Scientists engineered chicken embryos into creatures with a snout and palate similar to what would have been seen in dinosaurs such as Velociraptor and Archaeopteryx.
The study worked to replicate the molecular process that caused dinosaur snouts to turn into the very first bird beaks, Yale University reported.
"The beak is a crucial part of the avian feeding apparatus, and is the component of the avian skeleton that has perhaps diversified most extensively and most radically - consider flamingos, parrots, hawks, pelicans, and hummingbirds, among others," said Yale paleontologist and developmental biologist Bhart-Anjan S. Bhullar. "Yet little work has been done on what exactly a beak is, anatomically, and how it got that way either evolutionarily or developmentally."
A team of researchers performed a quantitative analysis of the anatomy of related fossils to come up with an analysis of how the beak evolved, and then searched for shifts in gene expression that led to these changes. The team found both major living lineages of birds (neognaths and paleognaths) differ from reptiles and mammals in that they have a median gene expression zone of two facial development genes during early embryonic development.
The researchers used small-molecule inhibitors to eliminate activity in the proteins from the "bird-specific" median signaling zone in chicken embryos. This allowed them to induce both the ancestral molecular activity and anatomy. The process reverted the beak structure successfully, and in a curious twist, caused the palatine bone on the roof of the mouth to return to its ancestral state.
"This was unexpected and demonstrates the way in which a single, simple developmental mechanism can have wide-ranging and unexpected effects," Bhullar said.
The findings suggest that if a single molecular mechanism facilitated this transformation, then there should be corresponding transformation visible in the fossil record.
"This is borne out by the fact that Hesperornis - discovered by Othniel Charles Marsh of the Yale Peabody Museum of Natural History - which is a near relative of modern birds that still retains teeth and the most primitive stem avian with a modernized beak in the form of fused, elongate premaxillae, also possesses a modern bird palatine bone," Bhullar said.
The findings were published in a recent edition of the journal Evolution.
