Produced by the Population Genetics and Evolution class, Furman University

The Jurassic: Troodontids
Troodontids were feathered maniraptorans that were closely related to dromaeosaurs, the ancestors of modern avians. Troodontids support the theory that birds evolved from dinosaurs because they provide evidence that derived, feathered, deinonychosaurs were radiating before avians arose. They were about the size of a small human with long, slender hind legs used to move quickly, and a long skull filled with saw-edged teeth. They had large, grasping hands and an enlarged claw on their second toe, similar to but smaller than the sickle claw of the Dromaeosauridae (Hutchinson 1995). What is most interesting about them, however, is that they have the largest brain to body size ratio of any non-avian dinosaur. The ratio is comparable to modern day flightless birds (Wikipedia 2010). Their brain cavities suggested that their sight and hearing were well developed (Hutchinson 1995). They had strong binocular vision and their extended middle ears suggested strong hearing and the ability to hear low-frequency sounds. Additionally, one ear was higher than the other, an adaptation seen in modern owls to locate small prey (Wikipedia 2010). Troodontids were also egg-layers. They probably had two oviducts and laid two eggs at a time in an ordered nest that they protected. Their eggs were arranged vertically, suggesting they were not rotated (Zelenitsky 2006).

Page by Laura Snyder
A troodontid. Photo From: Wikipedia

Hutchinson J. 1995. The Troodontidae. University of California Museum of Paleontology. Accessed on March 30, 2010.

Wikipedia. 2010. Troodontidae. Accessed March 30, 2010.

Zelenitsky DK. 2006. Reproductive traits of non-avian theropods. J Paleont Soc Korea. 22(1):209-216.