Cochlioceras roemeri Dzik, 1984 from Baltic erratic boulders, Rozewie, Poland; reconstruction of mature shell (a), longitudinal section through the siphuncle (b); cameral and siphuncular deposits in the phragmocone (c). 

Cochlioceras roemeri Dzik, 1984 from Baltic erratic boulders, Rozewie, Poland. 1. Medial section through adapical part of the phragmocone. 2. Medial section through adapical part of the phragmocone,  possibly Volkhovian. 3. Adult specimen in lateral (a) and ventral (b) views. 4. Medial section through the phragmocone, from erratic boulder E-262, E. reclinatus Zone, Lasnamagian, Międzyzdroje, Poland. 5. Medial section through the holotype phragmocone (a, b). 6. Medial section through the phragmocone; note small diameter of the apical part.

Diagnoza

Ventral siphuncle up to one third of the shell diameter, filled with deposits in its apical part; siphuncular deposits in form of massive rod at ventral side, with flat rings at septal necks; cameral deposits well developed.

Porównanie

C. roemeri does not differ externally from its congeners. Its uniqueness consists in its much wider siphuncle. It differs from C. burchardi also in its siphuncle lying a little away from the shell wall and, consequently, in its straight septal suture. Any comparison to the siphuncular structure of other congeneric species is impossible because of lack of data.

Autekologia

Występowanie geograficzne

Baltic erratic boulders, probably also Estonia

Zasięg czasowy

E. reclinatus Zone (Folkeslunda Limestone), but never in association with its coeval congener, C. burchardi.
One specimen was found in a boulder indistinguishable in lithology from those of the Paroistodus originalis Zone(untere rote Vaginatenkalk; Volkhovian).

Materiały muzealne

ZPAL N/001, 004, 006, 009, 010, 011

Literatura

Dzik, J. 1984. Phylogeny of the Nautiloidea. Palaeontologia Polonica 45, 1-255.