Endothiodon

Endothiodon (/ɛndoʊθiːoʊdɔːn/ "inner tooth" from Greek endothi (ἔνδοθῐ), "within", and odon (ὀδών), "tooth", most likely named for the characteristic of the teeth being placed internally to the maxilla) is an extinct genus of large dicynodont from the Late Permian. Like other dicynodonts, Endothiodon was an herbivore, but it lacked the two tusks that characterized most other dicynodonts. The anterior portion of the upper and lower jaw are curved upward, creating a distinct beak that is thought to have allowed them to be specialized grazers.

Endothiodon was widespread and is found across the southern region of what was then a single large continent known as Pangea. It was originally only found in southern Africa but has now also been found in India and Brazil, which were both close to Africa at the time. The finding in Brazil marks the first dicynodont to be reported for the Permian of South America. This finding also shows that part of the Rio do Rasto Formation in Brazil can now be correlated with deposits in India, Malawi, Mozambique, South Africa, Tanzania, Zambia, and Zimbabwe.

Originally there were thought to be nine species, but this was reduced down to just 3 species. A fourth species was later discovered. The four currently known species of Endothiodon are E. bathystoma, E. uniseries, E. whaitsi, and E. mahalanobsi. However, the basic distinction among the four species is size, which leads some to believe that E. uniseries, E. bathystoma, and E. whaitsi may actually represent an ontogenetic series rather than three distinct taxa. E. mahalanobsi, on the other hand, is most likely a separate, truly smaller species based on the size of both juvenile and adult forms that have been found. Apart from size, E. mahalanobsi also has a single longitudinal ridge on the snout (compared to three on the other species), a lower position of the pineal boss, and a swollen prefrontal bone.