ABSTRACT
This chapter employs the neotenous axolotl Ambystoma mexicanum (Amphibia: Urodela) as a case study to illustrate the development of limb muscles in tetrapods. It focuses on the study by Diogo and Tanaka (2014). One of the main reasons for this choice of taxon is that the axolotl is increasingly becoming one of the most popular model organisms in evolutionary, developmental, and regenerative studies, being a particularly powerful model of regeneration. In general, observations of the development of the axolotl fore- and hindlimb muscles agree with the scant detailed information available in the literature on the ontogeny of these muscles in axolotls and other urodeles. The ulnoradial muscle morphogenetic gradient observed in frogs is thus more similar to the ulnoradial gradient seen during the ontogenesis of the limb skeletal structures in other nonurodele tetrapod groups and during the ontogenesis of limb muscles seen in at least some of these groups.
