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Re: [dinosaur] Ornithischian cranial musculature and mouth anatomy



You can see and download a free preprint version of the paper here:

https://drive.google.com/file/d/14tODkwXq1SLBFRHY_ttWD0rgZzoM5mdK/view




Virus-free. www.avg.com

On Wed, Oct 17, 2018 at 9:29 PM Ben Creisler <bcreisler@gmail.com> wrote:

Ben Creisler
bcreisler@gmail.com


A new paper:


Ali Nabavizadeh (2018)
New reconstruction of cranial musculature in ornithischian dinosaurs: implications for feeding mechanisms and buccal anatomy.
The Anatomical Record (advance online publication)


The charismatic and diverse ornithischian dinosaurs exhibited some of the most extreme examples of cranial anatomy, inspiring decades of investigation into their muscular anatomy. Current ornithischian jaw muscle reconstructions, although parsimonious, pose concerns of small adductor muscles and caudallyâdisplaced insertions relative to mandibular proportions. Here, craniomandibular material of ornithischian genera spanning all subclades are reexamined for osteological correlates indicative of intracranial and oral soft tissues. M. adductor mandibulae externus (mAME) has traditionally been reconstructed as solely inserting along the caudal margin of the coronoid process for jaw closure. Here, a new mAME reconstruction is proposed in derived ornithischians, with the superficialâmost mAME layer reconstructed as a rostrolabial expansion of muscle, exiting the cranium rostroventrally beneath a unique, laterally flaring jugal and inserting along the lateral surface of the coronoid process and its rostrally extending, shelfâlike labial dentary ridge (LDR). Through previous dental microwear and morphological studies, ceratopsians, hadrosaurids, and ankylosaurs are known to have implemented a major palinal feeding component in their jaw motions, unlike other primarily basal ornithischians. This rostral fanâlike extension of muscle in these derived clades would create a greater mandibular support system and mechanical advantage along the labial margin of the jaw, cradling the entire mandible while lifting it up into occlusion and retracting it. In hadrosaurids and ankylosaurs, this rostrolabially expanding muscle also acts in medial rotation of the dentaries about their longâaxes. With these new reconstructions, the notion of a novel, unparsimonious "cheek" muscle is rejected, with further discussion of plausible buccal soft tissues.
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