Periodic Reporting for period 4 - DAWNDINOS (Testing the locomotor superiority hypothesis for early dinosaurs)
Reporting period: 2021-04-01 to 2022-03-31
The “DAWNDINOS” study combined evolutionary and biomechanical research that tested how the anatomy of extinct dinosaurs and their relatives (archosaurs; “ruling reptiles”) was related to their behaviour. We addressed the “locomotor superiority” hypothesis that early, bipedal dinosaurs evolved advantages in their locomotor performance over other Late Triassic archosaurs. This hypothesis was first proposed to explain what made dinosaurs distinct from other Triassic species, perhaps aiding their survival into the Jurassic period. However, the hypothesis remained untested or unfairly dismissed. We directly tested this question for the first time, and developed the best cutting-edge tools to do so.
Extant archosaurs (crocodiles and birds) allowed us to experimentally measure key factors (such as 3D skeletal motions and limb forces) that are involved in walking, running, jumping, standing up, and turning behaviours. We used biomechanical computer simulations to estimate how these behaviours were achieved, or whether more extreme behaviours (e.g. faster speeds) might still have been feasible but not observed. This refined our simulations by testing major assumptions, and validated them for studying extinct archosaurs. Additionally, we simulated extinct archosaurs, showing the diversity of behaviours they likely used.
In the final Period of the study, we used our simulation tools to predict how Triassic/early Jurassic archosaurs may have moved, and to compare how their performance in the behaviours related to locomotor traits, testing if the results fit expected patterns for “locomotor superiority.” Our results to date are not fully conclusive but do hint at some aspects of superior locomotor performance (e.g. running speed), offering some degree of support to the hypothesis that dinosaurs benefited from locomotor superiority over their contemporaries. We also have shown how bipedal locomotion evolved at least twice in extinct predecessors to crocodiles, but actual ancestors of crocodiles were unlikely to have ever been bipedal. Our new methods move the study of locomotion in extinct animals forward by “ground-truthing” those methods in studies of living animals and by establishing repeatable, transparent, openly accessible techniques for building and analysing digital models and simulations.
Extant archosaurs (crocodiles and birds) allowed us to experimentally measure key factors (such as 3D skeletal motions and limb forces) that are involved in walking, running, jumping, standing up, and turning behaviours. We used biomechanical computer simulations to estimate how these behaviours were achieved, or whether more extreme behaviours (e.g. faster speeds) might still have been feasible but not observed. This refined our simulations by testing major assumptions, and validated them for studying extinct archosaurs. Additionally, we simulated extinct archosaurs, showing the diversity of behaviours they likely used.
In the final Period of the study, we used our simulation tools to predict how Triassic/early Jurassic archosaurs may have moved, and to compare how their performance in the behaviours related to locomotor traits, testing if the results fit expected patterns for “locomotor superiority.” Our results to date are not fully conclusive but do hint at some aspects of superior locomotor performance (e.g. running speed), offering some degree of support to the hypothesis that dinosaurs benefited from locomotor superiority over their contemporaries. We also have shown how bipedal locomotion evolved at least twice in extinct predecessors to crocodiles, but actual ancestors of crocodiles were unlikely to have ever been bipedal. Our new methods move the study of locomotion in extinct animals forward by “ground-truthing” those methods in studies of living animals and by establishing repeatable, transparent, openly accessible techniques for building and analysing digital models and simulations.
In 5.5 years of the DAWNDINOS project, we published 29 papers in total. Furthermore, valuable data and methods we developed led to serendipitous unanticipated benefits in the form of four other publications as invited collaborations with external experts that were stimulated by the DAWNDINOS project’s main outputs.
We also conducted numerous outreach efforts at local schools (and internationally via “Skype A Scientist”, and other efforts) and engaged with the public repeatedly via diverse efforts online and in person. We brought the project to a global audience via the project website www.dawndinos.com (including numerous explanatory videos and do-it-at-home activities: https://dawndinos.com/home/outreach/). To date, that website has had 51,322 views and 23,973 visitors since it debuted in March 2017. We used social media to augment this dissemination and engagement (e.g. Twitter’s #DAWNDINOS hashtag). We also presented findings from the project at many technical scientific and public (university/museum) events. We co-organised a one-day online symposium in 2021 for scientists interested in our research area, called the Triassic Vertebrate Palaeontology Meetup.
Available data leave our main hypothesis (locomotor superiority) inconclusive but there is some evidence of differences between most Pseudosuchia and Ornithodira so the hypothesis has some support; yet may not be mutually exclusive from other alternative hypotheses (all may be supported to some degree; and compatible). We note that there is good evidence for convergent evolution (with dinosaurs) of bipedalism in the pseudosuchians and Poposaurus and Postosuchus; whereas early Crocodylomorpha were unlikely to have been bipedal as some have claimed; and it is unlikely that early archosauriforms like Euparkeria might have used bipedalism (to be presented in paper to be submitted in 2022).
We also conducted numerous outreach efforts at local schools (and internationally via “Skype A Scientist”, and other efforts) and engaged with the public repeatedly via diverse efforts online and in person. We brought the project to a global audience via the project website www.dawndinos.com (including numerous explanatory videos and do-it-at-home activities: https://dawndinos.com/home/outreach/). To date, that website has had 51,322 views and 23,973 visitors since it debuted in March 2017. We used social media to augment this dissemination and engagement (e.g. Twitter’s #DAWNDINOS hashtag). We also presented findings from the project at many technical scientific and public (university/museum) events. We co-organised a one-day online symposium in 2021 for scientists interested in our research area, called the Triassic Vertebrate Palaeontology Meetup.
Available data leave our main hypothesis (locomotor superiority) inconclusive but there is some evidence of differences between most Pseudosuchia and Ornithodira so the hypothesis has some support; yet may not be mutually exclusive from other alternative hypotheses (all may be supported to some degree; and compatible). We note that there is good evidence for convergent evolution (with dinosaurs) of bipedalism in the pseudosuchians and Poposaurus and Postosuchus; whereas early Crocodylomorpha were unlikely to have been bipedal as some have claimed; and it is unlikely that early archosauriforms like Euparkeria might have used bipedalism (to be presented in paper to be submitted in 2022).
This study pushed the frontiers of analysis of movement by combining the best measurements of performance with the best digital tools, to predict how form and function are coordinated to achieve maximal athletic behaviours. Our rigorous, integrative analyses have already helped move the field of evolutionary biomechanics forward, enabling new inquiries into how behaviour relates to underlying traits or even palaeoecology, environments or other factors.
Our project’s earlier analyses of extant archosaurs validated our modelling and simulation methods to be applied to extinct archosaurs; and gave insight into how crocodiles and birds use their muscles to move. We have obtained 3D scan data and constructed models for 13 species of extinct archosaur, and conducted predictive simulations for three of these so far, discovering new behaviours such as use of the tail in dynamic balance, bipedal abilities in otherwise quadrupedal species, and multiple gait transitions. We obtained limb forces that compared well with independent empirical predictions from living bipeds, and limb muscle recruitment patterns that were similar to those used in living archosaurs (without being forced by the simulations to be so). Importantly, along the way we have tested key assumptions of such digital models, such as that muscle sizes can be predicted from attachment areas evident on the skeleton, and that 3D orientations of joint axes can be estimated from bones alone, enabling rigorous tests of joint mobility or even passive stiffness. These data are informed but not dictated by our studies of extant archosaurs. Together, these are important methodological and biological advances and insights gleaned from our project.
Our project’s earlier analyses of extant archosaurs validated our modelling and simulation methods to be applied to extinct archosaurs; and gave insight into how crocodiles and birds use their muscles to move. We have obtained 3D scan data and constructed models for 13 species of extinct archosaur, and conducted predictive simulations for three of these so far, discovering new behaviours such as use of the tail in dynamic balance, bipedal abilities in otherwise quadrupedal species, and multiple gait transitions. We obtained limb forces that compared well with independent empirical predictions from living bipeds, and limb muscle recruitment patterns that were similar to those used in living archosaurs (without being forced by the simulations to be so). Importantly, along the way we have tested key assumptions of such digital models, such as that muscle sizes can be predicted from attachment areas evident on the skeleton, and that 3D orientations of joint axes can be estimated from bones alone, enabling rigorous tests of joint mobility or even passive stiffness. These data are informed but not dictated by our studies of extant archosaurs. Together, these are important methodological and biological advances and insights gleaned from our project.