[D] Hexinlusaurus multidens [sG] [T]
Barrett, Butler & Knoll, 2005
Jurassic Middle Bathonian Callovian
Ornithischia Genasauria Incertae Sedis
Xiashaximiao Formation, Sichuan, China
Genus - Typespecies
Hexinlusaurus multidens (Barrett, Butler & Knoll, 2005) > Agilisaurus multidens (He & Cai, 1983) > Yandusaurus multidens (He & Cai, 1983) > Othnielia multidens (He & Cai, 1983) Paul, 1996 > Xiaosaurus multidens (He & Cai, 1983) Peng, 1992 [probably in error]
Barrett, P.M., R.J. Butler & F. Knoll. 2005. Small-bodied ornithischian dinosaurs from the Middle Jurassic of Sichuan, China. JVP25:823-834. Breaks \\\'Yandusaurus\\\' multidens out of Yandusaurus, and gives it the name Hexinlusaurus (He Xin-Lu\\\'s reptile)
Knoll, Fabien, Muséum des Sciences Naturelles, Orléans, France; Barrett, Paul M.,The Natural History Museum, London, United Kingdom
\\\"Yandusaurus multidens\\\" is an ornithischian from the Lower Shaximiao Formation (?Bajocian) of Dashanpu (Sichuan Province, China). The name-bearing type (Zigong Dinosaur Museum T6001) is a relatively complete skeleton lacking only the rostral extremity of the skull, most of the mandibles, and the caudal extremity of the tail.
The paratype is constituted by a disarticulated and less satisfactorily preserved skeleton. \\\"Yandusaurus multidens\\\" is recurrently considered to be a junior synonym of Y. hongheensis, type-species of the genus, the material of which comes from the Xiashaximiao Formation [Upper Shaximiao Formation] (? Oxfordian) of Hongheba (Sichuan Province).
However, significant differences exist between the two species. For example, the coracoid of \\\"Y.\\\" multidens lacks the ridge on the lateral surface and the ventral embayment that are present in Y. hongheensis. In addition, the scapula is shorter than the humerus in the former whereas they are equal in length in the latter.
Maxillary tooth morphology, enamel thickness, and the degree of tooth wear also differ. The presence of more teeth in the maxilla of \\\"Y.\\\" multidens contradicts the hypothesis that this species represents juvenile individuals of the larger Y. hongheensis.
Consequently, these distinctions appear to be sufficient to warrant a generic distinction between these two species. Moreover, the validity of Y. hongheensis is currently questionable, further destabilising the genus.
\\\"Y.\\\" multidens was originally referred to the Hypsilophodontidae on the basis of similarities apparently shared with Dryosaurus (a taxon then thought to be a close relative of Hypsilophodon). Subsequently, various authors have either supported this referral or regarded \\\"Y.\\\" multidens as a fabrosaurid or basal ornithischian.
Although \\\"Y.\\\" multidens is definitely more primitive than the dryosaurid Dryosaurus, its phylogenetic position amongst ornithopods remains challenging. Cladistic analyses suggest that Agilisaurus louderbacki and Othnielia rex may be the sister taxa of \\\"Y.\\\" multidens.