Apsisaurus is an extinct genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of Early Permian varanopid 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...

 known from Texas

Texas

Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...

 of the United States

United States

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

. It was first named by Michel Laurin in 1991

1991 in paleontology

-Birds:* Sankar Chatterjee's discovery of a possible Triassic bird, Protoavis, if genuine, would push avian origins back almost 70 million years. The find ignites controversy over the connection between dinosaurs and birds....

 and the type species

Type species

In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...

 is Apsisaurus witteri. Apsisaurus witteri is known from the holotype

Holotype

A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...

 MCZ 1474, a three-dimensionally preserved partial skeleton

Skeleton

The skeleton is the body part that forms the supporting structure of an organism. There are two different skeletal types: the exoskeleton, which is the stable outer shell of an organism, and the endoskeleton, which forms the support structure inside the body.In a figurative sense, skeleton can...

 including an incomplete skull

Skull

The skull is a bony structure in the head of many animals that supports the structures of the face and forms a cavity for the brain.The skull is composed of two parts: the cranium and the mandible. A skull without a mandible is only a cranium. Animals that have skulls are called craniates...

 and mandible

Mandible

The mandible pronunciation or inferior maxillary bone forms the lower jaw and holds the lower teeth in place...

s. The skull roof of Archeria

Archeria

This article is about an extinct animal; for the plant genus, see Archeria Archeria was an eel-like anthracosaur which lived in the Early Permian. It was medium-sized aquatic predator....

is also articulate

Articulate

Articulate may refer to:*Articulate *Articulate sign*Articulate sound*Joint, also known as articulation*Word modified by an article...

d to the postcrania

Postcrania

Postcrania[p] in zoology and vertebrate paleontology refers to all or part of the skeleton apart from the skull. Frequently, fossil remains, e.g...

l skeleton. It was collected in the Archer City Bonebed 1 site, from the Archer City Formation of the Wichita Group, dating to the Early Permian epoch

Epoch (geology)

An epoch is a subdivision of the geologic timescale based on rock layering. In order, the higher subdivisions are periods, eras and eons. We are currently living in the Holocene epoch...

. Apsisaurus was formerly assigned as a "eosuchia

Eosuchia

Eosuchians are an extinct order of diapsid reptiles. Depending on which taxa are included the order may have ranged from the late Carboniferous to the Eocene but the consensus is that eosuchians are confined to the Permian and Triassic....

n" diapsid

Diapsid

Diapsids are a group of reptiles that developed two holes in each side of their skulls, about 300 million years ago during the late Carboniferous period. Living diapsids are extremely diverse, and include all crocodiles, lizards, snakes, and tuatara...

. In 2010, it was redescribed by Robert R. Reisz

Robert R. Reisz

Robert Rafael Reisz is a Canadian paleontologist and specialist in the study of early amniote and tetrapod evolution.Robert Reisz was born August 27, 1947, in Oradea, Romania. He received his B.Sc. , M.Sc. and Ph.D. from McGill University as Robert L. Carroll’s first doctoral graduate...

, Michel Laurin and David Marjanovic and classified as a basal

Basal (phylogenetics)

In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...

 varanopid 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...

.

The cladogram

Cladogram

A cladogram is a diagram used in cladistics which shows ancestral relations between organisms, to represent the evolutionary tree of life. Although traditionally such cladograms were generated largely on the basis of morphological characters, DNA and RNA sequencing data and computational...

 below is modified after Reisz, Laurin and Marjanovic, 2010.