The Pleistocene coyote, also known as the Ice Age coyote, is an extinct subspecies of coyote that lived in western North America during the Late Pleistocene era. Most remains of the subspecies were found in southern California, though at least one was discovered in Idaho. It was part of a carnivore guild that included other canids like foxes, gray wolves, and dire wolves. Compared to their modern Holocene counterparts, Pleistocene coyotes were larger and more robust, weighing, likely in response to larger competitors and prey rather than Bergmann's rule. Their skulls and jaws were significantly thicker and deeper than in modern coyotes, with a shorter and broader rostrum and wider carnassial teeth. These adaptions allowed it to cope with higher levels of stress, when it killed larger prey, compared to modern coyotes. Pleistocene coyotes were also likely more specialized carnivores than their descendants, as their teeth were more adapted to shearing meat, showing fewer grinding surfaces which were better suited for processing vegetation. The lower jaw was also deeper, and the molars showed more signs of wear and breakage than modern populations, thus indicating that the animals consumed more bone than today. Behaviorally, it is likely to have been more social than the modern coyote, as its remains are the third most common in the La Brea Tar Pits, after dire wolves and sabre-toothed cats, both thought to be gregarious species. Their reduction in size occurred within 1,000 years of the occurrence of the Quaternary extinction event, when the climate changed and the majority of their larger prey became extinct. Furthermore, Pleistocene coyotes were unable to successfully exploit the big game huntingniche left vacant after the extinction of the dire wolf, as that gap was rapidly filled by gray wolves. These gray wolves are likely to have actively killed off the larger-bodied coyotes, with natural selection favoring the modern gracile morph. Human predation on the Pleistocene coyote's dwindling prey base may have also impacted the animal's change in morphology.
''Canis latrans harriscrooki''
Canis latrans harriscrooki is another extinct Late Pleistocene coyote that once inhabited what is now Texas. Slaughter described it as being wolf-like and was distinguished from other coyotes by a well-developed posterior cusp on its p2, a longer tooth row relative to the depth of its mandible, a reduced distance between premolars, and a more vertical descending ramus. The cusp dentition was also found in two specimens from Mexico and one from Honduras. Slaughter identified some affinity with C. l. hondurensis. Nowak proposed the hypothesis that a warm-adapted coyote that was more wolf-like than modern coyotes once inhabited Pleistocene Texas and might still be represented by C.l. hondurensis.
''Canis latrans riviveronis''
Canis riviveronis is a coyote that once lived in Florida during the Pleistocene. The specimen is described as a coyote, but it being latrans was questionable. It differed from the extant coyote by having the anterior lobe of the carnassial relatively shorter, and the teeth broader. It was not a wolf nor an Indian dog.
