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A 2004 study that used 310 wolf skulls and over 700 dog skulls representing 100 breeds concluded that the evolution of dog skulls can generally not be described by heterochronic processes such as neoteny although some pedomorphic dog breeds have skulls that resemble the skulls of juvenile wolves.Compared to the wolf, dog dentition is relatively less robust (Olsen 1985; Hemmer 1990), which is proposed to be due to the relaxation of natural selection when wolves became commensal scavengers, or to artificial selection (Olsen 1985; Clutton-Brock 1995).
Ecological factors including habitat type, climate, prey specialization and predatory competition has greatly influenced the wolf's genetic population structure and cranio-dental plasticity. mosbachensis (which was once distributed from Western Europe to Khazakhstan) with C.The caniforms included the fox-like Leptocyon genus whose various species existed from 34 million YBP before branching 11.9 million YBP into vulpes (foxes) and canini (canines). The carbon dating gave a calendar-year age estimate that ranged between 16,945-13,905 YBP.The jackal-sized Eucyon existed in North America from 10 million YBP and by the Early Pliocene about 6–5 million YBP the coyote-like Eucyon davisi invaded Eurasia. In 1986, a study of skull morphology found that the domestic dog is morphologically distinct from all other canids except the wolf-like canids.This was followed by an explosion of Canis evolution across Eurasia in the Early Pleistocene around 1.8 million YBP in what is commonly referred to as the Wolf event. Puppies are born with short snouts, with the longer skull of dolichocephalic dogs emerging in later development (Coppinger 1995).It is associated with the formation of the Mammoth steppe and continental glaciation. Other differences in head shape between brachycephalic and dolichocephalic dogs include changes in the craniofacial angle (angle between the basilar axis and hard palate) (Regodón 1993), morphology of the temporomandibular joint (Dickie 2001), and radiographic anatomy of the cribriform plate (Schwarz 2000).The ventral edge of the dog's horizontal ramus of the mandible has a convex curve that does not exist in the wolf (Olsen 1985; Clutton-Brock 1995), and no discussion of this difference could be found in the literature. rufus), and dogs indicated that the cerebellum of the dog closely approximates that of the coyote, which is closely aligned with the jackals, and that the wolves show numerous brain traits distinct from the other species (Atkins and Dillon 1971).
However, Biknevicius and Van Valkenburgh (1997) noticed that the horizontal ramus of bone-processing predators is thicker dorso-ventrally at the point caudal to the site of bone processing. Wolves also have serological and biochemical traits distinct from dogs (Leone and Wiens 1956; Lauer, Kuyt & Baker 1969).
In North America it gave rise to early Canis which first appeared in the Miocene (6 million YBP) in south-western US and Mexico. "The difference in size and proportion between some breeds are as great as those between any wild genera, but all dogs are clearly members of the same species." In 2010, a study of dog skull shape compared to extant carnivorans proposed that "The greatest shape distances between dog breeds clearly surpass the maximum divergence between species in the Carnivora.
By 5 million YBP the larger Canis lepophagus appeared in the same region. lupus but was not sure if they evolved separately from C. Moreover, domestic dogs occupy a range of novel shapes outside the domain of wild carnivorans." The domestic dog compared to the wolf shows the greatest variation in the size and shape of the skull (Evans 1979) that range from 7 to 28 cm in length (Mc Greevy 2004).
Other authors have disagreed and have stated that these traits can overlap and vary within the two (Crockford 1999; Harrison 1973).
Wolf cubs have similar relative skull proportions as adult dogs and this was proposed as evidence that the domestic dog is a neotenic wolf.
The canids that had immigrated from North America to Eurasia – Eucyon, Vulpes, and Nyctereutes – were small to medium-sized predators during the Late Miocene and Early Pliocene but they were not the top predators. Tedford disagreed with previous authors and found that its cranio-dental morphology lacked some characteristics that are shared by C. latrans, and therefore there was not a close relationship but it did suggest C. arnensis of Europe showed striking similarities to C. lepophagus or a possible common ancestor that was derived from C. Wolves are dolichocephalic (long skulled) but not as extreme as some breeds of such as greyhounds and Russian wolfhounds (Mc Greevy 2004).