The origin of evolutionary novelties is a long-standing issue in evolutionary biology. Changes in developmental processes and mechanisms must underlie novel anatomical structures, but exactly how this works is a much more difficult question. I propose to investigate this, based on a literature survey and data from two research projects presently conducted in my lab, the possible re-evolution of an aquatic larval stage in lungless salamanders, and (in particular) the role of FoxN3 for the development of unique larval head skeletal structures in frog tadpoles. For example, knock-down of FoxN3 function has been shown to remove several unique larval structures only found in frog tadpoles, such as the elaborate, filigreed structure of the gill basket necessary for filter feeding, and the extra mouth structures present as unique novelties in frog tadpoles and especially well developed in tadpoles grazing algae. How did FoxN3, or the genetic network that is it part of, gain this new function? Based on such detailed empirical data, it should be possible to develop a general model for the evolution of anatomical novelties. During my visit, I will write a synthetic review paper that tries to deepen and sharpen our understanding of the origin of evolutionary novelties.