Adult caudal fin shape is imprinted in the embryonic fin fold.

Appendage shape is formed during development (and re-formed during regeneration) according to spatial and temporal cues that orchestrate local cellular morphogenesis. The caudal fin is the primary appendage used for propulsion in most fish species, and exhibits a range of distinct morphologies adapted for different swimming strategies, however the molecular mechanisms responsible for generating these diverse shapes remain mostly unknown. In zebrafish, caudal fins display a forked shape, with longer supportive bony rays at the periphery and shortest rays at the center. Here, we show that a premature, transient pulse of