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. ivakhnenkoi 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 scleral 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 scleral 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 scleral 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.
Discovery In 1999, the paleontologist Leonid P. Tatarinov described and named a new genus and species of gorgonopsian, Viatkogorgon ivakhnenkoi. The holotype specimen (cataloged as PIN 2212/61 in the Paleontological Institute of the Russian Academy of Sciences in Moscow), on which the scientific name is based, was found in 1992 at the Kotelnich locality of Kotelnichsky District, in Russia's Kirov Oblast. The Kotelnich locality contains a series of Permian exposures on the banks of the Vyatka River. The generic name Viatkogorgon refers to the Vyatka River, and to Gorgonops, the name of a related genus. The name "gorgon", referring to the monstrous hags of Greek mythology, is often used in the generic names of gorgonopsians. The specific name ivakhnenkoi honors the paleontologist Mikhail F. Ivakhnenko. The specific name was spelled V. ivachnenkovi in a 2001 article by the paleontologists Elena G. Kordikova and Albert J. Khlyupin, a spelling which Tatarinov modified slightly in 2004 as V. ivachnenkoi, while some other researchers have continued using the original spelling. Russian gorgonopsid discoveries began in the 1890s with the finding of Inostrancevia, one of the largest members of the group. There were fewer finds during the 20th century, with Viatkogorgon being the first recognized gorgonopsian from Russia, the only place outside Africa where the group is definitely known, since 1974. The holotype skeleton is one of the most complete gorgonopsian specimens known (a 2023 study called it the most complete), and preserves almost the entire postcranial skeleton (the rest of the skeleton apart from the skull). This includes elements rarely preserved intact in therapsids (the group in which gorgonopsians belong), such as the gastralia (or abdominal ribs, a feature found among reptiles, for example). The skull is relatively poorly preserved in comparison, with the left side and the palate badly broken. The skull roof is reconstructed in plaster, except for the snout tip and left postorbital bone (the bone that formed the hind border of the eye socket). Overall, the skull is also compressed from side to side, which makes it narrower than it would have been in life when viewed from above. The scleral rings (bony rings inside the eye), particularly the right one, are preserved, which is otherwise uncommonly preserved in theriodont (the sub-group of therapsids to which gorgonopsians belong) fossils. The proatlas, atlas and axis (the first bones of the vertebral column) are attached to the skull. Tatarinov only described the skull of Viatkogorgon in the 1999 article, wherein he also named the new scylacosaur genus Kotelcephalon, because the article was restricted in volume, but he preliminarily described the postcranium in 2004. In 2018, the paleontologists Christian F. Kammerer and Vladimir Masyutin redescribed the skull of Viatkogorgon and stated that a detailed description of the postcranium would greatly improve understanding of gorgonopsian skeletal anatomy, but noted it was unavailable for study during their research, as it was part of a traveling exhibition. They also named the new gorgonopsian Nochnitsa from Kotelnich in the article. In 2002, Ivakhnenko reported an additional, larger Viatkogorgon specimen (cataloged as PIN 4678/5), which is very poorly preserved.
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