A new proteid salamander from the early Oligocene of Romania with notes on the paleobiogeography of Eurasian proteids

ABSTRACT

The Proteidae represent a small group of perennibranchiate salamanders with a disjunct distribution in North America and southeastern Europe. Herein, we describe a new species of proteid salamander from the early Oligocene of Romania representing the geologically oldest member reported from the Cenozoic of Eurasia. Mioproteus gardneri, sp. nov., based on features of the vomers, dentaries, atlas, and vertebrae, appears to be closely allied with M. caucasicus and M. wezei, standing altogether as the sister group of Proteus, the only living European proteid. The apomorphies of the European clade, shared with the American members Necturus and Paranecturus, include the presence of dorsoventrally flattened anterior cotyles and alar-like processes, whereas a few other characters appear to be more derived in the European forms, such as the diverging anterior cotyles of the atlas enclosing an angle of 225°, the trunk vertebrae with strongly bifurcated neural spines, and unicipitate transverse processes. Peculiarly, the proteid remains from the early Oligocene locality of Suceag 1, Romania, were accompanied by the palaeobatrachid frog Albionbatrachus, a form closely linked to aquatic environments and having a limited fossil record in the Paleogene (upper Eocene of southern England, lower Oligocene of Romania, and upper Oligocene of Germany), suggesting that these fully aquatic groups probably used similar freshwater corridors to reach more southerly European territories.

ACKNOWLEDGMENTS

We are grateful to the geology students at UBB, Cluj-Napoca, who took part in the field trip missions during 2008–2010 (the list is too long to be included individually). C. Fărcaş drafted the geological map in Figure 1. M. Calvo and B. Sanchíz, Museo Nacional de Ciencias Naturales, Madrid, kindly facilitated the study of the recent collections of amphibians. We are grateful to P. Skutschas, Saint Petersburg State University, Russian Federation, to the editor J. Sterli, and to an anonymous reviewer for their constructive comments, which helped improve the manuscript. The European Community’s program ‘Research Infrastructure Action’ under the FP7 ‘Capacities,’ under SYNTHESYS at the Museo Nacional de Ciencias Naturales (CSIC) (ES-TAF: 5747), and MTA Domus Program (5697/35/2015/HTMT) provided financial support to M.V.