Fig. 2.

Comparative morphogenesis of lizard autopodia. In Aspidoscelis uniparens, the digital plate progresses through a round shape with the pentadactyl digital rays developing within and visible through the thin tissue (a). Subsequent thickening of digital rays and thinning of the interdigital mesenchyme (b) ultimately leads to loss of the interdigital tissue through apoptosis (c). In the chameleon hand, a semi round digital plate develops (d) with subsequent distal flattening. Clefting initiates at this distally flattened location (e). Two syndactylous digit bundles are approximately 180° apart in the anterior-posterior plane. The A. uniparens foot also passes through a semi round digital plate stage (g) which subsequently presents digit differentiation with subsequent interdigital cell death (h-i). The chameleon foot undergoes the same stages as in the hand (d-f), but terminates with a different complement of digits in syndactyly (j-l). dpo = days post oviposition; A = Anterior; P = Posterior