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Investigating the running abilities of Tyrannosaurus rex using stress-constrained multibody dynamic analysis - PubMed

  • ️Sun Jan 01 2017

Investigating the running abilities of Tyrannosaurus rex using stress-constrained multibody dynamic analysis

William I Sellers et al. PeerJ. 2017.

Abstract

The running ability of Tyrannosaurus rex has been intensively studied due to its relevance to interpretations of feeding behaviour and the biomechanics of scaling in giant predatory dinosaurs. Different studies using differing methodologies have produced a very wide range of top speed estimates and there is therefore a need to develop techniques that can improve these predictions. Here we present a new approach that combines two separate biomechanical techniques (multibody dynamic analysis and skeletal stress analysis) to demonstrate that true running gaits would probably lead to unacceptably high skeletal loads in T. rex. Combining these two approaches reduces the high-level of uncertainty in previous predictions associated with unknown soft tissue parameters in dinosaurs, and demonstrates that the relatively long limb segments of T. rex-long argued to indicate competent running ability-would actually have mechanically limited this species to walking gaits. Being limited to walking speeds contradicts arguments of high-speed pursuit predation for the largest bipedal dinosaurs like T. rex, and demonstrates the power of multiphysics approaches for locomotor reconstructions of extinct animals.

Keywords: Biomechanics; Computer simulation; Dinosaur; Locomotion; MBDA.

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Conflict of interest statement

The authors declare there are no competing interests.

Figures

Figure 1
Figure 1. Graph showing the femoral midshaft stress calculated from the joint reaction forces (2nd order Butterworth low-pass filtered at 5 Hz) from previously published models of (A) S. camelus and (B) T. rex (Sellers & Manning, 2007) using standard equations (Alexander, 1974).

Ostrich bone cross sections parameters were scaled from the literature (Brassey et al., 2013b). Derivation of T. rex cross section parameters are explained in the methods section.

Figure 2
Figure 2. Snapshot from GaitSym2016 showing the details of the model.

Muscle paths are in red and joints are in blue. The axes arrows are 1 m long.

Figure 3
Figure 3. Graphs showing the effects of changing the peak stress limit on gait parameters.

(A) maximum velocity; (B) Froude number; (C) stride length; (D) gait cycle duration.

Figure 4
Figure 4. Graphs showing the peak stress (2nd order Butterworth low-pass filtered at 5 Hz) calculated at the functional mid-point of the hindlimb segments at different peak stress cutoffs.

Foot contact times are also shown (black is ipselateral limb, grey is contralateral limb). The time axis represents two complete gait cycles, and the dashed line is drawn at 100 MPa which is the nominal stress limit for a safety factor of 2.

Figure 5
Figure 5. These graphs show the centre of mass horizontal velocities and the centre of mass vertical positions in the different peak load simulations.
Figure 6
Figure 6. These graphs show the energy transformations within the simulation: horizontal kinetic energy, gravitational potential energy, and also the sum of these two energy values.

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References

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Grants and funding

Software development for this project was funded by BBSRC (BB/K006029/1), Leverhulme Trust F/00 025/AK, NERC NE/C520447/1. This work made use of the facilities of N8 HPC Centre of Excellence, provided and funded by the N8 consortium and EPSRC (Grant No. EP/K000225/1). The Centre is co-ordinated by the Universities of Leeds and Manchester. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

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