''Speothos'' is a genus of

canid Canidae (; from Latin, '' canis'', " dog") is a biological family of dog-like carnivorans, colloquially referred to as dogs, and constitutes a clade. A member of this family is also called a canid (). There are three subfamilies found withi ...

found in Central and

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the sout ...

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

Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was finally confirmed in ...

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 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 species that contains the biological type specime ...

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 The short-eared dog (''Atelocynus microtis''), also known as the short-eared zorro or small-eared dog,de la Rosa, Carlos L.; and Nocke, Claudia. A Guide to the Carnivores of Central America: Natural History, Ecology, and Conservation. Austin: Uni ...

'' (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 sub-family 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 appea ...

'' (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 The maned wolf (''Chrysocyon brachyurus'') is a large canine of South America. It is found in Argentina, Brazil, Bolivia, Peru, and Paraguay, and is almost extinct in Uruguay. Its markings resemble those of foxes, but it is neither a fox nor a w ...

'' (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 which 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 exampl ...

modifications of the dentition with ''

Cuon The dhole (''Cuon alpinus''; ) is a canid native to Central, South, East and Southeast Asia. Other English names for the species include Asian wild dog, Asiatic wild dog, Indian wild dog, whistling dog, red dog, red wolf, and mountain wolf. ...

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