The re-examination of Scansoriopteryx – a sparrow-sized, pre-Archaeopteryx, bird-like creature that lived in what is today China during the Jurassic period, about 154 million years ago – challenges the widely accepted hypothesis that birds are derived from land-dwelling dinosaurs that gained the ability to fly.
Unearthed in Inner Mongolia in 2002, Scansoriopteryx was previously classified as a theropod dinosaur, from which many paleontologists believe flying dinosaurs and later birds evolved.
However, according to a new study published in the Journal of Ornithology, Scansoriopteryx was a tree-climbing animal that could glide.
The study’s authors, Dr Alan Feduccia from the University of North Carolina and Dr Stephen Czerkas of the Dinosaur Museum in Blanding, Utah, used advanced techniques to reveal structures in the Scansoriopteryx fossil not clearly visible before.
The techniques made it possible to interpret the natural contours of the bones. Many aspects of the fossil’s pelvis, forelimbs, hind limbs, and tail were confirmed, while it was discovered that it had elongated tendons along its tail vertebrae similar to Velociraptor.
“Scansoriopteryx lacks the fundamental structural skeletal features to classify it as a dinosaur,” the paleontologists said.
“Dinosaurs are not the primitive ancestors of birds. The Scansoriopteryx should rather be seen as an early bird whose ancestors are to be found among tree-climbing archosaurs that lived in a time well before dinosaurs.”
Scansoriopteryx has numerous bird-like features such as elongated forelimbs, wing and hind limb feathers, wing membranes in front of its elbow, half-moon shaped wrist-like bones, bird-like perching feet, a tail with short anterior vertebrae, and claws that make tree climbing possible.
The paleontologists identified the primitive elongated feathers on its forelimbs and hind limbs.
This suggests that Scansoriopteryx is a basal or ancestral form of early birds that had mastered the basic aerodynamic maneuvers of parachuting or gliding from trees.
The findings validate predictions that the ancestors of birds were small, tree-dwelling archosaurs which enhanced their incipient ability to fly with feathers that enabled them to at least glide.
Stephen A. Czerkas & Alan Feduccia. Jurassic archosaur is a non-dinosaurian bird. Journal of Ornithology, published online July 09, 2014; doi: 10.1007/s10336-014-1098-9