Abstract
The vast majority of pterosaurs are characterized by relatively large, elongate heads that are often adorned with large, elaborate crests. Projecting out in front of the body, these large heads and any crests must have had an aerodynamic effect. The working hypothesis of the present study is that these oversized heads were used to control the left–right motions of the body during flight. Using digital models of eight non-pterodactyloids (“rhamphorhyncoids”) and ten pterodactyloids, the turning moments associated with the head + neck show a close and consistent correspondence with the rotational inertia of the whole body about a vertical axis in both groups, supporting the idea of a functional relationship. Turning moments come from calculating the lateral area of the head (plus any crests) and determining the associated lift (aerodynamic force) as a function of flight speed, with flight speeds being based on body mass. Rotational inertias were calculated from the three-dimensional mass distribution of the axial body, the limbs, and the flight membranes. The close correlation between turning moment and rotational inertia was used to revise the life restorations of two pterosaurs and to infer relatively lower flight speeds in another two.
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Acknowledgements
I thank Mark Witton (University of Portsmouth) for providing the new Thalassodromeus sethi that was used as part of this study. I thank Jaime Wong (Department of Mechanical Engineering, University of Alberta) for bringing Eqs. 1 and 3 to my attention, for raising the possibility of a combined stability and turning function for a pterosaurian head plus cranial crest, and for reading a draft of the MS. The comments and suggestions of the three reviewers - Rodrigo Pêgas and two anonymous ones - made for a much improved paper.
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Henderson, D.M. Using your head — cranial steering in pterosaurs. Sci Nat 111, 29 (2024). https://doi.org/10.1007/s00114-024-01915-7
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DOI: https://doi.org/10.1007/s00114-024-01915-7