part of part of developmentally_induced_by ectoderm embryonic structure mesenchyme apical ectodermal ridge AAO:0010760 AER Distal ectodermal thickening which forms along the anterior-posterior limb axis. Signaling from this region influences proximal-distal patterning of the limb. Structure is missing in some lineages (salamanders, Eleutherodactylus coqui) however morphologically their indistinct distal ectoderm may still be involved in signaling.[AAO] EMAPA:32744 Proliferative region that is part of the developing fin fold or fin.[TAO] TAO:0002146 The AER of tetrapods regresses after specification of skeletal progenitors, the AER of teleosts form an elongating fin fold UBERON:0004356 UMLS:C1516037 XAO:0004121 ZFA:0001702 apical epidermal ridge crista ectodermalis apicalis maintaining mesenchyme in plastic proliferating state; maintaining expression of A-P axis genes; interacting with D-V proteins. Genes: AER induced by Fgf10 in mesenchyme. AER secretes Fgf8, which stimulates mitosis in the mesenchyme causing Fgf10 production - positive feedback loop multilayered ectodermal region at the distal tip of a limb or fin bud necessary for the proper development of the underlying mesenchyme[MP,modified]. Along with the zone of polarizing activity, it is a crucial organizing region during limb development[WP]. note that media, dorsal fins etc have AERs. relationship loss: subclass proliferative region (TAO:0000098)[TAO] uberon paired limb/fin bud