A Mexican Wolf (Canis lupus baileyi), the most genetically-distinct subspecies of Grey Wolf (Canis lupus) at the National Zoo in Washington, D.C.
One of the most famous stories in the history of paleontology is of how William Buckland, the noted 19th century geologist, determined that a pack of hyenas once inhabited Kirkdale Cave in Yorkshire, England by observing the markings living hyenas made on bones at the zoo. While the science of taphonomy would not fully emerge until the next century, it became clear that fossil bones could tell us about scavengers and predators as well as the preserved prey. It’s no surprise that hyenas especially would “make their mark” on so many bones, the extant Spotted Hyena (Crocuta crocuta being well known for its jaw strength and ability to crack bone (which provides mothers with extra calcium for milk, and these hyenas nurse their young for a relatively long period of time as pups are not weaned until they are a year older or more). Now, a new study of various wolf remains reveals a Pleistocene predator distinct from the Grey Wolves in Yellowstone or anywhere else in North America. The abstract of the new Current Biology paper “Megafaunal Extinctions and the Disappearance of a Specialized Wolf Ecomorph” by Leonard, et al. states;
The gray wolf (Canis lupus) is one of the few large predators to survive the Late Pleistocene megafaunal extinctions. Nevertheless, wolves disappeared from northern North America in the Late Pleistocene, suggesting they were affected by factors that eliminated other species. Using skeletal material collected from Pleistocene permafrost deposits of eastern Beringia, we present a comprehensive analysis of an extinct vertebrate by exploring genetic (mtDNA), morphologic, and isotopic (d 13C, d 15N) data to reveal the evolutionary relationships, as well as diet and feeding behavior, of ancient wolves. Remarkably, the Late Pleistocene wolves are genetically unique and morphologically distinct. None of the 16 mtDNA haplotypes recovered from a sample of 20 Pleistocene eastern-Beringian wolves was shared with any modern wolf, and instead they appear most closely related to Late Pleistocene wolves of Eurasia. Moreover, skull
shape, tooth wear, and isotopic data suggest that eastern-Beringian wolves were specialized hunters and scavengers of extinct megafauna. Thus, a previously unrecognized, uniquely adapted, and genetically distinct wolf ecomorph suffered extinction in the Late Pleistocene, along with other megafauna. Consequently, the survival of the species in North America depended on the presence of more generalized forms elsewhere.
Unfortunately there are no photographs or illustrations of the skulls studied to reach these conclusions, but as with other mammals the condition and placement of the teeth is absolutely key. This extinct group of wolves had a much higher amount of tooth wear and fracture than modern wolves (or even other groups of extinct carnivores like Dire Wolves and Saber-Toothed Cats), as well as having a skull shape that would have granted them greater bite forces. These wolves also seem to have had a relatively deep (I assume we’re talking from top to bottom) jaws, characteristic of bone-crackers like hyenas and living wolves that take down large prey. This wolf was not particularly larger than wolves currently living in Alaska or fossil wolves from the La Brea Tar Pits, but the construction of its skull and tooth wear make it apparent that it certainly was an effective predator and scavenger.
The evolution of these wolves is also covered in the paper, and it seems that the bone-crushing wolves and extant wolves share a common ancestor that came from Europe or elsewhere in the Old World, the genetic tests showing that the “new” wolves were not the ancestors of modern Grey Wolves. Instead, it seems that the more robust wolves to the north were middle-weights as far as carnivore ecology (Dire Wolves being larger, Coyotes being smaller), and when Dire Wolves became extinct the Grey Wolves began to become adapted to taking larger prey and cracking bones. The authors of the paper suggest that being an overspecialized “hypercarnivore” may have ultimately done the wolf in, its more generalized southern cousins better able to adapt to changing conditions at the end of the Pleistocene. I’m not particularly sure about this argument, but I’m not expert enough to prove it incorrect either.
In any event, I hope more researchers dive into the mountains of fossil remains languishing in museums all over the world; I almost have to wonder if there are just as many species waiting in dusty cabinets as there are still waiting in the rock.