Catoraphiceras sp.

Kröger, Björn & Pohle, Alexander, 2021, Early-Middle Ordovician cephalopods from Ny Friesland, Spitsbergen - a pelagic fauna with Laurentian affinities, European Journal of Taxonomy 783 (1), pp. 1-102 : 46

Catoraphiceras sp.

Figs 10A , 32A , 36D

Material examined

Specimen FMNH-P30425 from Profilstranda section, adjacent to Hinlopenstretet, Spitsbergen , bed PO 131, 128 m above base of Olenidsletta Member, V 2 b trilobite zone, Blackhillsian , Floian .

Description

The specimen is a 20 mm long orthoconic fragment of a phragmocone with a ca 3 mm long basal part of the body chamber. The conch cross section is slightly elliptically depressed with a width of 9.5–10.8 mm and a height of 8.7–9.2 mm (rW = 1.13; angle of expansion of conch height 9°).

The ornamentation consists of widely rounded annulations that form a shallow sinus at the prosiphuncular side of the conch and have a distance of ca 3 mm and an amplitude of ca 0.5 mm; the valley and ridges of the annulations are widely rounded. Fine details of the conch surface, which potentially exist, such as growth lines or striae, are not preserved. Roughly one annulation occurs per one chamber.

The chambers have a distance of 3–3.5 mm (ca three chambers occur at a distance similar to conch height, rCL = 0.33). The siphuncle is nearly marginal and has a diameter of 3.7 at the adapical end, and 3.9 mm at the adoral end (0.42 of conch height). The connecting ring is thick and consists of slightly concave segments. The shape and length of the septal necks is difficult to interpret because of the poor preservation of the specimen, but they appear to be short orthochoanitic. No cameral or endosiphuncular deposits occur.

Remarks

This is an annulated orthocone with a large siphuncle, larger than the range given for Catoraphiceras in the diagnosis of Hook & Flower (1977). The assignment of the fragment to Catoraphiceras is justified because all other characters are in agreement with the diagnosis of this genus and there is no other annulated orthocone with a marginal, empty siphuncle with slightly concave segments and short septal necks. Among the species of Catoraphiceras with depressed conch cross section C. colon (White, 1875) and C. resseri Ulrich et al., 1944 are most similar to specimen FMNH-P30425; the former mainly differs in having an annulation of only 2 annuli per distance similar to corresponding conch height, the latter differs in having a smaller siphuncle with rSD = 0.35. The siphuncle of Catoraphiceras sp. is also larger than the siphuncle of C. ibexense Hook & Flower, 1977 (rSD = 0.24). The single, relatively poorly preserved fragment available from the Olenidsletta Member, however, does not allow for the erection of a new species. The erection of a new species based on this fragmentary specimen is also not possible, because several species are known to contain endosiphuncular deposits, which may or may not exist in more apical, non-preserved, portions of specimen FMNH-P30425.

Figures

Fig. 10. Median section of orthocones from bed PO 131 of the Olenidsletta Member, Floian, Ordovician, Profilstranda section, Ny Friesland, Spitsbergen. A. Catoraphiceras sp., FMNH-P30425, with graptolite trapped in siphuncle. B–D. Proterocameroceras vallhallfonnense sp. nov. B. Specimen FMNH-P30429. C–D. Holotype, specimen FMNH-P30427. C. Complete specimen with asymmetric endosiphuncular deposits and imploded septa. D. Detail of holotype showing dorsal side of connecting ring and septal necks. Scale bars: A–B = 2 mm; C = 10 mm; D = 1 mm.

Fig. 32. Reconstruction and interpretation of details of connecting ring and septal necks in orthoconic cephalopods from the Olenidsletta Member, Floian, Ordovician, Profilstranda section, Ny Friesland, Spitsbergen. A. Catoraphiceras sp., FMNH-P30425, dorsal side of the connecting ring, see Fig. 10A. B. Cyptendoceratid gen. et sp. indet., FMNH-P30431, see Fig. 31B. C. Hemichoanella occulta sp. nov., FMNH-P30420, from bed PO 131, dorsal side of the connecting ring, see Fig. 36B. Black: septal neck and septum. Dark grey: connecting ring. Without scale.

Fig. 36. Protocycloceratid cephalopods from the Olenidsletta Member, Floian, Ordovician, Profilstranda section, Ny Friesland, Spitsbergen. A. Protocycloceras sp. FMNH-P30417, lateral view, from bed PO 123.3. B–C, E–H. Protocycloceras minor sp. nov. B, E–F. Specimen FMNH-P30411, holotype, from bed PO 131. B. Ventral view, prosiphuncular side. C. Specimen FMNH-P30412, from bed PO 131, with details of ornamentation well preserved. D. Catoraphiceras sp., FMNH-P30425, from bed PO 131, oblique lateral view. E. Adoral view of holotype with septal perforation visible. F. Fragment of holotype with chamber spacing G. Specimen FMNH-P30413 showing the shape of the septal curvature, dorsal view, antisiphuncular side. H. Specimen FMNH-P30410, with conch surface well preserved. I. Protocycloceras lamarcki (Billings, 1859), FMNH-P30418, from bed PO 04, with poorly preserved conch surface. Scale bars = 5 mm.