New Bystrowianid Chroniosuchians (Amphibia,
Anthracosauromorpha) from the Triassic
of Russia and Diversification of Bystrowianidae

M. A. Shishkina, I. V. Novikova, and J. Fortunyb

aBorissiak Paleontological Institute, Russian Academy of Sciences, Profsoyuznaya ul. 123, Moscow, 117997 Russia


bInstitut Català de Paleontologia Miquel Crusafont, Barcelona, Spain


Received September 16, 2013

Abstract—The first bystrowianids recorded in the Gamskian Horizon of the East European Platform, Vyushk-
oviana operta
gen. et sp. nov. and Dromotectum abditum sp. nov. (Amphibia, Chroniosuchia), are described
based on specimens from the Malaya Northern Dvina and Don river basins. The patterns of the dermal scute
evolution observed in bystrowianids warrant the subdivision of the group into the subfamilies Bystrowianinae
Vjuschkov 1957, Dromotectinae subfam. nov. and Axitectinae subfam. nov. The second and third show progres-
sive reduction of the external (paraxial) zone of the interosteoderm articulation. New data supporting close
proximity or phyletic succession of the chroniosuchid and bystrowianid types of the osteoderm design are
revealed. The concept of the Chroniosuchidae as a paraphyletic group is rejected. Evolutionary significance of
the key features distinguishing the bystrowianid subfamilies is analyzed.

Keywords: Bystrowianidae, Chroniosuchia, osteoderms, Triassic, East European Platform

DOI: 10.1134/S0031030114050098

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