Hesperornithoides

Hesperornithoides is a troodontid theropod dinosaur from the Upper Jurassic Morrison Formation of western North America.

Hesperornithoides Temporal range: Late Jurassic, ~Oxfordian–Tithonian PreꞒ Ꞓ O S D C P T J K Pg N
Main blocks of the holotype
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Dinosauria
Clade:	Saurischia
Clade:	Theropoda
Family:	†Troodontidae
Genus:	†Hesperornithoides Hartman et al., 2019
Species:	†H. miessleri
Binomial name
Hesperornithoides miessleri Hartman et al., 2019

Discovery

The fossil was found in Wyoming, as the site was carefully documented by the collectors.^[1]

Classification

A phylogenetic analysis was presented in an abstract in the Journal of Vertebrate Paleontology in 2005. The analysis decided the specimen was a close relative of Sinornithoides.^[2]

Significance

This dinosaur is very significant because it is the oldest known troodontid from North America. Until the discovery of Lori, troodontids were believed to have first originated and evolved in Asia and then migrated to North America. Most troodontids were discovered in Asia, and the previously oldest known troodontids, from the Lower Cretaceous, lived there.^[3]