Upper Jurassic–Upper Cretaceous, 160–65 mya
|Artist's impression of Sinornithoides|
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. The family are known for their 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.
During most of the 20th century, troodontid fossils were few and scrappy and they have therefore been linked, at various times, with many dinosaurian lineages. More recent fossil discoveries of complete and articulated specimens (including specimens which preserve feathers, eggs and embryos, and complete juveniles), have helped to increase understanding about this group. In 1994 a fossil of an adult Troodon was found sitting on a nest with eight eggs.
Anatomical studies, particularly studies of the most primitive troodontids, like Sinovenator, demonstrate striking anatomical similarities with Archaeopteryx and primitive dromaeosaurs, and demonstrate that they are relatives. The clade is called 'Paraves'.
- Family Troodontidae
- Undescribed/unnamed specimens
- "Troodontidae from Encyclopedia of Dinosaurs". credoreference.com. 2011 [last update]. http://www.credoreference.com/entry/estdino/troodontidae. Retrieved 15 May 2011.