Estonioceratidae Hyatt, 1900

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 : 65

Family Estonioceratidae Hyatt in Zittel, 1900

Gen. et sp. indet. A

Fig. 45E–F

Material examined

Specimen FMNH-P30342 , from Profilstranda section, Ny Friesland , Svalbard , bed PO 7.5, 4.5 m above base of Olenidsletta Member, V1 a trilobite zone , Blackhillsian , Floian .

Description

The specimen is a slightly curved, ca 19 mm long part of a body chamber, with a circular conch cross section with a diameter of 10.5 mm at the position of the last septum and 11 mm at the adoral end. The body chamber is simple conical, without constriction, and with a very shallow hyponomic? sinus at the concave side of the curvature. The conch surface is nearly smooth, ornamented only with very fine directly transverse growth lines. The shell is relatively thick, 1 mm at the base of the body chamber. The suture is directly transverse, and the septum has a concavity of ca 1.5 mm. The septal perforation is ca 1 mm in diameter and positioned ca 0.5 mm from the convex margin of the conch.

Remarks

The body chamber is strongly curved but lacks an impression zone, and with the exception of the last septum the phragmocone is not preserved, which shows that the curvature is exogastric and the siphuncle is positioned close to the conch margin. The available characters indicate that the fragment is part of an estonioceratid, but a more specific determination is impossible with the material at hand.

Figures

Fig. 45. Cephalopods from the Olenidsletta Member, Floian, Ordovician, Profilstranda section, Ny Friesland, Spitsbergen. A–B. Nyfrieslandoceras bassleroceroides gen. et sp. nov., FMNH-P30353, holotype, from bed PO 131. A. Ventral view, prosiphuncular side. B. Lateral view with ventral, prosiphuncular side toward the left. C–D. Order, gen. et sp. indet. A, FMNH-P30354, from bed PO 131. C. Dorsal (?) view. D. Lateral view, with dorsal (?), antisiphuncular side toward the right. E–F. Estonioceratid gen. et sp. indet.A., FMNH-P30342, from bed PO 7.5. E. Lateral view with ventral, prosiphuncular side toward the right. F. adoral view with preserved siphuncular perforation. G. Order, gen. et sp. indet. B, FMNH-P30424, from bed 4.8., lateral view with ventral, prosiphuncular side toward the right. Scale bar = 10 mm for all figures.