Fig. 3.

SEM 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 thins