Beloitoceras (?) sp., Foerste, 1924

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 : 83-84

Beloitoceras (?) sp.

Fig. 28F, I–J

Material examined

ESTONIA • 1 spec.; Raplamaa, Pirgu River outcrops; Adila Formation, Pirgu Regional Stage , GIT 426- 1081 .

Description

The specimen is a fragment of a nearly complete body chamber and part of a phragmocone. The conch is slightly exogastrically curved. The height and width of the 23 mm long phragmocone are 20–23 mm and 13.5–15 mm, respectively (angle of expansion = 8°; CHI = 1.4–1.5). The septa form wide lateral lobes and pointed angular saddles on the prosiphuncular side. The siphuncle is nearly marginal, empty and the septal foramen has a diameter of 1 mm at the apical end of the specimen (RSH = 0.05). The body chamber is slightly gibbous, reaching its greatest height of 24 mm at ca mid-length of the preserved part. Its preserved length is ca 25 mm.

Remarks

The relatively long and slender (but still gibbous) body chamber distinguishes this specimen from known species of Beloitoceras . Its uniqueness would justify the erection of a new species and genus. Alternatively, the specimen is related to Richardsonoceroides Kröger, Zhang & Isakar, 2009 , or Richardsonoceras priscum ( Eichwald, 1860) (see below). However, knowledge about the shape of the complete mature body chamber and information on the siphuncle is needed for a definitive determination. The specimen therefore is left in open nomenclature.

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.