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| Spinosaurus in Hone & Holtz, 2021. “Spinosaurus Mirror Pool” Artwork by Robert Nicholls twitter.com/Paleocreations |
ABSTRACT
The giant theropod Spinosaurus was an unusual animal and highly derived in many ways, and interpretations of its ecology remain controversial. Recent papers have added considerable knowledge of the anatomy of the genus with the discovery of a new and much more complete specimen, but this has also brought new and dramatic interpretations of its ecology as a highly specialised semi-aquatic animal that actively pursued aquatic prey. Here we assess the arguments about the functional morphology of this animal and the available data on its ecology and possible habits in the light of these new finds. We conclude that based on the available data, the degree of adaptations for aquatic life are questionable, other interpretations for the tail fin and other features are supported (e.g., socio-sexual signalling), and the pursuit predation hypothesis for Spinosaurus as a “highly specialized aquatic predator” is not supported. In contrast, a ‘wading’ model for an animal that predominantly fished from shorelines or within shallow waters is not contradicted by any line of evidence and is well supported. Spinosaurus almost certainly fed primarily from the water and may have swum, but there is no evidence that it was a specialised aquatic pursuit predator.
Keywords: behaviour; paleoecology; Theropoda; Spinosauridae; semi-aquatic
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| Life reconstruction of a Spinosaurus wading in the water and fishing. Illustration: Robert Nicholls |
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| Reconstructed skeleton of a moderately sized Spinosaurus showing its famous sail-back and tail plume. Scale bar = 1 m. |
David W.E. Hone and Thomas R. Holtz, Jr. 2021. Evaluating the Ecology of Spinosaurus: Shoreline Generalist or Aquatic Pursuit Specialist? Palaeontologia Electronica. 24(1):a03. DOI: 10.26879/1110
Plain Language Abstract
The large sail-backed carnivorous dinosaur Spinosaurus has long been a challenge to interpret becuase of its poor fossil record. Recent discoveries have found new and more complete material that has opened up opportunities to study this genus in more detail. It has been suggested that these animals were semi-aquatic, swimming well and actively pursuing prey such as sharks in water. Here this hypothesis is evaluated against an alternative idea that instead Spinosaurus primarily caught food as heron-like waders. Looking at the anatomy, mechanics, and environment of Spinosaurus, we find strong support for the heron model, but numerous contradictions with the pursuit predator model.
