Reassessing the earliest Oligocene vertebrate assemblage of Monteviale (Vicenza, Italy)

Abstract

The faunal assemblage of Monteviale (Vicenza, northern Italy) represents a rare condition among the earliest Oligocene assemblages of south-eastern Europe at the 'Grande-Coupure'. The lignitic fossiliferous strata lie above explosive basaltic breccias produced by a volcanic complex raised within a lagoon where the Calcareniti di Castelgomberto Formation (earliest Oligocene in age) was deposited. Systematic revision of the vertebrate remains from Monteviale reveals the presence of 15 taxa belonging to ?Butidae, Palaeobatrachidae, Trionychidae, Geoemydidae, Diplocynodontinae, Dugongidae, ?Pantolesta, Chiroptera, Rhinocerotidae, Anthracotheriidae and Palaeochoeridae. The fossiliferous deposit of Monteviale probably originated in a coastal lagoon characterized by salinity fluctuations, from brackish to fresh water, the latter evidenced by the presence of palaeobatrachid larvae. The terrestrial vertebrate assemblage indicates a humid forest environment with an age close to the Eocene–Oligocene boundary, lowermost Rupelian, MP21. Some of the mammal taxa (e.g. Epiaceratherium, Anthracotherium and ?Propalaeocherus) of Monteviale show a clear affinity with older (late Eocene) southern Asian species, suggesting a dispersal pattern across the several plates of south-eastern Europe and western Asia. By contrast, the herpetofauna (e.g. Trionyx, Bergouniouxchelys and Diplocynodon) suggests a closer relationship to European taxa.