Multiceratoidea, Mutvei, 2013

Kröger, Björn, 2025, The Lyckholm acme of cephalopods - Review of the late Katian (Vormsi-Pirgu regional stages) Ordovician cephalopods of Estonia, European Journal of Taxonomy 978, pp. 1-169 : 145

Multiceratoidea gen. et sp. indet. C

Fig. 28K–L

Material examined

ESTONIA • 1 spec.; Vormsi Island , Hosholm shore (tower locality); Adila Formation, Pirgu Regional Stage; GIT 878-234 .

Description

The specimen is an exogastrically curved fragment of a body chamber and one chamber of the phagmocone. The outer shell is not preserved but the surface was apparently smooth or ornamented with faint transverse lirae. At the base of the body chamber, the conch height and width are 17 mm and 14 mm, respectively (CHI = 1.21). The conch cross section is oval compressed with a narrower conch margin on the prosiphuncular side. The conch has an angle of expansion of 18°. The body chamber has a preserved length of ca 15 mm. In lateral view, both conch margins are curved, convex on the prosiphuncular and concave on the antisiphuncular side. The two preserved septa are 2.2 mm apart (RCL = 0.13), and their sutures form shallow lateral lobes. The siphuncle is located near the convex margin of the conch with a septal foramen which is too poorly preserved to be measured.

Remarks

The fragmentary character of this specimen does not allow further determination. It is not clear whether this fragment represents a mature individual or a juvenile specimen. Cyrtorizoceras tenue Strand, 1934 has a similar angle of expansion (18°) and a CHI of 1.25 but is too poorly known to be compared with the specimen described herein.

Figures

Fig. 28. Graciloceratidae Flower, 1950 and Oncoceratidae Hyatt, 1884 of the Vormsi–Pirgu regional stages, Estonia. A–D. Hiiumoceras hiiuense gen et sp. nov., paratype GIT 426-421, from Paluküla, Hiimuaa Island, Vormsi Regional Stage. A. Lateral view. B. View of antisiphuncular side. C. View of prosiphuncular side. D. Adapical view. E. Rizosceras teres sp. nov., holotype TUG 1745-188, from Saaremõisa (Lyckholm), Vormsi Regional Stage, view of prosiphuncular side with details of siphuncle visible. F, I–J. Beloitoceras (?) sp., specimen GIT 426-1081, from Pirgu river outcrops, Raplamaa, Pirgu Regional Stage. F. Lateral view. G–H. Beloitoceras uuemoisense sp. nov., holotype GIT 1745-290, from Uuemõisa, Läänemaa, Pirgu Regional Stage. G. Lateral view. H. View of antisiphuncular side. I. View of prosiphuncular side. J. Adapical view. K–L. Multiceratoidea gen. et sp. indet. C, specimen GIT 878- 234, from Hosholm shore (tower), Vormsi Island, Pirgu Regional Stage. K. Adapical view. L. Lateral view. Scale bar = 10 mm in all figures except E, same scale in A–D, and in F–K. Scale bar in E = 5 mm.