The “hunting dogs” are sister lineage to the true wolves. They were once widespread across Eurasia, Africa, and into North America. Today, the lineage is survived by two species, the dhole (Cuon alpinus) and the African wild dog or painted dog (Lycaon pictus).
But during the Pleistocene, a third species, much larger than two extant species, was ubiquitous. This species, called Xenocyon lycaonoides, was found all over Africa and all over Eurasia. It ranged into North America, where its remains have been described as Xenocyon texanus.
It was long accepted in paleontology that the dhole and African wild dog derived from Xenocyon lycaonoides, but new evidence that shows the African wild dog deriving from a Pliocene African species called Lycaon sekowei casts that idea into doubt. Further, because the dhole and African wild dog are so closely related to each other, it is doubtful that either derives from Xenocyon.
My take, based upon simple chronology and the genomic analysis of living species, is that Xenocyon and its offshoots were a sister lineage to that which leads to the dhole and African wild dog.
The best way to think of Xenocyon lycaonoides is that it was the gray wolf before there was a gray wolf. It was a pack-hunting canid that was able to expand its range over a wide range. It was roughly the size of a large northern gray wolf, and it would have been a formidable predator of large game.
On islands, though, Xenocyon evolution went a bit weird. On Java, two descendants of Xenocyon lycaonoides evolved. One was Merriam’s dog (Megacyon merriami). It was even larger than the mainland form, but over time, it was replaced by a smaller form that averaged 22 kg (48.5 pounds) called the Trinil dog (Mececyon trinilensis). A new analysis of these Pleistocene canids places both in the genus Xenocyon (which fits a cladistic classification model) and shows that the smaller Trinil dog derived from the larger Merriam’s dog. Increased competition from tigers and other large predators forced the larger Merriam’s dog to target smaller prey, and over time, they became smaller.
Anothe even more extreme insular form of Xenocyon evolved on the Pleistocene island of Corsica-Sardinia. This island is now two islands in the Mediterranean, but during the Pleistocene, they were connected to each other. On that Pleistocene island, Xenocyon lycaonoides became isolated on an island that was full of small prey, especially a species endemic pika. This Corsica-Sardinian canid became a specialist in hunting burrowing prey. It had the ability to thrust its head out laterally better than any living canid, which would have given it an advantage in catching quick-moving prey that would take refuge in burrow.
This species is called the Sardinian dhole (Cynotherium sardous), but it is not directly related to the modern dhole. It was the size of a golden jackal or a small coyote, and it went extinct after humans colonized Corsica-Sardinia at the very end of the Pleistocene. It was the last of the Xenocyon derivatives to go extinct.
The Mosbach wolf (Canis mosbachensis) was a contemporary of the larger Xenocyon lycaonoides. It was smaller canid that varied in size from an Eastern coyote to an Indian wolf. It eventually would evolve into the larger gray wolf, which would have a similar evolutionary trajectory to the Xenocyon. It would spread over much of the world. Many regional forms would evolve.
Domestication, of course, would give the gray wolf lots of opportunities for weirdness to come about. Yes, as weird as the so-called Sardinian dhole was, it was never as bizarrely put together as some of our domestic dog breeds.
These extinct “wolves in parallel” do tell us a lot about how a large canid can radiate across the a broad swathe of the planet and adapt to regional conditions and thrive.