This pattern is reminiscent of Ferugliotherium, a gondwanathere mammal from similarly aged deposits in Argentina, and Trapalcotherium is therefore recognized as a member of the same family Ferugliotheriidae.

The specific name, matuastensis, derives from Puesto El Matuesto, a shed used by the paleontologists who collected the fossils from the Allen Formation.

[3] The single tooth of Trapalcotherium is identified as a lower molar because it has two longitudinal rows of cusps; as a first molar because it is longer than wide; and as a left tooth because the left side (interpreted as labial, in the direction of the lips) bears more cusps than the right side (lingual, the direction of the tongue).

[4] Trapalcotherium is identified as a member of Gondwanatheria—a small and enigmatic group of mammals from Cretaceous and Paleogene of the southern continents (Gondwana)—on the basis of the transverse ridges and triangle on its crown.

The evolutionary affinities of gondwanatheres, which include the Ferugliotheriidae and the higher-crowned Sudamericidae, are controversial, though a relationship with multituberculates (a large group mainly known from the northern continents of Laurasia) has repeatedly been proposed; the identification of Trapalcotherium does not provide additional information that has a bearing on the relationships of the gondwanatheres.