Richardsonoceras sinuososeptatum (Roemer, 1861)
Phragrnocone of a subadult specimen in ventral (a), lateral (b), and adapertural (c ) views, and its medial section (d), UWR 32305; paratype; Ashgill, erratic boulder, Zawidowice, Poland .

Rlchardsonoceras slnuososeptatum (ROEMER, 1861); UWR 3230s; paratype, erratic boulder, Ashgillian (1),Zawidowice, Poland;

a Reconstruction of the subadult shell;

b longitudinal section through the siphuncle.

Diagnoza

Relatively short, exogastrically curved conchs with almond-shaped cross section, ventral side sharp; thick growth lines arched in outline and running obliquely, forming a sharp sinus at the ventral side.

Porównanie

Roemer's only preserved specimen attains 32 mm in diameter of immature phragmocone, which resembles the holotype of Beloitoceras heterocurvatum Strand, 1935. There is a close resemblance also in the aperture outline, as judged from the traces of growth lines discernible on the mould of the phragmocone. The mature living chamber of B. heterocurvatum declines in diameter adaperturally, as in the type species of the genus. The holotype of B. heterocurvatum agrees with the paratype of C. sinuososeptatum in the shape of connecting rings. One may thus suppose that the specimens are conspecific.
The specimen illustrated in the present paper is the only preserved original of C. sinuososeptatum. The other specimen figured by Roemer was lost during World War n. Its true specific assignment cannot be demonstrated but, due to the imprecision of Roemer's drawings, there is no certainty that the two specimens belonged to distinct species.

Autekologia

Występowanie geograficzne

Zasięg czasowy

Materiały muzealne

Literatura

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

Strand, T. 1935. The Upper Ordovician cephalopods of the Oslo area. Norsk Geologisk Tidsskrift 14, 1-117.