An outgrowth on the lateral trunk of the embryo that develops into a limb or paired fin. The limb/fin bud is divided into ectoderm and mesenchyme[cjm, modified from MP].
Comment:
Genes: In limb buds of chick and mouse, Shh expression is activated as soon as there is a morphological bud, whereas in S. canicula fin buds, consistent with reported data in other cartilaginous fishes, Shh is transcribed late in fin development[PMID:17187056]