Archaeopteryx, one of life on Earth’s first stabs at building a bird, evaded predators and cleared obstacles on the ground by bursting into flight like a startled pheasant, a new analysis suggests.
High-resolution x-ray images of the creature’s skeleton reveal tell-tale similarities with the bones of birds that cannot glide or soar but instead take to the air in frenetic, flapping bounds, scientists say.
The findings add to a debate that has surrounded the Late Jurassic beast since the first fossilised remains were recovered from a limestone quarry in Bavaria in the 19th century. While Archaeopteryx definitely sported an elaborate plumage, how and even whether it flew was far from clear.
“This is the best indication for active flight in Archaeopteryx that we’ve had in 150 years,” said Dennis Voeten, a palaeontologist at the European Synchrotron Radiation Facility in Grenoble. “But I am under no illusion that this will end the debate.”
Archaeopteryx is a star species in the story of avian evolution. The size of a magpie, it was a bizarre creature, with the feathers and wings of a bird and the teeth, claws and long bony tail of a dinosaur. Until recently, the 150m-year-old animal was considered the earliest bird known, but palaeontologists now believe it belonged to an evolutionary side branch to the one that led to modern birds.
But whether Archaeopteryx was a bird-like dinosaur or a dinosaur-like bird is only one of the questions around it that have kept scientists busy for the past century or so. When it came to the issue of flight, researchers divided into two opposing camps. One thought Archaeopteryx could get airborne much as modern birds do, though with an admittedly different flying style. The other camp thought Archaeopteryx might use its claws to scale trees and then simply glide back down again.
To shed light on the mystery, Voeten used a technique called synchrotron microtomography to look at the wing bones of three Archaeopteryx fossils without damaging them. The images revealed the sizes and shapes of the wing bones and also the thicknesses of the bone walls. Voeten then compared these measurements with those from land-based animals and other flying species ranging from pterosaurs to birds.
Writing in the journal Nature Communications, Voeten and his colleagues explain how the Archaeopteryx bones most closely matched those of birds they call “burst fliers”, which can launch themselves off the ground but are not able to glide or flap for long distances. In particular, the Archaeopteryx bones had incredibly thin walls, in some cases no more than a millimetre thick.
Peculiarities in the Archaeopteryx skeleton mean it would not have flown like modern birds. Living in the tropical archipelago that was Europe in the Late Jurassic, Archaeopteryx may have had an unusual flapping style, Voeten said, that involved bringing its wings forward and up before pulling them back down, mirroring the butterfly stroke used by swimmers.
“Archaeopteryx and pheasants may have shared a similar lifestyle that involved flying to cross barriers and dodge predators, but how they flew would have been very different,” said Voeten. If Archaeopteryx was indeed flying 150 million years ago, it suggests that the first species to take wing arose even earlier.
Gareth Dyke, a palaeontologist at Debrecen University in Hungary, called the research “remarkable”. “It’s amazing that we finally know something about the internal bone anatomy of this fossil and we can see the inside of their bones. No one would ever allow the bones to be sectioned and this has now been done with virtual imaging,” he said. “This is such an iconic fossil, and people have been arguing about it for years.”
At the time of Archaeopteryx, the skies were ruled by primitive forms of pterosaur, the flying reptiles that were thought to have been in decline before the asteroid strike 66m years ago that ended the reign of the dinosaurs. But in a separate study published in Plos Biology, palaeontologists at the University of Bath overturn that view. Working in northern Morocco, they unearthed the remains of six new species of pterosaur that date to just over 66m years old, evidence that the largest animals to take to the sky were thriving before the cataclysm cut them off in their prime.
