ABSTRACT
Information obtained from non-pentadactyl limbs is crucial to clarify how the functional and spatial associations between bones and muscles have changed during the evolution of morphological variation in limbs, as well as the development of the common limb birth defects found in humans and other species (Dunlap, 1967; Muntz, 1975; Shubin and Alberch, 1986; Kardon, 1998; Wagner and Chiu, 2001; Coates et al., 2002; Duprez, 2002; Wagner and Larsson, 2007; Weatherbee and Niswander, 2007; Ponssa et al., 2010; Laurin, 2011; Shwartz et al., 2012; Manzano et al., 2013). However, myological data on non-pentadactyl limbs are relatively rare in the literature. The scarcity of such information is surprising because limb reduction has long attracted researchers’ attention (e.g., Owen, 1849; Presch, 1975; Caputo et al., 1995; Diogo et al., 2013b) for its potential to elucidate broader evolutionary themes, such as evolutionary trends, anatomical convergence, and evolutionary reversals that violate “Dollo’s law” (Diogo and Abdala, 2010; Diogo and
Wood, 2012a; Diogo and Tanaka, 2014). Inferences of evolutionary patterns in limbs and the study of human limb birth defects are usually based on either external morphology or osteology, frequently ignoring muscular anatomy. Therefore, because anatomical and developmental studies usually focus on pentadactyl autopodia (hands/feet) and those dealing with deviations from the norm focus on reduction or gain of cartilages and/or bones, the muscular anatomy of non-pentadactyl limbs remains unexplored.
