Cameroceras regulus (Eichwald, 1860)

Fig. 5C

Endoceras regulus Eichwald, 1857: 177 .

Orthoceras turris Angelin in Angelin & Lindström, 1880: 6, pl. 6 figs 14–15.

Endoceras iucundum Stumbur, 1956: 181, 182, pl. 1 fig. 4, pl. 2 fig. 1, text-fig. 3.

Endoceras regulus – Eichwald 1860:1248, pl. 46 fig. 8.

Cameroceras regulus – Balashov 1968: 70, 101, pl. 5 fig. 3. — Kröger 2013: 7–8.

Endoceras iucundum – Balashov 1968: 101.

Diagnosis

Orthocones with a slightly depressed conch cross section; angle of expansion less than 5°; ornamented with fine transverse striae; sutures directly transverse, ca seven chambers occur on a distance similar to the conch cross section; siphuncular diameter up to 0.5 of corresponding conch cross section; siphuncle marginal, in contact with shell wall; siphuncular segments slightly concave in lateral view; septal necks holochoanitic. (Adopted from Balashov 1968.)

Material examined

ESTONIA • 1 spec.; Harju County, Nõmmeküla quarry; Kõrgessaare Formation, Vormsi Regional Stage; TUG 939-75 .

Type locality and horizon

Kõrgesaare, Hiiumaa Island, Estonia; Kõrgessaare Formation, Vormsi Regional Stage, late Katian, Ordovician.

Description

Specimen TUG 939-75 is a fragment of a phragmocone with parts of the outer shell preserved. The conch surface is smooth. The conch cross section is circular. The conch has a height of 33–34 mm at a length of 46 mm (angle of expansion = 1.2°). At the conch height of 34 mm the chamber length is 7 mm (RCL = 0.21). The siphuncle is marginally positioned with a diameter of 16 mm where the conch height is 34 mm. The septal necks are holochoanitic and form siphuncular segments, which have in longitudinal view slightly concave outlines (Fig. 5C). The siphuncle is filled with a massive sparitic infill, which preserved no details of the internal structure of the endosiphuncular deposits.

Remarks

The specimen can be identified as a C. regulus based on its large marginal siphuncle and its holochoanitic septal necks.