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Evolution and Development

Developmental mechanisms of large-scale evolutionary changes: Evolution of Avian Skull and Face.

Nature, Fig. 3ABra and MiceWe are working to understand evolution of the unique avian skull and face from a more basal reptilian (archosaurian) condition by using a combination of paleontological studies, such as morphometric analysis of fossils to comparative and functional studies on cranial development of birds and crocodilians. We first developed a database of CT scans of skulls of key lineages and species relevant to such project (primitive archosaurs, theropod dinosaurs and early birds). This project is spearheaded by a senior graduate student Anjan Bhullar in collaboration with Dr. Mark Norell (American Museum of Natural History) and Dr. Gabe S. Bever (Yale University), two of the key experts in the area of archosaurian and early avian evolution, and Dr. Jesus Marugan (U. of Madrid, Spain), a specialist in 2-D and 3-D skull morphometrics. Using the morphometrics approach, we are learning the extent and directionality of principal changes in features of the skull and face. These will allow us to formulate specific hypotheses, which will be tested using embryos of chickens and alligators. Such combination of morphological and developmental approaches can be very powerful in uncovering mechanisms for some of the key transitions during evolution of the highly modified avian skull and beak.