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Functional morphology of head and neck muscles in therizinosaurians Falcarius and Nothronychus

Ben Creisler

New in PLoS ONE:

David K. Smith (2015)
Craniocervical Myology and Functional Morphology of the Small-Headed
Therizinosaurian Theropods Falcarius utahensis and Nothronychus
PLoS ONE 10(2): e0117281.

Therizinosaurs represent a highly unusual clade of herbivorous
theropods from the Cretaceous of North America and Asia. Following
descriptions of the basicrania of the North American therizinosaurs
Falcarius utahenisis and Nothronychus mckinleyi, the craniocervical
musculature in both taxa is reconstructed using Tyrannosaurus,
Allosaurus, and some extant birds as models. These muscles are
subdivided into functional groups as dorsiflexors, lateroflexors, and
ventroflexors. Lateroflexors and dorsiflexors in Nothronychus, but not
Falcarius, are reduced, from the plesiomorphic theropod condition, but
are still well developed. Attachments in both genera are favorable for
an increase in ventroflexion in feeding, convergent with Allosaurus
fragilis. Falcarius and Nothronychus are both characterized by a flat
occipital condyle, followed by centra with shallow articular facets
suggesting neck function very similar to that of an ostrich Struthio
camelus. Neck movement was a combined result of minimal movement
between the individual cervical vertebrae.