Scutosaurus ("Shield lizard") was a genus of parareptiles. It was an armor-covered pareiasaur that lived around 265–254 million years ago in Russia, in the later Permian period. Its genus name refers to large plates of armor scattered across its body. It was a large anapsid reptile that, unlike most reptiles, held its legs underneath its body to support its great weight. Fossils have been found in the Sokolki Assemblage Zone of the Malokinelskaya Formation in European Russia, close to the Ural Mountains.
|Skeleton, American Museum of Natural History|
The first fossils were uncovered by Russian palaeontologist Vladimir Prokhorovich Amalitskii while documenting plant and animal species in the Upper Permian sediments in the North Dvina River, Arkhangelsk District, Northern European Russia. Amalitskii has discovered the site in 1899, and he and his wife Anne Amalitskii continued to oversee excavation until 1914, recovering numerous nearly complete and articulated (in their natural position) skeletons belonging to a menagerie of different animals. Official diagnoses of these specimens was delayed due to World War I. The first published name of what is now called Scutosaurus karpinskii was in 1917 by British zoologist David Meredith Seares Watson, who captioned a reconstruction of its scapulocoracoid based on the poorly preserved specimen PIN 2005/1535 "Pariasaurus Karpinskyi, Amalitz" (giving credit to Amalitskii for the name). Amalitskii died later that year, and the actual diagnosis of the animal was posthumously published in 1922, with the name "Pareiosaurus" karpinskii, and the holotype specimen designated as the nearly complete skeleton PIN 2005/1532. Three partial skulls were also found, but Amalitskii decided to split these off into new species as "P. elegans", "P. tuberculatus", and "P. horridus".
"Pariasaurus" and "Pareiosaurus" were both misspellings of the South African Pareiasaurus. In 1930, Soviet vertebrate paleontologist Aleksandra Paulinovna Anna Hartmann-Weinberg said that the pareiasaur material from North Dvina represents only 1 species, and that this species was distinct enough from other Pareiasaurus to justify placing it in a new genus. Though Amalitskii had used a unique genus name "Pareiosaurus", this was an accident, and she declared "Pareiosaurus" to be a junior synonym of Pareiasaurus, and erected the genus Scutosaurus. She used the spelling "karpinskyi" for the species name, but switched to karpinskii in 1937. At the same time, she also split off another unique genus "Proelginia permiana" based on the partial skull PIN 156/2. In 1968, Russian paleontologist N. N. Kalandadze and colleagues considered "Proelginia" to be synonymous with Scutosaurus. Because the remains are not well preserved, the validity of "Proelginia" is unclear. In 1987, Russian paleontologist Mikhail Feodosʹevich Ivakhnenko erected a new species "S. itilensis" based on skull fragments PIN 3919, and resurrected "S. tuberculatus", but Australian biologist Michael S. Y. Lee considered both of these actions unjustified in 2000. In 2001, Lee petitioned the International Commission on Zoological Nomenclature to formally override the spelling karpinskyi (because Watson clearly did not intend his work to be a formal description of the species, and karpinskii was much more popularly used) and list the author citation as Amalitskii, 1922.
Scutosaurus is a common fossil at the North Dvina site, and is known from 6 at least fairly complete skeletons, as well as numerous various isolated body and skull remains, and scutes. They all date to the Upper Tatarian (Vyatskian) Russian faunal stage, which may roughly correspond with the Lopingian epoch of the Upper Permian (259–252 million years ago). In 1996, Russian paleontologist Valeriy K. Golubev described the faunal zones of the site, and listed the Scutosaurus zone as extending from roughly the middle Wuchiapingian to the middle Changhsingian, which followed the "Proelginia" stage beginning in the early Wuchiapingian.
Scutosaurus was a massively built reptile, up to 3 metres (9.8 ft) in length, with bony armor, and a number of spikes decorating its skull. Despite its relatively small size, Scutosaurus was heavy, and its short legs meant that it could not move at speed for long periods of time, which made it vulnerable to attack by large predators. To defend itself Scutosaurus had a thick skeleton covered with powerful muscles, especially in the neck region. Underneath the skin were rows of hard, bony plates (scutes) that acted like a form of brigandine armor.
As a plant-eater living in a semi-arid climate, including deserts, Scutosaurus would have wandered widely for a long time in order to find fresh foliage to eat. It may have stuck closely to the riverbanks and floodplains where plant life would have been more abundant, straying further afield only during times of drought. Its teeth were flattened and could grind away at the leaves and young branches before digesting them at length in its large gut. Scutosaurus swallowed gastroliths to digest plants. Given that it needed to eat constantly, Scutosaurus probably lived alone, or in very small herds, so as to avoid denuding large areas of their edible plants.
The skull is about 50 centimetres (20 in) wide. It is very broad, flat, and strongly sculptured, and bears bony protuberances in the jugal (cheek) and rear regions. As with some species of Pareiasaurus, with which it is clearly related, the quadratojugal or cheekbones extend outwards and forwards, making an angle of about 120° with the maxillary border. With its large cheekbones, Scutosaurus may have been able to make a loud bellowing sound.
- Lee, M. S. Y. "The Russian Pariesaurs". The Age of Dinosaurs in Russia and Mongolia. Cambridge University Press. pp. 77–84. ISBN 978-0-521-54582-2.
- Palmer, D., ed. (1999). The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. London: Marshall Editions. p. 64. ISBN 1-84028-152-9.
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- Lee, M. S. Y. (2001). "Pareiasaurus karpinskii Amalitzky, 1922 (currently Scutosaurus karpinskii, Reptilia, Pareiasauria): proposed conservation of the specific name" (PDF). Bulletin of Zoological Nomenclature. 58 (3): 220–223.
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- Hartmann-Weinberg, A. (1930). "Zur Systematik der Nord-Düna-Pareiasauridae" [On the systematics of the North Dvina Pareiasauridae]. Palaeontologische Zeitschrift (in German). 12: 47–59. doi:10.1007/BF03045064.
- Hartmann-Weinberg, A. (1937). "Pareiasauriden als Leitfossilien" [Pareiasaurids as guide fossils] (in German) (1–2). Universitätsbibliothek Johann Christian Senckenberg: 649–712. Cite journal requires
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- 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". Bollettino della Società Geologica Italiana. 127 (3): 719.
- "International Chronostratigraphic Chart" (PDF). International Commission on Stratigraphy.
- Golubev, V. K. "Faunal and floral zones of the Upper Permian: 5.9. Terrestrial vertebrates". Stratotipy i opornye razrezyverkhnei permi Povolzh’ya i Prikam’ya [Stratotypes and Reference Sections of the Upper Permian in the Region of the Volga and Kama Rivers]. Ekotsentr.
- Sennikov, A. G.; Golubev, V. K. (2017). "Sequence of Permian Tetrapod Faunas of Eastern Europe and the Permian–Triassic Ecological Crisis". Paleontological Journal. 51: 602. doi:10.1134/S0031030117060077.
- Pareiasaurinae at Palaeos