Mecynoceras? polonicum (Gürich, 1896) from the Cheiloceras Zone, Early Famennian, Łagow - left wall of the Dule gorge, Poland; adult living chamber in dorsal (a) and septal (b) views, and medial section through a phragrnocon (c), ZPAL N/395.

Mecynoceras? polonicum (Gürich, 1896), Cheiloceras Zone, Early Farnennian, Poland. 1. Holorype in venual (a ) and latera l (b) views; Łagów, probably left wall of the Dule gorge (labelled as "lnturnescens Stufe"). 2 . Longitudinal section through a specimen from Kadzielnia. 3.  Adult specimen in dorsal (a) and lateral (b) views; Kadzielnia. 4 . Two oblique sections through a specimenfrom Żbik gorge at Dębnik, Cracow region.

Mecynoceras? polonlcum (Gürich, 1896) from the Cheiloceras Zone, Famennian, Holy Cross Mts., Poland; reconstructed adult shell in lateral and ventral views, and the outline of its aperture (a); longitudinal section through the siphuncle of a specimen from Kielce-Kadzielnia (b);  longitudinal section through a juvenile siphuncle of a specimen from Jablonna, bed J. 6.

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  possibly attributable to the species show a considerable change 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 elongated 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, Jabłonna, Lagow and Żbik gorge by Dębnik, Cracow area, Poland.

Zasięg czasowy

Early Famennian Cheiloceras Zone (Intumescenskalk of Gürich).

Materiały muzealne

UWR 2109
ZPAL N/234, 235, 356, 381, 382

Literatura

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