Meeting Abstract
Terrestrial vertebrates have repeatedly evolved elongate, limbless body plans, which require them to move using different types of locomotion than their limbed relatives do. All limbless terrestrial vertebrates can use lateral undulation, which involves side-to-side waves not unlike those used by swimming eels. After lateral undulation, concertina locomotion has been documented in the widest variety of limbless terrestrial taxa, including caecilians, amphisbaenians, snakes, and at least one lizard. Other types of limbless locomotion are less common and presumably more specialized. For example, we typically think of sidewinding as a gait that only a handful of very specialized species perform, mostly vipers from sandy desert environments. Some of these desert-dwelling vipers are so specialized that they only rarely use other types of locomotion. However, some non-viper species sidewind facultatively in particular circumstances, and a few may regularly sidewind under natural conditions. Numerous accounts report facultative sidewinding in species that more typically perform other types of locomotion. I have compiled these accounts, uncovering evidence that dozens of species perform sidewinding with varying proficiency under a variety of conditions. This compilation indicates that facultative sidewinding may be relatively widespread across several snake families.
