Probainognathus is a 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 meat-eating mammal-like reptile (Therapsids) that lived during the lower Upper Triassic

Triassic

The Triassic is a geologic period and system that extends from about 250 to 200 Mya . As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic. Both the start and end of the Triassic are marked by major extinction events...

 of South America

South America

South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...

. This creature had an incipient squamosal-dentary jaw

Jaw

The jaw is any opposable articulated structure at the entrance of the mouth, typically used for grasping and manipulating food. The term jaws is also broadly applied to the whole of the structures constituting the vault of the mouth and serving to open and close it and is part of the body plan of...

-cranium joint, which is a clearly mammal

Mammal

Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...

ian anatomical feature. It was at the very least closely related to the family of Chiniquodontidae

Chiniquodontidae

Chiniquodontidae is a family of meat-eating advanced mammal-like reptiles that lived during the Upper Triassic of South America and perhaps Europe. A further possible representative, Aleodon, has been identified from the Middle Triassic of Africa...

, in which some authors have included it. Some broadly similar teeth from Europe

Europe

Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

 were described under the name of Lepagia

Lepagia

Lepagia is a poorly known genus of meat-eating mammal-like reptile, , which lived during the Upper Triassic in Europe. Partly due to the paucity of remains the precise affinities of this genus are unclear. It seems reasonably closely related to Probainognathus, a somewhat earlier inhabitant of...

.

Known from about three dozen specimens, this creature was only about 10 cm long. Two skulls, including 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...

, were stolen from the University of La Rioja, Argentina

Argentina

Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...

, in February 1994. A pair of Probelesodon

Probelesodon

Probelesodon is an extinct genus of chiniquodontid cynodont. Fossils have been found from Argentina and Brazil of Triassic age. Specimens were first discovered from the Chañares Formation in La Rioja Provence, Argentina that date back to the Anisian stage of the early Middle Triassic. A new...

holotypes, (P. lewisi and P. minor), accompanied them.