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PeerJ. 2015 Sep 17;3:e1245. doi: 10.7717/peerj.1245. eCollection 2015.

The non-avian theropod quadrate I: standardized terminology with an overview of the anatomy and function.

Author information

1
Departamento de Ciências da Terra, Universidade Nova de Lisboa, GeoBioTec, Faculdade de Ciências e Tecnologia , Caparica , Portugal ; Museu da Lourinhã , Lourinhã , Portugal ; Current affiliation: Evolutionary Studies Institute, Center of Excellence in Palaeosciences, University of the Witwatersrand , South Africa.
2
Museu da Lourinhã , Lourinhã , Portugal ; Huffington Department of Earth Sciences, Southern Methodist University , Dallas, TX , USA ; Instituto Superior Técnico, Universidade de Lisboa , Lisboa , Portugal ; Museum für Naturkunde , Berlin , Germany.
3
Departamento de Ciências da Terra, Universidade Nova de Lisboa, GeoBioTec, Faculdade de Ciências e Tecnologia , Caparica , Portugal ; Museu da Lourinhã , Lourinhã , Portugal.

Abstract

The quadrate of reptiles and most other tetrapods plays an important morphofunctional role by allowing the articulation of the mandible with the cranium. In Theropoda, the morphology of the quadrate is particularly complex and varies importantly among different clades of non-avian theropods, therefore conferring a strong taxonomic potential. Inconsistencies in the notation and terminology used in discussions of the theropod quadrate anatomy have been noticed, including at least one instance when no less than eight different terms were given to the same structure. A standardized list of terms and notations for each quadrate anatomical entity is proposed here, with the goal of facilitating future descriptions of this important cranial bone. In addition, an overview of the literature on quadrate function and pneumaticity in non-avian theropods is presented, along with a discussion of the inferences that could be made from this research. Specifically, the quadrate of the large majority of non-avian theropods is akinetic but the diagonally oriented intercondylar sulcus of the mandibular articulation allowed both rami of the mandible to move laterally when opening the mouth in many of theropods. Pneumaticity of the quadrate is also present in most averostran clades and the pneumatic chamber-invaded by the quadrate diverticulum of the mandibular arch pneumatic system-was connected to one or several pneumatic foramina on the medial, lateral, posterior, anterior or ventral sides of the quadrate.

KEYWORDS:

Anatomy; Dinosaur; Mandibular articulation; Quadrate; Terminology; Theropod

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