Sprint performance of phrynosomatid lizards, measured on a high-speed treadmill, correlates with hindlimb length

We measured sprint performance of phrynosomatid lizards and selected outgro ups (n=27 species). Maximal sprint running speeds were obtained with a new measurement technique, a high-speed treadmill (H.S.T.). Animals were measur ed at their approximate field-active body temperatures once on both of 2 co nsecutive days. Within species, individual variation in speed measurements was consistent between trial days and repeatabilities were similar to value s reported previously for photocell-timed racetrack measurements. Multiple regression with phylogenetically independent contrasts indicates that inter specific variation in maximal speed is positively correlated with hindlimb span, but not significantly related to either body mass or body temperature . Among the three phrynosomatid subclades, sand lizards (Uma, Callisaurus, Cophosaurus, Holbrookia) have the highest sprint speeds and longest hindlim bs, horned lizards (Phrynosoma) exhibit the lowest speeds and shortest limb s, and the Sceloporus group (including Uta and Urosaurus) is intermediate i n both speed and hindlimb span.