Vertebrate models used to study limb/appendage regeneration.

<p><b>(a)</b> Phylogenetic relationship among three vertebrate taxa studied to determine conserved gene expression patterns in regenerating limb/appendages following blastema formation. These animal systems last shared a common ancestor ~420 million years ago. <b>(b)</b> Blastema tissues as shown by hematoxylin and eosin staining on paraffin tissue sections of regenerating zebrafish caudal fin, bichir pectoral fins and axolotl forelimbs. (* = blastema; dpa = days post-amputation).