this is from Lab Animal 44(7) 2015
The avian beak has been an illustrative model of evolutionary adaptation since Darwin first studied the Galapagos finches. Its diverse forms and functions make the beak a distinctive innovation in the evolutionary history of birds. The fossil record suggests that birds evolved from beakless ancestors, and developmental biology reveals that the beak forms from structures that are shared among vertebrates. Little is known, however, about the molecular mechanisms that underlie beak development and enabled the evolutionary transition away from snouts.
Now, a team of scientists at Harvard University (Cambridge, MA) has identified key pathways that promote avian beak develo9pment (Evolution doi:10.1111/evo.12684; published only 12 May 2015). By comparing the embryos of distantly related birds and reptiles, researchers determined that, during facial development, proteins of the FGF and WNT signaling pathways are expressed differently in birds than in reptiles. The team then confirmed the role of these pathways by administering FGF and WNT disruptors to developing chicken embryos. The resultant skeletal phenotype included a facial structure more similar to that of ancestral archosaurs than that of modern birds. “Our goal here was to understand the molecular underpinnings of an important evolutionary transition,” said first author Bhart-Anjan Bhullar.