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 (such as ''Trogosus)'' 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 (molar-like).

When Marsh first named and described the tillodonts, he explained:

When naming his new " pachyderm" species ''Trogosus castoridens'' ("beaver-toothed gnawing-hog"), 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 '' Basalina'' from Pakistan 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 Pakistan and Europe with those from North America adds evidence to a faunal interchange between these continents during the early Eocene.

Suborder Tillodontia
: Genus †''Azygonyx'' (), dentary, postcranial fragments
: Genus †'' Basalina'' (), poorly preserved jaw fragment with incomplete cheek tooth
: Genus †'' Benaius'' (), left lower jaw
: Genus †'' Dysnoetodon'' (), maxilla and lower jaw
: Family † Esthonychidae () (Syn. Anchippodontidae, Tillotheriidae)
:: Genus †'' Adapidium'' (), right lower jaw
:: Subfamily † Esthonychinae ()
::: Genus †'' Esthonyx'' (), lower mandibles, teeth
:: Genus †'' Megalesthonyx'' (), left mandible, teeth, feet bones
:: Subfamily † Trogosinae () (Syn. Anchippodus)
::: Genus †'' Tillodon'' (), skull
::: Genus †''Trogosus'' () (Syn. ''Tillotherium''), skull, lower jaws, teeth, vertebrae, ilium, limb bones, feet bones
: Genus †'' Franchaius'' (; synonymized with ''Plesiesthonyx'', ), less than 20 isolated teeth
: Genus †'' Higotherium'' (), fragmentary right mandible, teeth
: Genus †'' Interogale'' (), well-preserved mandible
: Genus †'' Kuanchuanius'' (), partial mandible, teeth
: Genus †'' Lofochaius'' (), poorly preserved skull with few teeth
: Genus †''Meiostylodon'' (), three isolated teeth
: Genus †'' Plesiesthonyx'' (), isolated molars
: Genus †''Plethorodon'' (), partial skull with upper cheek teeth
: Genus †'' Simplodon'' (), right upper jaw with cheek teeth
: Family † Yuesthonychidae ()
:: Genus †'' Yuesthonyx'' (), left mandibles, partial skull, teeth

Notes

References

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{{Taxonbar, from=Q2280456

Cimolestans
Eocene mammals
Paleocene mammals
Clawed herbivores
Taxa named by Othniel Charles Marsh
Paleocene first appearances
Eocene extinctions
Fossil taxa described in 1875
Mammal suborders
Prehistoric animal suborders