Jeholosaurus - Phylogeny

Phylogeny

Jeholosaurus is an ornithischian, as is e.g. shown by its ornithischian four-pronged pelvic structure with a pubis bone pointing downward and backwards, parallel to the ischium, while a forward-pointing prepubic process supports the abdomen.

The describers did not assign Jeholosaurus to any family, limiting themselves to a placement as Ornithischia incertae sedis. Using the comparative method, they pointed out some similarities to basal Euornithopoda: a small antorbital fenestra; the foramen on the quadratojugal; a large quadratic foramen; and the absence of a external fenestra in the lower jaw. However, they also noticed more derived euornithopod traits, such as the form of the greater and anterior trochanter of the thighbone, although the premaxilla not reaching the lacrimal, the high jaw joint and the premaxilla being on the same level as the maxilla, were again basal traits. The fused mandibular symphysis might indicate a relation with the Marginocephalia. Very basal ornithischian traits included the presence of six teeth in the premaxilla with only a short toothless sector in front and a short hiatus with the maxillary teeth.

Later cladistic analyses have recovered a basal position in the (Eu)ornithopoda. The following cladogram was based on analysis by Makovicky et al., 2011.

The following cladogram was based on analysis by Zheng and colleagues in 2009.

Han et al.found a similar topology to that of Makovicky et al., 2011, in 2012, with a clade composed of Jeholosaurus, Haya, and Changchunsaurus. They named this clade Jeholosauridae.