Danoceras sp. A

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 : 66

Danoceras sp. A

Fig. 27D

Material examined

ESTONIA • Vormsi Island, Hosholm shore (tower locality); Adila Formation , Pirgu Regional Stage; GIT 878 -269.

Description

The specimen comprises parts of a nearly complete mature body chamber and four chambers of the phragmocone, lacking the outer shell. At the base of the body chamber, the conch height and width are 34 mm and 29 mm respectively (CHI = 1.12). The conch cross section is oval, compressed with narrow dorsal and ventral margins, the ventral (prosiphuncular) margin is narrower. The body chamber is 28 mm long, very slightly exogastrically curved. At its base, a narrow band of oncomyarian, buttressed muscle scars occur. A wide, inconspicuous constriction occurs ca 5 mm adapically from the peristome. The peristome is incompletely preserved, and the hyponomic sinus is not seen. At the peristome, the conch height is 32 mm. The sutures form shallow lateral lobes. The adoralmost two sutures are crowded. Adapically, the sutures are 5 mm apart, where the conch height is 33 mm. The siphuncle is preserved near the conch margin. The septal foramen is ca 2 mm wide and the siphuncular segments apparently are relatively narrow, Danoceras -like.

Remarks

This single specimen differs from all known species of Danoceras in its small mature size in combination with a relatively long and tubular body chamber. However, based on this single, fragmentary preserved specimen the erection of a new species is not possible.

Figures

Fig. 27 (next page). Breviconic cephalopods from the Vormsi–Pirgu regional stages, Estonia. A. Dowlingoceras kallholnense Frye, 1987, specimen GIT 878-247, from Hosholm shore (tower),Vormsi Island, Pirgu Regional Stage, lateral view. B–C, E. Dowlingoceras sp., specimen GIT 878-249, from Vohilaid shore (E), Vohilaid Island, Pirgu Regional Stage. B. Lateral view. C. View of antisiphuncular side. D. Danoceras sp. A., specimen GIT 878-269, from Hosholm shore (tower), Vormsi Island, Pirgu Regional Stage, lateral view.E. Adoral view. F. Rizosceras teres sp. nov., holotype TUG 1745-188, from Saaremõisa (Lyckholm), Vormsi Regional Stage, lateral view. G–H. Kallholnoceras sp. G. GIT 878- 323, from Hosholm shore (tower), Vormsi Island, Pirgu Regional Stage, lateral view. H. Specimen GIT 878-233, from Vohilaid shore (E), Vohilaid Island, Pirgu Regional Stage, lateral view. I. Dowlingoceras tornense sp. nov., holotype GIT 840-254, from Hosholm shore (tower), Vormsi Island, Pirgu Regional Stage, lateral view. J. Dowlingoceras sp. B, specimen GIT 47-866, from Vohilaid shore (E), Vohilaid Island, Pirgu Regional Stage, lateral view. K. Diestoceras sp., specimen GIT 878-252, from Hosholm shore (tower), Vormsi Island, Pirgu Regional Stage, lateral view. L. Diestoceras stensioei (Troedsson, 1926), specimen GIT 426-987, from Piirsalu quarry, Pirgu Regional Stage. M. Diestoceratidae gen. et sp. indet., specimen TUG 1745-192, from Salu, Pirgu Regional Stage, view from antisiphuncular (?) side. N. Diestoceras stensioei (Troedsson, 1926), specimen GIT 840-264, from Hosholm shore (tower), Vormsi Island, Pirgu Regional Stage, lateral view. Scale bar = 10 mm, same scale in all figures.