Gonatocyrtoceras holzapfeli (Sobolew, 1912), reconstructed adult shell in lateral and ventral views, and the outline of its aperture (a);  longitudinal section through the siphuncle close to the apex and at the mid-length of a phragmocone (b); Cheiloceras Zone, Famennian, Łagów-Dule, Holy Cross Mts, Poland:

Diagnoza

Bulgy, weakly exogastricallycurved shell with mature living chamber declining in transverse diameter; aperture with deep ventral sinus and a pair of ventral lappets.

Porównanie

G. holzapfeli differs from its congeners in its more weakly curved shell (in average) and supposedly also in the outline of the mature aperture.
Variability. - There is great variation, mostly in shell curvature and the shape of the living chamber (length, cross section, and narrowing). The boundary between G. holzapfeli and G. guerichi is indistinct and there are specimens that can hardly be identified

Autekologia

Występowanie geograficzne

The species occurs at Dule in association with Paratornoceras lentiforme and Cheiloceras lagowiense.

Zasięg czasowy

Materiały muzealne

Literatura

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