Ground-Dwelling Dinosaurs May Not Have Evolved into Birds: Fossil Reveals Different Origins

Birds may not have evolved from ground-dwelling dinosaurs. In fact, they may have had nothing to do with these long-extinct animals. After re-examining a sparrow-sized fossil from China, scientists have found that birds probably did not evolve from theropod dinosaurs that then gained the ability to fly.

The fossil in question is that of Scansoriopteryx, which was first found in Inner Mongolia. Although it was first classified as a coelurosaurian theropod dinosaur, researchers have now found that this isn't the case. The scientists used advanced 3D microscopy and high resolution photography in order to reveal structures that previously weren't visible. This showed that the creature actually lacks the fundamental structural skeletal features to classify it as a dinosaur.

Previously, scientists believed that this tiny, tree-climbing animal was evidence that birds evolved from dinosaurs that developed the ability to fly. Yet now, it appears that Scansoriopteryx is more like an early bird whose ancestors are also to be found among tree-climbing archosaurs that lived in a time well before dinosaurs.

"The identification of Scansoriopteryx as a non-dinosaurian bird enables a reevaluation in the understanding of the relationship between dinosaurs and birds. Scientists finally have the key to unlock the doors that separate dinosaurs from birds," said Stephen Czerkas, one of the researchers, in a news release.

The fossil revealed a combination of plesiomorphic or ancestral non-dinosaurian traits along with highly derived features. In addition, Scansoriopteryx possessed unambiguous birdlike features such as elongated forelimbs and wing and hind limb feathers. The creature had probably mastered the basic aerodynamic maneuvers of parachuting or gliding from trees.

"Instead of regarding birds as deriving from dinosaurs, Scansoriopteryx reinstates the validity of regarding them as a separate class uniquely avian and non-dinosaurian," said Alan Feduccia, one of the researchers.

The findings are published in the Journal of Ornithology.