Dalecarlioceras bodense Frye, 1987

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 : 86

Dalecarlioceras bodense Frye, 1987

Fig. 34D–F

Dalecarlioceras bodense Frye, 1987: 90–92, fig. 5a–b.

Diagnosis

Rapidly enlarging, large Dalecarlioceras with compressed conch cross section; mature body chamber gibbous with maximum width and height at mid-length of ca 65–70 mm, aperture compressed, unconstricted with well-defined hyponomic sinus; mature body chamber in lateral view with straight dorsal profile and convex ventral side throughout its length; siphuncle small and situated close to the venter. (Adopted from Frye 1987.)

Material examined

ESTONIA • 1 spec.; Paluküla quarry; Kõrgessaare Formation, Vormsi Regional Stage; GIT 426-1099 • 1 spec.; Saaremõisa ( Lyckholm ); Kõrgessaare Formation , Vormsi Regional Stage; TUG 1745-213 .

Type locality and horizon

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

Description

The better-preserved of the two specimens is TUG 1745-213 ( Fig. 34A–B ); it is a mold of a complete mature body chamber and one chamber of the phragmocone. The specimen is slightly deformed. At the base of the body chamber, the conch height and width are 58 mm and 57 mm, respectively (CHI = 1.02). The cross section is nearly circular, with a slightly narrower margin on the prosiphuncular side. The length of the body chamber is 56 mm. In lateral view, the body chamber is nearly straight with convex margins on the pro- and antisiphuncular sides. Deformation during diagenesis has caused the antisiphuncular margin to be more curved than the prosiphuncular side. The greatest height is reached at ca mid-length of the body chamber with 66 mm. The peristome is slightly constricted with a height of 65 mm. The peristome is too poorly preserved to recognize the hyponomic sinus if present. At the base of the body chamber, traces of a thin, ca 5 mm wide, oncomyarian band of muscle-scars is preserved. The preserved chamber of the phragmocone is 5 mm long. The sutures are straight and directly transverse. The septal foramen is ca 1 mm distant from the conch margin and 6 mm in diameter (RSH = 0.09, RSP = 0.02).

The second specimen is a poorly preserved portion of a body chamber and one chamber of the phragmocone with a conch height of 60 mm at the base of the body chamber and a maximum height of 63 mm at the mid-length of the body chamber. The preserved length of the body chamber is 47 mm. The conch cross section of the specimen was apparently sub-circular.

Remarks

The two specimens described above can be assigned to D. bodense based on the similarities of the conch shape and dimensions with the types of this species.

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.