Thrausmosaurus is a genus of synapsid

Synapsid

Synapsids are a group of animals that includes mammals and everything more closely related to mammals than to other living amniotes. They are easily separated from other amniotes by having an opening low in the skull roof behind each eye, leaving a bony arch beneath each, accounting for their name...

 pelycosaur

Pelycosaur

The pelycosaurs are an informal grouping composed of basal or primitive Late Paleozoic synapsid amniotes. Some species were quite large and could grow up to 3 meters or more, although most species were much smaller...

s from the extinct family Varanopidae

Varanopidae

Varanopidae was a family of synapsid "pelycosaurs" that resembled monitor lizards and might have had the same lifestyle, hence their name. No known varanopids developed a sail like Dimetrodon. Their size varied from lizard-sized to dog-sized creatures. Varanopids already showed some advanced...

. Like all that resemble members of Varanopidae, Thrausmosaurus most likely resembled the modern monitor lizard

Monitor lizard

Monitor lizards are usually large reptiles, although some can be as small as in length. They have long necks, powerful tails and claws, and well-developed limbs. Most species are terrestrial, but arboreal and semiaquatic monitors are also known...

 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

Limestone

Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....

 Quarry, north of Fort Sill

Fort Sill

Fort Sill is a United States Army post near Lawton, Oklahoma, about 85 miles southwest of Oklahoma City.Today, Fort Sill remains the only active Army installation of all the forts on the South Plains built during the Indian Wars...

, Comanche County

Comanche County, Oklahoma

Comanche County is a county located in the U.S. state of Oklahoma. Built on former reservation lands of the Comanche, Kiowa, and Apache in Indian Territory, Comanche County was open for settlement on August 16, 1901 by lottery. The region has three cities and seven towns as well as the Fort Sill...

, Oklahoma

Oklahoma

Oklahoma is a state located in the South Central region of the United States of America. With an estimated 3,751,351 residents as of the 2010 census and a land area of 68,667 square miles , Oklahoma is the 28th most populous and 20th-largest state...

, USA

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

. These deposits are dated to the Kungurian

Kungurian

In the geologic timescale, the Kungurian is an age or stage of the Permian. It is the latest or upper of four subdivisions of the Cisuralian epoch or series. The Kungurian lasted between 275.6 ± 0.7 and 270.6 ± 0.7 million years ago...

 (Leonardian) of the Lower Permian

Permian

The PermianThe term "Permian" was introduced into geology in 1841 by Sir Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil; Murchison asserted in 1841 that he named his "Permian...

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Taxonomic history

Thrausmosaurus was designated by Fox to belong to the family Sphenacodontidae

Sphenacodontidae

Sphenacodontidae is a family of small to large, advanced, carnivorous, Late Pennsylvanian to middle Permian pelycosaurs. Primitive forms were generally small in size , but during the later part of the early Permian these animals grew progressively larger , to become the top predators of their...

 based on the structure and curvature of the teeth. The genus remained in Sphenacodontidae until the type material was reexamined. In 1986 the type specimen was reassigned to Synapsida incertae sedis

Incertae sedis

, is a term used to define a taxonomic group where its broader relationships are unknown or undefined. Uncertainty at specific taxonomic levels is attributed by , , and similar terms.-Examples:*The fossil plant Paradinandra suecica could not be assigned to any...

by R. R. Reisz, who was unable to identify the relationship of the material to other synapsids. 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

Nomen dubium

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

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