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

Research output: Contribution to journalArticle

Original languageEnglish
Article number2786
Number of pages9
JournalProceedings of the Royal Society B: Biological Sciences
Volume286
Issue number1898
Early online date6 Mar 2019
DOIs
DateAccepted/In press - 11 Feb 2019
DateE-pub ahead of print - 6 Mar 2019
DatePublished (current) - 13 Mar 2019

Abstract

Ichthyosaurs are an extinct group of fully marine tetrapods that were well adapted to aquatic locomotion. During their approximately 160 Myr existence, they evolved from elongate and serpentine forms into stockier, fish-like animals, convergent with sharks and dolphins. Here, we use computational fluid dynamics (CFD) to quantify the impact of this transition on the energy demands of ichthyosaur swimming for the first time. We run computational simulations of water flow 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. Our results show that morphology did not have a major effect on the drag coefficient or the energy cost of steady swimming through geological time. We show 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. Our analysis also provides important insight into the choice of scaling parameters for CFD applied to swimming mechanics, and underlines 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.

    Research areas

  • ichthyosaur, marine reptiles, marine tetrapods, swimming mechanics, fluid dynamics, CFD

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    Rights statement: This is the final published version of the article (version of record). It first appeared online via The Royal Society at https://doi.org/10.1098/rspb.2018.2786. Please refer to any applicable terms of use of the publisher.

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    Licence: CC BY

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