Foot and Ankle Function in the American Alligator

Alligators are capable of postural extremes—from a belly sprawl to a high walk—and the ankle is mobile enough in all three degrees of rotational freedom to achieve foot-ground contact across these diverse hindlimb poses. Alligator ankle anatomy and function has historically focused on the hinge-like peg-and-socket joint between the proximal tarsals (astragalus and calcaneum) and has largely ignored the complex set of bones that make up the ankle and foot.
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For the first time, we are able to reconstruct 6 degree-of-freedom movement for all bones in the distal limb across a variety of locomotor behaviors. Such a large multi-bone dataset poses several animation and data visualization challenges — addressing these have been the highlight of my PhD thesis. The ability to identify kinematic patterns and relationships to morphological features is critical for further interpretation of locomotor diversification in extinct Archosaur ancestors, many of which retain the same distinct ankle and foot structure. Much more work to come out of this research, stay tuned!
Methods overview, from left to right: XROMM (X-ray Reconstruction of Moving Morphology) at the Brown University Keck Facility, microCT at Harvard Center for Nanoscale Systems, reconstructed animations of Alligator limbs and pelves in Autodesk Maya, and coordinate system development for measurements of bone movement.

Collaborator: Stephen Gatesy


Turner ML and Gatesy SM. (2021). Alligators employ intermetatarsal reconfiguration to modulate plantigrade ground contact. The Journal of Experimental Biology. 224, jeb242240.

selected talks

Turner ML and Gatesy SM (2021). Intermetatarsal mobility in the American alligator. Society of Integrative and Comparative Biology Annual Meeting [virtual].

Turner ML and Gatesy SM (2020). Intermetatarsal mobility and grades of foot contact in the American alligator: building a new perspective on archosaurian foot evolution. Society of Vertebrate Paleontology Annual Meeting [virtual].