Palaeodawsonocerina, Kroger & Isakar, 2006

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 : 33-34

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/93268783-9656-7007-FD86-FD1DFC7FFE14

treatment provided by

Plazi (2025-03-07 10:46:31, last updated 2025-03-07 11:32:00)

scientific name

Palaeodawsonocerina
status

 

Palaeodawsonocerina ? sp.

Fig. 12K

Material examined

ESTONIA • 1 spec.; Hosholm shore; Adila Formation, Pirgu Regional Stage; TUG 939-78 .

Description

The specimen is a ca 39 mm long, 18–20 mm high, orthoconic fragment (angle of expansion 3°) of a phragmocone with well-preserved shell sculpture. The conch cross section is slightly deformed. The conch is annulated with ca four annulations in a distance equal to the corresponding conch cross section. The annulations are directly transverse. The conch is ornamented with ca 60 fine longitudinal lirae around the circumference and subordinate transverse growth lines or lirae, producing a reticulate pattern (ca 10 transverse lirae per annulation). The septa are only partially preserved, the siphuncle and septal necks are not preserved. The sutures are positioned in the troughs of the annulations and are directly transverse parallel to the annulations.

Remarks

The finely reticulate ornamentation and the general conch shape of this specimen is similar to other species assigned to P. senckenbergi . It differs from the latter in having a wider spacing of its longitudinal lirae (1 mm and 60 lirae around circumference versus five to seven lirae per mm in P. senckenbergi ). The fragmentary preservation of the internal characters leaves the genus level determination questionary because a similar fine reticulate ornamentation is known from Anaspyroceras , and Gorbyoceras (see e.g., Flower 1943b). Possibly, the specimen belongs to the same species as a specimen described by Strand (1934: 21) under G. clathratoannulatum , also ornamented with ca 60 longitudinal lirae.

Order Pseudorthocerida Flower & Caster, 1935

Family Proteoceratidae Flower, 1962

Flower R. H. & Caster K. E. 1935. The cephalopod fauna of the Conewango Series of the Upper Devonian in New York and Pennsylvania. Bulletins of American Paleontology 22 (75): 197-270. Available from https://www.biodiversitylibrary.org/page/30374188 [accessed 20 Jan. 2025].

Flower R. H. 1943 b. Studies of paleozoic Nautiloidea. I: Tissue remnants in the phragmocone of Rayonnoceras. II. Werneroceras in the Devonian of New York. III. A Ohioceras from Virginia. IV. Investigations of actinosiphonate cephalopods. V. New Ordovician cephalopods from Indiana with notes on stratigraphic problems. VI. Annulated orthoceraconic genera of Paleozoic Nautiloids. Bulletins of American Paleontology 28 (109): 1-140. Available from https://www.biodiversitylibrary.org/page/10679031 [accessed 20 Jan. 2025].

Flower R. H. 1962. Part 1, Revision of Buttsoceras, Part 2, Notes on the Michelinoceratida. State Bureau of Mines and Mineral Resources, New Mexico Institute of Mining and Technology, Memoir 10: 1-58. https://doi.org/10.58799/M-10

Strand T. 1934. The Upper Ordovician Cephalopods of the Oslo Area. Norsk geologiske Tidsskrift 14: 1-117.

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