Meeting Abstract
We recently showed that the walking cavefish, Cryptotora thamicola, walks with a diagonal-couplets lateral sequence tetrapodal gait. While other fishes have been observed making terrestrial excursions via a number of behavioral adaptations, they do not possess morphological modifications that support tetrapodal walking. Our understanding of the evolution of terrestrial locomotion has been limited by the lack of extant archetypal organisms from which we can experimentally quantify the morphological changes that result from gravitational loading. Here we provide a detailed skeletal analysis and show that Cryptotora possesses morphological traits that are otherwise seen only in terrestrial vertebrates for support of body weight during locomotion. Cryptotora exhibits the axial and appendicular skeletal innovations characteristic of those described in tetrapods that allow tetrapodal walking. These morphological features include vertebral zygapophyses, broad neural arches, and robust pectoral and pelvic girdles fused with the vertebral column. These skeletal features strengthen the body against gravitational loading and provide for attachment of large muscles. Comparison of the skeletal morphology of Cryptotora with a typical fish and salamander morphology illustrates the skeletal requirements for supporting body weight outside of water. Further study of this unique fish will contribute to our understanding of the evolution of walking.
