Functional-Morphology of the Limbs of Thylacoleo-Carnifex Owen (Thylacoleonidae, Marsupialia)

Abstract

The limb bones and girdles of an almost complete specimen of the extinct 'marsupial lion' Thylacoleo carnifex, from Moree, New South Wales, have been fully described pictorially, metrically and in text. To investigate limb function, intra- and inter-limb segment indices and limb proportions standardised against the presacral vertebral column, were calculated for 11 samples of extant Australian marsupials. Comparisons were made between these values, those for Thylacoleo and published data for extant placental carnivores. The Thylacoleo fore- and hindlimbs were almost equal in length (FL/HL, 94%) and relatively long compared to the vertebral column (79% and 84%). In the forelimb the radius was clearly longer than the humerus (115%), and the hindlimb the tibia was considerably shorter than the femur (82%). Amongst the marsupials, the main Thylacoleo indices were most similar to those of Sarcophilus, but with some significant differences, notably in propodial/epipodial length ratios. Compared to Panthera leo there were many marked similarities. Morphologically, the Thylacoleo scapula conforms to that found in walking and trotting, rather than climbing, viverrids; the pelvis similarly agrees with that of ambulators and cursors. It was concluded that Thylacoleo carnifex was a slow- medium cursor, possibly capable of leaping. There was also a series of adaptations such as the length of the radius, the stout olecranon, the blade-like fifth metatarsal and the massive terminal phalanx of digit I, clearly implying a carnivorous habit.