.... Focussing largely on mouse and chick studies, we concentrate on the positioning of the limbs, the formation of the limb bud, the establishment of the principal limb axes, the specification of pattern, the integration of pattern formation with growth and the determination of digit number. We also discuss...

...Joseph Pickering; Matthew Towers In an influential model of pattern formation, a gradient of Sonic hedgehog (Shh) signalling in the chick wing bud specifies cells with three antero-posterior positional values, which give rise to three morphologically different digits by a self-organizing mechanism...

... as an example where tail-driven patterning demands may have converged with the regulation of highly differentiated limbs in tetrapods. © 1994 by Company of Biologists 1994 vertebrate limb fin evolution phylogeny Hox gene digits The history of vertebrate limbs has long been a popular...

... specifies the developmental fate of that region. Because there are only five distinct Hox-encoded domains across the limb bud there is a developmental constraint prohibiting the evolution of more than five different types of digits. The expression patterns of Hox genes in modern embryonic limb buds also...