|Thescelosaurus skeleton on display at the Burpee Museum of Natural History|
The distribution of Thescelosaurinae is quite large. They are widespread through United States and Canada where most of their fossils have been found. They also have a small group in North-Eastern China and Mongolia.
Studies disagree about which genera are included in the Thescelosaurinae. The group is defined to include Parksosaurus and Thescelosaurus and a cladistic analysis by C.M. Brown in 2013 concluded that the genera Changchunsaurus, Haya, Jeholosaurus and possibly Koreanosaurus are also thescelosaurines.
|This cladogram is from Brown et al., (2013).|
All Thescelosaurines were originally included in the family Hypsilophodontidae, which is presently considered polyphyletic (unnatural). They are all now simply considered to be basal Euornithopods. They are the sister taxa to Orodrominae, a group containing Albertadromeus, Orodromeus, Oryctodromeus and Zephyrosaurus. Their parent taxon is Thescelosauridae along with Orodrominae. Currently, all genera originally included in Jeholosauridae are classified in Thescelosaurinae, possibly as a group inside it. If the group of Jeholosaurids is not considered natural than that might mean Jeholosauridae is a synonym of Thescelosaurinae. Recently, a phylogenetic analysis found them outside of Ornithopoda, the group they'd been allied with traditionally.
- "Thescelosaurinae". Paleobiology Database. Retrieved 20 June 2013.
- Brown, C. M.; Evans, D. C.; Ryan, M. J.; Russell, A. P. (2013). "New data on the diversity and abundance of small-bodied ornithopods (Dinosauria, Ornithischia) from the Belly River Group (Campanian) of Alberta". Journal of Vertebrate Paleontology. 33 (3): 495–520. doi:10.1080/02724634.2013.746229.
- Boyd CA. (2015) The systematic relationships and biogeographic history of ornithischian dinosaurs. PeerJ 3:e1523 https://doi.org/10.7717/peerj.1523