Tainionautilus Mojsisovics 1902

Genus Tainionautilus Mojsisovics, 1902 Type species Nautilus transitorius Waagen, 1879; subsequent designation by Diener (1915). Diagnosis Genus of the family Tainoceratidae with subinvolute or subevolute conch; whorl profile usually subquadrate with shallow midventral longitudinal groove. Umbilical margin usually pronounced and subangular in the intermediate stage, but rounded in the adult stage. Sculpture with blunt ribs on flanks and outer part of the venter; ribs sometimes forming nodes. Suture line with shallow external lobe and broadly rounded lateral lobe. Siphuncle small with subcentral position ventrad of septum centre. Included Permian species Pakistan (Waagen 1879; Reed 1931): Nautilus transitorius Waagen, 1879, Changhsingian, Salt Range; Nautilus Wynnei Waagen, 1879, Changhsingian, Salt Range; Tainoceras Noetlingi var. subglobosa Reed, 1931, Wuchiapingian, Salt Range; Dolomites (Mojsisovics 1869; Caneva 1906): Nautilus fugax Mojsisovics, 1869, Changhsingian; Pleuronautilus Darini Caneva, 1906, Changhsingian; NW Iran (this paper): Tainionautilus deinceps sp. nov., Changhsingian. Remarks Tainionautilus differs from Tainoceras mainly in the absence of the ventral row of nodes. In Tainionautilus, the ventrolateral nodes have been modified into radial, curved ribs directed posteriorly on the venter. Tainionautilus may be one of the genera of Palaeozoic nautiloids that survived the mass extinction at the Permian–Triassic boundary. In addition to the few species from the Late Permian, the species T. trachyceras (Frech, 1905) from Early Triassic strata of the Salt Range was mentioned by Frech (1905). Brühwiler et al. (2012) mentioned this species from the Fleminigites nanus Beds of the Smithian stage.