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Hungarosaurus (Late Cretaceous ankylosaur) dental wear from chewing



From: Ben Creisler
bcreisler@gmail.com

A new online paper:

Attila Osi, Paul M. Barrett, Tamás Földes and Richárd Tokai (2014)
Wear Pattern, Dental Function, and Jaw Mechanism in the Late
Cretaceous Ankylosaur Hungarosaurus.
The Anatomical Record (advance online publication)
DOI: 10.1002/ar.22910
http://onlinelibrary.wiley.com/doi/10.1002/ar.22910/abstract

Feeding in thyreophoran dinosaurs is poorly understood. Although the
group existed for over 130 million years, only the Early Jurassic
basal thyreophoran Scelidosaurus harrisonii and the Late Cretaceous
ankylosaurid Euoplocephalus tutus have been studied from this
perspective in detail. In contrast to the earlier, conservative
hypothesis of a simple "orthal pulping" feeding mode with no or
limited tooth-tooth contact, recent studies have demonstrated precise
dental occlusion with differing jaw mechanisms in these two species.
Here, we describe the first detailed study of feeding related
characters in a nodosaurid ankylosaur, Hungarosaurus tormai, from the
Late Cretaceous of Hungary. Dental wear patterns comprising small,
apical, and low-angled facets on the maxillary and steep, extended,
and bowl-like facets on the dentary teeth reveal sophisticated
tooth-tooth contact in this basal nodosaurid. The presence of two
different scratch generations (vertical and low-angled) on the dentary
teeth unambiguously demonstrate a multiphasic powerstroke, which is
further supported by the morphology of the quadrate-articular and
mandibular symphyseal joints and by the architecture of the
reconstructed jaw adductors. Chewing started with an initial slicing
phase associated with orthal movement that was followed by a
retractive powerstroke with significant occlusal contact. Because of
the curved tooth rows, these movements were probably facilitated by
some mediolateral translation and/or axial rotation of the mandibles
to produce precise shearing along the whole tooth row. These results
demonstrate that complex jaw mechanisms and dental occlusion were more
widespread among thyreophorans than thought previously and that
palinal movement was present in at least two ankylosaurian lineages.