Cyptendoceratid

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 : 50

Cyptendoceratid gen. et sp. indet.

Figs 9C , 31A–B , 32B

Material examined

Specimen FMNH-P30431 , from Profilstranda section, adjacent to Hinlopenstretet , Spitsbergen , from bed PO 131, 128 m above base of Olenidsletta Member, V2 b trilobite zone , Blackhillsian , Floian .

Description

The specimen is a 20 mm long, nearly tubular fragment of a phragmocone with a circular conch cross section, 20 mm in diameter. Eight chambers occur in the length of the fragment and the sutures are straight and directly transverse. The conch surface is poorly preserved but was apparently smooth. The chambers are internally imploded and crushed, preserving only a small part of the siphuncle. This is 7 mm in diameter and positioned between the conch center and conch margin at a distance of ca 4 mm from the conch margin. The septal necks are orthochoanitic and 0.7 mm long, where the septal distance is 3 mm. The connecting ring is relatively thin compared to the septa and septal necks and concave on the dorsal side (the side directed toward the conch center), but convex on the ventral side.

Remarks

The combination of a large, eccentric, but not marginal siphuncle with relatively narrowly spaced septa, partly concave connecting rings and short orthochoanitic septal necks are arguments to place this specimen in the Cyptendoceratidae . A combination of ventrally expanded and dorsally contracted siphuncular segments is not known from other cyptendoceratids. However, the limited information available from this species, based on a single relatively small fragment, does not allow for a better determination.

Figures

Fig. 9. Orthoconic cephalopods with large siphuncles from the Olenidsletta Member, Floian, Ordovician, Profilstranda section, Ny Friesland, Spitsbergen. A–B, D–E. Buttsoceras buldrebreenense sp. nov. A–B. Specimen FMNH-P30422, from bed PO 131. A. Adoral view of septum and septal perforation. B. Lateral view with prosiphuncular side toward right. C. Cyptendoceratid genus and species indet., FMNH-P30431, from bed PO 131. D. Specimen FMNH-P30423, from bed PO 131, lateral view. E. Specimen FMNH-P30421, holotype, lateral view, note faint transverse ornament partly preserved. F–G. Cyptendoceras sp. A, FMNH-P30426, from bed PO 07. F. Ventral view, prosiphuncular side. G. Adoral view of septum and septal perforation. H–I. Proterocameroceras valhallfonnense sp. nov., FMNH-P30277, from bed PO 131. H. Ventral view, prosiphuncular side. I. Adoral view of septum and septal perforation. Scale bar = 10 mm for all figures.

Fig. 31. Median section of details of septal necks and siphuncle of cyptendoceratids from Olenidsletta Member, adjacent to Hinlopenstretet, Spitsbergen. A–B. Cyptendoceratid gen. et sp. indet., FMNH-P30431 from bed PO 131, Floian, Ordovician, Profilstranda section, Ny Friesland, Spitsbergen. Dorsal side directed toward left. A. General view of the siphuncle. Scale bar = 2 mm. B. Details of dorsal side of connecting ring. Scale bar = 1 mm. C. Cyptendoceras sp. B, FMNH-P30166 from Profilbekken river basin, locality PR-phosphatic, uppermost Olenidsletta Member, V3 trilobite zone, Dapingian. Scale bar = 5 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.