Venyukovia

''Venyukovia'' (named after its discoverer, Pavel N. Venyukov) is an extinct genus of venyukovioid therapsid, a basal anomodont from the Middle Permian of Russia. The type and sole species, ''V. prima'', is known only by a partial lower jaw with teeth. ''Venyukovia'' has often been incorrectly spelt as ''Venjukovia'' in English literature. This stems from a spelling error made by Russian palaeontologist Ivan Efremov in 1940, who mistakenly replaced the 'y' with a 'j', which subsequently permeated through therapsid literature before the mistake was caught and corrected. ''Venyukovia'' is the namesake for the Venyukovioidea, a group of small Russian basal anomodonts also including the closely related ''Otsheria'', ''Suminia'', ''Parasuminia'' and ''Ulemica'', although it itself is also one of the poorest known. Like other venyukovioids, it had large projecting incisor-like teeth at the front and lacked canines, although the remaining teeth are simple compared to some other venyukovioids (e.g. ''Ulemica'', ''Suminia)'', but may resemble those of ''Otsheria''.

Description

Little can be said of the overall anatomy of ''Venyukovia'' beyond its mandibles and teeth. The partial jaw as preserved measures 52 mm long and is 18 mm high, including the crowns of the teeth. Like other venyukovioids, ''Venyukovia'' has large procumbent incisor-like teeth at its jaw tips, possibly two on either side, superficially resembling the incisors of some mammals. There are no canines, and the remaining ten 'cheek' teeth (identified by Amalitskii as molars and premolars) are relatively simple in shape with pointed, laterally compressed crowns. Ivakhneno (1996) compared ''Venyukovia'' favourably to ''Otsheria'', identifying a similar "shearing" dental apparatus between them compared to the more specialised jaws of ''Ulemica''. Like ''Otsheria'', the 'cheek' teeth are bulbous and roughly as wide as they are long.

Notably, ''Venyukovia'' appears to lack a lower dentary shelf, a bony structure on the lower jaws of the venyukovioids ''Ulemica'' and ''Suminia'' and the dicynodonts. This shelf was an attachment point for the powerful lateral adductor jaw muscle that allowed these anomodonts to chew, pulling the mandible backwards, and the absence of the lateral dentary shelf in ''Venyukovia'' suggests it may have also lacked this muscle, restricting its jaws to simple up-and-down motions.

Discovery and naming

The only known fossil of ''Venyukovia'' was discovered in 1908 by Russian geologist Pavel Nikolaevich Venyukov, for whom it would later be formally named after in 1922. The specimen, now catalogued as PIN ( Paleontological Institute) 48/1 was found by Venyukov isolated in a spoil heap of the Kargaly Mines of Orenburg. The mines had excavated the copper-bearing sandstones of the southern Cis-Ural mountains during the 18th and 19th centuries, and such Russian copper mines were of historical palaeontological significance for the discovery some of the first, albeit fragmentary fossils of Permian therapsids in the world. However, they had since shut down by the time ''Venyukovia'' was discovered, and the precise mining locality from where it was collected is unknown.

Venyukov brought his finds to Russian palaeontologist Vladimir P. Amalitskii (a.k.a. Amalitzky), and in a posthumous publication of his notes in 1922 were formally named and briefly described as ''Venyukovia prima''. Amalitskii described two specimens, a partial left mandible with the first right incisor attached (PIN 48/1) and a smaller specimen that he interpreted as the tip of a snout with teeth, later shown to be a mandibular symphysis. Notably, no type specimen of ''V. prima'' was given in this publication. This would not be amended until 1983 by Russian palaeontologist Peter Konstantinovich Chudinov who formally designated PIN 48/1 as the lectotype.

Amalitskii had not recognised ''Venyukovia'' as a non-mammalian synapsid, and instead had thought it was a triconodont mammal (similar to the first therapsid fossils from Russian copper mines, which were also initially mistaken for true mammals in 1838). The non-mammalian nature of ''Venyukovia'' was recognised by American palaeontologist George Gaylord Simpson just six years later in 1928, although he only regarded it as "clearly a reptile". ''Venyukovia'' was later correctly shown to be a therapsid by Efremov in 1938, although he interpreted it as a dinocephalian. The true anomodont affinities of ''Venyukovia'' were not recognised until 1942 by the English palaeontologist D. M. S. Watson, who would later coin the infraorder Venyukovioidea for it and similar forms from Russia that had been discovered since then with American palaeontologist Alfred Romer in 1956.

Historically, numerous more complete skulls and jaws were referred to ''Venyukovia'' from Isheevo, Tatarstan and named as a second species (''V. invisa'') by Efremov in 1940. In 1983, Chudinov synonymised ''V. invisa'' with ''V. prima'', however, in 1996 ''V. invisa'' and all its material were moved to their own genus entirely by Russian palaeontologist Mikhaïl Ivakhnenko, ''Ulemica''. Consequently, much of what has been historically written about the morphology and functional anatomy of ''Venyukovia'' is actually based upon ''Ulemica'' (e.g. Barghusen (1976), King (1994)). In the same paper, Ivakhnenko commented on similarities between the type specimen of ''Venyukovia'' and ''Otsheria'', highlighting that the jaw and dental anatomy of ''Venyukovia'' matches what would be expected from ''Otsheria'', a venyukovioid known only by its skull, and has even regarded them as potential synonyms. At the same time, Ivakhnenko also regarded the referred specimen PIN 48/2 as being more similar to ''Ulemica'' than ''Venyukovia''. Thus, ''Venyukovia'' is now represented solely by the lecotype mandible.

Classification

''Venyukovia'' is a member of the infraorder Venyukovioidea, a clade of basal anomodonts related to dicynodonts. Anomodonts were a highly successful group of therapsids, largely represented by dicynodonts but also by a handful of basal genera. ''Venyukovia'' was one of the first such basal anomodonts to be discovered, although it was mistaken to be an early mammal at first by Amalitskii due to its mammal-like dentition. Subsqeuent discoveries have since identified ''Venyukovia'' as part of a radiation of basal anomodonts in Eastern Europe for which it is now the namesake, the Venyukovioidea. ''Venyukovia'' has additionally also been variously assigned both family-level and subfamily-level ranked groups, the Venyukoviidae and Venyukoviinae. Despite being the group's namesake, it is unclear how ''Venyukovia'' is related to other venyukovioids and so how these subgroups cannot be reliably defined. This is largely due to the incompleteness of ''Venyukovia'' itself, and as such it has not been included in any phylogenetic analyses of basal anomodonts due to the low number of characteristics that can be scored for it in one.

Palaeoenvironment

Although found across various individual mines and mixed in spoil heaps, the fossil flora and fauna of the Kargaly Mines can be recognised as a fossil assemblage. Namely, they have been correlated to the better known Ocher Assemblage Zone to the East. The Kargaly Mines have produced a diverse array of tetrapod, fish, invertebrate (including bivalves, conchostracans, and insects) and plant fossils, although due to their often fragmentary nature specific identifications are uncertain.

Apart from ''Venyukovia'', other therapsids are mostly represented by dinocephalians, including the dubious predatory anteosaur '' Admetophoneus'' (possibly a synonym of ''Titanophoneus'') and potentially '' Syodon'' (though it is uncertain the referred specimen comes from these deposits), as well as the tapinocephalians '' Deuterosaurus jubilaei'' and '' Ulemosaurus'', although fragmentary remains of therocephalians have been identified. Other tetrapods include, '' Chalcosaurus'' (a lanthanosuchoid parareptile), early tetrapods such as the seymouriamorph '' Discosauriscus netschajevi'' and an unidentified gephyrostegid, while temnospondyls are known by the archegosauroid '' Platyoposaurus''.

Numerous fossils from a wide variety of plants have also been discovered in the copper sandstones of the Kargaly Mines. These include spore-bearing plants like lycopods, horsetails such as '' Paracalamites'', a '' Phyllotheca''-like species, and trunks of the tree-like ''Calamites'', as well as indeterminate ferns. Seed ferns are represented mostly by peltaspermaceans, including pinnate '' Permocallipteris'' and monopinnate '' Compsopteris'' leaf fronds, whereas the angaropeltacean '' Phylladoderma'' is rarer. Ginkgophytes are represented by the leaves '' Psygmophyllum'', '' Kerpia'', and ''Baiera'', while conifers are known by '' Tylodendron'' shoots, '' Steirophyllum'', and '' Cordaicarpus'' seeds.

From the sedimentology of the deposits, the locality has been interpreted as being located near the foothills of the Paleo-Urals, with abundant vegetation growing around high-energy streams with heavy run-off from the western slopes of mountains. The forests were dominated by conifers and ginkgophytes, with an undergrowth of ferns and seed ferns and horsetails along the riverbanks.

References

{{Taxonbar, from=Q2811866

Anomodont genera
Guadalupian synapsids
Guadalupian genus first appearances
Guadalupian genus extinctions
Permian Russia
Fossils of Russia
Fossil taxa described in 1922
Taxa named by Vladimir Prokhorovich Amalitskii
Anomodonts