p>Lectotype MB.C.11562 is unique among specimens of  Trocholites because of the relatively stout conch (Fig. 12C) combined with narrow umbilicus and prominent annuli that are visible on the shell surface as well as on internal mould.</p></div>	https://treatment.plazi.org/id/03AD87B1DD28424431289E399549F970	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Aubrechtová, Martina;Korn, Dieter	Aubrechtová, Martina, Korn, Dieter (2025): The coiled Middle Ordovician cephalopod genera Trocholites and Curtoceras (Tarphyceratida) from Baltoscandia and north-central Europe. European Journal of Taxonomy 982: 1-78, DOI: 10.5852/ejt.2025.982.2843, URL: https://europeanjournaloftaxonomy.eu/index.php/ejt/article/download/2843/12943
03AD87B1DD2B4242311F9B9E9393FE15.text	03AD87B1DD2B4242311F9B9E9393FE15.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Trocholites baldri Aubrechtová & Korn 2025	<div><p>Trocholites baldri sp. nov.</p><p>urn:lsid:zoobank.org:act: EE665BAD-AF26-4024-A9C5-8A558A5D376F</p><p>Fig. 17; Table 8</p><p>Diagnosis</p><p>Species of the genus  Trocholites with an adult conch diameter of more than 30 mm. Conch in the last whorl thickly discoidal (CWI ~ 0.50) and evolute (UWI ~ 0.45) with moderately high coiling rate (WER ~ 1.75). Whorl profile moderately depressed (WWI ~ 1.80) with rounded flanks and venter, weakly embracing (IZR ~ 0.14). Whorl width and whorl height slightly decreasing in last quarter volution. Phragmocone chambers moderately long (RCL ~ 0.28). Suture line nearly straight.</p><p>Etymology</p><p>After Baldr, the Norse god of light, beauty and purity.</p><p>Type material</p><p>Holotype</p><p>GERMANY – Mecklenburg-Vorpommern • Göhren (Isle of Rügen);  Lasnamägi Regional Stage; illustrated in Fig. 17; MB.C. 32170.</p><p>Description</p><p>Holotype MB.C.32170 (Fig. 17) is a specimen with a conch diameter of 31 mm; the specimen is largely an internal mould with few shell remnants. The body chamber is preserved for a little more than half a volution in length and decreases slightly in width and height; the whorl width is reduced from 9.2 mm to 8.6 mm and the whorl height from 15.8 mm to 15.5 mm. This means that during the last half volution the conch becomes markedly narrower (CWI decreases from 0.61 to 0.50) and increasingly umbilicate (UWI increases from 0.37 to 0.46) with a terminal coiling rate of WER = 1.76. During this growth interval, the whorl profile is depressed (WWI decreases from 1.83 to 1.72) and weakly impressed dorsally (IZR = 0.12 at the maximum whorl height) with broadly rounded flanks and venter. Fine traces of transverse ornament elements are locally preserved on the shell surface. The phragmocone chambers are moderately long (RCL = 0.28) in the last volution; the suture line is almost straight.</p><p>Remarks</p><p>Trocholites baldri sp. nov. is most similar to the species  T. macrostoma,  T. freyjae sp. nov.,  T. glacialis sp. nov., T. sp. 1 and T. sp. 3 but differs in the decrease of both whorl width and whorl height of the terminal body chamber.</p><p>Compared to the specimens of  Trocholites depressus, the holotype of  T. baldri sp. nov. is stouter (CWI ~ 0.50 vs 0.35–0.40), expands more rapidly (WER ~ 1.75 vs 1.65) and the whorl profile is more depressed (WWI ~ 1.80 vs 1.25–1.60).</p><p>Rather similar in conch geometry to the holotype of  T. baldri sp. nov. is the neotype of  T. contractus; however, in  T. contractus, the decrease of body chamber width and height is much greater, the phragmocone chambers are slightly shorter and the suture line has a deeper ventral lobe.</p></div>	https://treatment.plazi.org/id/03AD87B1DD2B4242311F9B9E9393FE15	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Aubrechtová, Martina;Korn, Dieter	Aubrechtová, Martina, Korn, Dieter (2025): The coiled Middle Ordovician cephalopod genera Trocholites and Curtoceras (Tarphyceratida) from Baltoscandia and north-central Europe. European Journal of Taxonomy 982: 1-78, DOI: 10.5852/ejt.2025.982.2843, URL: https://europeanjournaloftaxonomy.eu/index.php/ejt/article/download/2843/12943
03AD87B1DD2D424031199F3895F1F876.text	03AD87B1DD2D424031199F3895F1F876.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Trocholites freyjae Aubrechtová & Korn 2025	<div><p>Trocholites freyjae sp. nov.</p><p>urn:lsid:zoobank.org:act: 7EC4E3F9-662D-4F88-BC4F-81779A9EB017</p><p>Fig. 18; Table 9</p><p>Trocholites incongruus – Angelin 1880: 11, pl. 9 fig. 17.</p><p>Diagnosis</p><p>Species of the genus  Trocholites with an adult conch diameter of 30–40 mm. Conch in the last whorl thickly discoidal (CWI = 0.45–0.50) and evolute (UWI ~ 0.46). Whorl profile moderately depressed (WWI = 1.60–1.80) with trumpet-shaped aperture (ventral and lateral flares). Whorl width slightly increasing, whorl height slightly decreasing in last quarter volution. Phragmocone chambers moderately long to long (RCL = 0.20–0.40). Suture line straight or with shallow ventral lobe. Siphuncle subdorsal in position with relative diameter of ~ 0.20.</p><p>Etymology</p><p>After Freyja, the Norse goddess of love, beauty, fertility and war.</p><p>Type material</p><p>Holotype</p><p>GERMANY •  probably Brandenburg; Neben and Krueger Coll.; illustrated in Fig. 18A; MB.C. 32171.</p><p>Paratypes</p><p>ESTONIA • 1 spec.;  Osmussaar;  Lasnamägi Regional Stage; illustrated in Fig. 18C; TUG 46-167  .</p><p>GERMANY – Brandenburg • 1 spec.;  Niederfinow;  Lasnamägi Regional Stage; Neben and Krueger Coll.; illustrated in Fig. 18B; MB.C. 32172  .</p><p>SWEDEN • 1 spec.; Altsarbyn (earlier spelling Alsarbyn, Dalarna); Darriwilian Stage; Angelin Coll.; figured by Angelin (1880: pl. 9 fig. 17), re-illustrated here in Fig. 18D; NRM Mo 152355 .</p><p>Description</p><p>Holotype MB.C.32171 (Fig. 18A) is a specimen in the terminal growth stage with 31 mm conch diameter. With a diameter of 31 mm, the conch is discoidal (CWI = 0.48) and evolute (UWI = 0.46). The whorl profile is moderately depressed (WWI = 1.85) and impressed dorsally; it possesses broadly rounded flanks and venter. The body chamber is almost complete at about 220 degrees in length. In the last quarter, it slightly decreases in height from 8.4 mm to 8.0 mm. The aperture possesses conspicuous lateral and ventral flares, which give the aperture a trumpet-like appearance. Since the body chamber is exfoliated, the shell ornament is visible only on the chambered part of the conch, where it consists of rather sharp, densely spaced rursiradiate lirae; the internal mould of the body chamber shows faint impressions of raised lirae or narrow annuli.</p><p>Paratype MB.C.32172 (Fig. 18B) is a conch with 34 mm diameter and consists of 3.25 volutions; more than the last half whorl belongs to the incomplete body chamber. In the last half volution, the conch is thinly discoidal (CWI = 0.43) and evolute (UWI = 0.49). The whorl height decreases from 8.8 mm at the beginning of the body chamber to 8.2 mm in its apertural end; the whorl width of the body chamber increases slightly in this interval from 13.8 mm to 14.3 mm. The whorl profile becomes increasingly depressed in the last half a whorl (WWI changes from 1.58 to 1.74); it has rounded flanks and a very slightly flattened venter. The shell is ornamented with irregularly spaced, rursiradiate lirae, which are occasionally approximated and raised. The phragmocone chambers are moderately long (RCL ranges between 0.20 and 0.35) in the last half of the phragmocone.</p><p>Paratype TUG 46-167 (Fig. 18C) is a preadult specimen with 28 mm conch diameter; one third of the last volution is occupied by the body chamber. At its maximum diameter, the conch is discoidal (CWI = 0.44) and widely umbilicate (UWI = 0.52). The whorl profile shows broadly rounded flanks and a slightly flattened venter; it is moderately depressed (WWI = 1.80). Both the whorl width and whorl height increase gradually, but it appears that the whorl height in the last quarter whorl starts to decrease slightly. The phragmocone chambers are moderately long (RCL = 0.30–0.40) in the last whorl; the suture line is almost straight with a very shallow external lobe.</p><p>Paratype NRM Mo 152355 (Fig. 18D) is a preadult conch with 26 mm diameter with two whorls preserved; the body chamber is not present. At the maximum diameter, the conch is thickly discoidal (CWI = 0.50); the latest whorl profile is moderately impressed (IZR = 0.23) and moderately depressed (WWI = 1.76) with rounded flanks and venter. The coiling rate is low (WER = 1.65). The ornament is preserved only in small shell relicts; it consists of sharp, regularly spaced lirae and does not leave any traces on the internal mould. The phragmocone chambers are moderately long (RCL = 0.25 in the external volution); the latest two chambers appear to be shortened. The suture line is almost straight with a very shallow and wide external lobe. At the maximum diameter, the siphuncle has a subdorsal position (RSP = 0.86) and a relative diameter (RSH) of about 0.20.</p><p>Remarks</p><p>Trocholites freyjae sp. nov. differs from  T. macrostoma,  T. contractus,  T. baldri sp. nov.,  T. glacialis sp. nov., T. sp. 1 and T. sp. 3 in the combination of whorl width increase and whorl height decrease in the terminal body chamber.</p><p>In  Trocholites depressus, the whorl height may slightly decrease in last quarter volution, as in  T. freyjae sp. nov. However,  T. depressus differs in that the last whorl is more discoidal (CWI up to 0.40 vs up to 0.50), the whorl profile tends to be less depressed (WWI = 1.25–1.60 vs 1.60–1.80) and the siphuncle is marginodorsal (vs subdorsal) in position and relatively wider in diameter (RSH ~ 0.30 vs 0.20 in the last whorl).</p><p>Paratype NRM Mo 152355 was previously figured by Angelin (1880) and used by Schröder (1891) as a syntype of  Trocholites remelei . The type collection of that species consisting of three specimens (NRM Mo 152355, NRM Mo 152354, MB.C.11562) is revised herein and all three were found to represent different species.</p><p>Paratype NRM Mo 152355 differs from MB.C.11562 (lectotype of  T. remelei) by being more discoidal (CWI = 0.50 at dm 26 mm vs 0.59 at dm 22 mm) with less rapidly expanding whorls (WER = 1.65 at dm 26 mm vs 1.87 at dm 22 mm); its whorl profile is more depressed (WWI = 1.76 at dm 26 mm vs 1.43 at dm 22 mm) and less impressed (IZR = 0.23 at dm 26 mm vs 0.34 at dm 22 mm).</p><p>Paratype NRM Mo 152355 is additionally distinguished from NRM Mo 152354 (holotype of  Trocholites tureki sp. nov.) because it is stouter (CWI = 0.50 at dm 26 mm vs 0.41 at dm 22 mm) with more strongly depressed whorls (WWI = 1.76 at dm 26 mm vs 1.46 at dm 22 mm). Most remarkably, the shell surface of NRM Mo 152355 is ornamented only by sharp lirae and lacks any annuli or ribs, unlike in the representatives of  T. remelei and  T. tureki .</p></div>	https://treatment.plazi.org/id/03AD87B1DD2D424031199F3895F1F876	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Aubrechtová, Martina;Korn, Dieter	Aubrechtová, Martina, Korn, Dieter (2025): The coiled Middle Ordovician cephalopod genera Trocholites and Curtoceras (Tarphyceratida) from Baltoscandia and north-central Europe. European Journal of Taxonomy 982: 1-78, DOI: 10.5852/ejt.2025.982.2843, URL: https://europeanjournaloftaxonomy.eu/index.php/ejt/article/download/2843/12943
03AD87B1DD2E424E310E9C2496E3FC0F.text	03AD87B1DD2E424E310E9C2496E3FC0F.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Trocholites glacialis Aubrechtová & Korn 2025	<div><p>Trocholites glacialis sp. nov.</p><p>urn:lsid:zoobank.org:act: 09A65391-6E39-4073-8C94-89570D4005DC</p><p>Fig. 19; Table 10</p><p>Diagnosis</p><p>Species of the genus  Trocholites with an adult conch diameter of 35 mm. Conch in the last whorl thickly discoidal (CWI ~ 0.52) and evolute (UWI ~ 0.45). Whorl profile moderately depressed (WWI ~ 1.80) with rounded flanks and venter. Whorl width and whorl height slightly increasing in last quarter volution. Shell ornament with irregularly thick, rursiradiate lirae, adaperturally raised; sharp lirae on inner whorls. Phragmocone chambers moderately long (RCL ~ 0.25). Suture line straight.</p><p>Etymology</p><p>From the Latin  ‘ glacialis ʼ (adjective), meaning ‘glacial’ or ‘frozen’.</p><p>Type material</p><p>Holotype</p><p>POLAND – West Pomerania • Ustronie Morskie;  Lasnamägi or Uhaku Regional Stage; Müldner Coll.; illustrated in Fig. 19A; MB.C. 32173.</p><p>Paratype</p><p>GERMANY – Berlin • 1 spec.;  Schmargendorf; Ordovician; 1906; Schmidt Coll.; illustrated in Fig. 19B; MB.C. 11561  .</p><p>Description</p><p>Holotype MB.C.32173 (Fig. 19A) is an incomplete specimen with a conch diameter of 35 mm and shows about 3.5 whorls. At maximum diameter, the conch is discoidal and evolute (CWI = 0.52; UWI = 0.45); the last whorl is moderately depressed (WWI = 1.81). Both whorl height and whorl width slowly gradually increase in the last preserved whorl. The ornament is only preserved in small areas and consists of irregularly coarse, rursiradiate lirae, which are raised near the aperture. Sharp lirae are present in the inner whorls. The length of the body chamber and shape and distance of suture lines cannot be determined.</p><p>Paratype MB.C.11561 (Fig. 19B) with nearly identical dimensions and ratios shows that the body chamber occupies a little more than half of the last volution. The phragmocone chambers are moderately long (RCL ~ 0.25); the suture line is nearly straight.</p><p>Remarks</p><p>Trocholites glacialis sp. nov. differs from  T. contractus,  T. freyjae sp. nov.,  T. baldri sp. nov., T. sp. 1 and T. sp. 3 in the increase of both whorl width and whorl height in the terminal body chamber.</p><p>Trocholites macrostoma has a greater adult conch diameter (42 vs 35 mm) and in the last whorl, the conch is more discoidal (CWI ~ 0.43 vs 0.52) and more evolute (UWI ~ 0.53 vs 0.45).</p><p>In the last whorl of  Trocholites depressus, the conch is much more discoidal (CWI up to 0.40 vs ~ 0.52), the whorl profile is much less depressed (WWI 1.25–1.60 vs ~ 1.80) and the whorl height may slightly decrease adaperturally; phragmocone chambers tend to be longer (RCL = 0.30–0.40 vs 0.25) and the shell surface has ribs.</p></div>	https://treatment.plazi.org/id/03AD87B1DD2E424E310E9C2496E3FC0F	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Aubrechtová, Martina;Korn, Dieter	Aubrechtová, Martina, Korn, Dieter (2025): The coiled Middle Ordovician cephalopod genera Trocholites and Curtoceras (Tarphyceratida) from Baltoscandia and north-central Europe. European Journal of Taxonomy 982: 1-78, DOI: 10.5852/ejt.2025.982.2843, URL: https://europeanjournaloftaxonomy.eu/index.php/ejt/article/download/2843/12943
03AD87B1DD21424C31369937931CFB47.text	03AD87B1DD21424C31369937931CFB47.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Trocholites kadakaensis Aubrechtová & Korn 2025	<div><p>Trocholites kadakaensis sp. nov.</p><p>urn:lsid:zoobank.org:act: DF7112C8-6722-44CB-B68C-E09E540C98E6</p><p>Fig. 20; Table 11</p><p>Diagnosis</p><p>Species of the genus  Trocholites with an adult conch diameter of more than 42 mm. Conch in the last whorl thickly discoidal (CWI ~ 0.48) and evolute (UWI ~ 0.46). Whorl profile moderately depressed (WWI ~ 1.80) with rounded flanks and venter, moderately to weakly embracing (IZR = 0.35–0.15). Whorl width and whorl height slightly decreasing in last half volution; the coiling rate decreases to WER ~ 1.70. Phragmocone chambers at 30 mm diameter moderately long (RCL ~ 0.30). Suture line nearly straight.</p><p>Etymology</p><p>From Kadaka near Tallinn (Estonia), the locality of the holotype.</p><p>Type material</p><p>Holotype</p><p>ESTONIA •  Kadaka (Tallinn); Väo Formation, late Darriwilian Stage; 1920; Deubel Coll.; illustrated in Fig. 20; MB.C. 11563.</p><p>Paratype</p><p>ESTONIA • 1 spec.;  Tallinn; late Darriwilian Stage; Prantl and Zázvorka Coll.; NM-S6032  .</p><p>Description</p><p>Holotype MB.C.11563 (Fig. 20) is an incompletely preserved conch, which is almost in the terminal growth stage, measuring 42 mm in diameter. It consists of 3.25 volutions of which the last quarter volution belongs to the body chamber. In the last half volution, both the whorl width and whorl height decrease (from 20.1 mm to 19.8 mm and from 11.5 mm to 10.9 mm, respectively). The conch is discoidal (CWI = 0.48) and subevolute to evolute (UWI = 0.46). The whorl profile is moderately depressed (WWI = 1.82) with broadly rounded flanks and venter; it changes from strongly to weakly embracing (IZR decreases from 0.36 to 0.15). The coiling rate (WER) decreases from a value of 1.76 to 1.67 (WER wh changes from about 2.60 to 1.85 in the last half a whorl). Only small remains of the shell are preserved; its ornament consists of indistinct, low lirae. On the venter of the terminal body chamber, there are extremely fine and low longitudinal (spiral) lines. The phragmocone chambers are moderately long (RCL = 0.30 at dm = 30 mm). The suture line is almost straight and forms a very shallow and wide external lobe.</p><p>Paratype NM-S6032 is a partially preserved conch in the late ontogenetic stage with a maximum measurable diameter of 39 mm. Two volutions are preserved of which the last ~150 degrees of the outer volution belong to the body chamber. In the last half volution, the whorl height decreases from 10.8 to 9.9 mm. The conch is subevolute to evolute with UWI = 0.47 at the largest conch diameter. The whorl profile has broadly rounded flanks and a broadly rounded venter. The coiling rate based on whorl height (WER wh) decreases from 2.55 to 1.80 in the last half whorl. The suture line is almost straight with a very shallow and wide external lobe. At a diameter of 29 mm, remains of the siphuncle are preserved; the siphuncle is located near the dorsal shell wall but it is not in contact with it.</p><p>Remarks</p><p>Holotype MB.C.11563 belongs to the representatives of  Trocholites with a relatively large conch. Aside from the size, it has moderately long phragmocone chambers (RCL ~ 0.30) and the body chamber is contracted in both width and height. Very similar to this specimen is holotype MB.C.9718 of  T. zaryensis sp. nov., but this is smaller in the adult size (36 mm) and differs in the shape of the terminal body chamber. In  T. zaryensis, the height of the last whorl shows an increase in contrast to a decrease in  T. kadakaensis sp. nov.; it also shows a slight flattening of the venter.</p><p>Similar in conch geometry is also the holotype of  T. baldri sp. nov. In its last whorl, however, the decrease of the body chamber height is greater than in the holotype of  T. kadakaensis sp. nov.; the former is also smaller in adult size (~ 30 mm).</p><p>The decrease of the body chamber width and height is present also in the neotype of  Trocholites contractus . In that specimen, however, the proportions of the body chamber change much more rapidly and the adult conch diameter is smaller (~ 33 mm vs 41 mm). In addition, umbilicus in the last whorl of  T. contractus is wider (UWI ~ 0.53 vs 0.46), the expansion rate is lower (WER ~ 1.60 vs 1.70) and the whorl profile is more depressed (WWI ~ 1.95 vs 1.80); phragmocone chambers are longer (RCL ~ 0.23 vs 0.30).</p><p>The two specimens of  T. vodickai sp. nov. differ because their last whorl is more discoidal (CWI ~ 0.40 vs 0.48) and the whorl profile is much less depressed (WWI ~ 1.25–1.50 vs 1.80) without any distinct decrease in width and height towards the terminal aperture.</p><p>The last whorl in the holotype of  Trocholites splendor sp. nov. differs in having a narrower umbilicus (UWI ~ 0.35 vs 0.46), less depressed (WWI ~ 1.35 vs 1.80) whorl profile with increasing instead of decreasing whorl width and whorl height of the terminal body chamber.</p><p>The holotype of  Trocholites ruedemanni is similar to the holotype of  T. kadakaensis sp. nov. in expansion rate and imprint zone rate of the adult growth stage but differs from it by the slight uncoiling of the mature body chamber, shell ornament (nodes and costae) and a narrower umbilicus (UWI = 0.32 vs 0.43 at dm ~ 30 mm).</p><p>In the apertural part of the body chamber of the specimen MB.C.11563, there are several circular openings with a diameter of ~ 3 mm; these are identified as borings that belong to the ichnospecies  Trypanites sozialis Eisenack, 1934 (see Knaust et al. 2023; Vinn et al. 2023).</p></div>	https://treatment.plazi.org/id/03AD87B1DD21424C31369937931CFB47	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Aubrechtová, Martina;Korn, Dieter	Aubrechtová, Martina, Korn, Dieter (2025): The coiled Middle Ordovician cephalopod genera Trocholites and Curtoceras (Tarphyceratida) from Baltoscandia and north-central Europe. European Journal of Taxonomy 982: 1-78, DOI: 10.5852/ejt.2025.982.2843, URL: https://europeanjournaloftaxonomy.eu/index.php/ejt/article/download/2843/12943
03AD87B1DD23424D31E799CD97A0F887.text	03AD87B1DD23424D31E799CD97A0F887.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Trocholites luna Aubrechtová & Korn 2025	<div><p>Trocholites luna sp. nov.</p><p>urn:lsid:zoobank.org:act: 0E391219-F3BE-44A3-8ECB-42526225CF54</p><p>Fig. 21; Table 12</p><p>Diagnosis</p><p>Species of the genus  Trocholites with an adult conch diameter of about 50 mm. Conch in the last whorl thinly discoidal (CWI ~ 0.38) and evolute (UWI ~ 0.52) with low coiling rate (WER ~ 1.60). Whorl profile moderately depressed (WWI ~ 1.55) with rounded flanks and slightly flattened venter, weakly embracing (IZR ~ 0.14). Shell ornament with raised lirae or accumulation of lirae in the inner whorls, venter of body chamber with low, regularly spaced annuli and fine lirae. Phragmocone chambers long (RCL ~ 0.38). Suture line straight.</p><p>Etymology</p><p>From the Latin  ‘ luna ʼ (nomen) = ‘the Moonʼ, referring to the shape of the relatively large conch of the holotype.</p><p>Type material</p><p>Holotype</p><p>GERMANY – Brandenburg • Oderberg; Ordovician; 1970; Krueger Coll.; illustrated in Fig. 21; MB.C. 32174</p><p>Description</p><p>Holotype MB.C.32174 (Fig. 21) is a specimen partially embedded in the rock matrix. The conch has a diameter of 48 mm and represents the adult growth stage. It is thinly discoidal (CWI = 0.38) and evolute (UWI = 0.52) with a low coiling rate (WER = 1.60). In the last half volution, the whorl profile has continuously rounded flanks and slightly flattened venter; the whorl profile is moderately depressed (WWI = 1.56) and weakly impressed dorsally (IZR = 0.14). The body chamber is longer than half of a volution; the proximity of aperture is indicated by inconspicuous ventral flare. The ornament of the inner whorls consists of sharp raised lirae or accumulations of lirae; the venter of the terminal body chamber has low and equally spaced annuli and fine lirae. The phragmocone chambers are long (RCL = 0.38). The suture line is nearly straight, but extends with a very low saddle across the venter.</p><p>Remarks</p><p>Trocholites luna sp. nov. is similar to  T. vortex sp. nov., but differs in the lower coiling rate (WER = 1.60 vs 1.80), the more slender conch (CWI = 0.38 vs 0.47), the more depressed whorl profile (WWI = 1.56 vs 1.45) and the wider umbilicus (UWI = 0.52 vs 0.45) in the adult growth stage.</p><p>The holotype of  Trocholites luna sp. nov. is rather similar to the neotype of  T. macrostoma with respect to conch width and umbilical width, but differs in the less depressed last whorl (WWI = 1.56 vs 1.72) and the presence of annuli on the venter of the body chamber.</p><p>The two specimens of  T. vodickai sp. nov. differ from the holotype of  T. luna sp. nov. in the smaller adult size (40 mm vs 50 mm); the last whorl in the former is less evolute (UWI ~ 0.46 vs 0.52) and the shell ornament in inner whorls has fine, rursiradiate lirae instead of sharply raised lirae or accumulation of lirae.</p></div>	https://treatment.plazi.org/id/03AD87B1DD23424D31E799CD97A0F887	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Aubrechtová, Martina;Korn, Dieter	Aubrechtová, Martina, Korn, Dieter (2025): The coiled Middle Ordovician cephalopod genera Trocholites and Curtoceras (Tarphyceratida) from Baltoscandia and north-central Europe. European Journal of Taxonomy 982: 1-78, DOI: 10.5852/ejt.2025.982.2843, URL: https://europeanjournaloftaxonomy.eu/index.php/ejt/article/download/2843/12943
03AD87B1DD25424B310C9CC395B4FD0C.text	03AD87B1DD25424B310C9CC395B4FD0C.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Trocholites splendor Aubrechtová & Korn 2025	<div><p>Trocholites splendor sp. nov.</p><p>urn:lsid:zoobank.org:act: F1186D76-F91F-4FA4-B804-E73305EE1E11</p><p>Fig. 22; Table 13</p><p>Diagnosis</p><p>Species of the genus  Trocholites with an adult conch diameter of 50 mm. Conch in the last whorl thickly discoidal (CWI ~ 0.50) and subevolute (UWI ~ 0.35). Whorl profile weakly depressed (WWI ~ 1.35). Whorl width and whorl height slightly increasing in last quarter volution. Shell ornament with sharp lirae with fine growth lines on outer whorl; inner whorls with thin ribs or thickened lirae.</p><p>Etymology</p><p>From the Latin  ‘ splendor ’ (nomen), referring to the splendid ornament in the juvenile whorls in the holotype.</p><p>Type material</p><p>Holotype</p><p>POLAND – West Pomerania • Ustronie Morskie;  probably Lasnamägi Regional Stage; Müldner Coll.; illustrated in Fig. 22; MB.C. 32175.</p><p>Description</p><p>Holotype MB.C.32175 (Fig. 22) is a conch with 49 mm diameter and with 3.5 preserved volutions, the last of which is largely preserved as an internal mould. A little more than half of the last whorl belongs to the body chamber; at a short distance from the aperture, the internal mould possesses a conspicuous, thick ridge with a sinus-like ventral extension. The conch is thickly discoidal (CWI decreases from 0.57 to 0.50 in the last quarter of the last whorl) and subevolute (UWI = 0.36); the whorl profile is weakly depressed (WWI decreases from 1.52 to 1.34 in the last quarter whorl). The shell ornament is best preserved in inner whorls, where it consists of thin ribs or thickened lirae. Sharp lirae with fine growth lines are locally preserved in outer whorl; the ornament elements are not visible on the surface of the internal mould. The length of the phragmocone chambers can be measured in the first 2.5 whorls; the chambers are very long in the earliest half a whorl (RCL = 0.81) and then become significantly shorter to RCL = 0.44. At the end of the phragmocone, the RCL is only about 0.20. The conspicuous thickening or ridge near the aperture of the terminal body chamber is interpreted as a growth anomaly.</p><p>Remarks</p><p>The holotype of  Trocholites splendor sp. nov. is closely similar to some specimens of  T. hospes, but it possesses thin ribs or thickened lirae on the surface of inner whorls, instead of only fine lirae in  T. hospes . The shell ornament alone may not be a reliable character to form a basis for species distinction; however, the conch of  T. splendor is more slender (CWI = 0.50 at dm = 49 mm) and less depressed (WWI = 1.34 at dm = 49 mm) than in specimens of  T. hospes (Fig. 12).</p><p>The last whorl in the holotype of  Trocholites kadakaensis sp. nov. differs in being more evolute (UWI ~ 0.46 vs 0.35), more depressed (WWI ~ 1.80 vs 1.35) and decreasing instead of increasing whorl width and whorl height of the terminal body chamber.</p></div>	https://treatment.plazi.org/id/03AD87B1DD25424B310C9CC395B4FD0C	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Aubrechtová, Martina;Korn, Dieter	Aubrechtová, Martina, Korn, Dieter (2025): The coiled Middle Ordovician cephalopod genera Trocholites and Curtoceras (Tarphyceratida) from Baltoscandia and north-central Europe. European Journal of Taxonomy 982: 1-78, DOI: 10.5852/ejt.2025.982.2843, URL: https://europeanjournaloftaxonomy.eu/index.php/ejt/article/download/2843/12943
03AD87B1DD24424831029E309583FBE1.text	03AD87B1DD24424831029E309583FBE1.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Trocholites triangulus Aubrechtová & Korn 2025	<div><p>Trocholites triangulus sp. nov.</p><p>urn:lsid:zoobank.org:act: DA076484-0576-40B8-8666-5C40700CFCB6</p><p>Fig. 23; Table 14</p><p>Diagnosis</p><p>Species of the genus  Trocholites with an adult conch diameter of 26 mm. Conch in the last whorl thinly discoidal (CWI ~ 0.33) and evolute (UWI ~ 0.55). Whorl profile depressed (WWI ~ 1.50) with rounded flanks, venter narrowed down, whorl widest dorso-laterally. Whorl width and whorl height increasing in last quarter volution. Phragmocone chambers moderately long (RCL ~ 0.38). Suture line straight.</p><p>Etymology</p><p>From the Latin  ‘ triangulus ʼ (nomen) = ‘a triangle’, referring to the shape of the apertural whorl profile of the holotype given by the narrowed venter.</p><p>Material examined</p><p>Holotype</p><p>GERMANY – Mecklenburg-Vorpommern • Göhren (Isle of Rügen);  Lasnamägi Regional Stage; 1968; Krueger Coll.; illustrated in Fig. 23; MB.C. 32176.</p><p>Description</p><p>Specimen MB.C.32176 (Fig. 23) is a small adult conch with only 25 mm diameter; it is extremely discoidal (CWI = 0.33) and evolute (UWI = 0.57) with a depressed last whorl (WWI = 1.50). The venter of the outer whorl is not rounded but is narrowed down and the whorl appears to be widest dorso-laterally. The relative chamber length (RCL) is 0.38. The body chamber has a length of slightly more than half a volution and its aperture possesses lateral and ventrolateral flares (the ventral part cannot be seen).</p><p>Remarks</p><p>The holotype of  Trocholites triangulus sp. nov. is similar to specimens MB.C.32161 and MB.C.32160, which belong to  T. depressus, and specimen MB.C.32182 (T. sp. 4) (Fig. 7). However, the former differs by the ventrally narrowed external volution. The arched, keel-like shape of the outer ventral side of the conch is known in specimens of  Trocholites gracilis from the late Chazyan Valcour Limestone of New York (Flower 1943); the adult conch size (dm 24 mm) is similar to  Trocholites triangulus and suture line in both species is essentially straight. The last half a whorl in the latter is, however, depressed, instead of slightly compressed (WWI = 1.50 vs 0.93).</p></div>	https://treatment.plazi.org/id/03AD87B1DD24424831029E309583FBE1	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Aubrechtová, Martina;Korn, Dieter	Aubrechtová, Martina, Korn, Dieter (2025): The coiled Middle Ordovician cephalopod genera Trocholites and Curtoceras (Tarphyceratida) from Baltoscandia and north-central Europe. European Journal of Taxonomy 982: 1-78, DOI: 10.5852/ejt.2025.982.2843, URL: https://europeanjournaloftaxonomy.eu/index.php/ejt/article/download/2843/12943
03AD87B1DD274256311F9913922EFC12.text	03AD87B1DD274256311F9913922EFC12.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Trocholites tureki Aubrechtová & Korn 2025	<div><p>Trocholites tureki sp. nov.</p><p>urn:lsid:zoobank.org:act: 789D9C9E-67E0-45E5-9F31-3FCE54C8FB0F</p><p>Fig. 24; Table 15</p><p>Trocholites incongruus – Angelin 1880: 11, pl. 9 figs 15–16, 18.</p><p>Diagnosis</p><p>Species of the genus  Trocholites with conch in adult growth stage discoidal (CWI ~ 0.40) and evolute (UWI ~ 0.48). Whorl profile weakly depressed (WWI ~ 1.46) and weakly impressed (IZR ~ 0.17), rounded from lateral and ventral side. Coiling rate is low (WER ~ 1.71). Shell ornament with low annuli and / or widely spaced, and lirae.</p><p>Etymology</p><p>After Vojtěch Turek (Prague, Czech Republic) in the honour of his contribution to the knowledge on Palaeozoic cephalopods.</p><p>Type material</p><p>Holotype</p><p>SWEDEN • Altsarbyn (earlier spelling Alsarbyn), Dalarna; Darriwilian Stage; Wegelin Coll.; illustrated by Angelin (1880: pl. 9 figs 15–16, 18), re-illustrated here in Fig. 24A; NRM Mo 152354.</p><p>Paratype</p><p>ESTONIA • 1 spec.;  Osmussaar 1;  Uhaku Regional Stage; Toom Coll.; illustrated in Fig. 24B; GIT 362 - 721-2  .</p><p>Description</p><p>Holotype NRM Mo 152354 (Fig. 24A) is a subadult or adult conch with 22 mm diameter with nearly three whorls preserved. The last 45 degrees of the conch belong to the body chamber, which is incomplete. In the last 270 degrees, the conch becomes increasingly discoidal (CWI = 0.49–0.41) and increasingly umbilicate (UWI = 0.41–0.48). The whorl profile is rounded from ventral and lateral sides and weakly depressed; the WWI decreases from 1.50 (dm = 14.6 mm) to 1.25 (dm = 19.4 mm) and then again increases to 1.46 at the body chamber (dm = 22 mm). The coiling rate at the maximum diameter is low (WER = 1.71). The shell ornament consists of closely spaced, thin to raised lirae and low ribs, which are not reflected on the internal mould of the conch; the ribs are present from earliest preserved volution up to the external volution, where they form a rather deep ventral sinus. In the internal volutions, node-like elements are present laterally. The phragmocone chamber length (RCL) is 0.29 in the external volution; suture lines are almost straight with a shallow external lobe.</p><p>Paratype GIT 362-721-2 (Fig. 24B) is a nearly complete conch with 28 mm diameter and consists of four whorls; the last half a whorl belongs to the incomplete body chamber. At the maximum diameter, the conch is discoidal (CWI = 0.40) and evolute (UWI = 0.46). The whorl profile is ventrally and laterally rounded and weakly depressed; the WWI decreases from 1.50 to 1.29 (dm = 24 mm) and then increases to 1.40 (dm = 28 mm). The shell ornament consists from 1) widely spaced ribs which are in the last half a whorl replaced by 2) narrowly spaced ribs or accumulations of lirae (less prominent ventrally than laterally), and 3) fine lirae. Only the riblets are reflected on the internal mould of the conch. The phragmocone chamber length (RCL) is ~ 0.25 in the external volution and the last chamber is shortened; suture lines are almost straight.</p><p>Remarks</p><p>Holotype NRM Mo 152354, previously illustrated by Angelin (1880), was used by Schröder (1891) as one of three syntypes of  Trocholites remelei . All three specimens (NRM Mo 152355, NRM Mo 152354, MB.C.11562) are assigned here to different species on the basis of substantial differences in conch geometry and shell ornament. Holotype NRM Mo 152354 specifically differs from lectotype MB.C.11562 of  Trocholites remelei by being more discoidal (CWI = 0.41 vs 0.59 at dm ~ 22 mm), more evolute (UWI = 0.71 vs 0.87 at dm ~ 22 mm), less rapidly expanding (WER = 1.71 vs 1.87 at dm ~ 22 mm) and its whorls are less impressed (IZR = 0.17 vs 0.34 at dm ~ 22 mm); the ornament in NRM Mo 152354 is not visible on internal mould. The holotype NRM Mo 152354 also differs from paratype NRM Mo 152355 of  Trocholites freyjae sp. nov. because it is narrower (CWI = 0.41 at dm 22 mm vs 0.50 at dm 26 mm) with less depressed whorls (WWI = 1.46 at dm 22 mm vs 1.76 at dm 26 mm); in addition, the shell surface is annulated in NRM Mo 152355 (but with sharp lirae in NRM Mo 152354).</p><p>The holotype is unique in the collection by the presence of distinct lirae and annuli covering the entire shell surface and is therefore placed in a separate species.Another specimen, GIT 362-721-2, is assigned to the new species because it corresponds to the holotype in shell geometry. The only difference between the two is the presence of widely spaced ribs on the inner whorls of GIT 362-721-2. Most similar to both specimens is the specimen MB.C.32182 of T. sp. 4 and some representatives of  T. depressus (Fig. 7), which also have annuli or ribs on the shell surface. In the latter two species, however, the shell ornament is much finer and / or irregular in spacing and thickness. In addition, the specimens of  Trocholites depressus generally have lower coiling rate (WER ~ 1.65 vs 1.71) in the adult growth stage.</p></div>	https://treatment.plazi.org/id/03AD87B1DD274256311F9913922EFC12	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Aubrechtová, Martina;Korn, Dieter	Aubrechtová, Martina, Korn, Dieter (2025): The coiled Middle Ordovician cephalopod genera Trocholites and Curtoceras (Tarphyceratida) from Baltoscandia and north-central Europe. European Journal of Taxonomy 982: 1-78, DOI: 10.5852/ejt.2025.982.2843, URL: https://europeanjournaloftaxonomy.eu/index.php/ejt/article/download/2843/12943
03AD87B1DD394254310E993C9309FC8A.text	03AD87B1DD394254310E993C9309FC8A.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Trocholites vodickai Aubrechtová & Korn 2025	<div><p>Trocholites vodickai sp. nov.</p><p>urn:lsid:zoobank.org:act: 6CA0C13A-9BDC-41B9-8E08-AFE05FB363C5</p><p>Fig. 25; Table 16</p><p>Diagnosis</p><p>Species of the genus  Trocholites with an adult conch diameter of about 40 mm. Conch in the last whorl thinly discoidal (CWI ~ 0.40) and evolute (UWI ~ 0.46). Whorl profile weakly depressed (WWI = 1.25–1.50) with rounded flanks and slightly flattened venter in the adult stage. Shell ornament with fine, rursiradiate lirae; internal mould of body chamber with faint annular impressions. Phragmocone chambers moderately long (RCL = 0.30–0.40). Suture line straight.</p><p>Etymology</p><p>After Jakub Vodička (Prague, Czech Republic), for his contribution to the chitinozoan research in Bohemia.</p><p>Type material</p><p>Holotype</p><p>POLAND – West Pomerania • Ustronie Morskie;  Lasnamägi or Uhaku regional stages; Müldner Coll.; illustrated in Fig. 25A; MB.C. 32177</p><p>Paratype</p><p>GERMANY – Brandenburg • 1 spec.;  Hindenberg near Calau; Ordovician; Krueger Coll.; illustrated in Fig. 25B; MB.C. 32178  .</p><p>Description</p><p>Holotype MB.C.32177 (Fig. 25A) is an adult conch with 41 mm diameter, of which the last ~ 220 degrees of the external volution belongs to the body chamber. In the last quarter volution, the conch becomes more discoidal (CWI decreases from 0.46 to 0.40) and slightly more evolute (UWI changes from 0.44 to 0.46); the whorl profile shows broadly rounded flanks and venter. It is decreasingly depressed; during the last quarter of a volution, the WWI decreases from 1.37 to 1.27. The body chamber shows a terminal aperture with flares and a ventral sinus. The ornament consists of fine, rursiradiate lirae; faint annular impressions are present on the internal mould of the terminal body chamber. The phragmocone chambers are moderately long (RCL = 0.33).</p><p>Paratype MB.C.32178 (Fig. 25B) is a conch in the adult growth stage; it is distorted at one side and has a diameter of 39 mm. More than half of the last volution belongs to the body chamber. In the last quarter whorl, the conch is discoidal (CWI changes slightly from 0.46 to 0.44) and increasingly evolute (UWI changes from 0.37 to 0.45). The whorl profile is weakly depressed (WWI increases from 1.43 to 1.50) and shows broadly rounded flanks and a slightly flattened venter. At the maximum conch diameter, the whorl height appears to decrease slightly (from 11.9 mm to 11.5 mm) from about the mid-length of the terminal body chamber. The body chamber begins to produce flares at its terminal aperture. The shell is ornamented by fine, rursiradiate lirae; the internal mould of the body chamber has shallow annular impressions. The phragmocone chambers are rather long (RCL = 0.38).</p><p>Remarks</p><p>Trocholites vodickai sp. nov. is rather similar to  T. macrostoma but the latter has a more strongly depressed adult body chamber (WWI ~ 1.70 vs 1.25–1.50 in  T. vodickai) and a wider umbilicus (UWI ~ 0.55 vs ~ 0.45).</p><p>Trocholites vodickai sp. nov. shows some similarity to  T. vortex sp. nov., but the former are smaller in adult size (40 in contrast to more than 50 mm), the last whorl is more discoidal (CWI ~ 0.40 vs 0.47) with shorter phragmocone chambers in the last volution (RCL = 0.30–40 vs 0.47).</p><p>Trocholites luna sp. nov. differs from  T. vodickai sp. nov. in the greater adult size (50 mm vs 40 mm); the last whorl is more evolute (UWI ~ 0.52 vs 0.46) and the shell ornament in inner whorls has raised lirae or accumulation of lirae instead of fine, rursiradiate lirae.</p><p>The two specimens of  T. kadakaensis sp. nov. differ from those of  T. vodickai sp. nov. because their last whorl is less discoidal (CWI ~ 0.48 vs 0.40) and the whorl profile is much more depressed (WWI ~ 1.80 vs 1.25–1.50) with a distinct decrease in width and height towards the terminal aperture.</p><p>In the holotype of  T. zaryensis sp. nov., the last whorl is also less discoidal (CWI ~ 0.57 vs 0.40) and slightly more narrowly evolute (UWI ~ 0.42 vs 0.46); the whorl profile is more depressed (WWI ~ 1.82 vs 1.25–1.50).</p><p>Trocholites depressus is generally rather similar in conch geometry to  T. vodickai sp. nov. but the specimens of the former tend to have a more depressed whorl profile (WWI up to 1.60) in the last volution and the ornament on inner whorls has ribs.</p><p>Geographic and stratigraphic occurrence</p><p>Northern Poland and northern Germany; late Darriwilian, Middle Ordovician.</p></div>	https://treatment.plazi.org/id/03AD87B1DD394254310E993C9309FC8A	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Aubrechtová, Martina;Korn, Dieter	Aubrechtová, Martina, Korn, Dieter (2025): The coiled Middle Ordovician cephalopod genera Trocholites and Curtoceras (Tarphyceratida) from Baltoscandia and north-central Europe. European Journal of Taxonomy 982: 1-78, DOI: 10.5852/ejt.2025.982.2843, URL: https://europeanjournaloftaxonomy.eu/index.php/ejt/article/download/2843/12943
03AD87B1DD3B4252311D9EB4940BFDCF.text	03AD87B1DD3B4252311D9EB4940BFDCF.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Trocholites vortex Aubrechtová & Korn 2025	<div><p>Trocholites vortex sp. nov.</p><p>urn:lsid:zoobank.org:act: 115DF999-F5D6-4FE3-8853-72A8F451CC7C</p><p>Fig. 26; Table 17</p><p>Diagnosis</p><p>Species of the genus  Trocholites with an adult conch diameter of about 50 mm. Conch in the last whorl thickly discoidal (CWI ~ 0.47) and evolute (UWI ~ 0.46) with moderately high coiling rate (WER ~ 1.80). Whorl profile weakly depressed (WWI ~ 1.45), rounded, moderately embracing (IZR ~ 0.20). Shell ornament with growth lines or extremely fine, regularly spaced lirae; venter and outer flanks with thin and irregularly spaced annuli or raised lirae. Phragmocone chambers long in all growth stages (RCL ~ 0.45). Suture line nearly straight.</p><p>Etymology</p><p>From the Latin  ‘ vortex ʼ (nomen) = ‘a whirl’, referring to the perfectly spiral shape of the holotype.</p><p>Type material</p><p>Holotype</p><p>GERMANY – Mecklenburg-Vorpommern • Parchim;  Lasnamägi or Uhaku regional stages; 1969; Helms Coll.; illustrated in Fig. 26; MB.C. 22574.</p><p>Description</p><p>Holotype MB.C.22574 (Fig. 26) is a nearly complete conch with 49 mm diameter and is composed of five whorls; the initial chamber has probably not been preserved. The body chamber is preserved in length of about 230 degrees, but does not have the terminal aperture preserved. In the last half volution, the conch proportions change only slightly; the conch becomes more thickly discoidal (CWI changes from 0.45 to 0.47), less evolute (UWI decreases from 0.48 to 0.45) and the whorl profile becomes less depressed (WWI decreases from 1.52 to 1.45). The last whorl is moderately impressed (IZR = 0.19) and moderately expanding (WER= 1.80). The venter of the body chamber has two longitudinal grooves separated by a single ridge. The shell ornament consists of growth lines or extremely fine, regularly spaced lirae. On the venter and outer flanks, there are thin and irregularly spaced annuli or raised lirae. The phragmocone chambers are long (RCL = 0.47); the suture line is almost straight.</p><p>Remarks</p><p>Compared to representatives of other species of  Trocholites, the holotype of  T. vortex sp. nov. has a large conch diameter of about 50 mm. This may not yet represent the adult stage as there is no evidence of the terminal aperture and the rate of growth of the body chamber height and width does hardly change. In addition, the last phragmocone chambers are not shortened.</p><p>Some specimens of  Trocholites hospes attain comparatively large adult conch diameters, but their conchs with diameters of around 50 mm are much stouter (CWI ~ 0.60 vs ~ 0.45 in  T. vortex sp. nov. at 50 mm diameter) and more narrowly umbilicate (UWI ~ 0.35 vs ~ 0.45) with whorls more strongly impressed dorsally (IZR ~ 0.30 vs ~ 0.30).</p><p>Trocholites vortex sp. nov. differs from  T. luna sp. nov. in adult size exceeding 50 mm, the higher coiling rate (WER = 1.80 vs 1.60), the wider adult body chamber (CWI = 0.47 vs 0.38), the less depressed whorl profile (WWI = 1.45 vs 1.56) and the narrower umbilicus (UWI = 0.45 vs 0.52).</p><p>Trocholites vortex sp. nov. also resembles  T. vodickai sp. nov. in umbilical and whorl width, but  T. vortex has a greater adult size (over 50 mm vs 40 mm) and the phragmocone chambers are longer (RCL = 0.30–0.40 in last whorl of  T. vodickai).</p><p>Compared to  T. vortex sp. nov., the two specimens of  T. kadakaensis sp. nov. are smaller in adult size, have a lower coiling rate (WER ~ 1.70 vs 1.80) and the whorl profile is more depressed at dm ~ 40 mm (WWI ~ 1.80 vs ~ 1.50).The specimens of  T. depressus reach up to max. 40 mm diameter in adult size; they are generally more discoidal (CWI = 0.35–0.40 vs 0.47) with a much lower coiling rate (WER ~ 1.65 vs 1.80) and the ornament on inner whorls has ribs.</p></div>	https://treatment.plazi.org/id/03AD87B1DD3B4252311D9EB4940BFDCF	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Aubrechtová, Martina;Korn, Dieter	Aubrechtová, Martina, Korn, Dieter (2025): The coiled Middle Ordovician cephalopod genera Trocholites and Curtoceras (Tarphyceratida) from Baltoscandia and north-central Europe. European Journal of Taxonomy 982: 1-78, DOI: 10.5852/ejt.2025.982.2843, URL: https://europeanjournaloftaxonomy.eu/index.php/ejt/article/download/2843/12943
03AD87B1DD3D4253310B9F7795AEFB70.text	03AD87B1DD3D4253310B9F7795AEFB70.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Trocholites zaryensis Aubrechtová & Korn 2025	<div><p>Trocholites zaryensis sp. nov.</p><p>urn:lsid:zoobank.org:act: DB8D668B-9A0C-4F0F-B279-31D4CDED0A17</p><p>Fig. 27; Table 18</p><p>Diagnosis</p><p>Species of the genus  Trocholites with an adult conch diameter of about 36 mm. Conch in the last whorl thickly discoidal (CWI ~ 0.57) and subevolute (UWI ~ 0.42). Whorl profile moderately depressed (WWI ~ 1.82) with rounded flanks and slightly flattened venter. Whorl width slightly decreasing, whorl height slightly increasing in last quarter volution. Phragmocone chambers at 30 mm diameter moderately long (RCL ~ 0.30). Suture line nearly straight.</p><p>Etymology</p><p>From Żary (Poland), the locality of the holotype.</p><p>Type material</p><p>Holotype</p><p>POLAND •  Żary; probably Darriwilian Stage; 1860; Kirchner Coll.; illustrated in Fig. 27; MB.C. 9718.</p><p>Description</p><p>Holotype MB.C.9718 (Fig. 27) is a conch of an individual in the terminal growth stage with 36 mm diameter. The last nearly three quarters of the conch belong to the body chamber, which is preserved as an internal mould. In the last quarter of a whorl, the conch shape changes from pachyconic to thickly discoidal (CWI decreases from 0.68 to 0.57) and stays subevolute (UWI ~ 0.42); the whorl profile is moderately depressed (WWI decreases from 1.96 to 1.82) with broadly rounded flanks and venter. The whorl width decreases slightly (from 21.5 mm to 20.6 mm), but the whorl height increases slightly (from 11.0 mm to 11.3 mm) near the aperture. The venter of the terminal body chamber becomes slightly flattened; the aperture possesses ventral and lateral flares. The shell is visible in the inner whorls; it is ornamented with rursiradiate lirae. The internal mould of the body chamber has indistinct annular ridges. The phragmocone chambers are moderately long (RCL = 0.30 at dm = 30 mm).</p><p>Remarks</p><p>Holotype MB.C.9718 of  Trocholites zaryensis sp. nov. is very similar to holotype MB.C.11563 of  T. kadakaensis sp. nov., which has a larger adult size (42 mm) and in which the terminal body chamber decreases in width as well as in height. Also, the last whorl in the holotype of  T. kadakaensis is more discoidal (CWI ~ 0.48 vs 0.57).</p><p>Trocholites zaryensis sp. nov. differs from  T. hospes in the shape of the body chamber and the much smaller conch with a fully adult diameter about 42 mm, in contrast to  T. hospes with 50–60 mm. In addition, the whorl width in the last whorl slightly decreased in  T. zaryensis .</p><p>Compared to the holotype of  T. zaryensis sp. nov., the two specimens of  T. vodickai sp. nov. are more discoidal (CWI ~ 0.40 vs 0.57) and slightly more widely evolute (UWI ~ 0.46 vs 0.42); the whorl profile is less depressed (WWI ~ 1.25–1.50 vs 1.82).</p><p>The holotype of  Trocholites ruedemanni differs from the holotype of  T. zaryensis sp. nov. by the slightly uncoiled terminal body chamber, presence of nodes and fine costae on the shell of last two whorls, much less depressed whorl profile in the last volution (WWI = 1.54 vs 1.96 at dm ~ 31 mm) and a narrower umbilicus (UWI = 0.32 vs 0.41 at dm ~ 31 mm).</p></div>	https://treatment.plazi.org/id/03AD87B1DD3D4253310B9F7795AEFB70	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Aubrechtová, Martina;Korn, Dieter	Aubrechtová, Martina, Korn, Dieter (2025): The coiled Middle Ordovician cephalopod genera Trocholites and Curtoceras (Tarphyceratida) from Baltoscandia and north-central Europe. European Journal of Taxonomy 982: 1-78, DOI: 10.5852/ejt.2025.982.2843, URL: https://europeanjournaloftaxonomy.eu/index.php/ejt/article/download/2843/12943
03AD87B1DD3C425C31D7999C9664FC8D.text	03AD87B1DD3C425C31D7999C9664FC8D.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Trocholites sp. 1	<div><p>Trocholites sp. 1</p><p>Fig. 28; Table 19</p><p>Material examined</p><p>GERMANY • 1 spec.;  probably Brandenburg; Ordovician; Neben and Krueger Coll.; illustrated in Fig. 28; MB.C. 32179  .</p><p>Description</p><p>Specimen MB.C.32179 (Fig. 28) is a conch with a maximum diameter of 36 mm; it was sectioned in transverse plane. The conch consists of about 4.5 volutions. During ontogeny between 3.6 and 35.4 mm conch diameter, the relative conch width and coiling rate decrease markedly (CWI from 0.89 to 0.49; WER from 2.60 to 1.74) and the umbilical width increases (UWI changes from 0.21 to 0.41). The whorl profile has convex flanks and a flattened venter, which becomes rounded adaperturally; the dorsal impression (IZR) first increases from 0.17 to 0.37 up to 15 mm conch diameter and thereafter decreases from 0.37 to 0.23 in the subadult and adult stage. The whorl profile generally becomes less depressed during ontogeny (WWI decreases from 2.44 to 1.57), but the decrease is not gradual. The siphuncle appears to be located near the dorsal shell wall in inner whorls and moves to the subdorsal position in later whorls; the RSH is between 0.20–0.16.</p><p>Remarks</p><p>In several of the specimens of  Trocholites, the shell wall is noticeably thickened at the ventral and lateral sides of the conch and particularly the umbilical wall. This is best seen in specimen MB.C.32179, where the shell wall is about 0.5 mm thick at a conch diameter of 35 mm and even up to 0.7 mm thick at the umbilical wall.</p><p>The specimen MB.C.32179 is kept in open nomenclature due to insufficient preservation of external morphology and the siphuncle; also, it cannot be reliably inferred, whether the specimen represents an adult or subadult growth stage. However, some comparisons to other specimens of  Trocholites are still possible. Both the whorl width and whorl height of the terminal body chamber gradually increase in the specimen of  Trocholites sp. 1, as it does in  T. glacialis sp. nov. and T. sp. 3. However, in T. sp. 1 the whorl profile shows a flattened venter. The whorl profile is, at dm ~ 35 mm conch diameter, less depressed in the specimen MB.C.32179 of T. sp. 1 when compared to  T. glacialis (WWI = 1.57 vs 1.80), but more depressed than in the specimen of T. sp. 3 (WWI = 1.80 vs 1.30).</p><p>The specimen MB.C.32179 of  Trocholites sp. 1 differs from the specimen MB.C.32168 of  T. macrostoma in ontogenetic trajectories between conch diameters of 5 to 25 mm (Fig. 11). In the former specimen, UWI is lower (decrease followed by increase) and CWI higher (increase followed by decrease).</p><p>Similar to  Trocholites sp. 1 is  T. zaryensis sp. nov. but the outer volution of the latter is more discoidal (CWI = 0.57 vs 0.49) and much more depressed (WWI ~ 1.82 vs 1.57); the venter is flattened (vs rounded) all the way up to the aperture. In  T. kadakaensis sp. nov., the whorl profile is also much more depressed (WWI ~ 1.82 vs 1.57) than in  Trocholites sp. 1 .</p><p>The holotype of  Trocholites ruedemanni is a very similar in conch geometry to the specimen MB.C.32179 (and also the specimen MB.C.32180 of T. sp. 2) but  T. ruedemanni has nodes and costae on the umbilical wall of the outer two volutions; also the flattening of the ventral side seen in MB.C.32179 is not present (Flower 1943).</p><p>Trocholites sp. 2</p><p>Fig. 29; Table 20</p><p>Material examined</p><p>POLAND • 1 spec.;  Międzyzdroje; Darriwilian; illustrated in Fig. 29; MB.C. 32180  .</p><p>Description</p><p>A transverse section was made from specimen MB.C.32180 (Fig. 29), which is a conch with about 29 mm diameter. Three outer whorls are preserved; a part of the conch belongs to the body chamber. During ontogeny between 4.3 and 28.5 mm diameter, the conch decreases in width ratio and coiling rate (CWI from 0.74 to 0.55; WER from 2.52 to 1.66) and increases in umbilical width (UWI changes from 0.18 to 0.47). The whorl profile is rounded from all sides, moderately impressed and increasingly depressed (WWI change from 1.66 to 1.97). The whorl height and width gradually increase with conch growth. The siphuncle is not visible clearly in the section but appears to be marginodorsal or nearly so, and medium in diameter (estimated RSH between 0.15 and 0.20).</p><p>Remarks</p><p>Specimen MB.C.32180 is left in open nomenclature here because of poor preservation of external characters, as well as the siphuncle. The specimen appears most similar to MB.C.32179 of T. sp. 1 in the ontogenetic trajectories of conch dimensions and ratios (Fig. 11). However, the whorl profile in MB.C.32180 becomes more depressed (instead of less depressed) in growth (WWI generally increases from ~ 1.7 up to ~ 2). Also, the ventral side of the whorls is not flattened in MB.C.32180.</p><p>The conch geometry in the specimen MB.C.32180 is also similar in several aspects (mainly WER) to the geometry of the specimen MB.C.32168 ( T. macrostoma). However, the ontogenetic trajectories differ between conch diameters of 5 to 25 mm. In that interval in MB.C.32180, the UWI is lower (decreases and then increases) and CWI is higher (increases and then decreases); WWI is similar in late growth stages but lower in earlier growth stages.</p><p>Trocholites sp. 3</p><p>Fig. 30; Table 21</p><p>Material examined</p><p>GERMANY • 1 spec.;  probably Brandenburg; Ordovician; Neben and Krueger Coll.; illustrated in Fig. 30; MB.C. 32181  .</p><p>Description</p><p>A transverse section was produced from specimen MB.C.32181 (Fig. 30). This is a specimen with 31 mm conch diameter and shows 1.5 volutions preserved. During the last volution, the conch decreases in the whorl width ratio (CWI changes from 0.56 to 0.42) and increases in the umbilical width ratio (UWI changes from 0.34 to 0.42), while the coiling rate remains nearly constant (WER ~1.80). The last volution of the conch shows a decelerated increases in height, while the whorl width increases gradually. The whorl profile shows rounded flanks and venter; the whorl profile is widest in its dorsal half (i.e., not in the middle of the flank). The WWI is between 1.65 and 1.47 but changes in a fluctuating manner; at the greatest conch diameter, the whorl profile is weakly depressed (WWI = 1.30). The depth of the imprint zone is also irregular and decreases from a value of IZR = 0.33 to 0.23. The diameter of the siphuncle is about 0.20 of the apertural height; it has a position close to the dorsal shell wall or is even in contact.</p><p>Remarks</p><p>The insufficient preservation of the specimen MB.C.32181 prevents its unequivocal taxonomic assignment; the specimen is thus left in open nomenclature.</p><p>In  Trocholites sp. 3, both whorl width and whorl height of the terminal body chamber gradually increase, which is similar to  T. glacialis sp. nov. and T. sp. 1. However, the whorl profile of T. sp. 3 is, at 30 mm conch diameter, much less depressed (WWI ~ 1.30 in T. sp. 3, but ~ 1.80 in both T. sp. 1 and  T. glacialis).</p><p>Trocholites sp. 4</p><p>Fig. 31; Table 22</p><p>Material examined</p><p>GERMANY – Brandenburg • 1 spec.;  Liepe;  Lasnamägi or Uhaku Regional Stage, late Darriwilian; Müldner Coll.; illustrated in Fig. 31A; MB.C. 32182  .</p><p>Description</p><p>A transverse section was prepared from specimen MB.C.32182 (Fig. 31), but the conch is re-crystallised internally and therefore, some dimensions had to be estimated. The specimen has a conch diameter of 24 mm; it is thinly discoidal (CWI = 0.40), subevolute (UWI = 0.43) and moderately expanding (WER = 1.82). The whorl profile is weakly depressed (WWI = 1.26) and moderately impressed dorsally (IZR = 0.18). Flanks and venter are broadly convex. The maximum width of the whorl profile is reached in the midflank area. The ornament is poorly preserved and consists of irregularly spaced narrow ribs and lirae, which are straight on the flank and form a ventral sinus. The suture line is straight. The phragmocone chambers are moderately long (RCL = 0.26 at wh = 6.7 mm). Siphuncle can be measured at the largest whorl height, where it has a rather narrow diameter (RSH) of 0.21; it is close to the dorsal side throughout ontogeny.</p><p>Remarks</p><p>The specimen MB.C.32182 is left in open nomenclature because re-crystallisation prevented accurate measurements of internal conch characters.</p><p>In conch geometry,  Trocholites sp. 4 is most similar to  T. depressus, particularly to specimen MB.C.32161 (Fig. 7). However, the siphuncle does not seem to be in contact with the dorsal shell wall in T. sp. 4 and is much narrower (RSH = 0.21 vs 0.30 in  T. depressus).</p><p>The specimen of  Trocholites sp. 4 is also nearly identical in conch geometry to the two specimens of  T. tureki sp. nov. (Fig. 7), but the ornament in the former specimen is much finer and less regularly developed.</p></div>	https://treatment.plazi.org/id/03AD87B1DD3C425C31D7999C9664FC8D	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Aubrechtová, Martina;Korn, Dieter	Aubrechtová, Martina, Korn, Dieter (2025): The coiled Middle Ordovician cephalopod genera Trocholites and Curtoceras (Tarphyceratida) from Baltoscandia and north-central Europe. European Journal of Taxonomy 982: 1-78, DOI: 10.5852/ejt.2025.982.2843, URL: https://europeanjournaloftaxonomy.eu/index.php/ejt/article/download/2843/12943
03AD87B1DD33425D32A39EB293EDFA41.text	03AD87B1DD33425D32A39EB293EDFA41.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Curtoceras Ulrich, Foerste, Miller & Furnish 1942	<div><p>Genus  Curtoceras Ulrich, Foerste, Miller &amp; Furnish, 1942</p><p>Type species</p><p>Lituites Eatoni Whitfield, 1886; by original designation.</p><p>Diagnosis</p><p>Genus of the family  Trocholitidae with slowly expanding (WER decreasing up to ~ 1.80), subevolute to evolute conch (UWI increasing up to ~ 0.55), discoidal to extremely discoidal in shape (CWI decreasing up to ~ 0.30), with some part of the last half a whorl widely uncoiled. Whorl profile weakly compressed, equidimensional or weakly depressed (WWI ~ 0.90–1.10); whorls weakly embracing or not embracing, rounded or slightly flattened across venter and / or flanks. Siphuncle ventral in initial chamber, subdorsal or subcentral after one volution, septal necks short (&lt;0.20 of chamber height), orthochoanitic. Shell surface smooth or with raised lirae, low ribs or annuli that form ventral sinus. Suture line nearly straight or with shallow lateral and / or ventral lobe (Ulrich et al. 1942; Furnish &amp; Glenister 1964; Kröger &amp; Aubrechtová 2018).</p><p>Species included</p><p>North America (Billings 1862; Whitfield 1886; Foerste 1938):  Lituites Eatoni Whitfield, 1886;  Lituites internastriatus Whitfield, 1886;?  Schroederoceras minganense Foerste in Twenhofel, 1938;?  Lituites palinurus Billings, 1862 .</p><p>Great Britain (Blake 1882):  Nautilus (Trocholites) scoticus Blake, 1882 .</p><p>Northern Europe and Russia (Eichwald 1840; Lossen 1860; Schröder 1891; Hyatt 1894; Balashov 1953; Kröger &amp; Aubrechtová 2018):  Curtoceras abditus Kröger &amp; Aubrechtová, 2018;  Curtoceras kerstovense Balashov, 1953;  Nautilus teres Eichwald, 1840;  Curtoceras meyeri sp. nov.;  Trocholites macromphalus Schröder, 1891 .</p><p>Argentina (Aceñolaza et al. 1977):  Curtoceras kayseri Aceñolaza, Durand &amp; Taddei, 1977 .</p><p>Remarks</p><p>The morphology of  Curtoceras is similar to that of  Trocholites . The species of  Trocholites are less discoidal or even pachyconic in conch shape with more depressed and more impressed whorl profile; the body chamber is not uncoiled in  Trocholites and very often, the terminal aperture bears conspicuous flares. However, a clear separation of the two genera is difficult and possibly subjective; species with a transitional morphology or for which the fully adult growth stage is unknown are difficult to assign unequivocally to one of the two genera.</p><p>Discoceras differs from  Curtoceras in the much larger adult size (over 100 mm) and the presence of frilled, imbricated ornament elements. The whorl profile in  Discoceras is often more strongly compressed than in  Curtoceras, and subrectangular, subquadratic or trapezoidal in shape. However, separation of  Curtoceras and  Discoceras may be difficult in incomplete specimens or specimens representing juvenile or immature growth stages.</p><p>Geographic and stratigraphic occurrence</p><p>North America, Argentina, Great Britain, Estonia, Sweden (Island of Öland), St Petersburg and Kaliningrad region of Russia, northern Germany, northern Poland,?Tibet; Ordovician.</p></div>	https://treatment.plazi.org/id/03AD87B1DD33425D32A39EB293EDFA41	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Aubrechtová, Martina;Korn, Dieter	Aubrechtová, Martina, Korn, Dieter (2025): The coiled Middle Ordovician cephalopod genera Trocholites and Curtoceras (Tarphyceratida) from Baltoscandia and north-central Europe. European Journal of Taxonomy 982: 1-78, DOI: 10.5852/ejt.2025.982.2843, URL: https://europeanjournaloftaxonomy.eu/index.php/ejt/article/download/2843/12943
03AD87B1DD324222312C98CE93C1FD12.text	03AD87B1DD324222312C98CE93C1FD12.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Curtoceras teres (Eichwald 1840)	<div><p>Curtoceras teres (Eichwald, 1840)</p><p>Figs 32–35; Table 23</p><p>Nautilus teres Eichwald, 1840: 105 .</p><p>Curtoceras estonicum Balashov, 1953: 207, pl. 6 figs 1–2.</p><p>Lituites teres – Eichwald 1860: 1299. — Dewitz 1879: 177, pl. 4 fig. 4. — Schröder 1882: 57–58, pl. 2 fig. 2.</p><p>Discoceras teres – Schröder 1891: 161. — Schindewolf 1942: 351, text-fig. 5e; 1944: 218, text-fig.7.</p><p>Schroederoceras teres – Hyatt 1894: 467. — Schindewolf 1932: 171, text-fig. 3.</p><p>Discoceras (Schröderoceras) teres – Schindewolf 1939: 60, text-fig. 15, pl. 4 fig. 8.</p><p>Curtoceras teres – Balashov 1953: 246, pl. 5 fig. 2, pl. 7 fig. 4. — Dzik 1984: 42, 44.</p><p>Lituites Odini – Verneuil in Murchison et al. 1845: 360, pl. 25 fig. 8. — Lossen 1860: 23.</p><p>Curtoceras estonicum – Stumbur 1962: 136. — Balashov 1962: pl. 9 fig. 7; 1974: pl. 9, fig. 7.</p><p>? „  Lituites“ teres – Holm 1885: 10, pl. 5 figs 5–8.</p><p>non  Clymenia Odini Eichwald, 1840: 107 .</p><p>non  Clymenia Odini – Eichwald 1860: 1304, pl. 51 fig. 27.</p><p>Diagnosis</p><p>Species of the genus  Curtoceras with an adult conch diameter of 40–50 mm. The adult conch consists of up to 4 volutions; in the last whorl, coiling rate and conch width decrease (WER ah ~ 2.00 and CWI ~ 0.30), umbilical width increases (UWI ~ 0.50). Whorl profile rounded or weakly laterally and ventrally flattened, and very weakly embracing or not embracing (IZR varies between 0.00–0.06). Whorl profile changes from depressed in inner volutions (WWI ~ 1.65), in outer whorl typically equidimensional but may be weakly depressed or weakly compressed in some specimens (WWI as low as 0.82). Body chamber about 180 degrees in length, uncoiled after ~ 120 degrees; terminal aperture with ventral sinus and dorso-lateral and dorsal extension and slight flaring. Shell surface with distinct, regularly spaced lirae with acute and more or less symmetric crests on inner whorls, flattening out towards the outer whorl, where the lirae are slightly imbricated; ventral sinus of ornament present. Siphuncle about 0.16 of corresponding apertural height throughout ontogeny; siphuncle position ventral in initial chamber, central after first 180 degrees, shifted towards the dorsal shell wall in later growth stages (RSP varies between 0.60 and 0.75 of apertural height).</p><p>Material examined</p><p>ESTONIA • 1 spec.; Tallinn; Ordovician; Kirchner Coll.; illustrated in Fig. 33A; MB.C.9715 •   1 spec.; Aari quarry;  Lasnamägi Regional Stage ( Väo Formation); GIT 426 -499  •   1 spec.; Aa;  Lasnamägi Regional Stage; Stumbur Coll.; illustrated in Fig. 34C; GIT 426-530  •   1 spec.;  Osmussaar cliff;  Lasnamägi Regional Stage; Männil Coll.; GIT 697-567-1  •   1 spec.; Osmussaar;  Lasnamägi Regional Stage; Schmidt Coll.; illustrated in Fig. 34A; GIT 225-1092  •   1 spec.; Aari quarry;  Lasnamägi Regional Stage; Schmidt Coll.; illustrated in Fig. 34B; GIT 225-1062  •   1 spec.;  Osmussaar 1;  Lasnamägi Regional Stage; TUG 860-1309  •  1 spec.; same data as for preceding; GIT 697-130 •   1 spec.; Sõjamäe;  Lasnamägi Regional Stage ( Väo Formation); GIT 426-498  •   1 spec.;  Kadaka road ( Tallinn); Darriwilian Stage; illustrated in Fig. 34D–E; FMNH HS. P31459  .</p><p>GERMANY – Mecklenburg-Vorpommern • 1 spec.; Basedow-Stöckersoll; Ordovician; 2006; Meyer Coll.; illustrated in Fig. 32; MB.C.32183 . –  Brandenburg • 1 spec.; Strausberg; Lasnamägi Regional Stage; Neben and Krueger Coll.; MB.C.32188 •   1 spec.;  Leegebruch near Velten;  Lasnamägi or Uhaku regional stages; 1951; Gräber Coll.; MB.C. 11548a-d  •  1 spec.; Oderberg; Ordovician; Neben and Krueger Coll.; MB.C. 32187 •   1 spec.; Oderberg;  Aseri Regional Stage; 1964; Neben and Krueger Coll.; illustrated in Fig. 35B; MB.C. 32186  •   1 spec.; Potsdam;  Lasnamägi Regional Stage; illustrated in Fig. 33B; MB.C. 11544. – Locality unknown  •   1 spec.;  probably Brandenburg; Ordovician; Neben and Krueger Coll.; illustrated in Fig. 33C; MB.C. 32184  •   1 spec.;  probably Brandenburg; Ordovician; Neben and Krueger Coll.; illustrated in Fig. 35A; MB.C. 32185  .</p><p>POLAND – West Pomerania • 1 spec.; Bydgoszcz; Darriwilian Stage; previously figured by (Schindewolf 1933: text-fig. 8), re-illustrated here in Fig. 33D; MB.C.646 •   1 spec.;  Rybokarty near Gryfice; Darriwilian Stage; Wietersheim Coll.; MB.C. 11545  .</p><p>Description</p><p>Specimen MB.C.32183 (Fig. 32) is the most complete of the available specimens. It has a total conch diameter of 48 mm and is composed of two and three-quarter volutions. The conch is spirally coiled up to a diameter of 43 mm, the last short segment of the body chamber is detached from the preceding whorl and has an almost straight direction. At 43 mm conch diameter, the conch is subevolute (UWI = 0.40) with a very high coiling rate (WER = 2.39). The umbilical foramen is very small, measuring approximately 1× 2 mm. The entire specimen is covered with shell material. The ornament consists of coarse, lamellar growth lines with rursiradiate direction; they extend with a low lateral projection and form a very deep and wide ventral sinus.</p><p>Specimen MB.C.11544 (Fig. 33B) is an incomplete, but rather well-preserved conch of a nearly adult individual with 44 mm diameter. It consists of 3.25 whorls with the initial chamber preserved. In the last 0.75 volutions, in which the conch diameter grows from 25 mm to 43.5 mm, the conch becomes more discoidal (CWI decreases from 0.39 to 0.30) and the whorl profile changes from weakly depressed to equidimensional (WWI changes slightly from 1.11 to 1.00). Flanks and venter remain broadly convex and the whorls are only very weakly impressed dorsally or not impressed. In the course of the entire ontogeny (from 5.7 mm to 43.6 mm conch diameter), the coiling rate decreases significantly (WER decreases from 5.18 to 2.00) and the umbilicus widens (UWI increases from 0.16 to 0.47). The last quarter of the outer volution belongs to the body chamber, which begins to detach from the preceding whorl. The shell is ornamented with distinct, regularly spaced lirae with symmetric or only slightly imbricated crests; the lirae are sharp especially in the inner whorls, while in the outer whorl, they appear to flatten out. The ornament element extend with a ventral sinus. The phragmocone chambers are moderately long (RCL = 0.25 at dm = 30 mm). The suture line is straight.</p><p>Specimen GIT 225-1092 (Fig. 34A) is a nearly complete conch with a diameter of 52 mm and consists of 3.5 whorls; the body chamber occupies one third of the last whorl and is detached from the preceding volution. During ontogeny, the conch width and expansion become smaller (CWI decreases from 0.50 to 0.30, WER decreases from 2.64 to 2.04), while the umbilical width ratio increases (UWI changes from 0.39 to 0.47). The whorl profile is weakly depressed to equidimensional (WWI decreases from 1.30 to 0.99); it shows broadly convex flanks and venter in the inner whorls and becomes weakly flattened laterally and ventrally late in ontogeny. At the maximum conch diameter of 52 mm, the siphuncle is narrow (RSH = 0.13) and has a position between the centre and dorsal shell wall (RSP = 0.64). The shell wall is locally preserved; it is ornamented with sharp, evenly spaced lirae. The adult suture line shows a shallow lateral and a shallow ventral lobe.</p><p>Specimen GIT 426-530 (Fig. 34C) is a natural transverse section at one side. It is a conch with 50 mm diameter and consists of 3.25 volutions; the last quarter volution belongs to the body chamber. In the last two volutions, the conch becomes more widely umbilicate (UWI increases from 0.20 to 0.44) and less expanded (WER decreases from 3.88 to 2.07). At the maximum diameter of 50 mm, the conch is discoidal (CWI = 0.32) and the whorl profile is nearly circular (WWI = 1.05) with convex flanks and a weakly flattened venter. The initial part of the phragmocone is preserved but the first chamber cannot be measured accurately; the umbilical window is 0.5 × 0.2 mm in diameter. The shell surface is ornamented with sharp, equally spaced lirae, which extend with a steep ventral sinus; some indistinct spiral lines are visible on the body chamber. The phragmocone chambers are rather short (RCL = 0.20 in the last half a whorl). The suture line is almost straight, but extends with a very shallow lateral lobe and a shallow external lobe.</p><p>The four specimens MB.C.32187, MB.C.32184 (Fig. 33C), MB.C.9715 (Fig. 33A) and MB.C.11544 (Fig. 33B) are nearly identical in their conch proportions and the shell ornament to specimen GIT 426- 530. All of the specimens are adult or nearly adult conchs with about three whorls (dm = 37–47 mm). All show that the body chamber starts to uncoil after about 2.75 whorls (MB.C.9715 and MB.C.11545). In specimen MB.C.9715 (along with GIT 697-567-1 and GIT 225-1062), the aperture is preserved; it has a ventral sinus and a dorsolateral extension. The whorl profile at the maximum conch diameter ranges between weakly compressed and weakly depressed (WWI = 0.82–1.07) with broadly rounded flanks and venter; the dorsal impression is small. The umbilical width ratio (UWI) is between 0.42 and 0.50 and the conch width (CWI) between 0.29 and 0.35. The shell is ornamented with sharp, evenly distributed lirae with acute and more or less symmetric crests. The lirae are particularly distinct on the body chamber, where they form a deep ventral sinus. At the very end of the body chamber in MB.C.9715, the lirae are slightly frilled ventrally.</p><p>Specimen MB.C.646 (Fig. 33D) is a sagittal section through a subadult conch with 32 mm diameter and with the first 2.5 whorls preserved. The umbilical window is small (0.50× 0.25 mm). Throughout ontogeny, the coiling rate of the conch decreases markedly (WER is reduced from 5.56 to 2.18). The siphuncular diameter (RSH) increases during ontogeny from 0.12 up to 0.18. The siphuncle has a ventral position in the initial chamber but during the first three quarters of the length of the first volution migrates towards the dorsal shell wall (RSP = 0.69 at dm = 4.9 mm); up to the largest conch diameter, the relative position of the siphuncle remains approximately the same (RSP = 0.67 at dm = 31 mm). The septal necks are orthochoanitic or loxochoanitic and short (&lt;0.2 of the segment length). They are thicker than the free part of the septum. The connecting rings are essentially tubular in the first whorl but then become slightly concavo-convex or concave in shape, especially on the ventral side of the siphuncle. The brownish inner layer of the connecting ring wall is homogenous and about as thin as the septa. The outer, dark-grey layer of the ring is much thicker and the thickness is unevenly distributed. The initial chamber of the phragmocone is curved and cup-shaped, 1.82 mm in height and about 2.3 mm in width; the caecum is ~ 0.5 mm long. In the first whorl, the chambers shorten from RCL ~ 0.60 to RCL ~ 0.30. Further chambers change between 0.22 and 0.15. The section through the shell wall in the specimen indicates that the shell was ornamented with rather regularly spaced, slightly imbricated lirae; in the most apical part of the first whorl, the shell surface appears to be smooth. Inside of the conch, the septa are thickened at the point where they are attached to the inner surface of the shell wall.</p><p>Two additional specimens, GIT 225-1062 (Fig. 34B) and GIT 426-499, were studied from sagittal sections. The conch morphology is generally the same as in specimen MB.C.646. A difference is that, in GIT 225-1062 (Fig. 34B), the siphuncle is thinner (RSH as low as 0.12) and its diameter does not increase during ontogeny; however, the section through the specimen is not perfectly in the median plane and the values might thus be artificially lower. Both specimens are adult individuals. More complete of the two is the specimen GIT 225-1062, which shows the initial chamber (0.85× 1.80 mm). The last 185 degrees of the conch is occupied by the body chamber, which detaches from the preceding volution and shows the aperture. At the dorsal surface of the uncoiled part of the body chamber, the shell ornament of sharp, regularly spaced and imbricated lirae is preserved.</p><p>Two specimens were sectioned transversely. The larger of the two is specimen MB.C.32185 (Fig. 35A), which is a conch 45 mm in diameter with three whorls preserved. During ontogeny (between 8 mm and 45 mm conch diameter), the conch changes from thinly pachyconic to extremely discoidal (CWI decreases from 0.61 to 0.29) and from subinvolute to subevolute (UWI increases from 0.18 to 0.44); the whorl expansion rate is lowered (WER decreases from 3.57 to 2.00). The whorl profile shows broadly rounded flanks and venter, it changes from weakly depressed to weakly compressed (WWI decreases from 1.24 to 0.96). The siphuncle varies in diameter between 0.17 and 0.14 of the apertural height; it has a subcentral position in the earliest whorl (RSP = 0.55) and then moves further towards the dorsal shell wall and maintains the relative distance of RSP = 0.73. The other transversely sectioned specimen MB.C.32186 (Fig. 35B) is nearly identical to specimen MB.C. 32185 in conch dimensions and ratios; the only difference is the more depressed whorl profile (WWI = 1.13 at dm = 38 mm).</p><p>Specimen FMNH HS.P31459 (Fig. 34D) is a nearly complete conch (only the innermost whorls are covered by sediment) of an adult individual with the total diameter of about 47 mm. One lateral side of the specimen is hidden in the surrounding rock and the first half of the outer volution is slightly distorted; this hindered some measurements. The body chamber occupies the last half of a whorl. The aperture is partly preserved and shows the presence of a rounded and deep hyponomic sinus and very slight lateral flaring. At the base of the body chamber, structures resembling muscle attachment impressions are preserved (Fig. 34E). At the diameter of 44 mm, the conch is subevolute or evolute (UWI ~ 0.45) with a high coiling rate (WER ~ 2.20). The suture lines are straight and relatively closely spaced (RCL ~ 0.25). The ornament consists of rursiradiate lirae that form a deep and wide ventral sinus; the lirae are sharp especially in the inner whorl and flatten out towards later whorls.</p><p>Remarks</p><p>The holotype of “  Nautilus Teres ” was not available for our study; it was described by Eichwald (1840) but not illustrated in that publication. It came from the Orthoceratite Limestone (C1 horizon, late Darriwilian, Middle Ordovician) of the Estonian island of Osmussaar (formerly Odensholm in Swedish and Odinsholm in German).</p><p>Balashov (1953: 246, pl. 5 fig. 2) reproduced and assigned, as “ holotype ”, a specimen of “  Lituites Odini ” figured by Verneuil (1845: 360, pl. 25 fig. 8). Eichwald (1860) had assigned this specimen to “  Nautilus teres ” but he did not state whether it was part of the type collection or not. Furthermore, the present repository of the specimen or the type collection of Eichwald could not be traced. The herein studied material agrees closely with the latter specimen, but designation of a neotype from the presently studied collection is avoided because it cannot be confirmed that the type collection of Eichwald (1840) was lost.</p><p>Here we assign 19 specimens to  Curtoceras teres, which makes it the most abundant species in the studied material and allows some insight into the intraspecific variation. This concerns mainly the shape of the whorl profile. Generally, the WWI decreases as the conch grows (Fig. 11). In the early growth stages, the whorl profile is moderately depressed (WWI = 1.66 in specimen MB.C.32186), but in the adult stage it is between weakly depressed (WWI = 1.13 in specimen MB.C.32186), equidimensional (MB.C.11544, MB.C.32187, MB.C.32185) and weakly compressed (WWI = 0.82 in specimen MB.C.9715); the whorl profile is usually broadly rounded or sometimes weakly flattened ventrally and laterally. The differences in adult whorl profile are not accompanied by differences in any other characters or parameters. The lowest variation is recognised in WER and CWI; both decrease during ontogeny (Fig. 11), particularly in early growth stages (up to dm ~ 5 mm), after that the rate of decrease is getting smaller.</p><p>Besides the material described above,the Estonian geoscience data portal eMaapõu(https://geoloogia.info) lists several juvenile specimens of  Curtoceras (TUG 1745-331 to TUG 1745-337, University of Tartu, Natural History Museum) from the Aseri Regional Stage, which appear to fall within the variation observed in  C. teres . These specimens support the extension of the stratigraphic range of the species to the Aseri Regional Stage (Darriwilian Stage).</p><p>Curtoceras teres is similar to the stratigraphically coeval  C. estonicum (Island of Osmussaar and Tallinn Region of Estonia). According to the original description of Balashov (1953), the latter differs by having a square-shaped whorl profile in later growth stages and more sinuous suture lines; also, the siphuncle is closer to the dorsal side in  C. estonicum than in  C. teres . In the herein studied collection, there are four specimens (GIT 225-1092, GIT 697-130, GIT 426-498, TUG 860-1309) which have weakly rectangular whorl profile producing a ventral lobe and dorso-lateral saddle in the suture lines. However, there is no difference in conch geometry between these specimens, the holotype of  C. estonicum described by Balashov (1953) and the representatives of  C. teres with rounded whorl profile studied herein. For this reason and considering the variability of whorl profile shape in late growth stages of the latter,  Curtoceras estonicum is synonymised with  C. teres here.</p><p>In contrast to  Curtoceras teres, the early Sandbian  C. kerstovense from the St Petersburg Region (Russia) attains much larger adult size (up to 80 mm) with only the very end of the body chamber uncoiled from the preceding volution.  Curtoceras abditus from the Keila Regional Stage (Late Ordovician) of Estonia differs from  C. teres mainly in the reticulate shell ornament with strong transverse ornament elements, and in having a generally more robust conch in the early growth stage.</p><p>Among the species of  Trocholites,  Curtoceras teres is most similar to  T. depressus, especially in umbilical width (UWI) and conch width (CWI). However,  T. depressus has a much lower and much less rapidly decreasing coiling rate (particularly in early and mid-ontogeny; WER = 2.7–1.6 vs 9.9–1.9), the whorl profile tends to be more depressed (WWI = 1.67–1.2 vs 1.66– 0.82 in ontogeny) and the siphuncle is much wider (RSH ~ 0.30 vs 0.16) with a marginodorsal position; the ornament in  T. depressus has ribs on inner whorls instead of just sharp lirae.</p><p>Geographic and stratigraphic occurrence</p><p>Sweden (Island of Öland), Estonia, St Petersburg and Kaliningrad regions of Russia, northern Germany and northern Poland; Aseri–Uhaku regional stages, Darriwilian, Middle Ordovician.</p></div>	https://treatment.plazi.org/id/03AD87B1DD324222312C98CE93C1FD12	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Aubrechtová, Martina;Korn, Dieter	Aubrechtová, Martina, Korn, Dieter (2025): The coiled Middle Ordovician cephalopod genera Trocholites and Curtoceras (Tarphyceratida) from Baltoscandia and north-central Europe. European Journal of Taxonomy 982: 1-78, DOI: 10.5852/ejt.2025.982.2843, URL: https://europeanjournaloftaxonomy.eu/index.php/ejt/article/download/2843/12943
03AD87B1DD4D4223311B9E3D95A7FC2C.text	03AD87B1DD4D4223311B9E3D95A7FC2C.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Curtoceras meyeri Aubrechtová & Korn 2025	<div><p>Curtoceras meyeri sp. nov.</p><p>urn:lsid:zoobank.org:act: 69962EDA-B814-4DA9-84FA-8592B6E57609</p><p>Fig. 36; Table 24</p><p>Diagnosis</p><p>Species of the genus  Curtoceras with an adult conch exceeding 40 mm in diameter. At 40 mm diameter, the conch is discoidal (CWI ~ 0.45) and subevolute (UWI ~ 0.45) with high coiling rate (WER ~ 2.20); whorl profile with rounded flanks and venter, weakly depressed (WWI ~ 1.35) and weakly embracing (IZR = 0.05). Shell surface with lirae. Phragmocone chambers short (RCL ~ 0.10). Suture line almost straight or with a very shallow lateral lobe and a ventral saddle. Siphuncle subdorsal (RSP ~ 0.85) and narrow (RSH ~ 0.15).</p><p>Etymology</p><p>Named after Günter Meyer (Bernau), who donated a well-preserved  Curtoceras specimen to be studied herein.</p><p>Type material</p><p>Holotype</p><p>GERMANY •  unspecified locality in northern Germany;  ?Lasnamägi Regional Stage; illustrated in Fig. 36A; MB.C. 11550.</p><p>Description</p><p>Holotype MB.C.11550 (Fig. 36A) is a subadult conch with 41 mm diameter and has almost three whorls preserved; the body chamber is missing. In the last half whorl, the conch is discoidal (CWI = 0.46) and subevolute (UWI = 0.44); the coiling rate is high (WER = 2.20). The whorl profile has broadly rounded flanks and venter; it is weakly depressed (WWI = 1.35) and weakly embracing (IZR = 0.04) (Fig. 36B). The shell ornament is preserved only in a small area on the venter, where it consists of lirae that extend into a ventral sinus. The phragmocone chambers are short (RCL = 0.11). The suture line is almost straight or possesses a very shallow lateral lobe; however, on the venter of at least the last whorl, the suture line extends into a progressively pronounced saddle. The siphuncle is subdorsal in position (RSP = 0.85) and about 0.16 in relative diameter (RSH).</p><p>Remarks</p><p>Curtoceras meyeri sp. nov. differs from other species of  Curtoceras in the increasingly pronounced external saddle of the suture line starting with the third whorl, combined with the comparably high WWI and comparatively short phragmocone chambers.</p></div>	https://treatment.plazi.org/id/03AD87B1DD4D4223311B9E3D95A7FC2C	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Aubrechtová, Martina;Korn, Dieter	Aubrechtová, Martina, Korn, Dieter (2025): The coiled Middle Ordovician cephalopod genera Trocholites and Curtoceras (Tarphyceratida) from Baltoscandia and north-central Europe. European Journal of Taxonomy 982: 1-78, DOI: 10.5852/ejt.2025.982.2843, URL: https://europeanjournaloftaxonomy.eu/index.php/ejt/article/download/2843/12943
