Biomechanical Evaluation of Different Musculoskeletal Arrangements in Psittacosaurus and Implications for Cranial Function

Adam C. Taylor, Stephan Lautenschlager*, Zhao Qi, Emily J. Rayfield

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

21 Citations (Scopus)
265 Downloads (Pure)


The masseter muscle complex is a unique feature of extant mammals and their advanced cynodont precursors, originating from the zygomatic arch and inserting onto the lateral surface of the dentary. This muscle complex is absent in sauropsids, with the exception of the neomorphic m. pseudomasseter complex that is unique to psittaciform birds (parrots and cockatiels). The anterior position and anterodorsally inclined line of action of both muscle groups increases leverage of the jaw and is thought to contribute to increased bite force, particularly in psittaciforms. A corollary is that in mammals at least, the masseter places increased load on the zygomatic arch, which may be withstood by soft tissue temporal fascia. Recently the existence of a m. pseudomasster (mPSM) and m. adductor mandibulae externus ventralis (mAMEV) has been proposed in the ornithischian dinosaur Psittacosaurus. Here we use computed tomography, digital restoration of skull anatomy and adductor musculature and computational biomechanics to test how the presence of anterodorsally inclined muscle loads influences stress, strain, deformation and estimated bite forces in the skull of Psittacosaurus. We find that the m. pseudomasseter and m. amev increases bite force with an associated increase in cranial stress and deformation. There is, however, limited osteological evidence for the existence of these two additional muscles in the psittacosaur skull and geometric morphometric informed sensitivity analysis of our finite element models shows that bite position has a greater effect on loading-induced deformation than muscle loading or material property variation. Anat Rec, 300:49–61, 2017.

Original languageEnglish
Pages (from-to)49-61
Number of pages13
JournalAnatomical Record: Advances in Integrative Anatomy and Evolutionary Biology
Issue number1
Early online date21 Dec 2016
Publication statusPublished - 1 Jan 2017


  • dinosaur
  • evolution
  • function
  • skull
  • zygoma


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