Cameroceras regulus ( Eichwald, 1860 )

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 : 14-15

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.

Subclass Orthoceratoidea Teichert in Teichert & Yochelson, 1967

Order Actinocerida Teichert, 1933

Family Armenoceratidae Troedsson, 1926

Figures

Fig. 5. Endocerida of the Vormsi–Pirgu regional stages, Estonia. A–B. Cameroceras hasta (Eichwald, 1857). A. Specimen TUG 42-373 from Saaremõisa (Lyckholm) old quarry, Vormsi Regional Stage, dorsal view. B. Dorsal view of the deformed specimen TUG 1745-240 from Saxby old quarry, Pirgu Regional Stage. C. Cameroceras regulus (Eichwald, 1860), polished median section of specimen TUG 939-75 from Nõmmeküla quarry, Vormsi Regional Stage. Scale bars = 10 mm for all figures, same scale in A–B.