Predictive simulations of running gait reveal a critical dynamic role for the tail in bipedal dinosaur locomotion

Abstract

Locomotion has influenced the ecology, evolution, and extinction of species throughout history, yet studying locomotion in the fossil record is challenging. Computational biomechanics can provide novel insight by mechanistically relating observed anatomy to whole-animal function and behavior. Here, we leverage optimal control methods to generate the first fully predictive, three-dimensional, muscle-driven simulations of locomotion in an extinct terrestrial vertebrate, the bipedal non-avian theropod dinosaur Coelophysis. Unexpectedly, our simulations involved pronounced lateroflexion movements of the tail. Rather than just being a static counterbalance, simulations indicate that the tail played a crucial dynamic role, with lateroflexion acting as a passive, physics-based mechanism for regulating angular momentum and improving locomotor economy, analogous to the swinging arms of humans. We infer this mechanism to have existed in many other bipedal non-avian dinosaurs as well, and our methodology provides new avenues for exploring the functional diversity of dinosaur tails in the future.

Anatomically grounded estimation of hindlimb muscle sizes in Archosauria

“…In recent years there has indeed been a major push from not just identifying muscle attachments for extinct animals, but quantifying muscle sizes and forces driven primarily by enhanced computer modelling of feeding and locomotor behaviours (e.g. Bishop, Cuff, et al, 2021 ; Bishop, Falisse, et al, 2021 ; Bishop, Michel, et al, 2021 ; Gignac & Erickson, 2017 ; Herbst et al, 2022 ; Hutchinson, 2002 ; Snively et al, 2013 ; Snively & Russell, 2007 ). There remains plenty of room for improvement and innovation, as echoed by similar recent studies (Bates et al, 2021 ; Broyde et al, 2021 ; Rhodes et al, 2021 ).…”

“…Here we used the 3D computer model of Cleveland Museum of Natural History exhibit specimen number 10971 (see Allen et al, 2013 ; Bishop, Cuff, et al, 2021 ; Bishop, Falisse, et al, 2021 ), based on a moderate‐resolution laser scan of a mounted, composite exhibit skeleton (three adult individuals). We imported the skeleton of this model as.…”

“…Gatesy, 1990 ). There has been much interest in testing how extinct archosaurs moved and how major transitions in locomotion happened, including using biomechanical and musculoskeletal models (Alexander, 1985 ; Allen et al, 2021 ; Bishop, Falisse, et al, 2021 ; Charig, 1972 ; Cuff et al, 2019 , 2022 ; Dilkes, 1999 ; Gatesy, 1990 ; Gatesy & Dial, 1996 ; Gregory & Camp, 1918 ; Hutchinson, 2004a , 2004b ; Rhodes et al, 2021 ; Romer, 1923a , 1923b , 1923c ; Wiseman et al, 2021 ). Much of this interest ultimately stems from the radical transformations of musculoskeletal morphology across archosaurian evolution (see references above), raising the questions about how form relates to function across such transformations.…”

Analyzing Modeled Torque Profiles to Understand Scale-Dependent Active Muscle Responses in the Hip Joint

“…For example, a foraging rat might operate in Figure 9. Predicted active joint torque for a rat as large as a brontosaurus [40][41][42] and as small as a fruit fly based on the scaling rules presented.…”

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“…This raises exciting questions, such as when this suite of gaits evolved in pseudosuchians or how often it did, and what the ancestral state was for Archosauria (birds, crocodiles, and all extinct descendants of their common ancestor, including Mesozoic dinosaurs). More sophisticated three-dimensional models incorporating lateral motions and more realistic morphology (e.g., Bishop et al, 2021) or analysis of neuromuscular control and stability may provide further insight.…”