Body mass in six species of Plio‐Pleistocene carnivores was estimated based on the relationship between mass and cross‐sectional geometric properties, distal articular surface area, lengths and circumferences of proximal limb bones (femur and humerus) in 28 species of extant carnivores. All measures, except lengths, were found to give congruent body mass estimates. Two of the extinct carnivores (Smilodon fatalis and Panthera atrox) are estimated to be as much as one and a half times heavier than previously thought. Based on these results inferences are made concerning possible prey species.
The locomotor behaviour of some large extinct carnivores, including several species of Plio‐Pleistocene sabre‐tooth cats, is here reconstructed, based on a comparison of the cross‐sectional geometric properties and linear dimensions of their femora and humeri with those of large modern carnivores. The long bones are modelled as simple beams, thereby allowing the use of basic beam theory in assessing relevant functional parameters such as second moments of area of the diaphyses when subjected to compressive and bending stresses. Three Pleistocene carnivores, Smilodon fatalis, Homotherium serum, and Panthera atrox seem to have had ecological and functional equivalents among the late Miocene‐Early Pliocene genera, Barbourofelis, Machairodus, and Nimravides, respectively. Barbourofelis and Smilodon were ‘cat‐like’in dental morphology but some structural characteristics of their limb bones had ‘bear‐like’affinities. Machairodus and Homotherium were cursorial, whereas Nimravides and P. atrox display the limb morphology of true ambush predators. Various aspects of the postcranial skeleton of some of these extinct carnivores suggest that they may have employed locomotory gaits that lack modern analogs.
The craniofacial morphology of the extinct late Pleistocene dire wolf Canis dirus was compared with that of the living gray wolf Canis lupus, the spotted hyaena Crocuta crocuta and the extinct late Miocene bone-cracking canid Borophagus secundus. Fifteen indices that have previously been shown to reflect functional significance in the skull, jaws and related musculature of carnivorans were computed from a series of measurements made on the skulls of the four species and subjected to an analysis of variance and a principal components analysis. The results indicated that the extinct dire wolf was similar to the living gray wolf in 11 of the 15 indices. The dire wolf did not differ significantly from the gray wolf in the relative length of resistance arms to various tooth positions in the lower jaw or in the relative size, mechanical advantage and moment arm of the masseter muscle. The dire wolf was characterized by a relatively larger temporalis muscle that was capable of generating more force than that in the gray wolf. The extinct late Miocene borophagine dog B. secundus was intermediate between the two wolves and the spotted hyaena in most of the cranial and jaw indices, but displayed more similarity to the latter in several key features that can be attributed to their specialization for bone cracking. Borophagus secundus and the spotted hyaena tended to have short resistance arms and large jaw muscles with increased mechanical advantage for bites at various teeth. It is inferred that the dire wolf exhibited feeding behavior that approached that of the living gray wolf, but may have differed in killing technique, where it held longer to its struggling prey.
Canids and hyaenids display a high density of features of microwear on canine teeth that reflect· their similarity in killing strategy. However, hyaenids tend to have a higher percentage of short and wide features (pits) because of the high percentage of bone in their diet. Canines of felids display relatively fewer features than canids and hyaenids, which suggest that felids apprehend prey by delivering deep, strong bites that result in less abrasion of the canines. I suggest that canids rely more heavily on their canines and incisors for feeding than do felids. Smilodon jatalis, a large saber-tooth cat from the Pleistocene of North America, is similar to living felids in having relatively few features of canines, but differs from cheetahs (Acinonyx jubatus) and African lions (Panthera leo) in having relatively more pits. S. jatalis showed no consistent similarity in features of microwear on canine teeth to six large carnivores (leopard, Panthera pardus; cheetah; African lion; spotted hyaena, Crocuta crocuta; African wild dog, Lycaon pictus; gray wolf, Canis lupus), which suggests that its killing behavior and possibly dietary preference differed from modern predators. S. jatalis may have avoided contact with bone during killing and feeding encounters, which caused fewer features to form on the upper canines.
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