the paleontologist Ronald M. Nowak. In 1984 a study by Björn Kurtén recognized a geographic variation within the dire wolf populations and proposed two subspecies: Canis dirus guildayi (named by Kurtén in honor of the paleontologist John E. Guilday) for specimens from California and Mexico that exhibited shorter limbs and longer teeth, and Canis dirus dirus for specimens east of the North American Continental Divide that exhibited longer limbs and shorter teeth. Kurtén designated a maxilla found in Hermit's Cave, New Mexico as representing the nominate subspecies C. d. dirus. In 2021, a DNA study found the dire wolf to be a highly divergent lineage when compared with the extant wolf-like canines, and this finding is consistent with the previously proposed taxonomic classification of the dire wolf as genus Aenocyon (Ancient Greek: "terrible wolf") as proposed by Merriam in 1918. Evolution In North America, the canid family came into existence 40 million years ago, with the canine subfamily Caninae coming into existence about 32 million years ago. From the Caninae, the ancestors of the fox-like Vulpini and the dog-like Canini came into existence 9 million years ago. This group was first represented by Eucyon, and mostly by coyote-like Eucyon davisi that was spread widely across North America. From the Canini the Cerdocyonina, today represented by the South American canids, came into existence 6–5 million years ago. Its sister the wolf-like Canina came into existence 5 million years ago, however, they are likely to have originated as far back as 9 million years ago. Around 7 million years ago, the canines expanded into Eurasia and Africa, with Eucyon giving rise to the first of genus Canis in Europe. Around 4–3 million years ago C. chihliensis, the first wolf-sized member of Canis, arose in China and expanded to give rise to other wolf-like members across Eurasia and Africa. Members of genus Canis would later expand into North America. The dire wolf evolved in North America. However, the ancestral lineage that gave rise to it is debated with two competing theories. The first theory is based on fossil morphology, which indicates an expansion of genus Canis from out of Eurasia led to the dire wolf. The second theory is based on DNA evidence, which indicates the dire wolf arose from an ancestral lineage that originated in the Americas and was separate from genus Canis. Morphological evidence Morphological evidence based on fossil remains indicates