The apex predator of North America
for tens of millions of years, Borophagus (Cope 1892; Fig. 1; 80 cm in length), the bone-crushing traditional ‘dog’ of the Middle Miocene to the Late Pliocene entered the large reptile tree (LRT, 1742+ taxa; subset Fig. 2), but not with Canis, the wolf. Rather Borophagus nested at the base of the clade containing two South American members of Carnivora, Speothos, the South American bush dog, and Tremarctos, the South American spectacled bear.
So Borophagus is not a canid in the LRT (contra tradtion).
In Borophagus secudus
the premaxilla extends to mid-canine and contacts the frontals, as in other clade members.
According to Wikipedia
“Borophagus, like other borophagines, are loosely known as “bone-crushing” or “hyena-like” dogs.”
“Typical features of this genus are a bulging forehead and powerful jaws.
“Borophagus has been considered to be probably a scavenger by paleontologists in the past.[Its crushing premolar teeth and strong jaw muscles would have been used to crack open bone, much like the hyena of the Old World. However, Borophagus fossils are so abundant and geographically widespread that some paleontologists now argue that Borophagus must have been both the dominant carnivore of its time, and thus an active predator because carrion feeding alone could not have sustained such a large population.”
Cope ED 1892. A hyena and other Carnivora from Texas. American Naturalist 26:1028–1029.