Lower Rotational Inertia and Larger Leg Muscles Indicate More Rapid Turns in Tyrannosaurids Than in Other Large Theropods

Authors

Eric Snively, University of Wisconsin-La Crosse
Haley O'Brien, Oklahoma State University Center for Health Sciences
Donald M. Henderson, Royal Tyrrell Museum of Palaeontology
Heinrich Mallison, Museum fur Naturkunde
Lara A. Surring, Royal Tyrrell Museum of Palaeontology
Michael E. Burns, Jacksonville State UniversityFollow
Thomas R. Holtz Jr., University of Maryland at College Park
Anthony P. Russell, University of Calgary
Lawrence M. Witmer, Ohio University
Philip J. Currie, University of Alberta
Scott A. Hartman, University of Wisconsin-Madison
John R. Cotton, Ohio University

Department

Biology

Document Type

Article

Publication Date

2-21-2019

Abstract

Synopsis: Tyrannosaurid dinosaurs had large preserved leg muscle attachments and low rotational inertia relative to their body mass, indicating that they could turn more quickly than other large theropods.

Methods: To compare turning capability in theropods, we regressed agility estimates against body mass, incorporating superellipse-based modeled mass, centers of mass, and rotational inertia (mass moment of inertia). Muscle force relative to body mass is a direct correlate of agility in humans, and torque gives potential angular acceleration. Agility scores therefore include rotational inertia values divided by proxies for (1) muscle force (ilium area and estimates of m. caudofemoralis longus cross-section), and (2) musculoskeletal torque. Phylogenetic ANCOVA (phylANCOVA) allow assessment of differences in agility between tyrannosaurids and non-tyrannosaurid theropods (accounting for both ontogeny and phylogeny). We applied conditional error probabilities a(p) to stringently test the null hypothesis of equal agility.

Results: Tyrannosaurids consistently have agility index magnitudes twice those of allosauroids and some other theropods of equivalent mass, turning the body with both legs planted or pivoting over a stance leg. PhylANCOVA demonstrates definitively greater agilities in tyrannosaurids, and phylogeny explains nearly all covariance. Mass property results are consistent with those of other studies based on skeletal mounts, and between different figure-based methods (our main mathematical slicing procedures, lofted 3D computer models, and simplified graphical double integration).

Implications: The capacity for relatively rapid turns in tyrannosaurids is ecologically intriguing in light of their monopolization of large (>400 kg), toothed dinosaurian predator niches in their habitats.

Publication/Presentation Information

Snively E., et al.. 2019. Lower rotational inertia and larger leg muscles indicate more rapid turns in tyrannosaurids than in other large theropods. PeerJ 7:e6432 DOI 10.7717/peerj.6432

Recommended Citation

Snively, Eric; O'Brien, Haley; Henderson, Donald M.; Mallison, Heinrich; Surring, Lara A.; Burns, Michael E.; Holtz, Thomas R. Jr.; Russell, Anthony P.; Witmer, Lawrence M.; Currie, Philip J.; Hartman, Scott A.; and Cotton, John R., "Lower Rotational Inertia and Larger Leg Muscles Indicate More Rapid Turns in Tyrannosaurids Than in Other Large Theropods" (2019). Research, Publications & Creative Work. 23.
https://digitalcommons.jsu.edu/fac_res/23