Cerdocyonina

Cerdocyonina is a natural lineage whose common ancestor was sister to the Eucyon–Canis–Lycaon lineage. It is represented in the fossil record by Cerdocyon 6–5 million years ago, and by Theriodictis and Chrysocyon 5–4 million years ago. It most likely emerged from Central America.[3]^:150

The fossil of a large form of the extinct Theriodictis that dates 2 million years ago was found in Florida. The maned wolf and an extinct species of the crab-eating zorro were in North America around this time, which was before the Isthmus of Panama came into being, indicating the origin of the Cerdocyonina in North America.[2]^:53

Prior to the 1990s there have been different systematic hypotheses pertaining to the relationships among South American canids, most frequent was the notion of there being three genera and subgenera (after Langguth 1969[4] and 1970[5]):

• Genus Cerdocyon
  • Subgenus Atelocynus
  • Subgenus Cerdocyon
  • Subgenus Speothos
• Genus Dusicyon
  • Subgenus Lycalopex (Langguth recognized it as "Pseudalopex")
  • Subgenus †Dusicyon
• Genus Chrysocyon

Morphological and DNA evidence shows that the South American canids, being the most diverse group of canids on any continent, forms its own natural group.[2]

These taxa, representing diverse adaptations, can be diagnosed by the following synapomorphies: angular process of the mandible wide, may lack hooklike termination, expansion accommodates widened insertions for pterygoid muscle segments, especially that for the medial branch of the internal pterygoid; posterior cusp of p3 weak or absent; and m1 hypoconid and entoconid, joined by cristids. The Cerdocyonina lacks the strongly arched zygoma and often the second posterior cusp on p4 between the cingulum and the large first cusp, which marks them as primitive relative to Eucyon and its sister taxon the subtribe Canina, which shares these synapomorphies.

— Richard H. Tedford[1]

In 2018, a study found that the extinct South American Canis gezi did not fall under genus Canis and should be classified under the Cerdocyonina, however no genus was proposed.[6]

The cladogram below is based on the phylogeny of Lindblad-Toh et al. (2005),[7] modified to incorporate recent findings on Lycalopex species[8] and Dusicyon.[9]