Scutosaurus Temporal range: Lopingian ~ | |
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Skeleton at the American Museum of Natural History with an upright posture | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Reptilia |
Clade: | † Parareptilia |
Order: | † Procolophonomorpha |
Clade: | † Pareiasauria |
Genus: | † Scutosaurus Hartmann-Weinberg, 1930 |
Species: | †S. karpinskii |
Binomial name | |
†Scutosaurus karpinskii (Amalitskii, 1922) | |
Synonyms [1] | |
List
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Scutosaurus ("shield lizard") is an extinct genus of pareiasaur parareptiles. 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. [2] Fossils have been found in the Sokolki Assemblage Zone of the Malokinelskaya Formation in European Russia, close to the Ural Mountains, dating to the late Permian (Lopingian) between 264 and 252 million years ago.
The first fossils were uncovered by Russian paleontologist Vladimir Prokhorovich Amalitskii while documenting plant and animal species in the Upper Permian sediments in the Northern Dvina River, Arkhangelsk District, Northern European Russia. Amalitskii had 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. [3] Official diagnoses of these specimens was delayed due to World War I. [4] 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 [5] based on the poorly preserved specimen PIN 2005/1535 [4] "Pariasaurus Karpinskyi, Amalitz" (giving credit to Amalitskii for the name). [5] Amalitskii died later that year, and the actual diagnosis of the animal was posthumously published in 1922, with the name "Pareiosaurus" karpinskii, [3] and the holotype specimen designated as the nearly complete skeleton PIN 2005/1532. [1] Three partial skulls were also found, but Amalitskii decided to split these off into new species as "P. elegans", "P. tuberculatus", and "P. horridus". [3]
"Pariasaurus" and "Pareiosaurus" were both misspellings of the South African Pareiasaurus . [4] 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, [6] 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. [7] In 1968, Russian paleontologist N. N. Kalandadze and colleagues considered "Proelginia" to be synonymous with Scutosaurus. [8] 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. [1] 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. [4]
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 (osteoderms). It is the most completely known pareiasaur. All Scutosaurus specimens date to the Upper Tatarian (Vyatskian) Russian faunal stage, [1] which may roughly correspond with the Lopingian epoch of the Upper Permian [9] (259–252 million years ago). [10] 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. [11] [12]
Pareiasaurs were among the largest reptiles during the Permian. Scutosaurus is a rather large pareiasaur, measuring about 2.5–3 m (8 ft 2 in – 9 ft 10 in) in length and weighing up to 1,160 kilograms (2,560 lb). [13] The entire body would have been covered in rough osteoderms, which feature a central boss with a spine. These osteoderms appear to have been largely separate from each other, but may have been closely sutured together over the shoulder and pelvis as in Elginia . The limbs bore small conical studs. Pareiasaurs feature a short stout body, and a short tail. Scutosaurus has 19 presacral vertebrae. [1] Pareiasaurs, as well as many other common herbivorous Permian tetrapods, had a large body, barrel-shaped ribcage, and engorged limbs and pectoral and pelvic girdles. [14] The pareiasaur shoulder blade is large, plate-like, slightly expanded towards the arm, and vertically oriented. The acromion (which connects to the large clavicle) is short and blunt, like those of early turtles, and is placed at the bottom of the shoulder blade. In articulated specimens (where the positions of the jointed bones has been preserved), there is a small gap between the clavicle and the shoulder blade. Early pareiasaurs have a cleithrum which runs along the shoulder blade, but later ones including Scutosaurus lost this. [15] The digits on the hands and feet are short. [16] The dorsal vertebrae are short, tall, and robust, and supported large and strongly curved ribs. The broad torso may have conferred an expansive digestive system. [17]
The cheeks strongly flare out and terminate with long pointed bosses. The bosses of the skull are generally much more prominent than those of other pareiasaurs. The maxilla features a horn just behind the nostrils. The two holes on the back of the palate (the interpterygoid vacuities) are large. [1] All pareiasaurs have broad snouts containing a row of closely packed, tall, blade-like, and heterodont teeth with varying numbers of cusps depending on the tooth and species. [17] Scutosaurus has 18 teeth in the upper jaw (which feature anywhere from 9–11 cusps), and 16 in the lower (13–17 cusps). The tips of the upper teeth jut outward somewhat. The tongue side of the lower teeth bear a triangular ridge, and some random teeth in either jaw can have a cusped cingulum. Unlike other pareiasaurs, Scutosaurus has a small tubercle (a bony projection) on the base of the skull between the basal tubera. [1]
Scutosaurus was a massively built reptile, with bony armor, and a number of spikes decorating its skull. [2] 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. [18]
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.[ citation needed ]
Pareiasaurs had long been thought to be terrestrial, but it is difficult to assess their range of locomotion given the lack of modern anatomical analogues. In 1987, Ivakhnenko hypothesised that they were aquatic or amphibious due to the deep and low-lying pectoral girdle, short but engorged limbs, and thick cartilage on the limb joints, which are reminiscent of the aquatic dugong. Subsequent studies—including stable isotope analyses and footprint analyses—on various African and Eurasian remains have all reported results consistent with terrestrial behavior. Caseids have a broadly similar build to pareiasaurs, and possibly exhibited the same locomotory habits. Both have thin, porous long bones which is consistent with modern diving creatures, but the overall heavy torso would impede such a behavior. Nonetheless, similarly graviportal creatures have much thicker long bones. In 2016, zoologist Markus Lambertz and colleagues, based on the thin bones and short neck unsuited for reaching low-lying plants, suggested that caseids were predominantly aquatic and only came ashore during brief intervals. Overall, anatomical evidence seems to be at direct odds with isotopic evidence; it is possible that bone anatomy was more related to the animal's weight than its lifestyle. [19]
Like other pareiasaurs, Scutosaurus have been shown to have had a fast initial growth rate, with cyclical growth intervals. Following this possibly relatively short juvenile period, an individual would have reached 75% of its full size, and continued growing at a slower rate for several years more. This switch from fast to slow growth potentially signaled the onset of sexual maturity. [19]
Scutosaurus comes from the Salarevskaya Formation, which has a uniformly red coloration and comprises paleosol horizons, which deposit in cyclically shallow-water and dry area. The paleosol horizons are highly variable in shape and size throughout the formation, which may mean they came from different sources (polygenic). Paleosols gradually disappear in the upper part of the formation where the thickness of beds becomes much more discontinuous as well as irregular (from some millimeters to several meters), and the appearance of blue spots which may represent the accumulation of reduced iron oxides. These beds are capped off by a carbonate shell, varying from a small knot to up to a meter (3.3 ft) thick. The paleosols and shells feature holes left behind by plant roots, but these are absent in the clay-siltstone breccias and sand lenses. The formation has typically been explained as the result of several catastrophic floods washing over arid to semi-arid plains during wet seasons, featuring several temporarily filled channels and permanently dry lakes. [20]
Scutosaurus was a member of the pareiasaurian–gorgonopsian fauna dating to the Upper Tatarian, dominated by pareiasaurs, anomodonts, gorgonopsians, therocephalians, and cynodonts. Unlike earlier beds, dinocephalians are completely absent. Scutosaurus is identified in the Sokolki fauna, which features predominantly the former 3 groups. The only herbivore other than Scutosaurus is Vivaxosaurus . Carnivores are instead much more common, the largest identified being Inostrancevia (I. latifrons and I. alexandri); the other gorgonopsians are Pravoslavlevia and Sauroctonus progressus . Other carnivores include the therocephalian Annatherapsidus petri and the cynodont Dvinia ; chroniosuchid and seymouriamorph amphibians have also been identified, including Karpinskiosaurus , Kotlassia , and Dvinosaurus . [21] As for plants, the area has yielded various mosses, lepidophytes, ferns, and peltaspermaceaens. [20]
Pareiasaurs are an extinct clade of large, herbivorous parareptiles. Members of the group were armoured with osteoderms which covered large areas of the body. They first appeared in southern Pangea during the Middle Permian, before becoming globally distributed during the Late Permian. Pareiasaurs were the largest reptiles of the Permian, reaching sizes equivalent to those of contemporary therapsids. Pareiasaurs became extinct at the end of the Permian during the Permian-Triassic extinction event.
Diadectidae is an extinct family of early tetrapods that lived in what is now North America and Europe during the Late Carboniferous and Early Permian, and in Asia during the Late Permian. They were the first herbivorous tetrapods, and also the first fully terrestrial animals to attain large sizes. Footprints indicate that diadectids walked with an erect posture. They were the first to exploit plant material in terrestrial food chains, making their appearance an important stage in both vertebrate evolution and the development of terrestrial ecosystems.
Gorgonopsia is an extinct clade of sabre-toothed therapsids from the Middle to Upper Permian roughly 265 to 252 million years ago. They are characterised by a long and narrow skull, as well as elongated upper and sometimes lower canine teeth and incisors which were likely used as slashing and stabbing weapons. Postcanine teeth are generally reduced or absent. For hunting large prey, they possibly used a bite-and-retreat tactic, ambushing and taking a debilitating bite out of the target, and following it at a safe distance before its injuries exhausted it, whereupon the gorgonopsian would grapple the animal and deliver a killing bite. They would have had an exorbitant gape, possibly in excess of 90°, without having to unhinge the jaw.
Suminia is an extinct genus of basal anomodont that lived during the Tatarian age of the late Permian, spanning approximately from 268-252 Ma. Suminia is recognized the youngest non-dicynodont anomodont. Its fossil localities are primarily derived from the Kotel’nich locality of the Kirov Oblast in Russia. However, there have been some isolated specimen found in a few different localities, all from eastern European regions of Russia.
Caseidae are an extinct family of basal synapsids that lived from the Late Carboniferous to Middle Permian between about 300 and 265 million years ago. Fossils of these animals come from the south-central part of the United States, from various parts of Europe, and possibly from South Africa if the genus Eunotosaurus is indeed a caseid as some authors proposed in 2021. Caseids show great taxonomic and morphological diversity. The most basal taxa were small insectivorous and omnivorous forms that lived mainly in the Upper Carboniferous and Lower Permian, such as Eocasea, Callibrachion, and Martensius. This type of caseid persists until the middle Permian with Phreatophasma and may be Eunotosaurus. During the early Permian, the clade is mainly represented by many species that adopted a herbivorous diet. Some have evolved into gigantic forms that can reach 6–7 metres (20–23 ft) in length, such as Cotylorhynchus hancocki and Alierasaurus ronchii, making them the largest Permian synapsids. Caseids are considered important components of early terrestrial ecosystems in vertebrate history because the numerous herbivorous species in this family are among the first terrestrial tetrapods to occupy the role of primary consumer. The caseids experienced a significant evolutionary radiation at the end of the early Permian, becoming, with the captorhinid eureptiles, the dominant herbivores of terrestrial ecosystems in place of the edaphosaurids and diadectids.
Elginia is an extinct genus of pareiasaurid known from the Late Permian of Scotland and China. It was named for the area around Elgin in Scotland, which has yielded many fossils referred to as the Elgin Reptiles.
The Cistecephalus Assemblage Zone is a tetrapod assemblage zone or biozone found in the Adelaide Subgroup of the Beaufort Group, a majorly fossiliferous and geologically important geological group of the Karoo Supergroup in South Africa. This biozone has outcrops located in the Teekloof Formation north-west of Beaufort West in the Western Cape, in the upper Middleton and lower Balfour Formations respectively from Colesberg of the Northern Cape to east of Graaff-Reinet in the Eastern Cape. The Cistecephalus Assemblage Zone is one of eight biozones found in the Beaufort Group, and is considered to be Late Permian in age.
Sauroctonus is an extinct genus of gorgonopsian therapsids who lived during the end of the Middle Permian in what is now European Russia. The first fossils, discovered in Tatarstan, were first considered to belong to a new species of the South African genus Arctognathus, named A. progressus in 1938. The taxon will be designated as such until 1940, when it will be assigned to the genus Inostrancevia by Ivan Yefremov, before being definitively classified in a separate genus erected by Alexey Bystrow in 1955. The most complete known fossils of S. progressus include cranial and postcranial elements currently all recorded in Tatarstan. These elements show that the animal is a rather medium-sized gorgonopsian.
Chroniosuchus is an extinct genus of chroniosuchid from the upper Permian period. The genus was first named by Vjuschkov in 1957.
Viatkogorgon is a genus of gorgonopsian 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. ivachnenkoi 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 and a sclerotic ring. A larger, but poorly preserved specimen has also been assigned to the species.
Rubidgea is a genus of gorgonopsid from the upper Permian of South Africa and Tanzania, containing the species Rubidgea atrox. The generic name Rubidgea is sometimes believed to be derived from the surname of renowned Karoo paleontologist, Professor Bruce Rubidge, who has contributed to much of the research conducted on therapsids of the Karoo Basin. However, this generic name was actually erected in honor of Rubidge's paternal grandfather, Sydney Rubidge, who was a renowned fossil hunter. Its species name atrox is derived from Latin, meaning “fierce, savage, terrible”. Rubidgea is part of the gorgonopsian subfamily Rubidgeinae, a derived group of large-bodied gorgonopsians restricted to the Late Permian (Lopingian). The subfamily Rubidgeinae first appeared in the Tropidostoma Assemblage Zone. They reached their highest diversity in the Cistecephalus and Daptocephalus assemblage zones of the Beaufort Group in South Africa.
Kotlassia extinct genus of kotlassiine seymouriamorph from the Late Permian of Russia. The type, and currently only, species is K. prima.
Dvinosaurus is an extinct genus of amphibious temnospondyls localized to regions of western and central Russia during the middle and late Permian, approximately 265-254 million years ago. Its discovery was first noted in 1921 by Russian paleontologist Vladimir Prokhorovich Amalitskii in a posthumously published paper that documents the findings of a site in Russia's Arkhangelsk District. Its name is derived from the proximity of this site to the Northern Dvina River.
Megawhaitsia is an extinct genus of large therocephalian therapsids who lived during the Late Permian (Wuchiapingian) in what is now Eastern Europe. The only known species is M. patrichae, described in 2008 from several fossils discovered in various oblasts of European Russia. The fossils are representative of a large animal whose skull size is estimated to be 40–50 cm (16–20 in) long.
Aerosaurus is an extinct genus within Varanopidae, a family of non-mammalian synapsids. It lived between 252-299 million years ago during the Early Permian in North America. The name comes from Latin aes (aeris) “copper” and Greek sauros “lizard,” for El Cobre Canyon in northern New Mexico, where the type fossil was found and the site of former copper mines. Aerosaurus was a small to medium-bodied carnivorous synapsid characterized by its recurved teeth, triangular lateral temporal fenestra, and extended teeth row. Two species are recognized: A. greenleeorum (1937) and A. wellesi (1981).
Deltavjatia was a pareiasauromorph procolophonoid from the Tatarian stage of the Permian time period. It had a large body of about 1.5 m (4.9 ft) in length. Deltavjatia was an herbivore and lived in what is now Russia. The first specimen of Deltavjatia was a specimen of a skull and lower mandible, found in the Urpalov Formation in Kotelnich, Vyatka River. Since then, numerous mostly complete skeletons have been found, many of them being so well preserved due to the silty, anaerobic environment of the Kotelnich deposits that fossilised white blood cells are able to be distinguished in them. Analyses of the bone histology of Deltavjatia show that they grew very rapidly during the early stages of their ontogeny but that their growth rate drastically slowed down once they reached approximately half of their full body size.
Bunostegos is an extinct genus of pareiasaur parareptile from the Late Permian of the Agadez Region in Niger. The type species, Bunostegos akokanensis, was named from the Moradi Formation in 2003. It was a cow-sized animal with a distinctive skull that had large bony knobs, similar in form to those of other pareiasaurs but far larger. The species appears to have lived in a desert in the centre of the supercontinent of Pangaea.
Nochnitsa is an extinct genus of gorgonopsian therapsids who lived during an uncertain stage of the Permian in what is now European Russia. Only one species is known, N. geminidens, described in 2018 from a single specimen including a complete skull and some postcranial remains, discovered in the red beds of Kotelnich, Kirov Oblast. The genus is named in reference to Nocnitsa, a nocturnal creature from Slavic mythology. This name is intended as a parallel to the Gorgons, which are named after many genera among gorgonopsians, as well as for the nocturnal behavior inferred for the animal. The only known specimen of Nochnitsa is one of the smallest gorgonopsians identified to date, with a skull measuring close to 8 cm (3.1 in) in length. The rare postcranial elements indicate that the animal's skeleton should be particularly slender.
Glaurung is an extinct genus of weigeltisaurid reptile from the Upper Permian of Germany. The only known species is Glaurung schneideri. Originally considered a specimen of Coelurosauravus, a later study named it as a new genus after noting that it had several unique characteristics relative to other weigeltisaurids. These characteristics included a low skull, small eyes, smooth parietal and squamosal bones, and spiny jugal bones.
Parasaurus is a genus of pareiasaur known from fossils collected in the Kupferschiefer in Germany, dating to the Late Permian (Wuchiapingian). The type species, Parasaurus geinitzi, described by Hermann von Meyer in 1857, was the first pareiasaur ever described. The seven known specimens were redescribed in 2008.