Microraptor: A Controversial Dinosaur in the Origin of Flight
The Feathered Dinosaur
Microraptor gui, a small, feathered dinosaur that lived around 120 million years ago, has sparked a heated debate among paleontologists about its ability to fly and its significance in the evolution of birds.
Hip Anatomy and Flight Posture
One of the key controversies surrounding Microraptor is the position of its hindlimbs during flight. In 2010, a study by Alexander and colleagues proposed that Microraptor held its hindlimbs out to the side like a crocodile, creating a second set of wings. This posture would have allowed it to glide more efficiently.
However, a subsequent study by Brusatte and Brougham challenged this hypothesis. They argued that Microraptor’s hip anatomy, specifically the presence of reduced supracetabular crests and enlarged antitrochanters, would have prevented it from splaying its legs out in the manner proposed by Alexander and colleagues. This would have made the proposed posture “anatomically implausible,” according to Brusatte.
Preservation and Interpretation
The debate over Microraptor’s hip anatomy stems in part from the preservation of the dinosaur’s fossils. The hip specimens used by Alexander and colleagues were crushed flat, which may have led them to mistakenly conclude that the constraining features were absent. However, Brusatte and Brougham argue that even in the crushed state, it is clear that Microraptor possessed these features.
Relationship to Other Dromaeosaurids
Microraptor was closely related to other dromaeosaurid dinosaurs, including Hesperonychus, which was preserved with an uncrushed pelvis. In Hesperonychus, the constraining features of the hip are present, further supporting Brusatte and Brougham’s argument that Microraptor could not have splayed its legs out completely laterally.
Significance in the Origin of Flight
The significance of Microraptor in the origin of flight is still uncertain. Early birds already existed by the time Microraptor lived, and it is possible that it was simply one of many small feathered dinosaurs that independently evolved the ability to glide.
Brusatte argues that it is important to study Microraptor in the context of other dromaeosaurids and troodontids, which varied greatly in size, feathery integument, and presumed lifestyle. To claim that Microraptor’s gliding ability was a precursor to the origin of flight, it must be demonstrated that this ability was retained by the immediate ancestors of birds. This is not certain or even likely, based on current evidence.
Ongoing Debate
Despite the ongoing debate, Microraptor remains a fascinating and enigmatic dinosaur that provides valuable insights into the evolution of flight. Further research is needed to fully understand its role in the origin of birds and the diverse adaptations of feathered dinosaurs.
