Thoosuchus

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Thoosuchus
Temporal range: Early Triassic
Thoosuchus.jpg
Life restoration of Thoosuchus yakovlevi
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Amphibia
Order: Temnospondyli
Infraorder: Trematosauria
Superfamily: Trematosauroidea
Family: Thoosuchidae
Genus:Thoosuchus
Efremov, 1940
Species
  • T. acutirostrisEfremov, 1940 (type)
  • T. yakovlevi(Ryabinin 1926)
  • T. tardusGetmanov, 1989
  • T. tuberculatusGetmanov, 1989

Thoosuchus is an extinct genus of basal trematosauroid trematosaurian temnospondyl. Fossils have been found from Russia and date back to the Early Triassic. It is the type genus of the family Thoosuchidae, formerly called the subfamily Thoosuchinae and placed within Benthosuchidae. [1] [2] [3] The benthosuchids were originally composed of the majority of basal trematosaurian forms regarded as the ancestors of the trematosaurids. [4] [5] [6] [7] [8] Although the genus was first named in 1940, material from one species, E. yakovlevi, was originally tentatively referred to Trematosuchus in 1926. [9]

A genus is a taxonomic rank used in the biological classification of living and fossil organisms, as well as viruses, in biology. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclature, the genus name forms the first part of the binomial species name for each species within the genus.

In phylogenetics, basal is the direction of the base of a rooted phylogenetic tree or cladogram. The term may be more strictly applied only to nodes adjacent to the root, or more loosely applied to nodes regarded as being close to the root. Each node in the tree corresponds to a clade; i.e., clade C may be described as basal within a larger clade D if its root is directly linked to the root of D. The terms deep-branching or early-branching are similar in meaning.

Trematosauroidea superfamily of amphibians (fossil)

Trematosauroidea are an important group of Triassic temnospondyl amphibians. They flourished briefly during the Early Triassic, occurring worldwide before declining at the start of the Middle Triassic, although the group continued until the Late Triassic. They were medium-sized temnospondyls with wedge-shaped tails, narrow skulls, and, in advanced forms, elongated snouts. The latter feature was probably an adaptation for feeding on fish. The largest and most specialized family, the Trematosauridae, are the only batrachomorphs to have adapted to a marine lifestyle with the exception of the modern crab-eating frog.

Contents

For its family, Thoosuchus was fairly small, reaching a little over 60 cm with a 15 cm skull. [10]

Skull bony structure that forms the skeleton of head in most vertebrates, supports the structures of the face and provides a protective cavity for the brain, composed of two parts: the cranium and the mandible

The skull is a bony structure that forms the head in vertebrates. It supports the structures of the face and provides a protective cavity for the brain. The skull is composed of two parts: the cranium and the mandible. In the human, these two parts are the neurocranium and the viscerocranium or facial skeleton that includes the mandible as its largest bone. The skull forms the anterior most portion of the skeleton and is a product of cephalisation—housing the brain, and several sensory structures such as the eyes, ears, nose, and mouth. In humans these sensory structures are part of the facial skeleton.

Thoosuchus jakovlevi skull Thoosuchus jakovlevi.JPG
Thoosuchus jakovlevi skull

Thoosuchus superficially resembles the more derived trematosaurids, but can be distinguished from them on the basis of a deep, narrowing otic notch. [11] [12] It had widely spaced orbits and a moderately elongated skull roof that was well ornamented with ridges and grooves, especially on the parietals. [13] This ornamentation is also a characteristic of trematosaurids and has been described as representing a "zone of intensive growth". [14] [15] The well developed lateral line system of Thoosuchus is indicative of its presumed aquatic lifestyle.

Trematosauridae family of amphibians (fossil)

Trematosauridae are a family of large temnospondyl amphibians with many members. They first appeared during the Olenekian stage of the Early Triassic, and existed until around the Carnian stage of the Late Triassic, although by then they were very rare. By the Middle Triassic they had become widespread throughout Laurasia and Gondwana with fossils being found in Europe, Asia, Madagascar, and Australia.

Otic notch

Otic notches are invaginations in the posterior margin of the skull roof, one behind each orbit. Such notches are found in labyrinthodonts and some of their immediate ancestors, but not in their reptilian descendants. The presence or absence of the otic notches is one of the traits used to separate the amniotes from the amphibian grade tetrapods.

Parietal bone bones in the human skull which, when joined together, form the sides and roof of the cranium

The parietal bones are two bones in the human skull which, when joined together at a fibrous joint, form the sides and roof of the cranium. Each bone is roughly quadrilateral in form, and has two surfaces, four borders, and four angles. It is named from the Latin paries (-ietis), wall.

See also

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Temnospondyli Ancestors of modern amphibians adapted to life on land

Temnospondyli is a diverse subclass of small to giant tetrapods—often considered primitive amphibians—that flourished worldwide during the Carboniferous, Permian, and Triassic periods. A few species continued into the Cretaceous. Fossils have been found on every continent. During about 210 million years of evolutionary history, they adapted to a wide range of habitats, including fresh water, terrestrial, and even coastal marine environments. Their life history is well understood, with fossils known from the larval stage, metamorphosis, and maturity. Most temnospondyls were semiaquatic, although some were almost fully terrestrial, returning to the water only to breed. These temnospondyls were some of the first vertebrates fully adapted to life on land. Although temnospondyls are considered amphibians, many had characteristics, such as scales, claws, and armour-like bony plates, that distinguish them from modern amphibians.

Dvinosauria Suborder of prehistoric amphibians

Dvinosaurs are one of several new clades of Temnospondyl amphibians named in the phylogenetic review of the group by Yates and Warren 2000. They represent a group of primitive semi-aquatic to completely aquatic amphibians, and are known from the Late Carboniferous to the Early Triassic, being most common in the Permian period. Their distinguishing characteristics are a reduction of the otic notch; the loss of a flange on the rear side of the pterygoid; and 28 or more presacral vertebrae.

<i>Mastodonsaurus</i> genus of reptiles (fossil)

Mastodonsaurus is an extinct genus of temnospondyl amphibian from the Middle Triassic. It belongs to a Triassic group of temnospondyls called Capitosauria, characterized by their large body size and presumably aquatic lifestyles.

<i>Rhinesuchus</i> genus of amphibians (fossil)

Rhinesuchus is a large temnospondyl amphibian. Remains of the genus are known from the Permian of the South African Karoo Basin's Tapinocephalus and Cistecephalus assemblage zones, both belonging to the Beaufort Group. The skull of Rhinesuchus had a flat triangular shape with blunt snout similar to some of the other large amphibians, and had a palate filled with small sharp teeth, suggesting that it hunted fish. Also, the small eyes were on top of the head suggesting that it approached its prey from below. It is a popular misconception that Rhinesuchus is named after the Rhine River in Europe; Rhinesuchus actually gets its name from the Greek word for nose. The type species is Rhinesuchus whaitsi. Two more species, R. africanus and R. wadiai, are considered to be nomen dubium. R. broomianus and R. beaufortensis have been synonymized with R. whaitsi, while R. capensis has been moved out of the genus into Rhinesuchoides. Muchocephalus has also been synonymized with R. whaitsi.

Stereospondyli suborder of amphibians (fossil)

The Stereospondyli are a group of extinct temnospondyl amphibians. Relative to other early tetrapods (labyrinthodonts), they had simplified backbones, where the whole vertebra was made of a single intercentrum, topped by a neural arch. The whole vertebral structure was rather weak, meaning that most stereospondyls were aquatic. The family Plagiosauridae appear to have been wholly aquatic and retained their larval gills in adulthood.

<i>Cyclotosaurus</i> genus of reptiles (fossil)

Cyclotosaurus is an extinct genus of temnospondyl within the family Mastodonsauridae. It was of great size for an amphibian, reaching 3–4.3 m (9.8–14.1 ft) in length with an elongated 70 cm (28 in) skull.

<i>Intasuchus</i> species of amphibian (fossil)

Intasuchus is an extinct genus of temnospondyl amphibian from the Late Permian of Russia. It is known from a single species, Intasuchus silvicola, which was named in 1956. Intasuchus belongs to the family Intasuchidae and is probably its sole member, although other taxa such as Syndyodosuchus and Cheliderpeton have been assigned to the family in the past. Intasuchus most likely belongs to the group Archegosauroidea, Permian relatives of the large, mostly Mesozoic temnospondyl clade Stereospondyli.

<i>Konzhukovia</i> genus of amphibians (fossil)

Konzhukovia is an amphibian genus that belongs to an extinct group of temnopsondylls, the largest clade of basal tetrapods including about 198 genera, 292 species, and more than half of which were alive during the early Mesozoic period. The animal was a predator that lived about 260 million years ago, and could get up to about 3 meters in length. Specifically, Konzukovia lived during the Permian, between 252 and 270 million years ago according to the type of rock the fossil was found in. There are three species within this genus, K. vetusta, K. tarda, and K. sangabrielensis, the first two originating from Russia while the latest originating from Southern Brazil. The discovery of this specimen in Southern Brazil provided more evidence to support the idea that during this animals existence, there was a “biological corridor” because of the supercontinent Pangea, allowing these species to be found so far apart from each other. Konzhukovia belongs to the family Archegosauridae, a family consisted of large temnospondyls that most likely compare to modern day crocodiles. Since the discovery of the latest species, K. sangabrielensis Pacheco proposes that there must be the creation of a new family, Konzhokoviidae, a monophyletic group in a sister-group relationship with Stereospondlyi in order to accommodate the three species. Konzhukovia skulls usually exhibit typical rhinesuchid features including an overall parabolic shape, small orbits located more posteriorly, and the pterygoids do not reach the vomer. These animals were long-snouted amphibians that had clear adaptations made for fish catching, as well as exemplifying aquatic features.

<i>Benthosuchus</i> genus of amphibians (fossil)

Benthosuchus is an extinct genus of temnospondyl amphibian from the Early Triassic of Russia. The genus was named in 1937, and the type species, Benthosuchus sushkini, was named in 1940. Benthosuchus has traditionally been considered a member of the temnospondyl superfamily Trematosauroidea, and the family Benthosuchidae was established in 1940 to include Benthosuchus and the related trematosauroid Thoosuchus. Some recent phylogenetic studies have removed Benthosuchus from Trematosauroidea entirely, placing it as a closer relative of Mastodonsauroidea, another group of Triassic temnospondyls. Other studies retain Benthosuchus within Trematosauroidea, but since Benthosuchus and Thoosuchus have successively basal positions on these trees they form a paraphyletic grouping, not a valid clade. In either case, Benthosuchidae is a monotypic family containing only Benthosuchus.

Brachyopoidea superfamily of amphibians (fossil)

Brachyopoidea is a superfamily of temnospondyls that lived during the Mesozoic. It contains the families Brachyopidae and Chigutisauridae. The earliest records of brachyopids are from the Lower Triassic in Australia. The latest-surviving member of the superfamily is the chigutisaurid Koolasuchus from the Early Cretaceous of Australia.

Lydekkerinidae family of amphibians (fossil)

Lydekkerinidae is a family of stereospondyl temnospondyls that lived in the Triassic period. During the Triassic, lydekkerinids had a global distribution. They were small-bodied with wedge-shaped, roughly triangular heads. Fossils have been found in Russia, Greenland, India, South Africa, Madagascar, and Australia. The type genus is Lydekkerina, the namesake of the family and the most well-known lydekkerinid.

Stereospondylomorpha taxon of amphibians

Stereospondylomorpha is a clade of temnospondyls. It includes the superfamily Archegosauroidea and the more diverse group Stereospondyli. Stereospondylomorpha was first proposed by Yates and Warren (2000), who found Archegosauroidea and Stereospondyli to be sister taxa in their phylogenetic analysis. A similar clade is Archegosauriformes, named by Schoch and Milner (2000), which includes Stereospondyli and some Permian temnospondyls that are similar in appearance to stereospondyls, including the archegosauroids. However, according to Schoch and Milner's phylogeny, Archegosauroidea is a paraphyletic group of taxa that are successively basal to Stereospondyli, rather than a monophyletic sister taxon.

Limnarchia clade of amphibians (fossil)

Limnarchia is a clade of temnospondyls. It includes the mostly Carboniferous-Permian age Dvinosauria and the mostly Permian-Triassic age Stereospondylomorpha. The clade was named in a 2000 phylogenetic analysis of stereospondyls and their relatives. Limnarchia means "lake rulers" in Greek, in reference to their aquatic lifestyles and long existence over a span of approximately 200 million years from the Late Carboniferous to the Early Cretaceous. In phylogenetic terms, Limnarchia is a stem-based taxon including all temnospondyls more closely related to Parotosuchus than to Eryops. It is the sister group of the clade Euskelia, which is all temnospondyls more closely related to Eryops than to Parotosuchus. Limnarchians represent an evolutionary radiation of temnospondyls into aquatic environments, while euskelians represent a radiation into terrestrial environments. While many euskelians were adapted to life on land with strong limbs and bony scutes, most limnarchians were better adapted for the water with poorly developed limbs and lateral line sensory systems in their skulls.

Almasaurus is an extinct genus of trematosaurian temnospondyl within the family Latiscopidae. It is known from several skulls and some postcranial material found from the Argana Formation in Morocco, which dates back to the Late Triassic.

Bothriceps is an extinct genus of stereospondyl temnospondyl. It is a member of the infraorder Trematosauria and is the most basal brachyopomorph known. It is one of the only brachyopomorph that lies outside the superfamily Brachyopoidea, which includes the families Brachyopidae and Chigutisauridae. It shares several similarities to Keratobrachyops, another basal brachyopomorph, and may be closely related to or even synonymous with it.

<i>Lydekkerina</i> species of amphibian (fossil)

Lydekkerina is an extinct genus of stereospondyl temnospondyl. It is the type genus of the family Lydekkerinidae. Fossils have been collected from Early Triassic deposits in South Africa and Australia. The type species is L. huxleyi, first described in 1889. While most other stereospondyls were semiaquatic, Lydekkerina was exclusively terrestrial.

Luzocephalus is an extinct genus of temnospondyl amphibian from the Early Triassic of Russia. It is usually regarded as a member of the family Lydekkerinidae, although it has also been placed in the family Trematosauridae.

Capitosauria clade of reptiles (fossil)

Capitosauria is an extinct group of large temnospondyl amphibians with simplified stereospondyl vertebrae. Mainly living as piscivores in lakes and rivers, the Capitosauria and its sister taxon Trematosauria were the only major labyrinthodonts that existed during the Mesozoic in ecological niches broadly similar to those of modern crocodiles, and some grew to very large sizes. At 6 meter in length, the Mid-Triassic Mastodonsaurus giganteus is not only thought to have been the largest capitosaur, but possibly also the largest amphibian to have lived. The capitosaurs enjoyed a brief period of success in the early Triassic, but with the rise of crocodiles in the middle Triassic they went into decline, and the capitosaur lineage is not known beyond the Late Triassic.

<i>Trucheosaurus</i> genus of amphibians (fossil)

Trucheosaurus is an extinct genus of rhytidosteid temnospondyl from the late Permian period of Sydney Basin, New South Wales, Australia. It is known from the holotype materials MMF 12697a, a partially complete skull, AMF 50977, an articulated postcranial skeleton and BMNHR 3728, the counterpart of both skull and postcranial skeleton, recovered from the Glen Davis Formation. This genus was named by Watson in 1956, and the type species is Trucheosaurus major.

Selenocara is an extinct genus of mastodonsauroid temnospondyl. The type species is Selenocara groenlandica, described by Gunnar Säve-Söderbergh in 1935 on the basis of skull bones from the Lower Triassic Wordie Creek Formation of Greenland. Säve-Söderbergh originally described it as a new species of Wetlugasaurus.

References

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  10. http://www.angellis.net/Web/PDfiles/amphs.pdf
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  12. Damiani, RJ (2001). A systematic revision and phylogenetic analysis of Triassic mastodonsauroids (Temnospondyli: Stereospondyli). Zoological Journal of the Linnean Society133:379-482.
  13. Shishkin, M. A., Novikov, I. V. and Gubin, Y. M. (2000). Permian and Triassic temnospondyls from Russia. In: Benton, M. J., Shishkin, M. A., Unwin, D. M. and Kurochkin, E. N. (eds.), The Age of Dinosaurs in Russia and Mongolia. Cambridge University Press, pp. 35-59.
  14. Säve-Söderbergh, G. (1937). On the dermal skulls of Lyrocephalus, Aphaneramma, and Benthosaurus, labyrinthodonts from the Triassic of Spitsbergen and N. Russia. Bulletin of the Geological Institution of the University of Uppsala27:189–208.
  15. Bystrow, A. P. (1935). Morphologische Untersuchungen der Deckknochen des Schädels der Wirbeltiere. Acta Zoologica16:65–141.