Comparison of Skull Shape in Marsupial and Placental Carnivores

Abstract

A set of 11 measurements on 40 species of placental (Order Carnivora) and marsupial (Order Dasyurida) carnivores is analysed by means of correspondence analysis. Dasyurida have long mandibles and tooth rows, large muscle attachment areas on the mandible, long moment arms of the temporalis and masseter, and a low occiput and short temporal fossa. Skull shape is uniform in Dasyurida, with about the same variability as in a family of Carnivora. The temporalis of Dasyurida is relatively small, but this may be compensated for by the more rounded shape and longer moment arm. The Tasmanian tiger, Thylacinus cynocephalus, is more similar in skull shape to the red fox, Vulpes vulpes, than to the placental wolf, Canis lupus. The M5 of Dasyurida occupies the same geometric position as the MI in Carnivora, providing a possible explanation for the greater variability in cheek teeth in Carnivora. The Tasmanian devil, Sarcophilus harrisii, is similar to the Hyaenidae in having a shorter distance between the ultimate sectorial molar and the condyle. It is suggested that this is an adaptation to cracking open bones, as this mandible geometry brings the main bone-cracking teeth closer to the region of greatest muscle force.