Crassirensselaeria crassicosta (Koch, 1881)

Schemm-Gregory, Mena & Jansen, Ulrich, 2007, A new genus of terebratulid brachiopod from the Siegenian of the Rheinisches Schiefergebirge, Acta Palaeontologica Polonica 52 (2), pp. 413-422 : 415-420

Crassirensselaeria crassicosta (Koch, 1881)

Figs. 2 , 3 , 4A , 7 .

1881 Rensselaeria sp. nov.; Kayser 1881a: 263.

1881 Rensselaeria crassicosta sp. nov.; Koch in Kayser 1881b: 387.

1883 Rensselaeria crassicosta Koch ; Kayser 1883: 123–124, pl. 5: 2–5.

1904 Rensselaeria crassicosta C. Koch ; Fuchs 1904: 44–45, pl. 6: 1.

1913 Rhenorensselaeria crassicosta Koch ; Kegel 1913: 11, 127, 132, 135–136, pl. 6: 14, 15.

1923 Renssellaeria crassicosta Koch ; Quiring 1923: 91–92, 99–100, 102–103, 105–107, 109, 111.

1923 Rensselaeria crassicosta ; Helmbrecht and Wedekind 1923: 949– 950, 953.

1931 Rensselaeria (Rhenorensselaeria) crassicosta C. Koch ; Maillieux 1931: 6–8, 30–32, pl. 1: 11, a, b.

1931 Rensselaeria sp. cf. crassicosta C. Koch ; Wilschowitz 1931: 8, 11, pl. 2: 14–16.

1932 Rensselaeria crassicosta C. Koch ; Wilschowitz 1932: 14–15, 32, pl. 2: 15–17.

1934 Rhenorensselaeria crassicosta (C. Koch) ; Dahmer 1934: 17, 21, 31, 35.

1936 Rhenorensselaeria crassicosta (Koch) ; Dahmer 1936a: 643–645, 666, pl. 46: 5.

1936 Rhenorensselaeria crassicosta (Koch) ; Dahmer 1936b: 6, 9–12, pl. 6: 13.

1936 Rhenorensselaeria crassicosta (C. Koch) ; Rose 1936: 57.

1937 Rhenorensselaeria crassicosta (Koch) ; Dahmer 1937: 440, 444, 447–449, 452–454, 456–458.

1937 Rensselaeria crassicosta Koch ; Kutscher 1937: 198–200, 204, 209, 215, 217.

1940 Rhenorensselaeria crassicosta (Koch) ; Simpson 1940: 55, table 2.

1950 Rhenorensselaeria crassicosta ; Solle 1950: 307, 309–310, 313.

1957 Rhenorensselaeria crassicosta (Koch) ; Jentsch and Röder 1957: 124–125.

1967 Rhenorensselaeria crassicosta (Koch, 1881) ; Boucot et al. 1967: pl. 2: 2.

1974 Rhenorensselaeria crassicosta (Koch) ; Mittmeyer 1974: 70–72, table 2.

1981 Globithyris laticostata sp. nov.; Jux 1981: 102–104, fig. 2.

1981 Rhenorensselaeria crassicosta (Koch) ; Evans 1981: 521. [questionable].

1982 Rhenorensselaeria crassicosta (Koch) ; Mittmeyer 1982a: 13, 15, 18–21,? 23, 38, fig. 4a, b, table 1.

1982 Rhenorensselaeria crassicosta (Koch) ; Fuchs 1982: 232, 252, text−fig. 10.

1982 Rhenorensselaeria crassicosta (Koch) ; Mittmeyer 1982b: 259, 260, chart 1.

1997 Rhenorensselaeria crassicosta ; Mittmeyer 1997: 13.

2001 Rhenorensselaeria crassicosta (Koch) ; Thünker 2001: 27, 37–38, 67, 83, 86.

2004 Rhenorensselaeria crassicosta (Koch, 1881) ; Schindler et al. 2004: 143, 145, table 1.

Lectotype: Kayser (1881a) has not figured any specimens when he described the species in open nomenclature from the Taunusquarzit Beds of the Hunsrück area. Kayser mentioned in a footnote within a report (1881b) that Koch had named the species “ Rensselaeria ” crassicosta . According to the International Code of Zoological Nomenclature ( ICZN 2000: Article 50.2.) Koch is the author of the taxon, not Kayser. Only two years later, Kayser redescribed the species and figured specimens from the Hunsrück and Siegerland areas. Because nothing has been published by Koch himself on this species, it is impossible to get a clear picture of what was his original intention. However, we think that Kayser and Koch were in contact with each other, so that it is very probable that they had the same idea of the species, which can hardly be confused with other ones. In our opinion, the specimens figured by Kayser (1883) can be regarded as specimens of the type series sensu lato. We have chosen the specimen figured by Kayser (1883: pl. 5: 2) as the lectotype. The internal mould of an articulated shell ( Fig. 3 , MB.B 2090.1) is 18.3 mm wide, 22.9 mm long, and 25.1 mm thick. It is stored in the Museum für Naturkunde, Berlin.

Type locality: Häusling near Siegen , topographical mapsheet 1:25 000 Siegen 5114, Siegerland area (Rheinisches Schiefergebirge, Germany). Type horizon: Siegen Beds, exact position uncertain (Siegenian, middle Lower Devonian) .

Diagnosis.—The same as for the genus.

Stratigraphic range and distribution.—Rheinisches Schiefergebirge ( Germany): Lower, Middle, and Upper Siegen Beds, Taunusquarzit Beds; Northern Ardennes ( Belgium): Grès et Schistes de Solières; Hrubý Jeseník ( Czech Republic): beds of Siegenian age;?Southern Devon and Northern Cornwall ( Great Britain): Dartmouth Beds; Middle or Upper Siegenian (middle Lower Devonian). The species is abundant in Upper Siegenian strata, whereas it is rare in Lower and Middle Siegenian strata. It is useful especially in successions of restricted marine, intertidal and deltaic environments to recognise the lower and upper boundaries of the Siegenian stage, where other fossils are sparse or absent.

Description.—Shell medium−sized and strongly biconvex, subglobular, ventral valve slightly more convex than dorsal valve with maximum curvature in the umbonal region; brachythyrid; suboval in outline, slightly longer than wide.

Only fragments of external moulds could be studied; they show coarse and non−bifurcating costae. Costae and separating furrows are angular in cross section and terminate along a “zig−zag commissure”. On one ventral external mould the punctate shell structure is visible as minutes rods representing internal moulds of puncta ( Fig. 3M , AEG 146−5). Ventral interarea rarely preserved, approximately orthocline, concave in longitudinal section.

The internal mould of the ventral valve extends further beyond the hinge line than that of the dorsal valve. A pair of thick and relatively long, subparallel dental plates is present. There is a short and fine septum in the apical region which is commonly situated in a median or, more rarely, a submedian position leaving a furrow on the internal mould. In the extreme apical region there is a small round scar interpreted as a trace of a pedicle foramen. Muscle scars are generally not clearly developed; the region of the muscle field is deeply impressed and commonly narrow at the base in cross section. The ventral internal mould shows 20 to 24 well−developed and coarse costae which are rounded in cross section whereas the furrows are angular. Costae are hardly developed in the apical region and close to the hinge line. Generally, costae are wider than furrows.

The internal mould of the dorsal valve posteriorly extends little across the hinge line. The cardinal process consists of a pair of rod−like to bulbous lobes. Thick cardinal plate supporting the cardinal process. A free septalium is developed in some specimens, in others it is apparently buried in secondary shell material. There is a long median septum reaching about one third of valve length. The dorsal median septum is longer and higher than the ventral median septum. It varies from a thin ridge to a prominent thick ridge with a sharp anterior edge sometimes carrying a low and thin myophragm. We do not ascribe a taxonomic relevance to this difference regarding it as intraspecific variability. The mould of the brachidium is not preserved in any specimen. The cardinal process and the crural plates reach into the ventral valve. At the outer margin of the cardinal plate there is a pair of shallow and narrow cylindrical dental sockets diverging in anterolateral direction ( Fig. 3L 2 , MBG 5100). Adductor scars are situated on both sides of the median septum but their limits are not clearly discernible. They are deeply impressed in some specimens leaving small, posteriorly directed projections on the internal mould ( Fig. 3D , MB.B 2078.8).

Discussion.—In the Rheinisches Schiefergebirge, the genus Rhenorensselaeria is represented by two species, Rh. strigiceps (C.F. Roemer, 1844) ( Fig. 4B SMF 66104; Fig. 5 ) and Rh. demerathia Simpson, 1940 ( Fig. 4C , SMF XVII 687 o; Fig. 6 ). Crassirensselaeria gen. nov. differs from both species of Rhenorensselaeria by more globular shells contrasting with the elongate and suboval outlines of the latter, by internal apical features, and the number and size of costae of the internal moulds ( Table 1, Fig. 4 ). Our specimens of C. crassicosta (Koch, 1881) , including the lectotype, show 20 to 24 costae on the ventral internal mould. As already Fuchs (1904) pointed out, Kayser (1883) described this species with 8 to 14 costae but none of the studied specimens shows that small number of costae. Kayser probably counted only the costae of one half of a specimen. The ventral muscle field of C. crassicosta is deeply impressed with poorly individualised scars and cleary bordered by the long dental plates. In Rhenorensselaeria , the ventral muscle field is generally more shallow forming a flat surface bordered by low muscle−bounding ridges; individual posterior and anterior scars are often clearly recognisable. At the anterior end of the scars, a pair of protuberances on the internal moulds can be developed which lack in Crassirensselaeria .

Rhenorensselaerids close to Rh. strigiceps are described from the Armorican Massif (northwestern France; Renaud 1942), the Celtiberian Chains (northeastern Spain; Carls and Valenzuela−Ríos 1998), and the Dra Plains (southern Morocco; Jansen 2001). These forms generally show the same differences to C. crassicosta as Rh. strigiceps . The Moroccan form has slightly less costae than the Rhenish form. Further studies are planned to elucidate the rhenorensselaerid phylogeny in Europe and North Africa.

Rhenorensselaeria macgerriglei Boucot, 1967 from the Lower Devonian Gaspé Sandstone Group (Quebec, Canada) resembles the congeneric Rhenish forms in the presence of fine costae, a shallow ventral muscle field, and thinner dental plates than in C. crassicosta (compare Boucot et al. 1967). It is very similar (?conspecific) to Rh. demerathia . On the other hand, regarding its subglobular outline, the form from Gaspé resembles C. crassicosta .

Jux (1981) attributed specimens of “ Rhenorensselaeria ” crassicosta to the North American genus Globithyris Cloud, 1942 . He proposed a new species Globithyris laticostata that we consider as an ontogenetic stage of Crassirensselaeria crassicosta . In our opinion, C. crassicosta does not fit well in Globithyris as dental plates and hinge plates are much thicker than in the type species of Globithyris , G. callida ( Clarke, 1907) from Gaspé (Quebec, Canada) and Maine (eastern United States) ( Clarke 1907).

Figures

Fig. 2. Morphological terms of Crassirensselaeria crassicosta (Koch, 1881). A. Internal mould of articulated specimen (lectotype, MB.B 2090.1). Posterior view. Crural plates, dental plates, dorsal and ventral median septum preserved as negative forms. B. Latex cast of internal mould of articulated specimen (MBG 5083). Interior of posterior portions of both valves. Drawings by M.S.−G.

Fig. 3. Middle Lower Devonian rhenorensselaeriid brachiopod Crassirensselaeria crassicosta (Koch, 1881) from the Rheinisches Schiefergebirge, Germany. A. Lectotype. Internal mould of articulated specimen (MB.B 2090.1). Siegen Beds of Häusling near Siegen, Siegerland area, topographical mapsheet 1:25 000 Siegen 5114. Internal mould, posterior view (A1); internal mould, lateral view (A2); latex cast, interior of posterior portions of both valves (A3). B. Internal mould of articulated specimen (MB.B 2090.2). Siegen Beds of Häusling near Siegen, Siegerland area, topographical mapsheet 1:25 000 Siegen 5114. In posterior (B1), anterior (B2), and lateral (B3) views.C. Internal mould of articulated specimen (AEG 65). Upper Siegen Beds of Aegidienberg tunnel, Siebengebirge, topographical mapsheet 1:25 000 Königswinter 5309. Internal mould, posterior view (C1); latex cast, interior of posterior portions of both valves (C2). D. Internal mould of dorsal valve (MB.B 2078.8).Upper Siegen Beds of quarry Altenhof,leg.Schmidt 1924, topographical mapsheet 1:25 000 Wenden 5013.Internal mould, oblique posterior view (D1); latex cast, oblique view of the interior (D2). E. Internal mould of articulated specimen (AEG 295−1b). Upper Siegen Beds of Aegidienberg tunnel, Siebengebirge, topographical mapsheet 1:25 000 Königswinter 5309.Oblique posterior view. F. Internal mould of articulated specimen (AEG 110 lateral B3b). Upper Siegen Beds of Aegidienberg tunnel, Siebengebirge, topographical mapsheet 1:25 000 Königswinter 5309. Lateral view. G. Internal mould of articulated specimen (AEG 97−3). Upper Siegen Beds of Aegidienberg tunnel, Siebengebirge, topographical mapsheet 1:25 000 Königswinter 5309. Posterior view. H. Internal mould of ventral valve (AEG 110 lateral B3a). Upper Siegen Beds of Aegidienberg tunnel, Siebengebirge, topographical mapsheet 1:25 000 Königswinter 5309. Ventral view. I. Internal mould of articulated specimen (AEG 295−1a). Upper Siegen Beds of Aegidienberg tunnel, Siebengebirge, topographical mapsheet 1:25 000 Königswinter 5309. Posterior view. J. Internal mould of articulated specimen (MB.B 2096). Siegen Beds of Siegen, leg. Spriesterbach 1918, Siegerland area, topographical mapsheet 1:25 000 Siegen 5114.In lateral (J1) and posterior (J2) views.K. Internal mould of articulated specimen (MBG 5083). Siegen Beds of Brück an der Ahr, leg. Sprengler 1895, Siegerland area, topographical mapsheet 1:25 000 Siegen 5114. Internal mould, posterior view (K1); latex cast, interior of posterior portions of both valves (K2); latex cast, cardinalia (K3). L. Internal mould of dorsal valve (MBG 5100).Siegen Beds of Burggraben near Netphen, Siegerland area, topographical mapsheet 1:25 000 Hilchenbach 5014. Oblique posterior view (L1); apical region (L2). M. External mould of ventral valve (AEG 146−5). Upper Siegen Beds of Aegidienberg tunnel, Siebengebirge, topographical mapsheet 1:25 000 Königswinter 5309. Ornament. Scale bars 10 mm, except K3, L2, and M for which are 1 mm.

Fig. 4. View of cardinalia. All figures are latex casts of internal moulds of articulated speci− mens. A. Crassirensselaeria crassicosta (Koch, 1881). Lectotype (MB.B 2090.1) Siegen Beds (middle Lower Devonian); Häusling near Sie− gen, Siegerland area, topographical mapsheet 1:25 000 Siegen 5114. B. Rhenorensselaeria strigiceps (C.F. Roemer, 1844) (SMF 66104). Siegen Beds (middle Lower Devonian); Mine “Alte Mahlscheid” near Herdorf; leg. Bergrat Borrhezs 1894, Middle Rhine area, topographi− cal mapsheet 1:25 000 Betzdorf 5213. C. Rheno− rensselaeria demerathia Simpson, 1940 (SMF XVII 687 o). Saxler Beds (upper parts of Upper Siegen Beds, middle Lower Devonian); Quarry 3/4 km north of Demerath, Eifel area, topograph− ical mapsheet 1:25 000 Gillenfeld 5807.

Fig. 7. Rock slab with several specimens of Crassirensselaeria crassicosta (Koch, 1881) in life position (AEG 146−5), view of the underside of the bed. Upper Siegen Beds (middle Lower Devonian) of the Aegidienberg tunnel, Siebengebirge, topographical mapsheet 1:25 000 Königswinter 5309. Internal moulds in posterior view.

Fig. 5. Middle Lower Devonian rhenorensselaeriid brachiopod Rhenorensselaeria strigiceps (C.F. Roemer, 1844) from Germany. A. Internal mould of articulated specimen (SMF 66104) and latex cast. Siegenian of mine “Alte Mahlscheid” near Herdorf; leg. Bergrat Borrhezs 1894, Middle Rhine area, topographical mapsheet 1:25 000 Betzdorf 5213. Internal mould, posterior view (A1); internal mould, anterior view (A2); latex cast, interior of posterior portions of both valves (A3); internal mould, lateral view (A4). B. Internal mould of ventral valve (AEG 28−3). Upper Siegen Beds of Aegidienberg tunnel, Siebengebirge, topographical mapsheet 1:25 000 Königswinter 5309. Oblique posterior view. C. Internal mould of articulated specimen (AEG 267−1). Upper Siegen Beds of Aegidienberg tunnel, Siebengebirge, topographical mapsheet 1:25 000 Königswinter 5309. Posterior view. D. Rock slab with specimens in life position (AEG 267−1).Upper Siegen Beds of Aegidienberg tunnel, Siebengebirge, topographical mapsheet 1:25 000 Königswinter 5309.Posterior view of internal moulds.

Fig. 6. Middle Lower Devonian rhenorensselaeriid brachiopod Rhenorensselaeria demerathia Simpson, 1940 from Germany. A. Holotype. Internal mould of articulated specimen (SMF XVII 687 n). Saxler Beds (upper parts of Upper Siegen Beds) of a quarry 3/4 km north of Demerath, Eifel area, topographical mapsheet 1:25 000 Gillenfeld 5807. In posterior (A1) and lateral (A2) views. B. Internal mould of articulated specimen (SMF XVII 687 o) and latex cast. Saxler Beds of a quarry 3/4 km north of Demerath, Eifel area, topographical mapsheet 1:25 000 Gillenfeld 5807. Internal mould, posterior view (B1); latex cast, interior of posterior portions of both valves (B2). C. Internal mould of articulated specimen (SMF 26340 a) and latex cast. Saxler Beds of south of Meiserich, point 367,8, Eifel area, topographical mapsheet 1:25 000 Gillenfeld 5807. Internal mould, posterior view (C1); latex cast, interior of posterior portions of both valves (C2). D. Internal mould of ventral valve (SMF XVII 687 r). Upper Siegen Beds of Auderather Mühle, Ollenbach, Eifel area, topographical mapsheet 1:25 000 Gillenfeld 5807. Oblique posterior view.