Dietary diversity and evolution of the earliest flying vertebrates revealed by dental microwear texture analysis

Jordan Bestwick,Richard J Butler,David M Unwin,Mark A Purnell

doi:10.1038/s41467-020-19022-2

Jordan Bestwick, Richard J Butler + Show 2 more

Open Access

https://doi.org/10.1038/s41467-020-19022-2

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Abstract

Pterosaurs, the first vertebrates to evolve active flight, lived between 210 and 66 million years ago. They were important components of Mesozoic ecosystems, and reconstructing pterosaur diets is vital for understanding their origins, their roles within Mesozoic food webs and the impact of other flying vertebrates (i.e. birds) on their evolution. However, pterosaur dietary hypotheses are poorly constrained as most rely on morphological-functional analogies. Here we constrain the diets of 17 pterosaur genera by applying dental microwear texture analysis to the three-dimensional sub-micrometre scale tooth textures that formed during food consumption. We reveal broad patterns of dietary diversity (e.g. Dimorphodon as a vertebrate consumer; Austriadactylus as a consumer of ‘hard’ invertebrates) and direct evidence of sympatric niche partitioning (Rhamphorhynchus as a piscivore; Pterodactylus as a generalist invertebrate consumer). We propose that the ancestral pterosaur diet was dominated by invertebrates and later pterosaurs evolved into piscivores and carnivores, shifts that might reflect ecological displacements due to pterosaur-bird competition.

Highlights

Pterosaurs, the first vertebrates to evolve active flight, lived between 210 and 66 million years ago
As important components of Mesozoic biotas[4], robust reconstructions of pterosaur diets are crucial for understanding the ecological roles they performed within Mesozoic food webs, but for helping address broader ecological and evolutionary debates that enhance our understanding of Mesozoic ecosystems
Dietary studies are inherently difficult because pterosaurs have no modern descendants[10], and many dietary hypotheses are based on weakly supported analogies between the morphology and function of anatomical structures in extant animals and pterosaurs[4]

Summary

Results and discussion

Projecting pterosaur data into the reptile texture-dietary space plots them within the bounds of the reptiles, and where pterosaur taxa are represented by multiple specimens, there is tendency for them to cluster together rather than exhibit a random distribution across the entire texturedietary space (e.g. Darwinopterus, Dimorphodon) some are more broadly distributed (e.g. Dorygnathus, Pterodactylus; Fig. 2; Supplementary Fig. 2 and Supplementary Note 2). 2 and 3 and Supplementary Note 2) That these independent analyses produce similar results provides powerful evidence that the differences between pterosaur non-occlusal tooth textures are attributable to dietary differences. The high degree of overlap of Dimorphodon tooth textures with reptile carnivores and piscivores across PCs 1 and 2 (Fig. 2) suggests that the diet of Dimorphodon largely consisted of vertebrates, some consumption of ‘softer’ invertebrates cannot be entirely ruled out. Principal component 2 (25.1%) Increasing proportion of ‘softer’ invertebrates in diet

Carnivores

Methods

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