has part has part has developmental contribution from has developmental contribution from has potential to develop into has potential to develop into surface structure apical ectodermal ridge paired limb/fin bud 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 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]. VHOG:0001258 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] paired appendage bud paired limb/fin bud paired limb/fin paired limb/fin field presumptive structure