(...) Given that all living vertebrates capable of powered flight leap into the air—whether bats or birds—Pittman and colleagues hypothesize that dinosaurs did the same. Even though paleontologists previously debated whether dinosaurs evolved flight from the “ground up” by running and jumping, or from the “trees down” by gliding, the fact that living animals take off by leaping indicates that deinonychosaurs did, too, regardless of what substrate they pushed off from. “This isn’t exclusive to take off from the ground or from height,” Pittman notes, “so birds in a tree also leap to take off.”
(...) In addition to the deinonychosaurs most closely-related to birds, the paleontologists found that two other deinonychosaur lineages had wings capable of powered flight. Within a group of Southern Hemisphere raptors called unenlagines, a small, bird-like dinosaur called Rahonavis would have been able to fly. On a different branch, the four-winged, raven-shaded dinosaur Microraptor shared similar abilities. More than that, the researchers found a few other species on varied parts of the deinonychosaur family tree—such as Bambiraptor and Buitreraptor—that were getting anatomically close to fulfilling the requirements for flight. Flight wasn’t just for the birds, in other words. Many non-bird dinosaurs were evolving aerodynamic abilities, but only a few were able to actually flap their wings and fly.
“The new paper is really exciting and opens new views on bird origins and the early evolution of flight,” says Bernardino Rivadavia Natural Sciences Argentine Museum paleontologist Federico Agnolin. So far, other studies haven’t found the same pattern of dinosaurs evolving flight more than once. Given that dinosaur family trees are bound to change with the discovery of new fossils, Agnolin adds, this might mean that the big picture of how many times flight evolved might change. All the same, he adds, “I think that the new study is really stimulating.”
Aucun commentaire:
Enregistrer un commentaire