Data from: A quantitative method for inferring locomotory shifts in amniotes during ontogeny, its application to dinosaurs, and its bearing on the evolution of posture
Chapelle, Kimberley E. J., University of the Witwatersrand
Benson, Roger B. J., University of the Witwatersrand
Stiegler, Josef, George Washington University
Otero, Alejandro, National University of La Plata
Zhao, Qi, Chinese Academy of Sciences
Choiniere, Jonah N., University of the Witwatersrand
Published Nov 19, 2019 on Dryad.
Cite this dataset
Chapelle, Kimberley E. J. et al. (2019). Data from: A quantitative method for inferring locomotory shifts in amniotes during ontogeny, its application to dinosaurs, and its bearing on the evolution of posture [Dataset]. Dryad. https://doi.org/10.5061/dryad.j4869rd
Evolutionary transitions between quadrupedal and bipedal postures are pivotal to the diversification of amniotes on land, including in our own lineage (Hominini). Heterochrony is suggested as a macroevolutionary mechanism for postural transitions, but understanding postural evolution in deep time is hindered by a lack of methods for inferring posture in extinct species. Dinosaurs are an excellent natural laboratory for understanding postural transitions, because their lineage contains at least four instances of quadrupedality evolving from bipedality, and because heterochronic processes have been put forward as an explanatory model for these transitions. We extend a quantitative method for reliably inferring posture in tetrapods to the study of ontogenetic postural transitions, using measurements of proportional limb robusticity. We apply this method to ontogenetic series of living and extinct amniotes, with a focus on dinosaurs. Our method correctly predicts the general pattern of ontogenetic conservation of quadrupedal and bipedal postures in many living amniote species and infers the same pattern in some dinosaurs. Furthermore, it correctly predicts the ontogenetic postural shift from quadrupedal crawling to bipedal walking in humans. We also infer a transition from early ontogenetic quadrupedality to late-ontogenetic bipedality in the transitional sauropodomorph dinosaur Mussaurus patagonicus and possibly in the early branching ceratopsian Psittacosaurus lujiatunensis. The phylogenetic positions of these ontogenetic shifts suggest that heterochrony may indeed play a role in the macroevolution of posture, at least in dinosaurs. Our method has substantial potential for testing evolutionary transitions between locomotor modes, especially in elucidating the role of evolutionary mechanisms such as heterochrony.
Log10HC vs Log10FC regression coefficients
DFA results using femoral and humeral circumferences
Histograms displaying the distribution of the posterior probabilities of being bipedal over the 10 000 replicates in dinosaurs (using Log10HC and Log10FC).
Figure: Log10HL vs Log10FL. Line and point colours reflect observed posture during habitual locomotion (travel), Homo sapiens in grey. Point shapes reflect posture predicted by the DFA. Silhouettes for small, medium and large size class bipeds|quadrupeds and dinosaurs.