''Speothos'' is a genus of

canid Canidae (; from Latin, ''canis'', "dog") is a family (biology), biological family of caniform carnivorans, constituting a clade. A member of this family is also called a canid (). The family includes three subfamily, subfamilies: the Caninae, a ...

found in Central and

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...

. The genus includes the living bush dog, '' Speothos venaticus'', and an extinct

Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...

species, '' Speothos pacivorus''. Unusually, the fossil species was identified and named before the extant species was discovered, with the result that the

type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...

of ''Speothos'' is ''S. pacivorus''. S. pacivorus had a larger overall body size and a double-rooted second lower molar. It has been proposed that ''Speothos'' originated in the Brazilian highlands sometime during the Pleistocene. The paleobiogeography and evolutionary relationships of ''Speothos'' and other South American canids is unclear. Morphological data suggest that ''Speothos'' is most closely related to another small canid, '' Atelocynus'' (short eared dog). The skulls of both ''Speothos'' and ''Atelocynus'' have short nasals that terminate rostral to the maxillary-frontal suture, a character shared with ''

Vulpes '' Vulpes '' is a genus of the subfamily Caninae. The members of this genus are colloquially referred to as true foxes, meaning they form a proper clade. The word "fox" occurs in the common names of all species of the genus, but also appears in ...

'' (fox genus). ''Speothos'' and ''Atelocynus'' 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 between ''Speothos'' and '' Chrysocyon'' (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 similar

hypercarnivorous A hypercarnivore is an animal that has a diet that is more than 70% meat, either via active predation or by scavenging. The remaining non-meat diet may consist of non-animal foods such as fungi, fruits or other plant material. Some extant example ...

modifications of the dentition with ''

Cuon The dhole ( ; ''Cuon alpinus'') is a Canidae, canid native to South Asia, South, East Asia, East and Southeast Asia. It is anatomically distinguished from members of the genus ''Canis'' in several aspects: its skull is convex rather than conca ...

'' (dhole) and '' Lycaon'' (African wild dog). The crushing role of the post-carnassial molars is reduced. The lower carnassial (m1) of ''Speothos'' 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'' and ''Cuon'' exhibit reduction in both number and size of the post-carnassial molars.

References

Cerdocyonina Carnivoran genera Mammal genera with one living species Taxa named by Peter Wilhelm Lund {{canid-stub