Original paper

Anisian (Middle Triassic) bivalves from the Dolomites (Italy)

Posenato, Renato

Abstract

The Anisian (Middle Triassic) was an important phase in the evolution of marine biota, because reef-building metazoans re-appeared after the end-Permian mass extinction, and other taxa, such as bivalves, began their Mesozoic adaptive radiation. Anisian bivalves from the Dont Formation (Braies/Prags Group) of the Dolomites (Italy) are here figured and described for the first time. Most of the individuals were found in the fossil-lagerstätte of Monte Prà della Vacca / Kühwiesenkopf, a deposit containing a transported assemblage composed of abundant and well diversified terrestrial plants and marine nektonic and benthonic taxa, which accumulated in a basinal environment. Further bivalves were collected in other parts of the formation, which is more than 200 m thick in this section. Thirteen bivalve species are classified here. The most common, long ranging species are Mysidioptera cainalloi (Stoppani), Neomorphotis compta (Goldfuss), Entolium discites (Schlotheim), Newaagia noetlingi (Frech), Pleuromya cf. musculoides (Schlotheim), P. brevis (Assmann) and Neoschizodus? sp. Others, such as Plagiostoma striatum (Schlotheim) and Pseudoplacunopsis fissistriata (Winckler), have been found only in the plant bearing deposit, or in a fossiliferous horizon located in the upper part of the formation [Parallelodon esinensis (Stoppani), Pteria? sp., Entolium kellneri (Kittl), and Chlamys (Praechlamys) cf. schroeteri (Assmann)].

Keywords

bivalvessystematicsbiostratigraphymiddle triassicdolomitessouthern alpsitaly