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Alligator anatomy papers



From: Ben Creisler
bcreisler@gmail.com

A couple of recent papers about alligators that may be of interest:


Laura B. Porro, Keith A. Metzger, Jose Iriarte-Diaz & Callum F. Ross (2013)
In vivo bone strain and finite element modeling of the mandible of
Alligator mississippiensis.
Journal of Anatomy (advance online publication)
DOI: 10.1111/joa.12080
http://onlinelibrary.wiley.com/doi/10.1111/joa.12080/abstract


Forces experienced during feeding are thought to strongly influence
the morphology of the vertebrate mandible; in vivo strain data are the
most direct evidence for deformation of the mandible induced by these
loading regimes. Although many studies have documented bone strains in
the mammalian mandible, no information is available on strain
magnitudes, orientations or patterns in the sauropsid lower jaw during
feeding. Furthermore, strain gage experiments record the mechanical
response of bone at a few locations, not across the entire mandible.
In this paper, we present bone strain data recorded at various sites
on the lower jaw of Alligator mississippiensis during in vivo feeding
experiments. These data are used to understand how changes in loading
regime associated with changes in bite location are related to changes
in strain regime on the working and balancing sides of the mandible.
Our results suggest that the working side mandible is bent
dorsoventrally and twisted about its long-axis during biting, and the
balancing side experiences primarily dorsoventral bending. Strain
orientations are more variable on the working side than on the
balancing side with changes in bite point and between experiments; the
balancing side exhibits higher strain magnitudes. In the second part
of this paper, we use principal strain orientations and magnitudes
recorded in vivo to evaluate a finite element model of the alligator
mandible. Our comparison demonstrates that strain orientations and
mandibular deformation predicted by the model closely match in vivo
results; however, absolute strain magnitudes are lower in the finite
element model.
===


Chang-Yu Sun & Po-Yu Chen (2013)
Structural Design and Mechanical Behavior of Alligator (Alligator
mississippiensis) Osteoderms.
Acta Biomaterialia (advance online publication)
doi: http://dx.doi.org/10.1016/j.actbio.2013.07.016,
http://www.sciencedirect.com/science/article/pii/S1742706113003553



Alligator is a well-adapted living fossil covered with a dorsal armor.
This dermal shield consists of bony plates, called osteoderms,
interconnected by sutures and non-mineralized collagen fibers,
providing a dual function of protection and flexibility. Osteoderm
features a sandwich structure, combining an inner porous core and an
outer dense cortex, to offer enhancements for stiffness and energy
absorbance. In this study, we investigated multi-scale structure and
mechanical behaviors of the American alligator (Alligator
mississippiensis) osteoderm. Micro-computed tomography was applied to
reveal the complex neurovascular network. Through the observation
under optical and scanning electron microscopes, the osteoderm was
found to consist of woven bone in the dorsal region and lamellar-zonal
bone in ventral region. Nanoindentation and compressive tests were
performed to evaluate the mechanical properties of osteoderms. The
varying mineral contents and porosity result in a graded mechanical
property: from a hard and stiff dorsal cortex gradually transform to a
more compliant ventral base. Three protective mechanisms optimized for
alligator osteoderms were proposed and elucidated.