Tirolonautilus Mojsisovics 1902

Genus Tirolonautilus Mojsisovics, 1902 Type species Nautilus crux Stache, 1877, subsequent designation by Kummel (1953). Diagnosis Genus of the family Tainoceratidae with subinvolute or subevolute conch; whorl profile trapezoidal with concave venter and subangular ventrolateral shoulder. Flanks convergent or nearly parallel, umbilical margin broadly rounded. Sculpture with one row of longitudinally elongated ribs on the ventrolateral shoulder; flanks smooth or with weak ribs. Suture line with moderately deep, rounded external lobe and broadly rounded lateral lobe. Siphuncle small with subcentral position ventrad of septum centre. Included Permian species Southern Europe and Alps (Stache 1877; Merla 1930; Schréter 1974): Nautilus crux Stache, 1877, Changhsingian, Dolomites; Nautilus sebedinus Stache, 1877, Changhsingian, Dolomites; Nautilus Hoernesi Stache, 1877, Changhsingian, Dolomites [synonym of Tirolonautilus sebedinus (Stache, 1877)]; Metacoceras discoideum Merla, 1930, Changhsingian, Dolomites [synonym of Tirolonautilus crux (Stache, 1877)]; Tirolonautilus bicristatus Merla, 1930, Changhsingian, Dolomites [synonym of Tirolonautilus sebedinus (Stache, 1877)]; Tirolonautilus lativentralis Schréter, 1974, Changhsingian, Bűkk Mountains; Tirolonautilus cruciformis Schréter, 1974, Changhsingian, Bűkk Mountains. Saudi Arabia (Chirat et al. 2006): Tirolonautilus feltgeni Chirat et al. 2006, Changhsingian. Remarks Tirolonautilus can be identified by the distinctly trapezoidal whorl profile with the sulcate venter, the longitudinal ribs on the ventrolateral shoulder and the absence of sculpture on umbilical margin. The genus has a similar morphology to Tainionautilus, but the whorl profile is usually more compressed and the venter is more deeply concave. Tirolonautilus is a genus that has only been found in a few regions. Several species have been described from the Bellerophon Limestone of the Dolomites, including those by Stache (1877), Merla (1930), Posenato & Prinoth (2004) and Prinoth & Posenato (2007). Additionally, reports of Tirolonautilus have come from Saudi Arabia (Chirat et al. 2006) and Azerbaijan (Kotlyar et al. 1983).