Viatkogorgon

Viatkogorgon; Temporal range: Permian ~
	Holotype skeleton exhibited in Dinosaurium, Prague
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Synapsida
Clade:	Therapsida
Clade:	†Gorgonopsia
Genus:	†Viatkogorgon; Tatarinov, 1999
Type species
	Viatkogorgon ivachnenkoi; Tatarinov, 1999
Synonyms
	Viatkogorgon ivakhnenkoi Tatarinov, 1999;

Viatkogorgon is a genus of gorgonopsian (a type of therapsid, the group that includes modern mammals) that lived during the Permian period in what is now Russia. The first fossil was found at the Kotelnich locality near the Vyatka River and was made the holotype of the new genus and species V. ivachnenkoi in 1999. The generic name refers to the river and the related genus Gorgonops—the gorgons of Greek mythology are often referenced in the names of the group. The specific name honors the paleontologist Mikhail F. Ivakhnenko. The holotype skeleton is one of the most complete gorgonopsian specimens known and includes rarely preserved elements such as gastralia (abdominal ribs) and a sclerotic ring (a bony ring inside the eye). A larger, but poorly preserved specimen has also been assigned to the species.

The holotype specimen is about 80 cm (31 in) long, including the 14 cm (5.5 in) long skull, making Viatkogorgon a relatively small gorgonopsian. The assigned specimen is larger, with a 17 cm (6.7 in) long skull, and the holotype may have been young. As a gorgonopsian, it would have been skeletally robust with a somewhat dog-like stance, though with outwards-turned elbows. The snout was high, and the teeth were generally recurved (curved backward), pointed, and serrated. The canines (the saber teeth) were much larger than the incisors at the front and postcanines behind but relatively small for a gorgonopsian. Viatkogorgon was characterized by its unusually large eye socket and sclerotic ring. It was distinct from other gorgonopsians in that the lower end of the postorbital bar was narrow, and it had a very large sulcus (or furrow) at the back of the skull on each side. Since gorgonopsians have been described mainly from skulls, it is uncertain how widespread the postcranial features of Viatkogorgon were in other members of the group. The skeleton of Viatkogorgon was unusual in having gastralia, in that the tail was differentiated with a front and hind part, with the former less flexible, and in that some of the foot bones and its digits were reduced in size and interconnected.

Gorgonopsians were a group of carnivorous stem mammals with saber teeth that disappeared at the end of the Permian. Phylogenetic analysis has found Viatkogorgon to be one of the earliest-diverging gorgonopsians, after Nochnitsa, also from Kotelnich. All other gorgonopsians appear to belong to two, later-diverging Russian and African groups. Viatkogorgon's proportionally large sclerotic ring suggests nocturnal habits. Gorgonopsians would have been relatively fast predators, killing their prey by delivering slashing bites with their saber teeth. The skeleton of Viatkogorgon had features such as a vertebral column with increased vertical curvature, including the hind part of the tail, and restricted mobility of some digits of the feet, likened to a flipper-like structure indicating it may have been a relatively good swimmer. The age of the Vanyushonki Member of the Kotelnich succession, from which Viatkogorgon is known, is not determined but is thought to date to either the late or middle Permian epoch.