''Pseudotherium'' ("false beast") is an extinct genus of

prozostrodontia Prozostrodontia is a clade of cynodonts including mammaliaforms and their closest relatives such as Tritheledontidae and Tritylodontidae. It was erected as a node-based taxon by Liu and Olsen (2010) and defined as the least inclusive clade contai ...

cynodont Cynodontia () is a clade of eutheriodont therapsids that first appeared in the Late Permian (approximately 260 Megaannum, mya), and extensively diversified after the Permian–Triassic extinction event. Mammals are cynodonts, as are their extin ...

s from the

Late Triassic The Late Triassic is the third and final epoch (geology), epoch of the Triassic geologic time scale, Period in the geologic time scale, spanning the time between annum, Ma and Ma (million years ago). It is preceded by the Middle Triassic Epoch a ...

Argentina Argentina, officially the Argentine Republic, is a country in the southern half of South America. It covers an area of , making it the List of South American countries by area, second-largest country in South America after Brazil, the fourt ...

. It contains one species, ''P. argentinus'', which was first described in 2019 from remains found in the La Peña Member of the Ischigualasto Formation in the Ischigualasto-Villa Unión Basin.

Discovery and naming

The holotype and only known specimen, PVSJ 882, was discovered in 2006 by Argentine palaeontologist Ricardo N. Martínez during an expedition to the Ischigualasto Formation. It consists of a partial skull lacking the lower jaw, quadrate bones and most of the zygomatic arches and premaxillae. The generic name ''Pseudotherium'' is derived from the Greek words , meaning "false", and , meaning "beast". The specific name ''argentinus'' references the country of Argentina where it was found.

Description

''Pseudotherium'' would have been a relatively large cynodont; excluding its missing premaxillae, the holotype skull is in length. Running along the top of the skull was a prominent sagittal crest (an attachment point for jaw muscles). Like ''

Prozostrodon ''Prozostrodon'' is an extinct genus of probainognathian cynodonts that was closely related to mammals. The remains were found in Brazil and are dated to the Carnian age of the Late Triassic. The holotype has an estimated skull length of , indica ...

'', a contemporary prozostrodontian from Brazil, it possessed remnants of the prefrontal and postorbital bones. Most mammaliamorphs, on the other hand, lacked any trace of these bones. The snout of ''Pseudotherium'' is long and slender. As the premaxillae are incomplete, no incisors have been preserved. The canines were thin and curved, with unique longitudinal ridges on each side. Behind the canines were nine pairs of postcanine teeth; these were separated from the canines by a short diastema. The postcanines resembled those of '' Botucaraitherium'' and the brasilodontids, possessing three main cusps in a roughly symmetrical arrangement. The seventh and eighth postcanines also bore two and three accessory cusps, respectively. Unlike in tritylodontids and mammaliaforms, the roots were incompletely divided.

Classification

The following cladogram is from the phylogenetic analysis of Wallace ''et al.'', 2019. ''Pseudotherium'' was placed within Mammaliamorpha as the sister taxon of Tritylodontidae, a largely Jurassic group of mammaliamorphs. The authors however noted that ''Pseudotherium'' might be more basal than the cladogram suggests, possibly forming a polytomy with tritheledontids, tritylodontids and brasilodontids instead. A 2023 paper by Stefanello ''et al.'', describing a nearly complete new skull of ''Prozostrodon'', recovered ''Pseudotherium'' as the sister taxon of that genus, with the two genera forming the clade Prozostrodontidae at the base of

Prozostrodontia Prozostrodontia is a clade of cynodonts including mammaliaforms and their closest relatives such as Tritheledontidae and Tritylodontidae. It was erected as a node-based taxon by Liu and Olsen (2010) and defined as the least inclusive clade contai ...

. A cladogram from that study is shown below:

References

{{Taxonbar, from=Q66778552 Prozostrodontia Carnian genera Late Triassic synapsids of South America Triassic Argentina Fossils of Argentina Ischigualasto Formation Fossil taxa described in 2019