Longer is better - the functional benefit of long tails in limbless lizards: evidence from locomotion through contrasting substrates in a pygopodid legless lizard

Limbless vertebrates display a variety of morphologies, which are often linked to a species’ ecology and locomotion. Pygopodids, limbless gekkotans endemic to the Australo-Papuan region, exemplify a spectrum of ecomorphological variation in relative body-to-tail lengths. <em>D</em><em>elma molleri</em> inhabits grasslands and represents the short-bodied and long-tailed ecomorph. We predicted that its locomotor performance would be enhanced on grass substrates as opposed to structurally simpler substrates. To test this hypothesis, we assessed locomotion of <em>D. molleri </em>through three ecologically relevant substrates. Locomotor performance was significantly faster on the grass substrate over multiple distances. These data provide evidence of a functional performance benefit for limbless lizards with short bodies and long tails in grassy habitats, supports theories that such a morphology may have evolved to suit the occupation of these environments, and provide the first evidence of the functional benefit of long tails for locomotion through grass in a member of the Pygopodidae.