Belongs within: Carnivora.
Contains: Borophaginae, Caninae.
The Canidae are the dogs and foxes. Members of this family are found in all continents except Antarctica (though the single wild species in Australia, the dingo Canis dingo, is present due to prehistoric human introduction). All living species are placed in the subfamily Caninae; the remaining subfamilies are extinct. Living canids may be divided between three lineages (Faurby & Svenning 2015). Vulpes and its relatives are smaller fox-like canids; a second lineage including the genus Canis includes most of the larger dogs. The third lineage, including Dusicyon and its relatives, represents the South American canids. Many of these are small and fox-like; most of these species have been included in the past in the genus Dusicyon though the somewhat atypical nature of the effective type species of that genus, D. australis, has led to its division into a number of genera.
Dog’s life
Published 8 December 2008
Wild dogs, it has to be said, are often something of the poor relation among large carnivorans. While people ooh and aah over lions and tigers, are fascinated by bears, and giggle madly at otters, dogs tend to be given the cold shoulder. This has almost nothing to do with the subject of this post, other than that I am writing about dogs here, but it was a point I wanted to bring up.
The Canidae are one of the more basally-diverging groups of living carnivorans. Within the crown Carnivora, the first divergence is between the Feliformia on one hand, containing cats, mongooses and hyaenas, and the Caniformia on the other, containing dogs, bears, seals and weasels. Then within the Caniformia, the first divergence is between dogs and everything else. Fossils assigned to the Canidae date back to the late Eocene, nearly forty million years ago. However, these fossils all belong to extinct subfamilies, and the earliest members of the Canidae crown group don’t appear until the later part of the Miocene, about ten million years ago (Wang et al. 2004). All modern canids belong to the subfamily Caninae. The African hunting dog (Lycaon pictus), Asian dhole (Cuon alpinus) and South American bush dog (Speothos venaticus) have been suggested to form a separate subfamily Simocyoninae on the basis of dental characteristics (they have only one cusp on the heel of the carnassial teeth instead of two as in other Caninae—Macdonald 1984), but these species are not closely related (Bardeleben et al. 2005) and their shared dental features are probably independent adaptations to a more hypercarnivorous diet (I suspect it may also be related to their hypercarnivory that these three species seem to be the most obligately social of the canids). Just to further nail the coffin for the “Simocyoninae”, the type genus Simocyon is itself unrelated to the modern species. It’s not even a canid, but a fossil relative of Ailurus fulgens, the modern red panda (Salesa et al. 2006).
The two extinct subfamilies of Canidae, Hesperocyoninae* and Borophaginae, both diversified soon after the origin of the Canidae in the early Oligocene. The Hesperocyoninae were mostly relatively small (the largest, and the latest, of the hesperocyonines was Osbornodon fricki, which reached the size of a small wolf). Most hesperocyonines were hypercarnivorous, and the subfamily was never hugely diverse. They became extinct during the Oligocene, shortly before the diversification of the Caninae. The Borophaginae were a much more disparate bunch. The subfamily is best-known for the giant, hyaena-like, bone-cracking forms in the genera Epicyon and Borophagus (the latest species of Epicyon, E. haydeni, was the size of a large bear and the largest canid ever), but the borophagines actually covered the entire range of canid ecological diversity from large to small, from extreme hypercarnivore to extreme hypocarnivore. One borophagine genus, Cynarctoides, appears to have been completely herbivorous. Borophaginae became extinct about two million years ago at the end of the Pliocene.
*Hesperocyoninae as a whole may be paraphyletic with regard to the other subfamilies. But if I read Wang et al. (2004) correctly, it looks as though the majority of hesperocyonine genera (except, annoyingly enough, Hesperocyon itself) may still form a clade.
The Caninae did appear at about the same time as the other two subfamilies, but in contrast to the immediate radiations of the Hesperocyoninae and Borophaginae, the Caninae barely trickled along for the next thirty million years in the form of a series of small, conservative species all assigned to a single genus, Leptocyon. The Leptocyon lineage didn’t diversify until the extinction of the smaller borophagines. As discussed elsewhere, the basic division between crown canids is between Vulpes (most foxes) on one hand and a clade containing the wolf-like and South American canids on the other, with the positions of the grey foxes Urocyon, bat-eared fox Otocyon megalotis and tanuki Nyctereutes procyonoides relative to this split more uncertain. While not quite as diverse as the borophagines, modern canids are still an ecologically varied bunch. Anyone who has ever owned a dog can probably vouch for their tendency to try and eat anything that is physically capable of getting down their throat (and a few things that aren’t), and many dog species are omnivorous to some degree. Perhaps the most extreme example is the maned wolf Chrysocyon brachyurus, which feeds on fruit about as much as it does on meat (Dietz 1984).
There’s a lot more I could write about here—the taxonomy of dingoes and singing dogs, and of the wolf complex in general, the origins of the red wolf (and how the ICZN fumbles on hybrids), and the natures of Dusicyon australis and Dusicyon hagenbecki, just for starters. But I’ve used up a morning already, so maybe I’ll get back to them at a future date (I said maybe).
Systematics of Canidae
Characters (from Macdonald 1984): Skull with long muzzle; jaws well-developed, dental formula usually I3/3, C1/1, P4/4, M2/3 = 42, carnassial teeth and molars well developed, heel of carnassial teeth usually with two cusps (one in some species). Legs long; radius and ulna locked, preventing rotation; scaphoid and lunar fused; feet four-toed, digitigrade, claws usually non-retractile, vestigial first toe on front feet in most species, vestigial first claws on hind legs in Canis familiaris and C. dingo. Tail long and bushy. Male with well-developed baculum; blood trapped in penis up to an hour or more during mating, preventing withdrawal and forming copulatory tie.
<==Canidae |--Prohesperocyon Wang 1994WT08, WT96 | `--P. wilsoni (Gustafson 1986)WT08 `--+--+--BorophaginaeWT08 | `--CaninaeWT08 `--HesperocyoninaeWT96 |--Hesperocyon Scott 1890WT08, D07 | |--*H. gregarius (Cope 1873)WT96 [incl. Alloeodectes mcgrewiS96] | `--H. coloradoensis Wang 1994WT08 |--Ectopocynus Wang 1994WT08, WT96 | |--E. antiquus Wang 1994WT08 | `--+--*E. simplicidens Wang 1994WT96, WT08 | `--E. intermedius Wang 1994WT08 |--+--Caedocyon Wang 1994WT08, WT96 | | `--C. tedfordi Wang 1994WT08 | `--Paraenhydrocyon Wang 1994WT08, WT96 | |--P. josephi (Cope 1881)WT96 | `--+--*P. wallovianus (Cope 1881)WT96 | `--P. robustus (Matthew 1907)WT96 `--+--Osbornodon Wang 1994WT08, WT96 | |--*O. fricki Wang 1994WT96 | |--O. brachypus (Cope 1881)WT08 | |--O. iamonensis (Sellards 1916)WT08 | |--O. renjiei Wang 1994WT08 | |--O. scitulus (Hay 1924)T08 | |--O. sesnoni (Macdonald 1967)WT08 | `--O. wangi Hayes 2000WT08 `--+--Mesocyon Scott 1890WT08, WT96 | |--*M. coryphaeus (Cope 1879)WT96 | |--M. brachyops Merriam 1906WT08 | |--M. geringensisV91 | |--M. josephiV91 | |--M. temnodon (Wortman & Matthew 1899)WT08 | `--M. venatorV91 `--+--Cynodesmus Scott 1893WT08, D07 | |--*C. thooides Scott 1893WT96 | |--C. brachypusD07 | |--C. iamonensisV91 | `--C. martini Wang 1994WT08 `--+--Sunkahetanka Macdonald 1963WT08, WT96 | `--S. geringensis (Barbour & Schultz 1935)WT08 `--+--Philotrox Merriam 1906WT08, WT96 | `--P. condoni Merriam 1906WT08 `--Enhydrocyon Cope 1879WT08, WT96 |--E. basilatus Cope 1879WT08 |--E. crassidens Matthew 1907WT08 |--E. geringensisB96 |--E. pahinsintewakpa (Macdonald 1963)WT08 `--E. stenocephalus Cope 1879WT08
*Type species of generic name indicated
References
Bardeleben, C., R. L. Moore & R. K. Wayne. 2005. A molecular phylogeny of the Canidae based on six nuclear loci. Molecular Phylogenetics and Evolution 37 (3): 815–831.
[B96] Bryant, H. N. 1996. Nimravidae. In: Prothero, D. R., & R. J. Emry (eds) The Terrestrial Eocene–Oligocene Transition in North America pp. 453–475. Cambridge University Press.
Dietz, J. M. 1984. Maned wolf. In: Macdonald, D. (ed.) All the World’s Animals: Carnivores pp. 74–75. Torstar Books Inc.: New York.
[D07] Dixon, D. 2007. The Complete Illustrated Encyclopedia of Dinosaurs & Prehistoric Creatures. Hermes House: London.
Faurby, S., & J.-C. Svenning. 2015. A species-level phylogeny of all extant and late Quaternary extinct mammals using a novel heuristic-hierarchical Bayesian approach. Molecular Phylogenetics and Evolution 84: 14–26.
Macdonald, D. W. 1984. The dog family. In: Macdonald, D. (ed.) All the World’s Animals: Carnivores pp. 48–49. Torstar Books Inc.: New York.
Salesa, M. J., M. Antón, S. Peigné & J. Morales. 2006. Evidence of a false thumb in a fossil carnivore clarifies the evolution of pandas. Proceedings of the National Academy of Sciences of the USA 103 (2): 379–382.
[S96] Storer, J. E. 1996. Eocene-Oligocene faunas of the Cypress Hills Formation, Saskatchewan. In: Prothero, D. R., & R. J. Emry (eds) The Terrestrial Eocene–Oligocene Transition in North America pp. 240–261. Cambridge University Press.
[V91] Valkenburgh, B. van. 1991. Iterative evolution of hypercarnivory in canids (Mammalia: Carnivora): evolutionary interactions among sympatric predators. Paleobiology 17 (4): 340–362.
[WT96] Wang, X., & R. H. Tedford. 1996. Canidae. In: Prothero, D. R., & R. J. Emry (eds) The Terrestrial Eocene–Oligocene Transition in North America pp. 433–452. Cambridge University Press.
[WT08] Wang, X., & R. H. Tedford. 2008. Dogs: Their fossil relatives and evolutionary history. Columbia University Press: New York.
Wang, X., R. H. Tedford, B. Van Valkenburgh & R. K. Wayne. 2004. Ancestry: evolutionary history, molecular systematics, and evolutionary ecology of Canidae. In: Macdonald, D. W., & C. Sillero-Zubiri (eds) The Biology and Conservation of Wild Canids pp. 39–54. Oxford University Press.