Abstract

Topic: Effects of body plan evolution on the hydrodynamic drag and energy requirements of swimming in ichthyosaurs

Source: Ji, C., Motani, R., Jiang, D., Rieppel, O., Hao, W., Sun, Z., & Schmitz, L. (2019). Effects of body plan evolution on the hydrodynamic drag and energy requirements of swimming in ichthyosaurs. Proceedings of the Royal Society B: Biological Sciences, 286 (1896), 20182786. https://doi.org/10.1098/rspb.2018.2786

Speaker: CHUNG-HSUAN, LU (Peregrine)

Advisor: Not shown here

This research investigated the effects of body plan evolution on the hydrodynamic drag and energy requirements of swimming in ichthyosaurs. Ichthyosaurs were an extinct group of fully marine tetrapods that were well adapted to aquatic locomotion. During their approximately 160 million years of existence, they evolved from elongate and serpentine forms into stockier, fish-like animals, convergent with sharks and dolphins. The authors used computational fluid dynamics (CFD) to quantify the impact of this transition on the energy demands of ichthyosaur swimming for the first time. The computational simulations of water flow conducted using three-dimensional digital models of nine ichthyosaurs and an extant functional analogue, a bottlenose dolphin, providing the first quantitative evaluation of ichthyosaur hydrodynamics across phylogeny. The results showed that morphology did not have a major effect on the drag coefficient or the energy cost of steady swimming through geological time. The results also showed that even the early ichthyosaurs produced low levels of drag for a given volume, comparable to those of a modern dolphin, and that deep ‘torpedo-shaped’ bodies did not reduce the cost of locomotion. The analysis provided important insight into the choice of scaling parameters for CFD applied to swimming mechanics and underlined the great influence of body size evolution on ichthyosaur locomotion. A combination of large bodies and efficient swimming modes lowered the cost of steady swimming as ichthyosaurs became increasingly adapted to a pelagic existence.