New records of the Late Carboniferous ammonoid genus Eoshumardites in the Kolyma–Omolon Region, and notes on the evolution of Eoshumarditidae

Abstract

A new species, Eoshumardites popowi Kutygin sp. nov., is described from the Upper Carboniferous of the upper reaches of the Paren’ River in the Gizhiga Province of the Kolyma–Omolon Region. The ontogeny of the sutural and shell morphology of the new species is described. In the level of sutural organization, E. popowi occupies an intermediate position between E. lenensis (Popow) and E. sublenensis Klets. It has been suggested that Eoshumardites evolved from the genus Syngastrioceras rather than Aktubites and, on this basis, a new monotypic endemic family, Eoshumarditidae, has been proposed. This family existed in the Kasimovian synchronously with members of the family Parashumarditidae.