Dwarfing a Giant: Allometry and Ontogeny of Elephant Limb Bones

Dwarfing a Giant: Allometry and Ontogeny of Elephant Limb Bones Victoria L. Herridge, and John R. Hutchinson; Department of Biology, University College London, Gower Street, London, WC1E 6BT, UK ([email protected]), Structure and Motion Laboratory, Department of Veterinary Basic Sciences, The Royal Veterinary College, University of London, Hatfield, Hertfordshire, AL9 7TA, UK Elephants are the largest living terrestrial mammals. They represent the endpoint taxa for our current understanding of many inter-specific allometric relationships and the constraints imposed by large body size, particularly in locomotion. Despite ranging from just over 100kg at birth to 7,000kg in full-grown males, recent research suggests that juvenile elephants do not differ from their adult conspecifics in their kinematics. The highly derived, graviportal skeletal morphology of elephants has been closely linked with elephant locomotor abilities, and yet the intraspecific allometry and ontogeny of elephant limb bones has been little studied. This is necessary to our understanding of the morphology and adaptation of extinct elephant species, especially the dwarfed species of elephant found on islands 800,000—10,000 years ago. The smallest of these dwarf elephants, Palaeoloxodon falconeri, is estimated to have had an adult body mass of just 150kg (equivalent in size to a neonate African elephant), compared to its 10,000kg ancestor, P. antiquus. Biometric data have been collected from growth series of African elephant (Loxodonta africana) and fossil dwarf elephant limb bones, as well as from fossil P. antiquus material, to assess how dwarf elephant limb bone morphology compares with elephants of similar size. Additionally, the intraspecific allometry of extant elephant limb bones through ontogeny is assessed. These data shed further light on the effects of scaling on morphological and biomechanical adaptation.