Pseudogzheloceras—a new genus of Carboniferous nautilids (Cephalopoda) from Europe and North Africa

Abstract

Analysis of morphology, stratigraphic and geographic distribution of the group of nautilid species, mainly from the Westphalian of Western Europe, and the Bashkirian and Moscovian of the Donets Basin (Eastern Ukraine) made it possible to establish a new genus Pseudogzheloceras Dernov, gen. nov. This genus includes tainoceratids with an evolute discoidal conch. The umbilical perforation is present. Cross section of the adult whorls is sub-square or almost rectangular. Surface ornamentation is represented by large transverse ribs on the flanks. Siphuncle is sub-central or is situated between the venter and the centre of the whorl (the position of the siphuncle is not known for the most species). Suture line has ventral, lateral and dorsal lobes; sometimes a lobe or saddle is present on the umbilical area. The new genus differs from the genus Gzheloceras by the sub-square or almost rectangular whorls cross section and coarser surface ornamentation. Pseudogzheloceras Dernov, gen. nov. is distinguished from the genus Parametacoceras Miller et Owen, 1934 (Pennsylvanian of North America, Westphalian of Western Europe, Moscovian of the Donets Basin and Moscow Syneclise) by the presence of transverse ribs on the flanks of the body chamber. The new genus includes the following species: Pseudogzheloceras costatum (Hind, 1905) comb. nov., Ps. falcatum (Sowerby in Prestwich, 1840) comb. nov., Ps. rotifer (Salter, 1864) comb. nov., Ps. postcostatum (Bisat, 1930) comb. nov., Ps. donetzense (Kruglov in Librovitch, 1939) comb. nov., Ps. orthocostatum (Kruglov in Librovitch, 1939) comb. nov., Ps. tacitum (Shimansky, 1957) comb. nov., and, possibly, Ps. maklai (Shimansky, 1967) comb. nov. These species had previously belonged to the genera Pleuronautilus, Metacoceras, Huanghoceras, and Gzheloceras. The new genus is known from the Westphalian of Western Europe and North Africa, Pennsylvanian of the Donets Basin and Moscow Syneclise, and possibly the Upper Pennsylvanian of the Fergana Depression. The research results have a great importance for studying the relationships between nautilid faunas of Carboniferous palaeobasins, as well as clarifying the taxonomy and phylogeny of non-ammonoid Carboniferous cephalopods.