African wild dogs are rather unique among canids in that they naturally possess only four digits on their front paws. The dewclaws are missing.
Or are they?
In a study published in PeerJ in September, researchers report that they have discovered these dewclaws. They exist as vestigial metacarpals that are deep within the skin of their front wrists.
The reduction of the dewclaws (or "first digit") has coincided with shift in the muscles around the front feet. This shift gives African wild dogs greater awareness of their feet and body position when running.
The African wild dog and the dhole are specialists in a type of hunting that involves running down ungulate prey over a long distance chase. Wolves do a similar type of hunting behavior, but they also adjust their behavior to ambush small prey. They are much more of a generalist predator than dholes and African wild dogs are.
All extant canids belong to the subfamily Caninae. this subfamily first appeared in the fossil record about 34 million years ago with Leptocyon, a very small fox-like dog. The other two subfamilies are now extinct. One was the Hesperocyoninae, the most basal lineage of all dogs. They looked more or less like someone had hybridized a gray fox with a ring-tail. The other lineage was the Borophoginae which included a whole host of different forms and shapes. The lineage never produced a specialized running dog of any kind, even though it produced the largest dog species ever recorded, Epicyon.
The larger Borophaginae were probably ambush predators. Epicyon is thought to have pounced on its prey in much the same way that foxes do. The difference is that Epicyon hunted big prey. These large ambush predators existed for nearly 15 million years, only going extinct 6 million years ago.
The Hesperocyoninae were outcompeted by the growing Borphagine radiation around 16 million years ago. The modern ancestors of Caninae remained smaller and adopted a more cursorial niche, a niche they would exploit when large Felids began colonizing North America. Cats are better adapted to hunting in the ambush style, and they simply outcompeted the Borophagine dogs.
With the extinction of that branch of Canidae, the extant modern lineage of dogs could exploit the cursorial hunter niche. All extant species do have adaptations for running, but these adaptation are the least derived in gray foxes and raccoon dogs, which both still climb trees, and most derived in African wild dogs and (to lesser extent) in dholes.
Developing a running foot from a climber's paw is a difficult feet of evolution. Both odd-toed and even-toed ungulates have a lot longer history to adapt their feet for this purpose
But in the case of the African wild dog, these adaptations are moving along.
Maybe in another ten million years, this species will have hooves!
