Microphon exiguus: an Aquatic Neotonic Kotlassiid Seymouriamorph (Reptiliomorph) From Permian Russia

New finds of Microphon exiguus (Seymouriamorpha, Kotlassiidae) in the Severodvinian beds of the Sukhona River Basin, Russia

Author:

Bulanov

Abstract:

New data on the morphology and ontogeny of the Permian kotlassiid Microphon exiguus Ivachnenko, 1983 (Tetrapoda, Seymouriamorpha), based on the collection from the Ust’e Strelny locality (Russia, Vologda Region; Severodvinian Regional Stage), are reported. At the definitive stage, M. exiguus retains the larval skull habitus (short preorbital region, a few marginal teeth, widely open posttemporal fenestra) and seismosensory grooves. These features, along with the reduced nasolacrimal duct, are indicative of an important role of pedomorphosis in the evolution of Severodvinian kotlassiids and, in particular, the genus Microphon, which should be regarded as a neotenic, permanently aquatic Permian amphibian.