The phylogeny below was redrawn from Wayne, 1993. Only 10 of the 34 species of canids (including all of the canids that have been exhibited at the Fort Worth Zoo) have been included. For a more complete phylogeny, see the reference above. The diagram includes links to species at the Fort Worth Zoo.
- The canids are an old lineage, separating from the other carnivores about 60 million years ago. Separation of a "wolf" branch, a "South American" branch, and a "red fox" branch occurred more recently, 7-10 million years ago.
- Mitochondrial DNA analysis of both modern and historical specimens of red wolves failed to distinguish red them as a species separate from gray wolves or coyotes. They appear to be a hybrid species, and can interbreed with either gray wolves or coyotes.
- The position of the swift fox has been inferred from that of the kit fox in Wayne, 1993.
- Two different dates for the origin of dogs have been suggested. Mitochondrial DNA analysis suggests a date between 60-100,000 years ago -- well before the beginning of human agriculture. Other genetic and archeological evidence suggests a more recent date -- about 15,000 years ago. Neolithic cave drawings also show dogs hunting with humans.
- All domestic dogs are the descendants of a few ancestral wolf stocks originating in Asia. Surprisingly this includes New World dogs, who were once thought to have been independently domesticated from New World wolves.
- Wayne, Robert K. (1993) Molecular evolution of the dog family. Trends in Genetics 9: 218-224.
- Pennisi, Elizabeth. A shaggy dog history. Science (22 November 2002):1540-1542.
- Museum of Natural History: Evolution of Dogs.
- Savolainen, Peter, et al. Genetic Evidence for an East Asian Origin of Domestic Dogs. Science (22 November 2002): 1610-1613.
- Vila, Carles, et al. Multiple and ancient origins of the domestic dog. Science (13 Jun 1997): 1687-1689.
- Zgurski, Jessie. The origin of the domestic dog (a review).