Latest Triassic bivalves and gastropods from South Germany - implications for the end-Triassic mass extinction and the early evolution of veneroid bivalves

 

Authors: Nützel A, Nose M, Hautmann M

Article in press: Received 1 April 2025; Accepted in revised form 29 July 2025; Online 12 October 2025

Keywords: Kössen Formation, Northern Calcareous Alps, Rhaetian, Euheterodonta, Caenogastropoda, Heterobranchia,

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Abstract

A fossil assemblage of small bivalves and gastropods from the latest Triassic (Rhaetian) Kössen Formation at the Brauneck Mountain in the Bavarian Alps is reported. It consists of the bivalve species Pseudocorbula alpina (Winkler, 1859) and at least three gastropod species including Ampezzopleura brauneckensis sp. nov. and Jurilda stoppanii (Winkler, 1861) comb. nov. The fossils are well-preserved including protoconch preservation in the gastropods and preserved hinges in the bivalves. The gastropod genera Ampezzopleura and Jurilda are reported from the Rhaetian for the first time. Both genera are also known from pre-Rhaetian and post-Triassic strata and hence they survived the end-Triassic mass extinction event. Their occurrence in the Rhaetian fills a gap in their stratigraphic distribution and removes them from the list of Rhaetian Lazarus taxa. The new material of Pseudocorbula alpina (Winkler, 1859) demonstrates a dentition of the AI, AIII, 3b, PI, PIII / AII, AIV, 2, 4b, PII type, which was possibly ancestral to the isocyprinid hinge of early veneroids. Therefore, Pseudocorbula alpina provides insights into the early evolution of the Venerida, which are among the most specious bivalve clades today.