Dalecarlioceras sp.

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 : 88-89

Dalecarlioceras sp.

Fig. 34C

Material examined

ESTONIA • Vohilaid Island, Vohilaid shore (E); Adila Formation, Pirgu Regional Stage; GIT 878-250.

Description

GIT 878-250 is a fragment of a phragmocone with part of the body chamber, in which details of the siphuncle are well-preserved. The conch increases in height from 35 mm to 49 mm over 31 mm (angle of expansion 25°). At a height of 38 mm, its width is 30 mm (CHI = 1.27), and the conch cross section is ovate with a slightly narrower margin on the prosiphuncular side. The preserved part of the body chamber is 40 mm long. In lateral view, the conch is nearly straight with a convex margin on the prosiphuncular side and a straight margin at the antisiphuncular side, which is slightly convex near the adoral end of the body chamber. The sutures are straight and directly transverse, 6 mm apart where the conch height is 49 mm (RCL = 0.12). The siphuncle is close to the conch margin, ca 3 mm in diameter where the conch height is 35 mm (RSH = 0.09). The siphuncular segments are expanded within the chambers, with their greatest width near the adoral end of the segments.

Remarks

The near mature size of this specimen is indicated by the convex shape of its antisiphuncular body chamber margin. The fragmentary preservation of the specimen does not permit species level determination.

Figures

Fig. 34. Dalecarlioceras Frye, 1987 of the Vormsi–Pirgu regional stages, Estonia. A–B. Dalecarlioceras constrictum Frye, 1987, specimen GIT 878-251, from Hosholm shore (tower), Vormsi Island, Pirgu Regional Stage. A. View of the prosiphuncular side. B. Lateral view. C. Dalecarlioceras sp., specimen GIT 878-250, from Hosholm shore (tower), Vormsi Island, Pirgu Regional Stage, lateral view. D–F. Dalecarlioceras bodense Frye, 1987, specimen TUG 1745-213, from Saaremõisa (Lyckholm), Vormsi Regional Stage. D. Adapical view. E. Lateral view. F. View of the antisiphuncular side. Scale bar = 20 mm in all figures, same scale in A–C, and in D–F.