Achaenodon robustus (Cope 1873, Eocene) was tradionally considered an artiodactyl, but here nests between basal hippos and Cambaytherium. The skull was extremely wide with strong jaw muscles filling the space around the narrow cranium and crests.
Cambaytherium thewissi (Rose et al. 2014; Eocene, 55 mya; 45-75 lbs) was originally considered a basal perissodactyl, but nests here between Hippopotamus and Janjucetus. The anterior palate has the same three lobes found in Hippopotamus. The posterior mandible has a long retroarticular process as in Anthracobune. Cambaytherium was found on the marine coastline of island India, close to where pakicetid aand archaeocete whales were convergently evolving from terrestrial tenrec ancestors.
Cope ED 1873. Fourth notice of extinct Vertebrata from the Bridger and the Green River Tertiaries. Paleontological Bulletin 17:1–4.
Rose, KD et al. (8 other authors) 2014. Early Eocene fossils suggest that the mammalian order Perissodactyla originated in India. Nature Communications. 5 (5570). doi:10.1038/ncomms6570.
Rose KD et al, 2020. Anatomy, Relationships, and Paleobiology of Cambaytherium (Mammalia, Perissodactylamorpha, Anthracobunia) from the lower Eocene of western India, Journal of Vertebrate Paleontology (2020). DOI: 10.1080/02724634.2020.1761370