A great disagreement has existed between paleontologists and developmental biologists about the development of the wrist bones of modern birds and the possible evolution of modern birds from dinosaurs. The source of the century long argument has been firmly rooted in the unwillingness in both parties to exchange information or communicate. Alexander Vargas at the University of Chile and colleagues combined both areas of research for the first time to prove that the bird wrist did evolve from the dinosaur wrist.
Vargas and company combined an examination of the dinosaur and early bird fossils in the world’s museums with a newly developed method of studying bird embryo skeletons in three dimensions. The result is the first complete description of how a four-boned bird wrist may have developed from dinosaurs that had seven bones in their wrists. The discovery is predicated on the work of John Ostrom. Ostrom showed how one modern bird bone called the semilunate could have been formed from the merging of two bones in a dinosaur wrist.
Ostrom’s work could never be verified by observation of the development of modern birds in the embryonic stage of growth. Vargas and his team were able to show the first evidence from the embryonic development of modern birds that shows the merging of two bones to form the semilunate. The researchers were also able to show how the pisiform could have been lost to early birds but evolved again for modern birds because the bone adds force to the downward wing movement in flight but limits the upward movement of the wing. The team also showed that the cartilaginous structure of bird writs developed from similar dinosaur structures.
One has to understand that paleontologists and developmental biologists are first people. People have egos and agendas. Often both groups compete for limited research funding. Vargas and his lab are the first to break the impasse and prove bird wrists developed from dinosaur wrists. It is unfortunate that Ostrom did not live to see his work verified.
