Lituites lituus de Montfort, 1808

Aubrechtová, Martina & Korn, Dieter, 2022, Taxonomy and ontogeny of the Lituitida (Cephalopoda) from Orthoceratite Limestone erratics (Middle Ordovician), European Journal of Taxonomy 799 (1), pp. 1-108 : 48-56

Lituites lituus de Montfort, 1808

Figs 31–32 , 33A–B , 34–35 , Tables 9–10

Lituites lituus de Montfort, 1808: 278 , text–fig. on p. 278.

Lituites lituus – Lossen 1860: 15, pl. 1a–d. — Remelé 1880: 432; 1890: 7, pl. 1 fig. 1. — Angelin 1880: 8, pl. 9 fig. 8. — Noetling 1882: 156, pl. 11 fig. 1. — Holm 1891: 20, pl. 3 figs 1–2. — Sweet 1958: 141, pl. 14 fig. 5, pl. 15 fig. 4. — Neben & Krueger 1971: pl. 31 fig. 1. — Dzik 1984: 137, pl. 41 fig. 1. — Aubrechtová & Meidla 2020: 279, text-figs 9, 10f, h–i, k.

Lituites procerus – Balashov 1953: 233, pl 14 fig. 2; 1962: pl. 7 fig. 9.

Diagnosis

Species of the genus Lituites with coiled conch ca 25–30 mm in diameter; coiling tight or whorls slightly detached. Backcoiled part of the conch moderately to strongly curved, expansion angle ca 5°. Straight part of the conch orthoconic or slightly cyrtoconic with expansion angle ca 8°. Shell ornament with coarse annuli, clearly developed along the whole length of the conch including the coiled part and terminal body chamber; growth lines and lirae present in between the annuli. Ornament elements rectiradiate or weakly prorsiradiate (backcoiled part); ventral sinus moderately deep, lateral sinus comparatively wider and shallower, dorsolateral sinus shallow, dorsal projection low.

Type material

Neotype GERMANY • Brandenburg, Oderberg (Bralitz); Ordovician (late Lasnamägi Regional Stage, late Darriwilian), Upper Grey Orthoceratite Limestone; Neben and Krueger Coll.; previously illustrated by Neben & Krueger (1971: pl. 31 fig. 1), re-illustrated here in Fig. 33A ; MB.C.30527 .

Additional material

GERMANY • 1 spec.; near Berlin; Ordovician; MB.C.11639 • 1 spec.; Mecklenburg-Vorpommern, Bansin (Gothensee, Usedom ); Ordovician; v. Mensebach Coll.; MB.C.11657 • 2 specs; Mecklenburg- Vorpommern , Gross Zicker ( Island of Rügen ); Ordovician, Upper Grey Orthoceratite Limestone; Krueger 1966 Coll.; MB.C.2497 , MB.C.11990 .

SWEDEN • 1 spec.; Södra Sandby, Skåne; Ordovician, Seby Limestone (transition between the Upper Red and Upper Grey Orthoceratite Limestone); Bottke Coll.; MB.C.29650 .

ESTONIA • 1 spec.; Karula, Lääne-Viru County; Ordovician, Upper Grey Orthoceratite Limestone; Dames 1876 Coll.; MB.C.9714 .

COUNTRY UNKNOWN • 1 spec.; “ West Prussia ”; Ordovician, Echinosphaerites Limestone; Kiesow 1901 Coll.; MB.C.30528 • 1 spec.; Ordovician; MB.C.11640 .

Description

Neotype MB.C.30527 ( Figs 33A , 34A–E ) consists of the coiled part (2.5 tightly coiled volutions; dm = 29 mm; WER dm = 2.17, WER ah = 2.14; WWI = 0.86 at wh = 9 mm) and the moderately curved uncoiled part (length = 220 mm; EA ~ 6°). The terminal aperture is not preserved. The shell ornament in the penultimate whorl consists of shallow annuli standing 1.6 mm apart. These annuli bear five sharp growth lines, while the interspaces between the annuli are either smooth or occupied by very delicate growth lines. The annuli weaken on the last whorl and are only barely visible at the beginning of the backcoiled part. In the middle of the backcoiled part, about 50 mm apart from the beginning, the shell ornament shows raised lirae in distances of 0.8–1.1 mm; between them there are four or five delicate growth lines. The lirae are imprinted on the internal mould and appear as shallow undulation. They extend with shallow ventral sinus, low and symmetric ventrolateral projection, wide and very shallow lateral sinus and low dorsal projection. In the backcoiled part of the conch, narrow annuli appear again (up to 4 mm apart) and are covered by lirae (up to 0.7 mm apart); ventral sinus is deep but rounded. The phragmocone chambers are variable in length but the CLR generally decreases towards the aperture from 0.56–0.42.

Specimens MB.C.11990 ( Fig. 32 ) and MB.C.2497 ( Fig. 33B ) are rather well-preserved conchs which consist of the coiled parts (2.25–2.5 tightly coiled volutions; dm = 30 mm; Fig. 34 ) and the moderately curved uncoiled parts (length more than 200 mm; EA ~ 5°). The whorl expansion rate is between 2.10 and 2.20 ( Fig. 34F–O ). Terminal apertures are not preserved. In specimen MB.C.2497, the coiled part has regularly spaced annuli standing 1.5 mm apart. Sharp growth lines occur on the annuli and also in their interspaces. In contrast to the annuli, the growth lines are not imprinted on the internal mould. The backcoiled part is ornamented with irregularly spaced, rectiradiate to prorsiradiate lirae (0.2–0.4 mm apart) that do not leave traces on the internal mould; strong annuli are not developed. The straight part of the conch bears lirae (up to 0.5 mm apart) and the internal mould bears imprints or relatively narrow annuli; ventral sinus is deep, lateral sinus is comparatively shallow. The phragmocone chambers are variable in length, both within individual specimens and between the two specimens. In specimen MB.C.11990, the chamber length ratio varies between 0.18 and 0.56 without any ontogenetic trend. Only the chambers in front of the body chamber are shorter ( Fig. 35C–D ). In specimen MB.C.2497, the phragmocone chambers are much longer (CLR = 0.33–0.69) and shorter chambers are usually restricted to an earlier ontogenetic stage, while longer chambers occur later in ontogeny ( Fig. 35A–B ).

Specimen MB.C.11657 consists of the coiled conch (dm = 24 mm; the whorls are only very slightly detached from the preceding, detachment increases gradually and the maximum interspace width is 0.70 mm just before uncoiling) and the moderately curved backcoiled part of the conch (length = 100 mm; wh = 20 mm). The shell ornament of the coiled part consists of annuli and very fine growth lines (preserved only on the inner half of the last whorl). In the innermost whorl, the annuli appear only as imprints on the internal mould and are 1.3 mm apart. In the remaining coiled conch, the annuli are up to 1.9 mm apart. The lateral sinus is shallow and disappears towards the end of the coiled part. At the end of the backcoiled part and in the straight part, the ornament consists of annuli, which become wider (up to ca 7 mm apart) and flat; the intercalated lirae have distances of up to 0.5 mm. Annuli as well as lirae are visible on the internal mould. The lateral sinus of the ornament elements is very shallow in the straight conch, but its depth increases during ontogeny; the dorsal projection is low and flanked by a shallow dorsolateral sinus.

Remarks

Modéer (1796) introduced the name Orthocera lituus (without referring to or depicting any specimens); some authors consequently considered Modéer (1796) the author of Lituites lituus and the type species of Lituites . Most researchers, however, regarded de Montfort (1808) as the author as he was the first to use the name Lituites lituus and is herein assumed as the author of the species name. De Montfort (1808) himself did not refer to the work of Modéer (1796).

De Montfort (1808) made only a general description of the species and did not mention or describe any particular type specimens and any type locality. The only provided illustration shows a lituiticonic conch with tightly coiled apical part and a sigmoidal backcoiled part. However, since the illustration is only an artistic representation, it cannot be determined whether it shows a particular specimen of Lituites lituus or only a general conch morphology based on multiple specimens; moreover, there are several species of the genus Lituites with tightly coiled apical part of the conch, such as L. lasaulxii .

Lituites lituus and L. perfectus (discussed below) were the first and for quite some time the only species assigned to Lituites . Their initial descriptions were only very general and indicated that the distinction between the two species is the tightly ( L. lituus ) or loosely ( L. perfectus ) coiled apical part of the conch. The use of the names L. lituus and L. perfectus was inconsistent during the 19 th century, when many authors developed own ideas for the species definition. Remelé (1880) attempted to draw firm lines between the two species based on the degree of coiling, the coiled conch diameter, the shape of whorl profile, the shape of the backcoiled conch part, the expansion angle and the ornament. He also defined some new species ( Remelé 1880, 1890) of Lituites . Noetling (1882) and Holm (1891) stressed out the great intraspecific variation and ontogenetic changes of the characters and questioned their validity for the separation of L. lituus and L. perfectus .

Not much was added to the discussion on this particular matter during the 20 th century, but several specimens were illustrated and described ( Balashov 1953; Sweet 1958; Neben & Krueger 1971; Dzik 1984). In their study of Estonian lituitids, Aubrechtová & Meidla (2020) synonymised Lituites lituus and L. perfectus because of transitional morphologies between the two species and a great amount of ontogenetic variation in their material.However, the presently studied collection contains more completely preserved specimens, particularly specimens from the Neben & Krueger and the Bottke collections. The study of these specimens enabled the revision of the concepts of L. lituus and L. perfectus . Since the type material of the two species is not sufficiently known, neotypes were selected for both taxa.

The neotypes were chosen based on the most reliable and detailed descriptions and illustrations in previous literature, i.e., Remelé (1880, 1890), Noetling (1882) ( Fig. 31A ), Holm (1891) and Dzik (1984) ( Fig. 31B ).

Lituites lituus differs from L. perfectus in having a smaller diameter of the coiled conch (up to 30 mm but up to 40 mm in L. perfectus ) and tightly or almost tightly coiled volutions (openly coiled in L. perfectus ); in addition, the backcoiled part of L. lituus is moderately to strongly curved (weakly curved or straight in L. perfectus ), the conch has a greater expansion angle (5°–8° but 1°–4° in L. perfectus ) and the shell has a coarser ornament (annuli along the whole conch length).

The species most similar to L. lituus is L. lasaulxii , which has more strongly curved backcoiled part and the shell ornament lacks annuli at the coiled part of the conch and the straight part only has growth lines (not lirae) on the surface of the annuli.

Lituites procerus Remelé, 1890 also has a tightly coiled conch up to 30 mm in diameter as L. lituus , but its uncoiled part is only weakly curved or straight; the shell of the coiled part has ribs instead of annuli in some specimens. Lituites bottkei sp. nov. has loosely coiled volutions and a finer ornament with biconvex ornament elements in the coiled part. Lituites clavis is tightly coiled but its coiled part has a greater diameter (34 mm) than that in L. lituus , the backcoiled part expands rather slowly (expansion angle of ~2°) and the uncoiled part is ornamented with flat (instead of prominent) annuli. The uncoiled part in L. nebeni sp. nov. is only weakly curved and very slender (almost tubular upon uncoiling) with expansion angle up to 4°; the shell ornament consists of flat (instead of prominent) annuli.

Geographic and stratigraphic occurrence

Norway, Sweden, Estonia (in situ) and northern Germany, northern Poland and the Kaliningrad Region ( Russia) (in erratics within Pleistocene gravels); Darriwilian to early Sandbian (Middle to early Late Ordovician).

Lituites lituus is a stratigraphically significant species in Baltoscandia indicating a mid-Lasnamägian age (e.g., Jaanusson 1960; Evans et al. 2014).

Figures

Fig. 31. Lituites lituus de Montfort, 1808; reproductions from the literature. A. Reproduction of the illustration by Noetling (1882: pl. 11 fig. 1). B. Reproduction of the illustration by Dzik (1984: pl. 41 fig. 1). Scale bar units = 1 mm.

Fig. 32. Lituites lituus de Montfort, 1808 from the Upper Grey Orthoceratite Limestone; specimen MB.C.11990 (Helms 1966 Coll.) from Gross Zicker (Island of Rügen, Mecklenburg-Vorpommern). Scale bar units = 1 mm.

Fig. 33. Lituites lituus de Montfort, 1808 (A–B) and Lituites cf. lituus de Montfort, 1808 (C) from the Upper Grey Orthoceratite Limestone.A. Neotype MB.C.30527 (Neben & Krueger Coll.) from Oderberg, Bralitz (Brandenburg); previously figured by Neben & Krueger (1971: pl. 31 fig. 1); magnification of the coiled part on the right. B. Specimen MB.C.2497 (Helms 1966 Coll.) from Gross Zicker (Island of Rügen, Mecklenburg-Vorpommern); magnification of the coiled part on the right. C. Specimen MB.C.30529 (Münchner Coll.) from the Island of Chrząszczewska (former Gristow), West Pomerania, Poland. Scale bar units = 1 mm.

Fig. 34. Lituites lituus de Montfort, 1808. A. Outline of coiled conch part of neotype MB.C.30527. B–E. Conch proportions and coiling rates of neotype MB.C.30527. F. Outline of coiled conch part of specimen MB.C.2497. G–J. Conch proportions and coiling rates of specimen MB.C.2497. K. Outline of coiled conch part of specimen MB.C. 11990. L–O. Conch proportions and coiling rates of specimen MB.C. 11990. Scale bar units = 1 mm.

Fig. 35. Septum distances in Lituites lituus de Montfort, 1808 from the Upper Grey Orthoceratite Limestone. A, C = empirical data points; B, D = three data points averaged. A–B. Specimen MB.C.2497 (Helms 1966 Coll.) from Gross Zicker (Island of Rügen, Mecklenburg-Vorpommern). C–D. Specimen MB.C.11990 (Helms 1966 Coll.) from Gross Zicker (Island of Rügen, Mecklenburg-Vorpommern).