The Scaling of Postural Mechanics in Felidae and Artiodactyla


Meeting Abstract

3.4  Tuesday, Jan. 4  The Scaling of Postural Mechanics in Felidae and Artiodactyla WIKTOROWICZ-CONROY, AM*; PICKERING, P; SCHMITT, DO; DOUBE, M; SHEFELBINE, SJ; HUTCHINSON, JR; The Royal Veterinary College, Univ of London; The Royal Veterinary College, Univ of London; Duke University; Imperial College London; Imperial College London; The Royal Veterinary College, Univ of London awiktorowicz@rvc.ac.uk

Smaller animals generally adopt more crouched postures while larger animals tend to have straighter limbs. This reflects the scaling of the effective mechanical advantage (EMA) of the limbs, which is based on limb orientation, ground reaction force vectors, and muscle moment arms. The clade Felidae (cats) has been suggested to not follow this trend of postural scaling. Studies of the scaling of their appendicular skeletons have demonstrated pervasive skeletal allometry related to this unusual lack of locomotor scaling. In contrast, the clade Artiodactyla (even-toed ungulates) exhibits unusual bone scaling (often following elastic similarity) that suggests that they may be an excellent example of the “typical mammalian” trend of postural and EMA scaling. To examine the links between skeletal and locomotor scaling we measured the scaling of all major limb bones and the kinematics and kinetics of felids and artiodactyls. We used CT scans to measure whole-bone geometry and scaling for a wide range of species in each clade. For felids our experiments focused on 6 species (domestic cats to tigers); for artiodactyls we collected data from 10 species (blackbuck antelope to giraffe). We quantified joint angles at midstance, joint moments and EMA over a wide range of gaits, from walks through to gallops. Our results show different skeletal scaling in the two clades that matches differences in locomotor scaling, although similarities remain in some aspects of both forms of scaling. Therefore to some degree the scaling of the appendicular skeleton might be somewhat reliable for inferring locomotor scaling in some clades (where such data are lacking), but this deserves broader investigation to test it more thoroughly.

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