Mecynoceras  polonicum (GURICH, 1896) from
Cheiloceras Zone. Earl y Famcnnian in  Lagow - left wall of Dule gorge, Poland;
 Adult living chamber in dorsal (a) and septal (b) views, and medial section through a phragrnocon (c), ZPAL N/395.

Mecynoceras  polonlcum (GURICH, 1896) from Chelloceras Zone, Famennian in Poland;

a Reconstructed adult shell in lateral and ventral views,and the outline of its aperture;

b longitudinal section through a siphuncle, ZPAL N/381, Kielce-Kadzielnia;

c longitudinal section through a juvenile siphuncle, ZPAL N/234. Jablonna, bed J. 6,Holy Cross Mts.

Diagnoza

Slightly exogastrically curved shell with siphunc1e situated somewhat dorsally of center; radial lamellae developed only at septal necks; connecting rings inflated.

Porównanie

M.  polonicum differs from its closest relative, M. rex, in the centro-dorsal siphuncle with considerably inflated rings, more streamlined shell, and the weakly exogastric
curvature. Some juvenile shell fragments from Jablonna (ZPAL N/234, 235) possibly attributable to M.  polonicum are indicative of considerable changes in siphuncular structure during ontogeny. The outline of juvenile connecting rings shows more resemblance
to M. rex than does the adult form; the juvenile rings are much more elongate than the adult ones and, as judged from the poorly preserved specimens, the radial lamellae extend also on the connecting rings.

Autekologia

Występowanie geograficzne

Kadzielnia, Jablonna, Lagow and Zbik gorge by Debnik, Cracow area, Poland.

Zasięg czasowy

The species has been recorded from the Early Famennian Cheiloceras Zone of Kadzielnia, Jablonna, and Lagow (lntumescenskalk of GURICH), as well as from coeval strata of the Zbik gorge by Debnik, Cracow area, Poland.

Materiały muzealne

Literatura

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