Opis

Diagnosis. — Suture with clearly delimited semicircular flank lobe; more or less involute conch tending to develop acute venter. 

Remarks. — These are clymenias with deeply involute conchs and acute venter. Advanced members of the clade developed periodic narrow ‘horns’ along the ventral keel. Among species from the Holy Cross Mountains, several are transitional between such forms and Costaclymenia. To preserve clarity of classification it seems necessary to extend the range of this family to encompass also those ancestral forms that are provisionally classified here in Nanoclymenia. It is only a matter of convenience whether to separate this clade from the family Costaclymeniidae, here restricted to forms with a tabulate venter, or not. An acute venter alone is a poor diagnostic character for high rank ammonoid taxa, and this feature appeared independently several times in the evolution of clymenias. 

Synonimy

Zasięg czasowy

Literatura

Dzik, J. 2006. The Famennian "Golden Age" of conodonts and ammonoids in the Polish part of the Variscan sea. Palaeontologia Polonica 63, 1-359.