Report
Teaser, summary, work performed and final results
Periodic Reporting for period 2 - DAWNDINOS (Testing the locomotor superiority hypothesis for early dinosaurs)
Teaser
The “DAWNDINOS†study combines evolutionary and biomechanical research that tests how the anatomy of extinct dinosaurs and their relatives (archosaurs; “ruling reptilesâ€) was related to their behaviour. We are testing the old “locomotor superiority†hypothesis that...
Summary
The “DAWNDINOS†study combines evolutionary and biomechanical research that tests how the anatomy of extinct dinosaurs and their relatives (archosaurs; “ruling reptilesâ€) was related to their behaviour. We are testing the old “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 remains untested or unfairly dismissed. We are directly testing this question for the first time, but first we are focusing on developing the best tools to do so.
Extant archosaurs (crocodiles and birds) have 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 are now using 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 is refining our simulations by testing major assumptions, and is validating them for studying extinct archosaurs.
Work performed
\"In the first three years of the DAWNDINOS project, we completed our experimental studies of the five behaviours of crocodiles and birds and finished most analysis of these data, including two published papers plus one in press and two in review. This work led to the development of new protocols for analgesia and anaesthesia in crocodiles and tinamou birds in 2 publications, benefitting animal care and welfare. We also have collected 3D digital scans of the skeletons of almost all of our fossil archosaur subjects for our modelling and simulation studies and have begun modelling and simulating these taxa; in addition to publishing two studies explaining and refining relevant simulation approaches. We completed two key digital modelling studies of the dinosaur Mussaurus, which was closely related to the giant sauropod dinosaurs but was still of moderate size; showing that its forelimbs could not be planted on the ground for usage in quadrupedalism and that it shifted from a quadruped to a biped as it grew from hatchling to adult. Our third follow-on study spanned 79 3D models of extinct and extant archosaurs to establish a predictive framework for which species were bipedal or quadrupedal, showing that it had good potential to do so in the future with species in our study whose locomotor stance is uncertain. We conducted numerous outreach efforts at schools, engaged with the London public for a project-focussed event, and brought the project to a global audience via www.dawndinos.com as well as via social media (e.g. Twitter’s #DAWNDINOS hashtag), and we presented findings from the project at many technical scientific and public events.\"
Final results
This study pushes the frontiers of experimental and computational 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 in a given species. Our rigorous, integrative analyses will 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 palaeontological research is moving forward as well- for example, we have assembled a 3D model of the skeleton of the early crocodile-relative Batrachotomus and found that it clearly was quadrupedal as expected, but shows some hints of the bipedal locomotor capacity that later members of its lineage (e.g. Poposaurus) evolved. Importantly, along the way we are testing 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.
In ongoing research on this project, we are resolving how Nile crocodiles and tinamou birds move by predicting how their muscles are turned on and off to generate certain behaviours, and comparing these predicted behaviours against experimentally measured ones. This “validation†procedure is crucial for our simulations of extinct archosaurs, which themselves are needed to directly address the locomotor superiority hypothesis for dinosaurs. We are pushing the boundaries of optimal control simulations in biomechanics as a field, because these methods have generally only been applied to humans with some experimental data (e.g. in vivo muscle activity; 3D joint motions); and because such methods to date have only been applied to extinct taxa (or non-humans) with fairly simple or implausible assumptions. By applying these simulation tools to species with near-gold-standard experimental data and rigorously examining the underlying assumptions we expect to achieve important advances in the methodology of dynamic computer simulation of musculoskeletal function. Indeed, applying these tools to the very unusual forms and functions of extant and extinct archosaurs will push these tools to their limits, providing challenges that should hone those tools over time.
We are unsure how the results of our study will end up, and that is why we are conducting it—while we know that crocodiles and birds move very differently today, and we will find out more about those differences, the big challenge is conclusively testing how extinct archosaurs moved. It is very possible that we may find conclusive differences between the behaviours of extinct archosaurs; or differences that are totally unexpected. To some degree the former is expected- for example, some members of the crocodile lineage were large and armoured and one would not expect them to have been capable of extreme locomotor abilities; in contrast, early dinosaurs (and some early crocodiles) were small and slender-limbed; features that originally led to the advancement of the locomotor superiority hypothesis.
This project is important because dinosaurs fascinate scientists and the public alike. While much recent focus has been on how birds evolved from non-avian dinosaurs and why the latter group went extinct at the end of the Cretaceous period, the early history of dinosaurs and their kin remains murky. Yet the fossil record from this time is wonderful and quickly improving, so there is untapped potential for addressing major questions about the dawn of the dinosaurs, such as the locomotor superiority hypothesis; or how and why bipedalism evolved in archosaurs. Furthermore, the DAWNDINOS project will advance the usage of computer simulation methods. This advancement will build confidence
Website & more info
More info: https://dawndinos.com/.