part of part of has part has part has developmental contribution from has potential to develop into embryo embryonic structure surface structure apical ectodermal ridge paired limb/fin bud 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]. 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] The tetrapod limb is derived from a posterior part of the fin endoskeleton of elasmobranchs and basal bony fish, the so-called metapterygium, a series of endoskeletal elements that is the first to form in the developing paired fins. (...) In addition, there is an independent endoskeletal element called the protopterygium that develops anterior to the metapterygium in many basal fishes (e.g., the bichir and sturgeon). Teleosts have lost the metapterygium whereas the sarcopterygians, on the other hand, have lost the protopterygium. Sarcopterygians thus develop all their endoskeletal structures from the metapterygium and consequently the tetrapod limb skeleton is derived from the metapterygium.[uncertain][VHOG] UBERON:0004357 VHOG:0001258 limb - fin bud paired appendage bud paired limb/fin bud uberon paired limb/fin paired limb/fin field presumptive structure