SCIENCE, DAVIDE BONNADONNASongbirds and fluffy chicks are known to be the descendants of monstrous dinosaurs, but exactly how certain lineages evolved into today’s birds has been a mystery. A steady shrinking of one group, bipedal carnivores known as theropods, may have driven the dinosaur-bird transition, according to results published last week (August 1) in Science.
An analysis of nearly 120 dinosaur species and more than 1,500 skeletal features revealed that the theropod lineages that are thought to have been direct ancestors of birds evolved skeletal adaptations four times faster than other dinosaurs. These avian ancestors consistently miniaturized over a 50-million-year period, which likely facilitated the evolution of flight, and features such as skulls with shorter snouts, but bigger brains and eyes, the authors noted.
“What was impressive was the consistency of the size change along the dinosaur-to-bird transition, with every descendant smaller than its ancestor,” study author Michael Lee of the South Australian Museum in Adelaide told the BBC.
Tinier theropods may have found it easier to adapt to different resources—such as habitats or prey—than their larger kin. “It would ...
