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.

[1] 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.

The authors however noted that Pseudotherium might be more basal than the cladogram suggests, possibly forming a polytomy with tritheledontids, tritylodontids and brasilodontids instead.

[1] Probainognathus Prozostrodon Therioherpeton Tritheledontidae Pseudotherium Tritylodontidae Botucaraitherium Brasilodontidae Sinoconodon Mammaliaformes 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.

A cladogram from that study is shown below:[2] Lumkuia Chiniquodon Probainognathidae Ecteniniidae Protheriodon Prozostrodon Pseudotherium Therioherpeton Irajatherium Riograndia Diarthrognathus Pachygenelus Tritylodontidae Botucaraitherium Brasilodon Mammaliaformes