The first two Jeholosaurus specimens were found in 2000 at Lujiatun near Beipiao City, Liaoning Province, China, and named and described the same year by Xu Xing, Wang Xioalin and You Hailu.

The specific name refers to the geographical area of Shangyuan where the fossil site is located.

It was found in a layer of the early Yixian Formation, dating from the Barremian, about 126-124 million years old.

[2] The layers consist of fluvial sandstone interspersed with tuff and it is thought that an enormous volcanic eruption occurred burying everything within a fifty to sixty-mile radius.

The deeply inset ventral margin of the maxilla suggests fleshy cheeks may have been present.

[1] Some distinguishing traits of Jeholosaurus include: a row of small foramina on the outer surface of the nasal immediately above the premaxillary articulation and parapophyses absent from dorsal vertebrae 1 and 2.

The describers did not assign Jeholosaurus to any family, limiting themselves to a placement as Ornithischia incertae sedis.

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.

[7] Pisanosaurus Heterodontosauridae Eocursor Lesothosaurus Thyreophora Stormbergia Agilisaurus Hexinlusaurus Marginocephalia Orodromeus Haya Changchunsaurus Jeholosaurus Hypsilophodon to Iguanodontia 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.

[8] Heterodontosauridae Eocursor Thyreophora Lesothosaurus Agilisaurus Hexinlusaurus Yandusaurus Nanosaurus Haya Jeholosaurus Changchunsaurus Orodromeus Koreanosaurus Zephyrosaurus Yueosaurus Thescelosaurus Marginocephalia Parksosaurus Talenkauen Macrogryphosaurus Gasparinisaura Galleonosaurus Leaellynasaura Anabisetia Diluvicursor Hypsilophodon Rhabdodontidae Muttaburrasaurus Tenontosaurus Dryomorpha