Inostrancevia

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Inostrancevia
Temporal range: Wuchiapingian[1][2]259.0–252.3 Ma
Inostrancevia.jpg
PIN 2005/1578, the holotype skeleton of Inostrancevia alexandri
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Clade: Synapsida
Clade: Therapsida
Clade: †Gorgonopsia
Family: †Gorgonopsidae
Subfamily: †Inostranceviinae
Genus: †Inostrancevia
Amalitsky, 1922
Type species
†Inostrancevia alexandri
Amalitsky, 1922
Species
  • I. alexandri Amalitsky 1922
  • I. latifrons Pravoslavlev, 1927
  • I. uralensis Tatarinov 1984
Synonyms
  • Amalitzkia Pravoslavlev, 1927

Inostrancevia is an extinct genus of carnivorous therapsids, containing the largest members of gorgonopsians, predators characterized by long, saber-tooth-like canines. The various species inhabited the European Russia during the Upper Tatarian (Vyatskian), a Russian regional stage equivalent to the Wuchiapingian stage of the Late Permian period, dating from approximately 259 to 252.3 million years ago. The genus name was described posthumously, after the Bolshevik Revolution, by the Russian paleontologist Vladimir P. Amalitsky in 1922, in honor of geologist Aleksandr Inostrantsev.

The first fossils attributed to I. alexandri are found in Arkhangelsk Oblast, near the Northern Dvina at the end of the 19th century, making it the first gorgonopsian know from Russia, the only place outside Africa where they are officially recognized. Some fossils of the species in question are among the most complete remains of gorgonopsians ever identified to date, the majority of other members of the group are known only from skulls, which are often deformed or damaged. Other fossils, including fragmentary, belonging to other species are discovered everywhere in the western regions of Russia, including I. uralensis in the Orenburg Oblast.

The animal is easily identified by the arrangement of large canines, similar to those of some later predators, the longest of which reach 15 cm (5.9 in) in length and may have served to shear the skin of prey. This feature makes it one of the most specialized predatory tetrapods in Paleozoic history.

Inostrancevia is regularly confused by the general public with the South African Gorgonops, due to their similar appearance and various media tending to refer them by the name of the group they belong to rather than their genus names.

Discovery[]

Inostrancevia is the first gorgonopsian discovered in Russian territory, the only known region outside of Africa where the group is officially recognized.[3] The first fossils were found in the of the and in the Oblast of Arkhangelsk[4] as part of the Northern Dvina River excavations led by Amalitsky during the end of the 19th century. Two nearly complete skeletons were found alongside several other skeletal remains, one of which was mounted and exhibited in Saint Petersburg in 1900 with the other following a few years later. Proper descriptions of the findings were published posthumously in 1922, shortly before the Stalinist period in the USSR.[1][5]

The genus name was named by the Russian paleontologist Vladimir P. Amalitsky[5] in honour of the Russian geologist Aleksandr Inostrantsev.[6] In the original description, the taxon was spelled Inostranzevia.[7] However, following the large and influential 1928 monograph on the North Dvina gorgonopsians, Pavel Aleksandrovich Pravoslavlev altered the spelling to Inostrancevia and the new name stuck, and thus according to ICZN regulations, it must be maintained.[1]

Description[]

The proportions of Inostrancevia detail a large bodied, yet agile predator. The humerus and especially the femur are relatively elongate, suggesting this animal was proportionally longer-limbed and perhaps more cursorial in nature than other gorgonopsids. The front limbs are much more heavily built, with Inostrancevia possessing a robust and wide humerus. The scapula of Inostrancevia is unlike any other gorgonopsid in that it is massively expanded, yet relatively thin and plate like.[7] The skull of Inostrancevia is equally well built. Analyses show that Inostrancevia‘s jaws were capable of opening at a large gape angle, as opposed to a comparatively smaller gape in contemporary gorgonopsids such as Sauroctonus.[8] Like several other gorgonopsians, Inostrancevia was characterized by strongly developed canine teeth, with those of the upper jaw up to 15 cm (5.9 in) long, the root corresponding to half its length. The dentition of Inostrancevia can be compared to those of saber-toothed cats, such as Smilodon or other mammals with this similar morphology.

Inostrancevia alexandri[]

Mounted skeleton of Inostrancevia alexandri (cataloged PIN 1758), exposed at the Museo delle Scienze, Trento, Italy

The holotype fossil of I. alexandri, PIN 2005/1578, was discovered by the little Dvina river of the Arkhangelsk province in Russia and consists of a near complete skeleton and a skull with a length of around 51 cm (20 in).[9] Subsequent fossil discoveries of other equally complete specimens such as PIN 1758 provide a detailed picture of the anatomy of Inostrancevia. Other referred specimens include other skull material from the same locality. These two fossil skeletons attributed to the species both indicate a size of around 3 m (9.8 ft) in length. The skull of I. latifrons is wide towards the back, with a tall, long snout containing reduced palatal teeth. Posterior to the canine of the dentary, there are no teeth unlike in other notable gorgonopsid species.[9]

Inostrancevia latifrons[]

Scale chart, showing Inostrancevia latifrons size compared to a human

Inostrancevia latifrons is perhaps the largest of the genus, with skull lengths of over 60 cm (24 in) in length indicating a size approaching 3.5 m (11.5 ft) long and a mass of 300 kg (661.3 lbs), making the genus Inostrancevia the largest known gorgonopsian, along with the similarly sized South African genus Rubidgea. I. latifrons holotype is known from a complete skull, PIN 2005/1857 from the same province as I. alexandri, and referred material includes another skull from the same locality along with an incomplete skeleton from Zavrazhye, a village located in the northeast of Vladimir Oblast.[9] I. latifrons is distinguishable from I. alexandri not only in size, but also a comparatively lower and wider snout, a wider parietal region, fewer teeth and finally less developed palatal tuberosities.[9]

Inostrancevia uralensis[]

Inostrancevia uralensis is known from only scant remains of part of the braincase. Unlike the other two species, I. uralensis was discovered by the Ural river of the Orenburg province. The species is smaller than I. latifrons, and is diagnosed by fenestra ovale in shape of a slot elongated transversally.[9]

Classification[]

Inostrancevia alexandri tooth (top) compared to the tooth of the dubious therapsid Leogorgon klimovensis (bottom)
Reconstruction of the head of Inostrancevia latifrons, the largest species of the genus

Shortly after its description in 1927, the genus Inostrancevia is classified in the eponymous family erected under the name of Inostranceviidae alongside the related genus Pravoslavlevia.[4] In 1989, Sigogneau-Russell published a monograph which divided the gorgonopsids into three subfamilies: Gorgonopsinae, Rubidgeinae and Inostranceviinae.[10] With the exception of the basal genera Viatkogorgon and Nochnitsa, studies published by paleontologists Christian Kammerer, Vladimir Masyutin and Eva Bendel in 2018 prove that advanced gorgonopsians are divided into two major clades, one consisting of African representatives and the other Russian (including Inostrancevia, but also many related contemporaries such as Suchogorgon and Sauroctonus).[3][11] Previous analyzes did not find gorgonopsians to be grouped geographically, with some studies placing Russian genera such as Inostrancevia in African families, no one suspecting that different groups of gorgonopsians would be endemic to different regions.[12]

Placement of Inostrancevia within the taxon Gorgonopsia according to Bendel et al. (2018):[11]

◄ Gorgonopsia
 

Nochnitsa

 
 
 

Viatkogorgon

 
 
Russian clade
 

Suchogorgon

 
 
 

Sauroctonus

 
 
 

Pravoslavlevia

 
 

Inostrancevia

 
 
 
 
African clade
 

Eriphostoma

 
 
 

Gorgonops

 
 
 

Arctognathus

 
 

Lycaenops

 
 
 

Smilesaurus

 
 

Arctops

 
 
 

Rubidgeinae

 
 
 
 
 
 
 

Paleobiology[]

An I. alexandri attacking a juvenile Scutosaurus

Hunting strategy[]

Perhaps the most famous feature of the gorgonopsian group is the presence of large, sabre like canines on both the top and bottom jaw. How they used these deadly weapons is debated; the bite force of sabre-tooth predators like Inostrancevia, using three-dimensional analyses, was determined by Lautenschlager et al. to uncover answers.[8] Their findings detail that, despite the morphological convergence amongst sabre-toothed predators, there existed a diversity in possible killing techniques. The similarly sized gorgonopsid Rubidgea was capable of a bite force of 715 newtons. Although lacking the necessary jaw strength of being capable of crushing bone,[13] the analysis detailed that large bodied gorgonopsids possessed a stronger bite than other sabre-toothed carnivores. The study also indicated that the jaw of Inostrancevia was capable of a massive gape, perhaps enabling the gorgonopsid to deliver a lethal bite similar to the hypothesised killing technique of Smilodon, another sabre-toothed predator.[8][14]

Paleoecology[]

Reconstruction of a pack of Inostrancevia latifrons chasing a Scutosaurus by swimming

During the Late Permian when Inostrancevia lived, the Southern Urals (close in proximity to the Sokolki assemblage) were located around latitude 28–34°N and defined as a “cold desert” dominated by fluvial deposits.[15] The Salarevo formation in particular (a horizon where Inostrancevia hails from) was deposited in a seasonal, semi-arid to arid area with multiple shallow water lakes which was periodically flooded.[16] The Paleoflora of much of European Russia at the time was dominated by a genus of Peltaspermaceaen, Tatarina, and other related genera, followed by ginkophytes and conifers. On the other hand, ferns were relatively rare and sphenophytes were only locally present. [15]Inostrancevia was the top predator of its environment, existing alongside a number of notable species including the pareiasaur Scutosaurus and the dicynodont Vivaxosaurus which were likely prey items. Other, smaller predators existed alongside Inostrancevia such as the smaller related gorgonopsid Pravoslavlevia and the therocephalian Annatherapsidus.[17]

References[]

  1. ^ a b c Pravoslavlev, P. A. (1927). "Gorgonopsidae from the North Dvinsky excavations of V. P. Amalitsky" (PDF). Academy of Sciences of the Union of Soviet Socialist Republics. Leningrad: 170.
  2. ^ Kukhtinov, D. A.; Lozovsky, V. R.; Afonin, S. A.; Voronkova, E. A. (2008). "Non-marine ostracods of the Permian-Triassic transition from sections of the East European platform". Boll.Soc.Geol.It. (Ital.J.Geosci.). 127 (3).
  3. ^ a b Kammerer, Christian F.; Masyutin, Vladimir (2018). "Gorgonopsian therapsids (Nochnitsa gen. nov. and Viatkogorgon) from the Permian Kotelnich locality of Russia". PeerJ. 6: e4954. doi:10.7717/peerj.4954. PMC 5995105. PMID 29900078.
  4. ^ a b Ivakhnenko, M. F. (2001). "Tetrapods from the East European Placket—Late Paleozoic Natural Territorial Complex". Proceedings of the Paleontological Institute of the Russian Academy of Sciences (in Russian). 283: 1–200 [103].
  5. ^ a b Amalitsky, V. P. (1922). "Diagnoses of the new forms of vertebrates and plants from the upper Permian of North Dvina". Bulletin of the Russian Academy of Sciences. Saint Petersburg. 16 (6): 329–340.
  6. ^ "Inostrancevia". Paleofile. Retrieved 4 January 2014.
  7. ^ a b Amalitskii, V.P., 1922. Diagnoses of the new forms of vertebrates and plants from the Upper Permian on North Dvina. Известия Российской академии наук. Серия математическая, 16(0), pp.329-340.
  8. ^ a b c Lautenschlager, S., Figueirido, B., Cashmore, D.D., Bendel, E.M. and Stubbs, T.L., 2020. Morphological convergence obscures functional diversity in sabre-toothed carnivores. Proceedings of the Royal Society B, 287(1935), p.20201818.
  9. ^ a b c d e Benton, Michael J.; Shishkin, M. A.; Unwin, David M. (2000). "The Age of Dinosaurs in Russia and Mongolia". ResearchGate: 21.
  10. ^ Sigogneau-Russell, Denise (1989). Wellnhofer, Peter (ed.). Theriodontia I: Phthinosuchia, Biarmosuchia, Eotitanosuchia, Gorgonopsia. Encyclopedia of Paleoherpetology. Vol. 17 B/I. Stuttgart: Gustav Fischer Verlag. ISBN 978-3437304873.
  11. ^ a b Bendel, Eva-Maria; Kammerer, Christian F.; Kardjilov, Nikolay; Fernandez, Vincent; Fröbisch, Jörg (2018). "Cranial anatomy of the gorgonopsian Cynariops robustus based on CT-reconstruction". PLOS ONE. 13 (11): e0207367. Bibcode:2018PLoSO..1307367B. doi:10.1371/journal.pone.0207367. PMC 6261584. PMID 30485338.
  12. ^ Gebauer, E.V.I. (2007). Phylogeny and evolution of the Gorgonopsia with a special reference to the skull and skeleton of GPIT/RE/7113 ('Aelurognathus?' parringtoni) (PDF) (PhD thesis). Tübingen: Eberhard-Karls Universität Tübingen. pp. 1–316.
  13. ^ Benoit, J., Browning, C. and Norton, L.A., 2021. The first healed bite mark and embedded tooth in the snout of a middle Permian gorgonopsian (Synapsida: Therapsida). Frontiers in Ecology and Evolution, p.403.
  14. ^ Brown, J.G., 2014. Jaw function in Smilodon fatalis: a reevaluation of the canine shear-bite and a proposal for a new forelimb-powered class 1 lever model. PLoS One, 9(10), p.e107456.
  15. ^ a b Bernardi, M., Petti, F.M., Kustatscher, E., Franz, M., Hartkopf-Fröder, C., Labandeira, C.C., Wappler, T., van Konijnenburg-van Cittert, J.H., Peecook, B.R. and Angielczyk, K.D., 2017. Late Permian (Lopingian) terrestrial ecosystems: a global comparison with new data from the low-latitude Bletterbach Biota. Earth-Science Reviews, 175, pp.18-43.
  16. ^ Yakimenko, E.Y., Targul’yan, V.O., Chumakov, N.M., Arefev, M.P. and Inozemtsev, S.A., 2000. Paleosols in upper permian sedimentary rocks, Sukhona river (Severnaya Dvina basin). Lithology and Mineral Resources, 35(4), pp.331-344.
  17. ^ Golubev, V.K., 2000. The faunal assemblages of Permian terrestrial vertebrates from Eastern Europe. PALEONTOLOGICAL JOURNAL C/C OF PALEONTOLOGICHESKII ZHURNAL, 34(SUPP/2), pp.S211-S224.

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