The giant hyena Pachycrocuta brevirostris: Modelling the bone-cracking behavior of an extinct carnivore

Abstract

The giant hyena Pachycrocuta brevirostris was the largest bone-cracking carnivore that ever existed. With the mass of a lioness, it had massive limbs with shortened distal bones and a heavy, powerfully built mandible with robust, well-developed premolars. All these features reflect its adaptation for dismembering ungulate carcasses, transporting large pieces of them without dragging to the denning site and fracturing bones. This paper estimates the relative contribution of hunting and scavenging to the diet of this extinct hyena, using a combined biomechanical and taphonomic approach. Analysis of the bone-cracking behavior of P. brevirostris was based on the abundance of skeletal elements in the large mammals assemblage from Venta Micena (Guadix-Baza basin, southeast Spain), a locality currently interpreted as an early Pleistocene hyena den. The distribution of major limb bones of ungulates among complete elements, isolated epiphyses and diaphyses were analyzed using contingency tables and correspondence analysis. Results obtained showed that the bones with greater marrow contents (femur, humerus and tibia) were preferentially fractured by the hyenas, while those others with less nutritional value (radius and metapodials) were better represented as complete elements in the assemblage. The quantitative analysis of the preservational state of skeletal elements allowed testing specific patterns of bone modification by the giant hyenas, such as a proximodistal sequence of consumption for humerus and tibia, thus revealing the highly specialized bone-cracking behavior of P. brevirostris. Regression equations adjusted with modern carnivores for body size on craniodental and postcranial measurements provide an average estimate of mass of ∼110 kg for the giant hyena. The high moment arms for masseter and temporalis muscles indicate a substantial strength for bone fracturing with the well-developed premolar teeth. Jaw depth provided resistance against dorsoventral loads during bone-cracking activities. However, the moment arm of resistance for an object positioned at the canines reveals a loss of bite strength compared with spotted hyenas and thus less predatory abilities. These results are in agreement with the scavenging niche deduced for P. brevirostris from taphonomic analysis.