Both dire wolves (Canis dirus) and gray wolves (C. lupus) lived in North America during the late Pleistocene. The former were far more common than the latter south of the ice sheet that covered most of Canada then. Gray wolves did occur as far south as California, but were uncommon over much of the continent, possibly because of competition with dire wolves, large Ice Age coyotes (C. latrans), and dholes (Cuon alpinus). However, in Alaska north of the ice sheet, gray wolves were the only species of large canid. Scientists refer to this population as Beringian wolves. Though their size and build was similar to that of the extant gray wolf, they had stronger jaws and more robust teeth. Paleoecologists assert this powerful bite was an evolved adaptation that allowed them to successfully prey upon large Pleistocene megafauna such as horse, bison, and musk-ox. Fossils of Beringian wolves range in age from 7500 BP->50,000 BP. This population of gray wolves became extinct about the same time as the Pleistocene megafauna. (Evidence from DNA in Alaskan permafrost suggests horses occurred there until ~7500 BP). Pleistocene Beringian wolves were not ancestral to present day Alaskan gray wolves. Instead, wolves living in Alaska today descend from wolves that expanded their range north following the dissolution of the ice sheet. (See also: https://markgelbart.wordpress.com/2014/04/11/extinct-pleistocene-ecomorphs-of-the-cougar-puma-concolor-and-the-timber-wolf-canis-lupus/ )
Map showing potential migration route for Beringian wolves.
I tried to find a photo of exceptionally large gray wolves on google images, but they were all marred with the despicable sadistic hunters who had murdered them. I hate anyone who would go hunting for wolves.
Wolf fossils found in Natural Trap Cave, Wyoming puzzled scientists for many years because they had features intermediate between gray wolves and dire wolves. A recent study, using a statistical analysis of anatomical measurements, determined these wolves were Beringian wolves, the same extinct ecomorph that lived in Alaska during the late Pleistocene. Measurements of the jaws and lower teeth of these Wyoming wolves matched those of Beringian wolves. The jaws and teeth were smaller on average than those of dire wolves, but larger than those of other populations of gray wolves. Natural Trap Cave is located exactly south of the ice free corridor that existed between the Cordilleran and Laurentide ice sheets before and after the Last Glacial Maximum. Beringian wolves followed herds of bison (Bison antiquus) and musk-oxen (Bootherium bombifrons) when they migrated back and forth through the corridor. The authors of this study predict fossils of Beringian wolves may be found as far west as Oregon and possibly farther east than Indiana.
I hypothesize Beringian wolves were an hybrid species, resulting from crossbreeding between Canis lupus x Canis dirus. A recent study of mammoth DNA determined that Columbian mammoths (Mammuthus columbi) interbred with woolly mammoths (M. primigenius) where the 2 species ranges overlapped, such as the Great Lakes region. (See: https://markgelbart.wordpress.com/2016/02/18/the-southern-and-northern-range-limits-of-the-columbian-mammoth-mammuthus-colombi/ ). This explained why fossils of mammoths from this region showed characteristics intermediate between the 2 species. The same explanation may hold true for Beringian wolves, though convergent evolution is the alternate hypothesis for their more robust bite. My hypothesis would be easy to test, if dire wolf DNA were available. Surprisingly, despite this species’ abundance in the fossil record, dire wolf DNA has never been extracted. There have been well over a thousand specimens of dire wolves excavated from the La Brea Tar Pits, but the chemical used to remove the tar from the bones also destroys DNA. The humid environmental conditions in Florida, where dire wolf remains are also abundant, probably degrades DNA, making this another unfit potential source.
I wonder if Beringian wolves ever followed herds of megafauna when they wondered as far south as the southern Appalachians. A study of Beringian wolf bone chemistry determined bison and musk-oxen were their favorite foods. As I noted here ( https://markgelbart.wordpress.com/2016/05/16/the-extinct-helmeted-musk-ox-bootherium-bombifrons-and-appalachian-grassy-balds-during-the-pleistocene/ ), I believe the woodland musk-ox was the first species of megafauna to colonize grassy balds. Maybe gray wolf/dire wolf hybrids followed them. A wolf tooth found in north Georgia at Ladds has been alternately identified as gray wolf (by Clayton Ray) and dire wolf (by Ronald Nowak). They could both be right.
Fox-Dobbs, K.; A. Leonard and P. Koch
“Pleistocene Megafauna from Eastern Beringia: Paleoecological and Paleoenvironmental Interpretation of Stable Carbon and Nitrogen Isotope and Radicarbon Records”
Paleogeography, Paleoclimatology, and Paleoecology 2008
Gold, DA; et. al.
“Attempted DNA Extraction from Rancho La Brea Columbian Mammoth (Mammuthus columbi: prospects for Ancient DNA Extraction from Asphalt Deposits”
Ecological Evolution 2014
Leonard, Jennifer; et. al.
“Megafaunal Extinction and the Disappearance of a Specialized Wolf Ecomorph”
Current Biology 17 2007
Meachen, J.; A. Brannick and T. Fry
“Extinct Beringian Wolf Morphology Found in the Continental U.S. has Implications for Wolf Migration and Evolution”
Ecology and Evolution 2016