Abstract
The early evolution of gorgonopsians is poorly understood. New material from the Kotelnich locality in Russia expands our knowledge of middle/earliest late Permian gorgonopsians from Laurasia. Two gorgonopsian taxa are recognized from Kotelnich: Viatkogorgon ivakhnenkoi Tatarinov, 1999 and Nochnitsa geminidens gen. et sp. nov. Nochnitsa can be distinguished from all known gorgonopsians by its unique upper postcanine tooth row, composed of pairs of teeth (a small anterior and larger posterior) separated by diastemata. Both Viatkogorgon and Nochnitsa are relatively small gorgonopsians, comparable in size to the South African middle Permian taxon Eriphostoma. Inclusion of Viatkogorgon and Nochnitsa in a phylogenetic analysis of gorgonopsians recovers them in basal positions, with Nochnitsa representing the earliest-diverging gorgonopsian genus. All other sampled gorgonopsians fall into two major subclades: one made up entirely of Russian taxa (Inostrancevia, Pravoslavlevia, Sauroctonus, and Suchogorgon) and the other containing only African gorgonopsians. The high degree of endemism indicated in this analysis for gorgonopsians is remarkable, especially given the extensive intercontinental dispersal inferred for coeval therapsid groups.
Highlights
The therapsid subclade Gorgonopsia was an abundant but morphologically conservative group of saber-toothed carnivores that included the apex predators of the late Permian (Sigogneau-Russell, 1989; Kammerer, 2015, 2016)
In the Russian gorgonopsians Inostrancevia, Sauroctonus, and Suchogorgon, there is a series of large, well-developed foramina on the palatine, near the border with the maxilla. These foramina appear to be absent in most African gorgonopsian taxa
Nochnitsa is recovered as the earliest-diverging gorgonopsian taxon, followed by Viatkogorgon a large clade containing the remaining gorgonopsian operational taxonomic units (OTUs). This clade is broken into two major subclades, one containing only Russian gorgonopsians (Suchogorgon, Sauroctonus, Pravoslavlevia, and Inostrancevia) and the other containing all the African gorgonopsians included in the analysis
Summary
The therapsid subclade Gorgonopsia was an abundant but morphologically conservative group of saber-toothed carnivores that included the apex predators of the late Permian (Sigogneau-Russell, 1989; Kammerer, 2015, 2016). Its proportions in the zygoma, including the short contribution to the posterior base of the postorbital bar, are very similar to those of Nochnitsa It is substantially taller in the subtemporal bar (which is taller in general than that of Nochnitsa) and more obscured by the more anteriorly-extending squamosal (which extends almost to the level of the postorbital bar.) In lateral view, the ventral portion of the jugal contribution to the subtemporal bar is barely exposed, unlike the condition in Nochnitsa, where it is longer than the dorsal portion (Fig. 4D). In the Russian gorgonopsians Inostrancevia, Sauroctonus, and Suchogorgon, there is a series of large, well-developed foramina on the palatine, near the border with the maxilla (this region is not well preserved in Pravoslavlevia) These foramina appear to be absent in most African gorgonopsian taxa (this portion of the palatine is not exposed in Nochnitsa or Viatkogorgon). This clade is broken into two major subclades, one containing only Russian gorgonopsians (Suchogorgon, Sauroctonus, Pravoslavlevia, and Inostrancevia) and the other containing all the African gorgonopsians included in the analysis
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