Diagnoza
Relatively short, exogastrically curved conchs with almond-shaped cross section, ventral side sharp, and thick growth lines, the latter being arched in outline and running obliquely, forming a sharp sinus at the ventral side. Porównanie
ROEMER (1861) erected the species C. sinuososeptatum from two fragmentary specimens, one of which (figured in the present paper) was exogastrically curved, while the
other was almost straight. When erecting the new species B. heterocurvatum, diagnosed to include both endogastrically and exogastrically curved forms, STRAND (1934) included only the exogastrically curved specimen of ROEMER and designated the other specimen as the holotype of C. sinuososeptatum. SWEET (1959a) subsequently restricted the range of B. heterocurvatum
to exogastric forms only, and erected a new species, Parryoceras strandi, for the endogastrically curved specimen of STRAND. Two exogastrically curved specimens figured by STRAND differ
widely in the size of their mature living chamber (32 and 21.5 nun in diameter). ROEMER'S only preserved specimen attains 32 mm in diameter of immature phragmocone, which resembles the holotype of B. heterocurvatum. 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. As
illustrated by STRAND, 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. To solve this problem, the holotype of R. sinuososeptatum is needed . Autekologia Występowanie geograficzne Zasięg czasowy Materiały muzealne Literatura
Dzik, J. 1984a. Phylogeny of the Nautiloidea. Palaeontologia Polonica 45, 1-255 | 