Tuesday, 17 January 2023

Shrinking dinosaurs became modern birds

It is known that modern birds evolved from dinosaurs, but a new study published in the journal Science shows that the key to this transformation was, for one particular group of giant lizards called theropods, to continually get smaller and smaller over a 50-million-year time span. Researchers present a detailed family tree of these dinosaurs and their bird descendants which maps out this transformation.
They showed that the branch of theropod dinosaurs which gave rise to modern birds were the only dinosaurs that kept getting smaller. These bird ancestors also evolved new adaptations four times faster than other dinosaurs. "Birds evolved through a unique phase of sustained miniaturisation in dinosaurs," says lead author Michael Lee, from the University of Adelaide's School of Earth and Environmental Sciences.
"Being smaller and lighter in the land of giants, with rapidly evolving anatomical adaptations, provided these bird ancestors with new ecological opportunities, such as the ability to climb trees, glide and fly.
Ultimately, this evolutionary flexibility helped birds survive the deadly meteorite impact which killed off all their dinosaurian cousins." The study examined over 1500 anatomical traits of dinosaurs to reconstruct their family tree. The researchers used sophisticated mathematical modelling to trace evolving adaptions and changing body size over time and across dinosaur branches.
Paleontologists looking at fossils of meat-eating dinosaurs, particularly those that were small bipedal like the Veloceraptors, have pointed out years ago how they share an uncanny number of traits with modern birds: everything from wishbones, light hollow skeletons and three-fingered hands that folded like bird wings to an array of bright, complex feathers. Many of them also had some ability to glide, perhaps even fly.
A new fossil specimen of Archaeopteryx