Probelesodon sanjuanensis is a member of Eucynodontia, a lineage that includes mammals and their closest extinct relatives. As with the other eucynodonts (Probainognathus, Exaeretodon, and Ecteninion) and the oldest-known dinosaurs (Eoraptor and Herrerasaurus) featured on this site, Probelesodon was collected from the late Triassic sediments of Argentina.
Eucynodontia is diagnosed by a number of craniodental advances that are adaptations for a more complex mastication system. Probelesodon, like other eucynodonts, possesses a mosaic of primitive and advanced characters. It is similar to mammals in the possession of a well-developed, posteriorly-extended palate, a double occipitial condyle, and the loss of the pineal foramen. Primitive characters found in Probelesodon include the presence of the postorbital and prefrontal bones, the presence of a postorbital bar, and a quadrate-articular jaw articulation. Within Eucynodontia, Probelesodon is the sister taxon to Chiniquodon. Like Probainognathus and Ecteninion, it is carnivorous and possesses recurved, multicuspid cheek teeth.
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