A new study that integrates developmental and paleontological data reveals previously unsuspected evolutionary transformations during the emergence of the bird wrist, consistent with its derivation from non-avian dinosaurs. From early dinosaurs with as many as nine wrist bones, modern birds evolved to develop only four ossifications. Their identity is uncertain, with different labels used in palaeontology and developmental biology. We examined embryos of several species and studied chicken embryos in detail through a new technique allowing whole-mount immunofluorescence of the embryonic cartil

Modern Birds Existed Before Dinosaur Die-Off | National Geographic ANIMALS NEWS Modern Birds Existed Before Dinosaur Die-Off Modern birds originated a hundred million years ago—long before the demise of dinosaurs, according to new research. By Sara Goudarzi Published February 8, 2008 • 3 min read Modern birds originated a hundred million years ago—long before the demise of dinosaurs, according to new research. In searching for the first ancestors of modern birds , studies have shown discrepancies between results from fossils and genetic analyses. Fossil records suggest that modern birds originated 60 million years ago, after the end of the Cretaceous period about 65 million years ago when dinosaurs died off. But molecular studies suggest that the genetic divergences between many lineages of birds occurred during the Cretaceous period. Now a new study based on molecular evidence suggests that avian ancestors were flapping their wings some 40 million years earlier than thought. In the new study researchers applied a new method of research that looks at mutation rates across lineages. "My goal for this study was to once and for all reconcile divergence estimates from these two sources of information," said lead study author Joseph Brown, a graduate student at the University of Michigan in Ann Arbor. The study appeared recently in the journal BMC Biology . Dating Methods When dating biological events, molecular geneticists rely on a concept known as the molecular clock. Over long stretches of time, mutations accrue, or "tick," at a fairly constant rate. By measuring the degree of genetic mutations, scientists can estimate how far back in time a species diverged. In large groups of distantly related species—such as different families or orders of birds—the molecular clock is much "sloppier" than previously thought, Brown said. This is because different lineages of birds can accumulate mutations at different rates, so applying a single rate t