Gatunek typowy
Tumulites varians McCaleb, Quinn et Furnish, 1964

Opis

Shell thick-discoidal to subglobose, moderately involute, usually with narrow umbilicus;  surface is ornamented by a series of transverse sinuous lirae; the sculpture forms umbilical ribs, which curve to form a prominent salient at the position of the first lateral saddle and a rounded sinus across the venter; a narrow shallow ventro-lateral groove is also present at the salient; lirae are mostly bifurcated at the junction of the rib; ribs, numbering about 16 per whorl, diminish in prominence with increase in shell size. 

Synonimy

Zasięg czasowy

Carboniferous; Serpukhovian – Bashkirian

Literatura

McCaleb, J.A.; Quinn, J.H. & Furnish W.M. 1964. The ammonoid family Girtyoceratidae in the southern Midcontinent. Circular of the Oklahoma Geological Survey 67: 1–41.