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

Abstract

The vertebral column of Thylacoleo carnifex has been described pictorially, metrically and in text. The column was then analysed by the models of Slijper (1946). Functional comparisons were made with Panthera leo and phylogenetic affinities with Trichosurus vulpecula were investigated. The analysis revealed that head- sacrum length in Thylacoleo was about three-quarters of that in Panthera and three times that in Trichosurus. Relative to trunk length, cervical, thoracic and lumbar lengths in Thylacoleo were similar to those of the lion but different from those of the possum. The Thylacoleo skull and sacrum were relatively longer than those of the possum and the lion. The shape of the sagittal stress curve, the analysis of neural spine lengths and angulations, and the orientations of the zygapophyseal articulations of Thylacoleo suggested the following: the heavy head was supported on a long neck, which revealed little sagittal bending stress and was equipped with relatively high neural spines. T1-3 spines were especially long and stout, and also caudally inclined. These features suggest strong ligamentous and muscular support and considerable mobility of the neck. Although the sacrum was long and robust, implying powerful hindlimbs, the lumbar sagittal stress curve did not show the high values expected, probably due to the counterbalancing effect of the long muscular tail, implied by the large caudal vertebrae.