classification of the dire wolf as genus Aenocyon. Radiocarbon dating The age of most dire wolf localities is determined solely by biostratigraphy, but biostratigraphy is an unreliable indicator within asphalt deposits. Some sites have been radiocarbon dated, with dire wolf specimens from the LaBrea pits dated in calendar years as follows: 82 specimens dated 13,000–14,000YBP; 40 specimens dated 14,000–16,000YBP; 77 specimens dated 14,000–18,000YBP; 37 specimens dated 17,000–18,000YBP; 26 specimens dated 21,000–30,000YBP; 40 specimens dated 25,000–28,000YBP; and 6specimens dated 32,000–37,000YBP. A specimen from Powder Mill Creek Cave, Missouri, was dated at 13,170YBP. Description The average dire wolf proportions were similar to those of two modern North American wolves: the Yukon wolf (Canis lupus pambasileus) and the Northwestern wolf (Canis lupus occidentalis). The largest northern wolves today have a shoulder height of up to and a body length of . Some dire wolf specimens from Rancho LaBrea are smaller than this, and some are larger. The dire wolf had smaller feet and a larger head when compared with a northern wolf of the same body size. The skull length could reach up to or longer, with a broader palate, frontal region, and zygomatic arches compared with the Yukon wolf. These dimensions make the skull very massive. Its sagittal crest was higher, with the inion showing a significant backward projection, and with the rear ends of the nasal bones extending relatively far back into the skull. A connected skeleton of a dire wolf from Rancho LaBrea is difficult to find because the tar allows the bones to disassemble in many directions. Parts of a vertebral column have been assembled, and it was found to be similar to that of the modern wolf, with the same number of vertebrae. Geographic differences in dire wolves were not detected until 1984, when a study of skeletal remains showed differences in a few cranio-dental features and limb proportions between specimens from California and Mexico (A.d.guildayi) and those found from the east of the Continental Divide (A.d.dirus). A comparison of limb size shows that the rear limbs of A.d.guildayi were 8% shorter than the Yukon wolf due to a significantly shorter tibia and metatarsus, and that the front limbs were also shorter due to their slightly shorter lower bones. With its comparatively lighter and smaller limbs and massive head, A.d.guildayi was not as well adapted for running as timber wolves and coyotes. A.d.dirus possessed significantly longer limbs than