Upper Jurassic–Upper Cretaceous
|Skeleton of an unnamed troodontid|
Troodontidae is a family of bird-like theropod dinosaurs. They were found mainly in Mongolia, China and North America. The first specimen, just a single tooth, was found in central Montana in 1855 by Ferdinand Hayden.
For a long time, troodontid fossils were few and scrappy. Recently more complete specimens have been found. There are now complete and articulated specimens, including feathers, eggs and embryos, and complete juveniles. In 1994 a fossil of an adult Troodon was found sitting on a nest with eight eggs.
Anatomical studies of the most primitive troodontids, like Sinovenator, demonstrate striking similarities with Archaeopteryx and primitive dromaeosaurids. This proves they are relatives: they are a clade called Paraves.
The family have relatively large brains, a skull with many air pockets, a retractable second toe claw (it could be pulled in) and many teeth. The number of teeth ranges from 96 in Saurornithoides mongoliensis to 120 in the Troodon.
Taxonomy[change | change source]
- Family Troodontidae
- Undescribed/unnamed specimens
References[change | change source]
- The word is pronounced "Troödontidae", that is, the two letters o are pronounced separately.
- Mackovicky, Peter J. & Norell, Mark A. 2004. Troodontidae. In Weishampel, David B; Dodson, Peter & Osmólska, Halszka. The Dinosauria. 2nd ed, Berkeley: University of California Press. pp. 184–195. ISBN 0-520-24209-2
- Norell, Mark A. et al 1994. A theropod dinosaur embryo and the affinities of the Flaming Cliffs dinosaur eggs. Science 266 (5186): 779–782. PMID 17730398