Diagnoza

After SOBOLEW: "Horn-like curved shell elliptic in cross section, with the long axis running dorso-ventrally. Shell smooth, with indistinct transverse str'ation. Longitudinal
ribs discernible in moulds. Air chambers low. Siphuncle at the inner (concave) side."

Porównanie

SOBOLEW (1912) figured one relatively large but incomplete specimen. Some additional specimens collected by myself confirm the correctness of this diagnosis. The "longitudinal ribs discernible in moulds" of SOBOLEW are the attachment scars of retractor muscles.
The dorsal (convex) side of the shell is a little flattened, whereas the ventral side is parabolic in outline. The living chamber is cylindrical without any significant terminal modifications, with a ventral rudimentary funnel sinus. The connecting rings are recrystallized. There are no deposits. The intrapopulation variability consists in shell size and coiling.
The phylogenetic relations of this species are unclear. It may be a descendant of Protophragmoceras (Silurian; Discosorida) or Devonocheilus (Late Devonian; Oncoceratida).

Autekologia

Występowanie geograficzne

Zasięg czasowy

Materiały muzealne

Literatura

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