New study rearranges family tree of birds

Enlarge / The new data indicates that hoatzins, shown here, are the last survivors of a lineage that branched off shortly after the rest of the dinosaurs went extinct. (credit: Cláudio Dias Timm )

The typical narrative about the asteroid-driven mass extinction that occurred 65 million years ago is that it killed off all the dinosaurs and enabled the era of the mammals. That could just be what the dinosaurs want you to think, though. From a different perspective, the aftermath of the extinction saw an explosion of dinosaur diversity, producing the greatest number of living species among any group of tetrapods (vertebrates with four limbs).

We just happen to call those species birds.

The fact that the origins of major groups of birds was so sudden makes it difficult to figure out the evolutionary relationships among them, as the fossil record, when present, shows groups appearing at roughly the same time. A recent attempt to sort out relationships via DNA sequences put some species in close proximity that some in the field found surprising. Now, a new paper is out with a different approach—it rearranges the tree a bit and suggests that many modern birds are descendants of a raptor-like ancestor.