Tillodontia


Tillodontia is an extinct suborder of eutherian mammals known from the Early Paleocene to Late Eocene of China, the Late Paleocene to Middle Eocene of North America where they display their maximum species diversity, the Middle Eocene of Pakistan, and the Early Eocene of Europe. Leaving no descendants, they are most closely related to the pantodonts, another extinct group. The tillodonts were medium- to large-sized animals that probably feed on roots and tubers in temperate to subtropical habitats.

Description

Tillodonts had rodent-like incisors, clawed feet and blunt, cusped teeth. They were mostly medium-sized animals, although the largest of them could reach the size of a large bear.
The cranium ranged in length from and had a characteristic elongated rostrum, an elongated mandibular symphysis, and a shortened basicranial region. The second upper and lower incisors are large in most species, the first upper and lower premolars are small or absent, the fourth upper and lower premolars are molariform.
When Marsh first named and described the tillodonts, he explained:
When naming his new "pachyderm" species Trogosus castoridens'', Leidy added that it was a fossil "which would appear to have pertained to the stock from which diverged the Rhinoceros and Mastodon, the Peccary, and perhaps the Beaver."

Classification

Franchaius from the early Eocene of Europe, Benaius, Lofochaius, Meiostylodon, and Huananius from the early Paleocene of China, and Yuesthonyx from the late Paleocene of China are primitive forms. Interogale from the late Paleocene of China, and Anchilestes probably from the middle Paleocene of China, were once assigned to Anagalida, but may also be primitive tillodonts.
The monophyly of the subfamily Trogosinae is unchallenged, but Esthonychines most likely includes the ancestors of Trogosinae and therefore is probably paraphyletic. Tillodontia is mostly known from dentaries and teeth. The cranium is best known from Trogosinae and the postcranium from Trogosus.
Azygonyx and Esthonyx from North America, Franchaius and Plesiesthonyx from Europe, and possibly Basalina from Pakistan and an unassigned specimen from India are all morphologically closely related but obviously geographically quite widespread. In contrast, Asian tillodonts tend to be smaller and less derived. This possible link between specimens from the Indian subcontinent and those from Europe and America adds evidence to a faunal interchange between these continents during the early Eocene.
Suborder Tillodontia