Date of Award
5-2026
Document Type
Thesis
Degree Name
Master of Science (MS)
Department
Biological Sciences
Committee Chair/Advisor
Dr. Richard Blob
Committee Member
Dr. Samantha Price
Committee Member
Dr. Roshna Wunderlich
Abstract
Several of the earliest tetrapod lineages exhibited polydactyl limbs, with seven or eight digits per limb rather than the typical five or fewer seen in extant lineages. How these digit configurations might have been used during terrestrial locomotion is unclear, given the lack of living models in which their performance can be studied and limited evidence from fossil trackways. However, polydactyly occasionally appears in natural populations of American alligators (Alligator mississippiensis), animals with body plans that broadly resemble those of early tetrapods. To test how polydactyl limbs similar to those of early tetrapods might have functioned on land, we used high-speed video and an EMED-ST pressure mat to measure the foot pressures and limb kinematics of polydactyl alligators (~1.5 m in length, N=3) during walking. We also generated trackways from these alligators while walking over clay. Our data indicated that average footfall pressures and locomotor kinematics from polydactyl limbs do not significantly differ from those of non-polydactyl limbs. Moreover, pressure pad trials and trackways show that supernumerary digits are used inconsistently, with pressure recordings or digit impressions only in roughly half of our total trials. These results indicate that polydactyl digits make limited contributions to terrestrial propulsion, providing important context for understanding the evolutionary loss of digits during the invasion of land by Paleozoic vertebrates.
Recommended Citation
Brewington, Trevor P., "Polydactyl Precursors: Insights Into Early Tetrapod Locomotion From Polydactyl American Alligators" (2026). All Theses. 4758.
https://open.clemson.edu/all_theses/4758
Author ORCID Identifier
0009-0006-4594-1922