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Temporal range: Lower Permian
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Chordata
Family: Varanopidae
Genus: Thrausmosaurus
Fox, 1962
Type species
Thrausmosaurus serratidens
Richard C. Fox, 1962

Thrausmosaurus is a genus of synapsid pelycosaurs from the extinct family Varanopidae. Like all that resemble members of Varanopidae, Thrausmosaurus most likely resembled the modern monitor lizard and may have had the same lifestyle. The type and only species was described by R. C. Fox in 1962, from three fossilized jaw fragments bearing teeth. The specimens were recovered from the fissure-fill deposits uncovered in a Limestone Quarry, north of Fort Sill, Comanche County, Oklahoma, USA. These deposits are dated to the Kungurian (Leonardian) of the Lower Permian. [1]

Synapsid class of tetrapods

Synapsids, synonymous with theropsids [not to be confused with Therapsida, which are subordinate to Synapsida], are a group of animals that includes mammals and every animal more closely related to mammals than to other living amniotes. They are easily separated from other amniotes by having a temporal fenestra, an opening low in the skull roof behind each eye, leaving a bony arch beneath each; this accounts for their name. Primitive synapsids are usually called pelycosaurs or pelycosaur-grade synapsids; more advanced mammal-like ones, therapsids. The non-mammalian members are described as mammal-like reptiles in classical systematics; they can also be called stem mammals or proto-mammals. Synapsids evolved from basal amniotes and are one of the two major groups of the later amniotes; the other is the sauropsids, a group that includes modern reptiles and birds. The distinctive temporal fenestra developed in the ancestral synapsid about 312 million years ago, during the Late Carboniferous period.

Pelycosaur order of tetrapods

The pelycosaurs are an informal grouping composed of basal or primitive Late Paleozoic synapsids, sometimes erroneously referred to as "mammal-like reptiles". They consist of all synapsids except for the therapsids and their descendants. Some species were quite large, growing to a length of 3 metres (10 ft) or more, although most species were much smaller. Because more advanced groups of synapsids evolved directly from 'pelycosaurs', the term had fallen out of favor among scientists by the 21st century, and is only used informally, if at all, in the modern scientific literature. The supplied etymology presents a problem, as follows: pelycosaur has the basically supplied meaning 'basin lizard', but there is an original etymological mismatch in that Greek pélix is 'wooden bowl' and pelíkē 'basin', whereas pélyx is 'ax' like pélekys 'double-edged ax'. This imperfect term pelycosaur has been fairly well abandoned by paleontologists because it no longer matches cladistic features.

Varanopidae family of synapsids

Varanopidae is an extinct family of amniotes that resembled monitor lizards and might have had the same lifestyle, hence their name. Typically, they are considered synapsids that evolved from an Archaeothyris-like synapsid in the Late Carboniferous, but a recent study has recovered them as diapsid reptiles. A varanopid from the latest Middle Permian Pristerognathus Assemblage Zone is the youngest known varanopid and the last member of the "pelycosaur" group of synapsids.


Taxonomic history

Thrausmosaurus was designated by Fox to belong to the family Sphenacodontidae based on the structure and curvature of the teeth. The genus remained in Sphenacodontidae until the type material was reexamined. [1] In 1986 the type specimen was reassigned to Synapsida incertae sedis by R. R. Reisz, who was unable to identify the relationship of the material to other synapsids. [1] This opinion was reaffirmed by Sullivan and Reisz in 1999. Upon further examination of the specimens, Evans et al. in 2009 reaffirmed the validity of the genus name and placed the genus in the Varanopidae. However they were unable to determine enough distinct characters to maintain the species Thrausmosaurus serratidens, and thus declared the name nomen dubium . [1]

Sphenacodontidae family of tetrapods

Sphenacodontidae is an extinct family of small to large, advanced, carnivorous, Late Pennsylvanian to middle Permian pelycosaurs. Primitive forms were generally small, but during the later part of the early Permian these animals grew progressively larger, to become the top predators of their environments. Sphenacodontid fossils are so far known only from North America and Europe.

<i>Incertae sedis</i> indicates uncertainty on taxonomic position

Incertae sedis or problematica are terms used for a taxonomic group where its broader relationships are unknown or undefined. Alternatively, such groups are frequently referred to as "enigmatic taxa". In the system of open nomenclature, uncertainty at specific taxonomic levels is indicated by incertae familiae, incerti subordinis, incerti ordinis and similar terms.

In zoological nomenclature, a nomen dubium is a scientific name that is of unknown or doubtful application.

See also

Related Research Articles

<i>Dimetrodon</i> genus of synapsids

Dimetrodon is an extinct genus of synapsids that lived during the Cisuralian, around 295–272 million years ago (Ma). It is a member of the family Sphenacodontidae. The most prominent feature of Dimetrodon is the large neural spine sail on its back formed by elongated spines extending from the vertebrae. It walked on four legs and had a tall, curved skull with large teeth of different sizes set along the jaws. Most fossils have been found in the southwestern United States, the majority coming from a geological deposit called the Red Beds of Texas and Oklahoma. More recently, fossils have been found in Germany. Over a dozen species have been named since the genus was first described in 1878.

Caseasauria taxon of tetrapods

Caseasauria is one of the two main clades of early synapsids, the other being the Eupelycosauria. Caseasaurs are currently known only from the Late Carboniferous and the Permian, and include two superficially different families, the small insectivorous or carnivorous Eothyrididae, and the large, herbivorous, potentially aquatic Caseidae. These two groups share a number of specialised features associated with the morphology of the snout and external naris.

<i>Secodontosaurus</i> genus of synapsid

Secodontosaurus is an extinct genus of "pelycosaur" synapsids that lived from between about 285 to 272 million years ago during the Early Permian. Like the well known Dimetrodon, Secodontosaurus is a carnivorous member of the Eupelycosauria family Sphenacodontidae and has a similar tall dorsal sail. However, its skull is long, low, and narrow, with slender jaws that have teeth that are very similar in size and shape—unlike the shorter, deep skull of Dimetrodon, which has large, prominent canine-like teeth in front and smaller slicing teeth further back in its jaws. Its unusual long, narrow jaws suggest that Secodontosaurus may have been specialized for catching fish or for hunting prey that lived or hid in burrows or crevices. Although no complete skeletons are currently known, Secodontosaurus likely ranged from about 2 to 2.7 metres in length, weighing up to 110 kilograms (250 lb).

<i>Varanops</i> genus of synapsid

Varanops is an extinct genus of Early Permian varanopid synapsids known from Texas and Oklahoma of the United States. It was first named by Samuel Wendell Williston in 1911 as a second species of Varanosaurus, Varanosaurus brevirostris. In 1914, Samuel W. Williston reassigned it to its own genus and the type species is Varanops brevirostris.

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

Captorhinus is an extinct genus of captorhinid reptiles that lived during the Permian period. Its remains are known from Oklahoma, Texas, Europe, India, the Pedra de Fogo Formation, Parnaíba Basin, Brazil and the Madumabisa Mudstone, Zambia.

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

Colobomycter is an extinct genus of small parareptile known from the Early Permian of Oklahoma. The genus was first described from fossil remains in 1958, at which time it was believed to represent a synapsid, specifically, a pelycosaur. However, the discovery of new material and reexamination of the holotype led to its reclassification as a member of the Eureptilia. More recent studies indicate that Colobomycter is properly placed within the amniote clade Parareptilia, closely related to the taxon Acleistorhinus. Together, the two taxa form the Family Acleistorhinidae.

<i>Aerosaurus</i> genus of synapsid

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).

<i>Delorhynchus</i> genus of reptiles

Delorhynchus is an extinct genus of lanthanosuchoid parareptile known from the late Early Permian Garber Formation of Comanche County, Oklahoma, south-central United States. It contains the type species D. priscus as well as a better preserved second species D. cifellii.

Watongia is an extinct genus of non-mammalian synapsids from Middle Permian of Oklahoma. Only one species has been described, Watongia meieri, from the Chickasha Formation. It was assigned to family Gorgonopsidae by Olson and to Eotitanosuchia by Carroll. Reisz and collaborators assigned the genus in Varanopidae.

Acleistorhinidae family of reptiles (fossil)

Acleistorhinidae is an extinct family of Early Permian-aged lanthanosuchoid parareptiles. Presently, the clade consists of only two taxa, Colobomycter and Acleistorhinus, both collected from the Permian of Oklahoma. Sister taxa include Chalcosaurus, Lanthaniscus and Lanthanosuchus.

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

Acleistorhinus (ah-kles-toe-RYE-nuss) is an extinct genus of parareptile known from the Early Permian of Oklahoma It is notable for being the earliest known anapsid reptile yet discovered. The morphology of the lower temporal fenestra of the skull of Acleistorhinus bears a superficial resemblance to that seen in early synapsids, a result of convergent evolution. Only a single species, A. pteroticus, is known, and it is classified in the Family Acleistorhinidae, along with Colobomycter.

<i>Heleosaurus</i> genus of synapsid

Heleosarus scholtzi is an extinct species of basal synapsids, known as pelycosaurs, in the family of Varanopidae during the middle Permian. At first H. scholtzi was mistakenly classified as a diapsid. Members of this family were carnivorous and had dermal armor, and somewhat resembled monitor lizards. This family was the most geologically long lived, widespread, and diverse group of early amniotes. To date only two fossils have been found in the rocks of South Africa. One of these fossils is an aggregation of five individuals.

Ambedus is an extinct genus of diadectid reptiliomorph. Fossils have been found from the Early Permian Dunkard Group of Monroe County, Ohio. The type species A. pusillus was named in 2004. The genus name comes from the Latin word ambedo meaning "to nibble", in reference to its herbivorous diet. The specific name pusillus means "tiny" in Latin.

Georgenthalia is an extinct genus of dissorophoid temnospondyl from the Lower Permian. It is an amphibamid which lived in what is now the Thuringian Forest of central Germany. It is known from the holotype MNG 11135, a small, complete skull. It was found in the Bromacker locality of the Tambach Formation. It was first named by Jason S. Anderson, Amy C. Henrici, Stuart S. Sumida, Thomas Martens and David S. Berman in 2008 and the type species is Georgenthalia clavinasica.

<i>Orovenator</i> genus of tetrapods that developed two holes (temporal fenestra) in each side of their skulls, about 300 million years ago

Orovenator is an extinct genus of diapsid from Lower Permian deposits of Oklahoma, United States. It is known from two partial skulls from the Richards Spur locality in Oklahoma. The holotype OMNH 74606 consists of a partial skull preserving snout and mandible, and the referred specimen, OMNH 74607, a partial skull preserving the skull roof, vertebrae and palatal elements. It was first named by Robert R. Reisz, Sean P. Modesto and Diane M. Scott in 2011 and the type species is Orovenator mayorum. The generic name means "mountain", oro, in Greek in reference to the Richards Spur locality, which was mountainous during the Permian period and "hunter", venator, in Latin. The specific name honours Bill and Julie May. Orovenator is the oldest and most basal neodiapsid to date.

Abyssomedon is an extinct genus of a nyctiphruretid parareptile known from the late Early Permian Garber Formation of Comanche County, Oklahoma, south-central United States. It contains a single species, Abyssomedon williamsi, which represents the third known nyctiphruretid species, the oldest species of the family and the first to be discovered in North America.


  1. 1 2 3 4 Evans, David C., Maddin, Hillary C., & Reisz, Robert R. 2009 “A Re-evaluation of Sphenacodontid Synapsid Material from the Lower Permian Fissure Fills near Richards Spur, Oklahoma” Palaeontology52(1):219–227