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?Yandusaurus? multidens in SVP2003 abstracts
There are lots of dinosaur papers in the SVP2003 abstracts, downloadables in:
One of the most interesting for ornithopod´s friends is that of Knoll & Barret
suggesting that ?Yandusaurus? multidens don´t pertain to the genus Yandusaurus,
a topic previosly discussed in this list.
The ref is:
Knoll, F. & Barret, P. M. 2003. Systematic revision ff "Yandusaurus" Multidens,
a Middle Jurassic Ornithopod from China. Journal of Vertebrate Palaeontology,
23(supplement to number 3), 68A
And the published abstract is:
SYSTEMATIC REVISION OF "YANDUSAURUS" MULTIDENS, A MIDDLE JURASSIC ORNITHOPOD
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
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.