On Triassic Murchisonia-like gastropods—surviving the end-Permian extinction to become extinct in the Late Triassic

Abstract

High-spired Murchisonia-like slit-band gastropods are an important component of late Paleozoic gastropod faunas. Twenty-seven genera of such gastropods have been reported from the Permian, most of which representing the caenogastropod family Goniasmatidae. Only four genera, Trypanocochlea, Wannerispira, Laschmaspira, and Altadema crossed the Permian/Triassic boundary. Based on the study of newly collected specimens and material from natural history collections, we studied the surviving genera as well as the Triassic recovery of this group. Two new species (Laschmaspira lirata sp. nov. and Altadema hausmannae sp. nov.) and one new subfamily (Cheilotomoninae) are introduced. Murchisonia-like caenogastropods, chiefly Goniasmatidae, were diverse and abundant until the Permian, barely survived the end-Permian extinction, regained a certain generic diversity within the Triassic with the evolution of several new genera but failed by far to regain their Permian generic diversity. This once successful and diverse group shares a similar fate (surviving the end-Permian extinction, a reduced Triassic diversity and extinction during Late Triassic crises) as conodonts, orthoceratids, conulariids, and others. This diversity pattern does not qualify for the “Dead Clade Walking” phenomenon, i.e., the extinction shortly after a major mass extinction event (survival without recovery) because they have survived for ca. 30 Ma (at least until the Norian) and even produced a number of new genera. The exact time of their extinction is unknown but there are no safe Rhaetian occurrences. Their extinction is part of a long-term selective trend against the character “shell-slit”.

Keywords

• gastropoda
• goniasmatidae
• diversity
• recovery
• end-permian extinction
• triassic
• italy
• austria