[dinosaur] Cryptoclidus (Plesiosauria) limited neck mobility (free pdf)

Ben Creisler
[email protected]

A new paper in open access:

Tanja Wintrich, René Jonas, Hans-Joachim Wilke, Lars Schmitz & P. Martin
Sander (2019)
Neck mobility in the Jurassic plesiosaur Cryptoclidus eurymerus: finite
element analysis as a new approach to understanding the cervical skeleton
in fossil vertebrates.
PeerJ 7:e7658
doi: https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.7717_peerj.7658&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=LlUsIVPWy7-n8BmwPCCVnjC94RziD31hpHS0IGtgOXw&s=OzIksSS5HJ7eP3VLn0eqQv3EOafUy4AEbjC0Ie7G2uE&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__peerj.com_articles_7658_&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=LlUsIVPWy7-n8BmwPCCVnjC94RziD31hpHS0IGtgOXw&s=Pp4lm6nQ0BBYbi46bDueywOIvEkF9iKptLzZ14xhWcg&e= 

Free pdf:
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The sauropterygian clade Plesiosauria arose in the Late Triassic and
survived to the very end of the Cretaceous. Plesiosauria evolved the
greatest species diversity of any marine reptile clade, attaining a global
distribution. Plesiosauria consist of two clades, Rhomaleosauridae and
Neoplesiosauria. Basal Neoplesiosauria have long necks with at least 30
cervicals, but show qualitative osteological evidence for a stiff neck.
Here we quantify neck mobility in lateral, ventral, and dorsal directions
based on finite element modeling of neck vertebrae from the Middle Jurassic
plesiosaur Cryptoclidus eurymerus. We model the mobility in a single motion
segment, consisting of two adjacent cervical vertebrae and the joints
connecting them. Based on the model with a maximum intervertebral spacing
of 3 mm, we find that in Cryptoclidus, the maximum angle of lateral
deflection in the motion segment was 2°. The maximum angle of ventral
deflection was 5° and of dorsal deflection was 5°. When these values are
multiplied by the number of cervical vertebrae, it becomes apparent that
neck mobility was limited in all directions. The maximum angle of total
lateral deflection in the neck was 67°. The maximum angle of total ventral
deflection was 148° and of total dorsal deflection was 157°. This raises
the question of the function of such a long, multi-segment but immobile
neck. We posit that the long neck served in hydrodynamic and visual
camouflage, hiding the bulk of the body from the small but abundant prey,
such as schooling fish and squid. Neck immobility may have been
advantageous in withstanding strong hydrodynamic forces acting on the neck
during predatory strikes.





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