Deckeroceras balticum, Kröger, 2025

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 : 94-96

publication ID	https://doi.org/10.5852/ejt.2025.978.2801
publication LSID	lsid:zoobank.org:pub:422E6F06-B4C8-4840-854C-811145D88B32
persistent identifier	https://treatment.plazi.org/id/93268783-962B-7079-FDAE-FC33FC73FE4C
treatment provided by	Plazi (2025-03-07 10:46:31, last updated 2025-03-07 11:32:00)
scientific name	Deckeroceras balticum
status	sp. nov.

Treatment

Deckeroceras balticum sp. nov.

urn:lsid:zoobank.org:act:05BFB795-1743-407B-8866-5030650628D2

Fig. 36A View Fig

Winnipegoceras sp. – Teichert 1930: 294, pl. 8 fig. 23.

Diagnosis

Deckeroceras with mature conch height of ca 65 mm, nearly circular to slightly compressed conch cross section at mature body chamber; mature body chamber strongly curved and contracted.

Etymology

Refers to type region.

Type material

Holotype

ESTONIA • Vohilaid Island , Vohilaid shore (E): Adila Formation, Pirgu Regional Stage; GIT 878-227 View Materials .

Description

The specimen is a fragment of a mature body chamber and five chambers of the phragmocone. The outer shell of the specimen is not preserved. At the base of the body chamber, the conch is ca 65 mm high. At the apical end of the specimen, 32 mm from the base of the body chamber, the conch height is 49 mm, and the conch cross section was nearly circular or slightly compressed. The angle of expansion of the phragmocone is ca 28°. The sutures are directly transverse and 8 mm apart where the conch height is 49 mm (RCL = 0.15). The siphuncle and the septal foramen are either not preserved or not visible. The body chamber is strongly curved and ca 65 mm long. In lateral view the convex side of the conch is much more strongly curved than the concave side, resulting in a relatively narrow mature aperture (height ca 40 mm).

Remarks

A specimen from Piirsalu, Estonia, figured and described in Teichert (1930), is identical in size and shape, and can be assigned to the same species, based on the knowledge of this more complete specimen, described herein.

Comparison

The two other species of this genus ( D. adaense , D. clermontense Foerste 1935b , known from the type-region and from the Elgin Member of the Maquoketa Shale, Iowa, USA) have smaller adult sizes

(maximum conch heights 40–50 mm), and in D. clermontense Foerste, 1935a the mature body chamber is less strongly curved.

Order Ascocerida Kuhn, 1949

Family Ascoceratidae Barrande, 1867

References

Barrande J. 1867. Systeme Silurien du centre de la Boheme, I. ere partie, Recherches Paleontologiques, vol. II, Classe de Mollusques, Ordre des Cephalopodes, ser. 1. Privately published, Praha. https://doi.org/10.5962/bhl.title.14776

Eichwald E. D. von 1860. Lethaea Rossica ou Paleontologie de la Russie. Premiere Section de l'ancienne Periode, contenant la Flore de l'ancienne Periode et la Faune jusqu'aux Mollusques. Schweizerbart, Stuttgart. https://doi.org/10.5962/bhl.title.52391

Foerste A. F. 1935 b. The cephalopods of the Maquoketa shale of Iowa. Denison University Bulletin, Journal of the Scientific Laboratories 30 (5): 231-257.

Foerste A. F. 1935 a. Big Horn and related cephalopods. Denison University Bulletin, Journal of the Scientific Laboratories 30: 1-96.

Hyatt A. 1900. Cephalopoda. In: Zittel K. A. V. (ed.) Textbook of Paleontology, 1. Second Edition, Translated and Edited by C. R. Eastmann: 502-592. Macmillan and Co, London.

Kuhn O. 1949. Lehrbuch der Palaozoologie. Schweitzerbart, Stuttgart.

Teichert C. 1930. Die Cephalopoden-Fauna der Lyckholm-Stufe des Ostbaltikums. Palaontologische Zeitschrift 12: 264-312. https://doi.org/10.1007/BF03044452

Figures

Fig. 36. Ascoceratidae Barrande, 1867 and Uranoceratidae Hyatt, 1900 of the Vormsi–Pirgu regional stages, Estonia. A. Deckeroceras balticum sp. nov., holotype GIT 878-227, from Vohilaid shore (E), Vohilaid Island, Pirgu Regional Stage, lateral view. B–C. Redpathoceras saxbyense sp. nov., holotype GIT 426-346, Saxby shore (N),Vormsi Island, Vormsi Regional Stage.B. View of the prosiphuncular side. C. Lateral view. D. Schuchertoceras deformis (Eichwald, 1860), specimen GIT 878-191, from Vohilaid shore (E), Vohilaid Island, Pirgu Regional Stage, oblique lateral view. E. Redpathoceras saxbyense sp. nov., paratype GIT 76-97, from Moe stratotype outcrop, Pirgu Regional Stage.F–G. Schuchertoceras deformis (Eichwald, 1860), specimen TUG 2-734, Uuemõisa, Läänemaa, Pirgu Regional Stage. F. View of the antisiphuncular side. G. Lateral view. Scale bar = 20 mm, same scale in all figures.