Meeting Abstract
Snake-like body forms have evolved convergently dozens of times in most major lineages of vertebrates. Despite studies of various clades with snake-like species, we still lack an understanding of their evolutionary dynamics and distribution on the vertebrate tree of life. We also do not know whether this convergence in body form coincides with convergence at other biological levels. Here, we present the first vertebrate-wide analysis of how many times snake-like forms have evolved, as well as rates of its evolution and reversion to a non-snake-like form. We then focus on five examples of snake-like form evolution in squamates and test if they are convergent in vertebral number and shape, as well as their surface locomotor performance and kinematics. We do this by comparing each snake-like species to closely related tetrapodal species and determining whether the direction of vertebral or locomotor change matched in each case. The five lineages examined are obscure, rare species that live in remote locations, providing a valuable glimpse into their biology. They are the skink lizards Brachymeles lukbani, Lerista praepedita, and Isopachys anguinoides, the basal squamate Dibamus novaeguineae, and the basal snake Malayotyphlops cf. ruficaudus. Our results support convergence among these species in the number of trunk and caudal vertebrae, and in vertebral aspect ratios, but not relative vertebrae length. We also find that the snake-like species are relatively slower than their limbed counterparts, with the exception of Malayotyphlops, and move with lower frequency and higher amplitude body undulations. This is among the first evidence of locomotor convergence across distantly related, snake-like species.
