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It's in the loop: shared sub-surface foot kinematics in birds and other dinosaurs shed light on a new dimension of fossil track diversity

Tuner, M, Falkingham, PL and Gatesy, S (2020) It's in the loop: shared sub-surface foot kinematics in birds and other dinosaurs shed light on a new dimension of fossil track diversity. Biology Letters, 16 (7). ISSN 1744-957X

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Abstract

The feet of ground-dwelling birds retain many features of their dinosaurian ancestry. Experiments with living species offer insights into the complex interplay among anatomy, kinematics and substrate during the formation of Mesozoic footprints. However, a key aspect of the track-making process, sub-surface foot movement, is hindered by substrate opacity. Here, we use biplanar X-rays to image guineafowl walking through radiolucent substrates of different consistency (solid, dry granular, firm to semi-liquid muds). Despite substantial kinematic variation, the foot consistently moves in a looping pattern below ground. As the foot sinks and then withdraws, the claws of the three main toes create entry and exit paths in different locations. Sampling these paths at incremental horizons captures two-dimensional features just as fossil tracks do, allowing depth-based zones to be characterized by the presence and relative position of digit impressions. Examination of deep, penetrative tracks from the Early Jurassic confirms that bipeds had an equivalent looping response to soft substrates approximately 200 Ma. Our integration of extant and extinct evidence demonstrates the influence of substrate properties on sinking depth and sub-surface foot motion, both of which are significant sources of track variation in the fossil record of dinosaurs.

Item Type: Article
Additional Information: Morgan L. Turner, Peter L. Falkingham and Stephen M. Gatesy. It's in the loop: shared sub-surface foot kinematics in birds and other dinosaurs shed light on a new dimension of fossil track diversity. Biology Letters 17(7) DOI: 10.1098/rsbl.2020.0309
Uncontrolled Keywords: 06 Biological Sciences
Subjects: C Auxiliary Sciences of History > CC Archaeology
Q Science > QH Natural history > QH301 Biology
Q Science > QL Zoology
Divisions: Biological & Environmental Sciences (new Sep 19)
Publisher: Royal Society, The
Date Deposited: 02 Jul 2020 09:06
Last Modified: 02 Jul 2020 09:15
DOI or Identification number: 10.1098/rsbl.2020.0309
URI: http://researchonline.ljmu.ac.uk/id/eprint/13219

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