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| Isotemnus | |
|---|---|
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| Teeth ofIsotemnus ctalego | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | †Notoungulata |
| Family: | †Isotemnidae |
| Genus: | †Isotemnus Ameghino 1897 |
| Type species | |
| †Isotemnus primitivus Ameghino, 1897 | |
| Species | |
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| Synonyms | |
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Isotemnus is anextinctgenus ofnotoungulate belonging to the familyIsotemnidae. It lived from the Late Paleocene to the MiddleEocene of what is nowArgentina.
This genus was smaller thanThomashuxleya andPeriphragnis, and did not exceed 50 kilograms in weight. Its build was comparable to a modernpeccary, with a body relatively massive and strong and sturdy legs. Compared to other Eocene notoungulates, like basalNotohippidae andNotostylopidae,Isotemnus had an humerus whose distal part had a high medial trochlear crest, while the bicipital radial tuberosity was almost unexistant. The astragalus had a broad and low trochlea with a short neck. The calcaneus had rectangular fibular facets, and an unusually thick sustentaculum. Several of the distinctive anatomical leg characteristics ofIsotemnus could be due to its smaller size;Periphragnis andThomashuxleya, while very similar, had different characteristics.
Isotemnus is the eponymous genus of the familyIsotemnidae, a possibly paraphyletic group of notoungulates including the most basal forms oftoxodonts.Isotemnus was one of the most archaic and basal of the isotemnids. The type species isIsotemnus primitivus, first described in 1897 byFlorentino Ameghino, based on fossil remains found in terrains dating back from the Early Eocene ofArgentinePatagonia. Other species were later attributed to the genus, such asI. ctalego (Early Eocene),I. haugi (Early Eocene, initially described asLeifunia haugi),I. latidens (Middle Eocene). Fragmentary remains attributed toIsotemnus were discovered in Late Paleocene formations in Argentina.
