Produced by the Population Genetics and Evolution class, Furman University

The Cretaceous: Microraptors
Microraptors were a group of very small four-winged dromeaosaurid dinosaurs, representing an intermediary stage between the evolution of birds and dinosaurs. They are the smallest recorded dinosaurs measuring about 39 cm in length, with about 24 cm of that belonging to their tail (Hecht 2000). They had a combination of unserrated and partially serrated teeth, a constricted waist, and long upper arm bones, all shared characteristics between primitive birds and troodontids. The feathers were fully formed on all four legs, and there was a feather fringe on the tail. They were fast running two-legged dinosaurs, with feet structured for the grasping of branches, suggesting they may have been arboreal. This arboreal lifestyle could further explain the flight adaptation, likely developing from gliding behavior between trees (Mayell 2003). There is a debate among scientists as to whether flight evolved in a “ground up” or “tree down” manner. But the discovery of this four winged animal supports the idea that they adapted to gliding rather than running for velocity, since the feathers on the back of their legs would be a hindrance to their running ability. However, “ground up” proponents suggest that the feathers were positioned in such a way to avoid interference. However when glide tests were performed on 3D models of microraptors the “ground up” flight method was found to require an anatomically unlikely head for balance (Ruben 2010).

Page by Megan Aprill
Image of a microraptor, from: The Other Journal

Hecht J. 2000. Micro-raptor. New Scientist. Accessed April 5, 2010.

Mayell H. 2003. Four Winged Dinosaurs Found in China, Experts Announce. National Geographic. Accessed April 5, 2010.

Ruben J. 2010. Paleobiology and the origins of avian flight. P Natl Acad Sci USA 107:2733-2734. Accessed April 5, 2010.

Wikipedia. 2010. Microraptor. Accessed April 5, 2010.