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The ectodermal placodes are focal thickenings of the cranial embryonic ectoderm that contribute extensively to the cranial sensory systems of the vertebrates. The ectodermal placodes have long been thought of as representing a coherent group, which share a developmental and evolutionary history. However, it is now becoming clear that there are substantial differences between the placodes with respect to their early development, their induction and their evolution. Indeed, it is now hard to consider the ectodermal placodes as a single entity. Rather, they fall into a number of distinct classes and it is within each of these that the members share a common development and evolution.

Original publication




Journal article


Philos Trans R Soc Lond B Biol Sci

Publication Date





1655 - 1660


Animals, Biological Evolution, Ectoderm, Embryonic Induction, Head, Ophthalmic Nerve, Vertebrates