| Venyukovia | |
|---|---|
 | |
| Speculative life restoration ofVenyukovia | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Synapsida |
| Clade: | Therapsida |
| Suborder: | †Anomodontia |
| Infraorder: | †Venyukovioidea |
| Genus: | †Venyukovia Amalitskii,1922 |
| Species: | †V. prima |
| Binomial name | |
| †Venyukovia prima Amalitskii, 1922 | |
Venyukovia (named after its discoverer, Pavel N. Venyukov) is an extinctgenus ofvenyukovioidtherapsid, a basalanomodont from theMiddle Permian of Russia.[1] Thetype and sole species,V. prima, is known only by a partial lower jaw with teeth.Venyukovia has often been incorrectly spelt as'Venjukovia' inEnglish literature. This stems from a spelling error made by Russian palaeontologistIvan Efremov in 1940, who mistakenly replaced the 'y' with a 'j', which subsequently permeated through therapsid literature before the mistake was caught and corrected.[2]Venyukovia is the namesake for the Venyukovioidea, a group of small Russian basal anomodonts also including the closely relatedOtsheria,Suminia,Parasuminia andUlemica, 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 ofOtsheria.
Little can be said of the overall anatomy ofVenyukovia 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.[3] 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.[4] Ivakhnenko (1996) comparedVenyukovia favourably toOtsheria, identifying a similar "shearing" dental apparatus between them compared to the more specialised jaws ofUlemica.[5] LikeOtsheria, the 'cheek' teeth are bulbous and roughly as wide as they are long.[6]
Notably,Venyukovia appears to lack a lower dentary shelf, a bony structure on the lower jaws of the venyukovioidsUlemica andSuminia and thedicynodonts. 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 inVenyukovia suggests it may have also lacked this muscle, restricting its jaws to simple up-and-down motions.[7]
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The only known fossil ofVenyukovia was discovered in 1908 by Russian geologistPavel Nikolaevich Venyukov, for whom it would later be formally named after in 1922. The specimen, now catalogued asPIN (Paleontological Institute)48/1 was found by Venyukov isolated in aspoil heap of theKargaly Mines ofOrenburg.[8] The mines had excavated thecopper-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.[9][10] However, they had since shut down by the timeVenyukovia was discovered, and the precise mining locality from where it was collected is unknown.[8][11]
Venyukov brought his finds to Russian palaeontologistVladimir P. Amalitskii (a.k.a. Amalitzky), and in a posthumous publication of his notes in 1922 were formally named and briefly described asVenyukovia prima.[8] 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 amandibular symphysis.[3][4] Notably, notype specimen ofV. prima was given in this publication. This would not be amended until 1983 by Russian palaeontologistPeter Konstantinovich Chudinov who formally designated PIN 48/1 as thelectotype.[3][8]
Amalitskii had not recognisedVenyukovia as a non-mammaliansynapsid, and instead had thought it was atriconodont mammal (similar to the first therapsid fossils from Russian copper mines, which were also initially mistaken for true mammals in 1838).[4][9] The non-mammalian nature ofVenyukovia was recognised by American palaeontologistGeorge Gaylord Simpson just six years later in 1928, although he only regarded it as "clearly a reptile".[12]Venyukovia was later correctly shown to be a therapsid by Efremov in 1938, although he interpreted it as adinocephalian. The true anomodont affinities ofVenyukovia were not recognised until 1942 by the English palaeontologistD. M. S. Watson, who would later coin theinfraorder Venyukovioidea for it and similar forms from Russia that had been discovered since then with American palaeontologistAlfred Romer in 1956.[13][14]
Historically, numerous more complete skulls and jaws were referred toVenyukovia from Isheevo,Tatarstan and named as a second species (V. invisa) by Efremov in 1940. In 1983, Chudinov synonymisedV. invisa withV. prima, however, in 1996V. invisa and all its material were moved to their own genus entirely by Russian palaeontologistMikhaïl Ivakhnenko,Ulemica.[3][5] Consequently, much of what has been historically written about the morphology and functional anatomy ofVenyukovia is actually based uponUlemica (e.g. Barghusen (1976), King (1994)).[15][16] In the same paper, Ivakhnenko commented on similarities between the type specimen ofVenyukovia andOtsheria, highlighting that the jaw and dental anatomy ofVenyukovia matches what would be expected fromOtsheria, a venyukovioid known only by its skull, and has even regarded them as potential synonyms.[17] At the same time, Ivakhnenko also regarded the referred specimen PIN 48/2 as being more similar toUlemica thanVenyukovia. Thus,Venyukovia is now represented solely by the lecotype mandible.[5]
Venyukovia is a member of the infraorder Venyukovioidea, aclade 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.[4] Subsequent discoveries have since identifiedVenyukovia 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 bothfamily-level andsubfamily-level ranked groups, the Venyukoviidae and Venyukoviinae. Despite being the group's namesake, it is unclear howVenyukovia is related to other venyukovioids and so these subgroups cannot be reliably defined. This is largely due to the incompleteness ofVenyukovia itself, and as such it has not been included in anyphylogenetic analyses of basal anomodonts due to the low number of characteristics that can be scored for it in one.[2][7]
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 (includingbivalves,conchostracans, andinsects) and plant fossils, although due to their often fragmentary nature specific identifications are uncertain.[8]
Apart fromVenyukovia, other therapsids are mostly represented by dinocephalians, including the dubious predatoryanteosaurAdmetophoneus (possibly a synonym ofTitanophoneus) and potentiallySyodon (though it is uncertain the referred specimen comes from these deposits), as well as thetapinocephaliansDeuterosaurus jubilaei andUlemosaurus, although fragmentary remains oftherocephalians have been identified.[18] Other tetrapods include,Chalcosaurus (alanthanosuchoidparareptile), early tetrapods such as theseymouriamorphDiscosauriscus netschajevi and an unidentifiedgephyrostegid, whiletemnospondyls are known by thearchegosauroidPlatyoposaurus.[8]
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 likelycopods, horsetails such asParacalamites, aPhyllotheca-like species, and trunks of the tree-likeCalamites, as well as indeterminate ferns.Seed ferns are represented mostly bypeltaspermaceans, including pinnatePermocallipteris and monopinnateCompsopteris leaf fronds, whereas theangaropeltaceanPhylladoderma is rarer.Ginkgophytes are represented by the leavesPsygmophyllum,Kerpia, andBaiera, whileconifers are known byTylodendron shoots,Steirophyllum, andCordaicarpus seeds.[8]
From thesedimentology 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.[8]
