Fig. 6

Variation in the muscle iliacus externus among selected hyloids. On the left is shown a phylogenetic tree for hyloid anurans [9], where color fields have been added to indicate the ecology and dominant locomotor patterns for the various taxa. For reference, on the right is shown the musculature in a representative hyloid taxon in dorsal view, with the most common muscle pattern seen in jumping frogs. Color branches of the tree indicate different states of a fundamental morphological character that relates to the locomotor behavior of anurans; i.e., notably the relative length of the muscle iliacus externus [54, 56, 58] which is colored in green. Three states are recognized for that muscle. Blue represents the condition in more saltatory frogs, where the origin of the muscle iliacus externus is on the anterior half of the iliac shaft and the muscle covers more than 70 % of the iliac shaft length. Red represents the condition in frogs that predominantly walk, where the origin of the muscle iliacus externus is on the middle of the iliac shaft and the muscle covers between 40 and 70 % of the shaft. Lastly, yellow represents the state seen in some hopping frogs, where the muscle iliacus externus originated on the posterior half of the iliac shaft. According to the phylogeny [9], the shortening of the muscle iliacus externus would have evolved at least three times in the clade that includes three hyloid linages: ceratophryids, Odontophrynus + Macrogenioglottus, and Telmatobius. This clade is formed by terrestrial (or secondarily aquatic) taxa that predominantly hop