Fig. 3From: Hand/foot splitting and the ‘re-evolution’ of mesopodial skeletal elements during the evolution and radiation of chameleonsSEM of Aspidoscelis uniparens hand and foot morphogenesis. Aspidoscelis uniparens hands and feet undergo the same stages of morphogenesis as presented in Fig. 2 in dorsal view (a, e, i; c, g, k), respectively. In distal view (b, f, j), the hand shows an Apical Ectodermal Ridge (AER) which is initially very robust as a distal ectodermal thickening and is present at the midline between the dorsal and ventral half of the developing limb. At later stages, the AER narrows significantly as it spans a greater anterior-posterior domain. In the foot (d, h, l), we see a similar situation with a very straight and stereotypical AER which is initially robust and later thinsBack to article page