The evolution and ecology of gigantism in terror birds (Aves, Phorusrhacidae)

LaBarge, T. W., Gardner, J. D. ORCID: https://orcid.org/0000-0001-5790-632X and Organ, C. L. (2024) The evolution and ecology of gigantism in terror birds (Aves, Phorusrhacidae). Proceedings of the Royal Society B-Biological Sciences, 291 (2021). 20240235. ISSN 1471-2954 doi: 10.1098/rspb.2024.0235

Abstract/Summary

Terror birds (Aves, Phorusrhacidae) were large flightless apex predators in South America during the Cenozoic. Here, we estimate a new phylogeny for phorusrhacids using Bayesian inference. We demonstrate phylogenetic evidence for a monophyletic Patagornithinae and find significant support for a distinct crown group associated with the quintessential ‘terror bird’ characteristics. We use this phylogeny to analyse the evolution of body size and cursoriality. Our results reveal that size overlap was rare between co-occurring subfamilies, supporting the hypothesis that these traits were important for niche partitioning. We observe that gigantism evolved in a single clade, containing Phorusrhacinae and Physornithinae. The members of this lineage were consistently larger than all other phorusrhacids. Phorusrhacinae emerged following the extinction of Physornithinae, suggesting the ecological succession of the apex predator niche. The first known phorusrhacine, Phorusrhacos longissimus, was gigantic but significantly smaller and more cursorial than any physornithine. These traits likely evolved in response to the expansion of open environments. Following the Santacrucian SALMA, phorusrhacines increased in size, further converging on the morphology of Physornithinae. These findings suggest that the evolution and displacement of body size drove terror bird niche partitioning and competitive exclusion controlled phorusrhacid diversity.

Item Type	Article
URI	https://centaur.reading.ac.uk/id/eprint/123749
Identification Number/DOI	10.1098/rspb.2024.0235
Refereed	Yes
Divisions	Life Sciences > School of Biological Sciences > Ecology and Evolutionary Biology
Publisher	The Royal Society
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