Troodontidae

Troodontids; Temporal range: ; Late Jurassic–Late Cretaceous, 160–66 Ma PreꞒ Ꞓ O S D C P T J K Pg N
	Mounted skeletal cast of an unnamed Alaskan troodontid, Perot Museum
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Dinosauria
Clade:	Saurischia
Clade:	Theropoda
Clade:	Eumaniraptora
Family:	†Troodontidae; Gilmore, 1924
Type species
	Troodon formosus; Leidy, 1856
Subgroups
	†Albertavenator; †Almas; †Archaeornithoides?; †Geminiraptor; †Jianianhualong; †Jinfengopteryx; †Koparion?; †Liaoningvenator; †Paronychodon?; †Sinornithoides; †Talos; †Tochisaurus; †Xixiasaurus; †Sinovenatorinae; †Troodontinae;
Synonyms
	Saurornithoididae Barsbold, 1974

Troodontidae is a family of bird-like theropod dinosaurs.^[1] 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.^[2]

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.^[3]

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.

Replica skull of an undescribed troodontid, SPV 300/45.

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.^[2]

Taxonomy

Family Troodontidae
- Almas
- Anchiornis
- Archaeornithoides
- Borogovia
- Byronosaurus
- Halszkaraptor
- Jinfengopteryx
- ?Koparion
- Latenivenatrix
- Mei
- Saurornithoides
- Sinornithoides
- Sinusonasus
- Sinovenator
- Stenonychosaurus
- Tochisaurus
- Troodon (nomen dubium)
- Urbacodon
- Xixiasaurus
- Zanabazar
Undescribed/unnamed specimens
- SPS 100/44 = EK troodontid
- SPV 300/45 ("Lesse")
- WDC DML 001 ("Lori")

References

↑ The word is pronounced "Troödontidae", that is, the two letters o are pronounced separately.
↑ ^2.0 ^2.1 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

[1] The word is pronounced "Troödontidae", that is, the two letters o are pronounced separately.

[Mac-2] 2.0 ^2.1 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

[3] 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

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