Beloitoceras siljanense Frye, 1987

Figs 29C, 30A

Beloitoceras siljanense Frye, 1987: 86–88, figs 3e–f, 4, 6c.

Beloitoceras siljanense – Kröger 2013: 20, figs 9c–d, 11, tab. 2. ― Pohle et al. 2022: fig. 2.

Diagnosis

Beloitoceras with compressed cross section; in longitudinal section, antisiphuncular conch margin nearly straight approaching mature peristome; angle of expansion of phragmocone typically more than 17°; mature conch with maximum height and width at peristome. (Adopted from Frye 1987.)

Material examined

ESTONIA • 1 spec.; Haapsalu holm; Adila Formation, Pirgu Regional Stage; TUG 939-56 .

Type locality and horizon

Kallholn, Dalarna, Sweden; Boda Limestone, late Katian.

Description

The specimen is a fragment of a phragmocone with a conch height that increases from 20 mm to 29 mm and respective conch width increasing from 13 mm to 21 mm (angle of expansion = 18°). The conch cross section is oval compressed with narrower prosiphuncular side (CHI: 1.4–1.5). The conch surface is not preserved. The sutures form shallow lateral lobes and rounded saddles on the venter and dorsum. Mid-laterally, the sutures are 3.3 mm apart where the conch height is 24 mm (RCL = 0.14). The septal necks are cyrtochoanitic. The siphuncle is relatively narrow, and slightly expanded within the chambers (Fig. 29C)

Remarks

This specimen can be identified as B. siljanense because of the characteristic straightened dorsal conch margin as well as of the relatively large angle of expansion.