| Speothos Temporal range:Pleistocene to Recent | |
|---|---|
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Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Carnivora |
| Family: | Canidae |
| Subfamily: | Caninae |
| Tribe: | Canini |
| Genus: | Speothos Lund, 1839 |
| Type species | |
| †Speothos pacivorus | |
| Species | |
| Synonyms | |
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Speothos is a genus ofcanid found inCentral andSouth America. The genus includes the livingbush dog,Speothos venaticus, and an extinctPleistocene species,Speothos pacivorus. Unusually, the fossil species was identified and named before the extant species was discovered, with the result that thetype species ofSpeothos isS. pacivorus. S. pacivorus had a larger overall body size and a double-rooted second lower molar. It has been proposed thatSpeothos originated in the Brazilian highlands sometime during the Pleistocene.[1]
The paleobiogeography and evolutionary relationships ofSpeothos and other South American canids is unclear. Morphological data suggest thatSpeothos is most closely related to another small canid,Atelocynus (short eared dog). The skulls of bothSpeothos andAtelocynus have short nasals that terminate rostral to the maxillary-frontal suture, a character shared withVulpes (fox genus).Speothos andAtelocynus also possess very small frontal sinuses that are minimally expanded. Recent analyses of molecular (mtDNA) data alone and in combination with morphological data support a sister-taxon relationship betweenSpeothos andChrysocyon (maned wolf); it has been suggested that these highly derived canids diverged at least 3 million years ago, invading South America as separate lineages.
Speothos is distinctive in that it shares similarhypercarnivorous modifications of the dentition withCuon (dhole) andLycaon (African wild dog). The crushing role of the post-carnassial molars is reduced. The lower carnassial (m1) ofSpeothos lacks the entoconid, creating a trenchant (cutting) heel on the tooth. The hypoconid on the heel (talonid) of the m1 fits into a basin in the M1 when the teeth are in occlusion.Speothos andCuon exhibit reduction in both number and size of the post-carnassial molars.[2]
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