[dinosaur] Dromaeosaurid sickle claw function (free pdf)

Ben Creisler
[email protected]


A new paper with free pdf:

Peter J. Bishop (2019)
Testing the function of dromaeosaurid (Dinosauria, Theropoda) ‘sickle
claws’ through musculoskeletal modelling and optimization.
PeerJ 7:e7577
doi: https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.7717_peerj.7577&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=XNM6T0qTNhwGzEzbr5_mPMKnNencLDit7xQzV5t2nu4&s=Ro6TeAY178ahZiCEfMUnn1J187iuA4s_gilWG70NNe0&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__peerj.com_articles_7577_&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=XNM6T0qTNhwGzEzbr5_mPMKnNencLDit7xQzV5t2nu4&s=RnZMmAVtiP3UNj3ISenTg7M-h_rAOyQCsawp93cy1aE&e= 

Free pdf:
https://urldefense.proofpoint.com/v2/url?u=https-3A__peerj.com_articles_7577.pdf&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=XNM6T0qTNhwGzEzbr5_mPMKnNencLDit7xQzV5t2nu4&s=8mo8shhrWGsB8bi3JZKL0kXejUmktBvvXNU1Jnj1j1g&e= 


Dromaeosaurids were a clade of bird-like, carnivorous dinosaurs that are
well known for their characteristic morphology of pedal digit II, which
bore an enlarged, sickle-shaped claw and permitted an extreme range of
flexion–extension. Proposed functions for the claw often revolve around
predation, but the exact manner of use varies widely. Musculoskeletal
modelling provides an avenue to quantitatively investigate the biomechanics
of this enigmatic system, and thereby test different behavioural
hypotheses. Here, a musculoskeletal model of the hindlimb and pes of
Deinonychus was developed, and mathematical optimization was used to assess
the factors that maximize production of force at the claw tip. Optimization
revealed that more crouched hindlimb postures (i.e., more flexed knees and
ankles) and larger flexor muscle volumes consistently increased claw
forces, although the optimal degree of digit flexion or extension depended
on assumptions of muscle activity and fibre operating range. Interestingly,
the magnitude of force capable of being produced at the claw tip was
relatively small, arguing against regular transmission of a large
proportion of body weight into a substrate principally via the claw tip.
Such transmission would therefore likely have needed to occur via more
proximal parts of the foot. Collectively, the results best support a
grasping function for digit II (e.g., restraint of prey smaller than the
dromaeosaurid’s own body size), although other behaviours involving flexed
hindlimbs cannot be excluded.


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