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Tail propelled aquatic locomotion in a theropod dinosaur

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journal contribution
posted on 12.06.2020, 11:15 by Nizar Ibrahim, David Unwin, S Maganuco, M Fabbri, C Dal Sasso, M Auditore, David Martill, J Wiemann, G Bindelli, S Zouhri, D Matarelli, Ulrich Joger, A Amane, J Jacubczak, George Lauder, Stephanie Pierce
In recent decades, intensive research on non-avian dinosaurs has strongly suggested that these animals were restricted to terrestrial environments1. Historical proposals that some groups, such as sauropods and hadrosaurs, lived in aquatic environments2,3 were abandoned decades ago4–6. It has recently been argued that at least some of the spinosaurids—an unusual group of large-bodied theropods of the Cretaceous era—were semi-aquatic7,8, but this idea has been challenged on anatomical, biomechanical and taphonomic grounds, and remains controversial9–11. Here we present unambiguous evidence for an aquatic propulsive structure in a dinosaur, the giant theropod Spinosaurus aegyptiacus7,12. This dinosaur has a tail with an unexpected and unique shape that consists of extremely tall neural spines and elongate chevrons, which forms a large, flexible fin-like organ capable of extensive lateral excursion. Using a robotic flapping apparatus to measure undulatory forces in physical models of different tail shapes, we show that the tail shape of Spinosaurus produces greater thrust and efficiency in water than the tail shapes of terrestrial dinosaurs and that these measures of performance are more comparable to those of extant aquatic vertebrates that use vertically expanded tails to generate forward propulsion while swimming. These results are consistent with the suite of adaptations for an aquatic lifestyle and piscivorous diet that have previously been documented for Spinosaurus7,13,14. Although developed to a lesser degree, aquatic adaptations are also found in other members of the spinosaurid clade15,16, which had a near-global distribution and a stratigraphic range of more than 50 million years14, pointing to a substantial invasion of aquatic environments by dinosaurs.

Funding

We thank M. Azroal, H. Azroal, M. Fouadassi and all other expedition members from the 2015, 2018 and 2019 seasons for assistance in the field; A. A. Ha for help in preparing the fossils; the Moroccan Ministry of Mines, Energy and Sustainable Development for providing fieldwork permits; F. Manucci for helpful discussions about the flesh reconstruction of Spinosaurus; and P. Fahn-Lai for coding assistance. This research was supported by a National Geographic Society grant to N.I. (CP-143R-170), a National Geographic Emerging Explorer Grant to N.I., contributions from the Board of Advisors of the University of Detroit Mercy to N.I., a Jurassic Foundation grant to M.F., a Paleontological Society grant to M.F., an Explorers Club grant to M.F., as well as financial support from the Lokschuppen Rosenheim, the Museo di Storia Naturale di Milano, J. Pfauntsch and A. Lania.

History

Citation

Ibrahim, N., Maganuco, S., Dal Sasso, C. et al. Tail-propelled aquatic locomotion in a theropod dinosaur. Nature 581, 67–70 (2020). https://doi.org/10.1038/s41586-020-2190-3

Version

AM (Accepted Manuscript)

Published in

Nature

Volume

581

Issue

7806

Pagination

67 - 70 (4)

Publisher

Nature Research

issn

0028-0836

eissn

1476-4687

Acceptance date

19/02/2020

Copyright date

2020

Spatial coverage

England

Language

English

Publisher version

https://www.nature.com/articles/s41586-020-2190-3