Evolving Flight

“I’m interested in how the incredible biodiversity we see today has come to be”, says Daniel Field, a vertebrate palaeontologist and one of last year’s YIBS Dissertation Improvement Grant recipients.

Recent technological advances are enabling researchers to use new methods of fossil analysis. These are at the core of Daniel’s dissertation research, which is a cutting-edge study of the evolution of flight in birds. YIBS funding has helped him access this technology and analyze specimens from the enormous collection of fossils and vertebrates curated by the Yale Peabody Museum. His research also takes him to field sites around the world where he photographs and documents a diversity of bird species and their often wildly diverging characteristics, shapes, colors and lifestyles.

- This research really started when we discovered some previously overlooked fossil specimens in museum collections. There is an ancient bird, Ichthyornis, which is about 86 million years old but, despite the fact that it is so old, shares a lot of features with modern birds. In fact if you looked at the skeleton of this animal you really wouldn’t be able to distinguish it from a modern bird very easily. It was first described by the famous Yale palaeontologist O.C. Marsh in 1880 and since then there are a lot of interesting evolutionary questions that just haven’t been answered.

Using these overlooked fossil specimens, Daniel hopes to shed light on the evolution of bird anatomy and test hypotheses about how the flight apparatus of Ichthyornis would have looked in comparison with modern birds. The YIBS research grant has allowed his team to get fossil samples from the University of Kansas and Yale’s Peabody collections micro CT scanned, giving the researchers a set of incredibly high-resolution three-dimensional models of the fossil bird’s anatomy.

- We generated models for these extraordinarily well-preserved fossils so now we can comapre the Chukar, a modern bird that is a type of partridge, to Ichthyornis and then to something that is even more distantly related to modern birds, like Archeopteryx, and see how the flight apparatus has become increasingly modern. The CT scan lets us the anatomy of flight in 3D very easily. Using these 3D models we can rotate the bones and quantify the range of motion in modern birds. Then, we ask whether the same range of motion would have been possible down the family tree, to understand when the capacity to flap your wings like a modern bird came to be.

The technology that makes studying vertebrate morphology possible is changing rapidly. On his desk, Daniel has a number of glass jars containing preserved specimens of small reptiles. Unlike normal specimens, these are colored a deep indigo.

- They are stained with a special dye that differentially colors muscles, nerves and the vascular system. This means we can CT scan them and make 3D models that include the brain, musculature and feathers and make even more accurate observations about the flight apparatus and how it works.