The formation of the Isthmus of Panama, about 3 Mya, joined South America to North America, allowing canids to invade South America, where they diversified. However, the last common ancestor of the South American canids lived in North America some 4 Mya and more than one incursion across the new land bridge is likely given the fact that more than one lineage is present in South America. Two North American lineages found in South America are the gray fox (Urocyon cinereoargentus) and the now-extinct dire wolf (Aenocyon dirus). Besides these, there are species endemic to South America: the maned wolf (Chrysocyon brachyurus), the short-eared dog (Atelocynus microtis), the bush dog (Speothos venaticus), the crab-eating fox (Cerdocyon thous), and the South American foxes (Lycalopex spp.). The monophyly of this group has been established by molecular means.
The formation of the Isthmus of Panama about 3 Mya joined South America to North America allowing canids to invade South America where they diversified However the last common ancestor of the South American canids lived in North America some 4 Mya and more than one incursion across the new land bridge is likely given the fact that more than one lineage is present in South America Two North American lineages found in South America are the gray fox (Urocyon cinereoargentus) and the now-extinct dire wolf (Aenocyon dirus) Besides these there are species endemic to South America the maned wolf (Chrysocyon brachyurus) the short-eared dog (Atelocynus microtis) the bush dog (Speothos venaticus) the crab-eating fox (Cerdocyon thous) and the South American foxes (Lycalopex spp) The monophyly of this group has been established by molecular means