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1 Online-Ressource (15 Seiten)
Content:
The stem amniote Orobates pabsti has been reconstructed to be capable of relatively
erect, balanced, and mechanically power-saving terrestrial locomotion. This suggested
that the evolution of such advanced locomotor capabilities preceded the origin of crowngroup
amniotes. We here further investigate plausible body postures and locomotion
of Orobates by taking soft tissues into account. Freely available animation software
BLENDER is used to first reconstruct the lines of action of hindlimb adductors and
retractors for Orobates and then estimate the muscle strain of these muscles. We
experimentally varied different body heights in modeled hindlimb stride cycles of
Orobates to find the posture that maximizes optimal strains over the course of a
stride cycle. To validate our method, we used Caiman crocodilus. We replicated the
identical workflow used for the analysis of Orobates and compared the locomotor
posture predicted for Caiman based on muscle strain analysis with this species’ actual
postural data known from a previously published X-ray motion analysis. Since this
validation experiment demonstrated a close match between the modeled posture
that maximizes optimal adductor and retractor muscle strain and the in vivo posture
employed by Caiman, using the same method for Orobates was justified. Generally, the
use of muscle strain analysis for the reconstruction of posture in quadrupedal vertebrate
fossils thus appears a promising approach. Nevertheless, results for Orobates remained
inconclusive as several postures resulted in similar muscle strains and none of the
postures could be entirely excluded. These results are not in conflict with the previously
inferred moderately erect locomotor posture of Orobates and suggest considerable
variability of posture during locomotion.
Content:
Peer Reviewed
Note:
This article was supported by the German Research Foundation (DFG) and the Open Access Publication Fund of Humboldt-Universität zu Berlin.
In:
Frontiers in Ecology and Evolution, Lausanne : Frontiers Media, 9,2021
Language:
English
DOI:
10.3389/fevo.2021.659039
URN:
urn:nbn:de:kobv:11-110-18452/24158-3
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