Archosauria: Avemetatarsalia to Neornithes
2° Nominal Author
This clade has been recognized for some time as a monophyletic assemblage of basal ornithopods, although united by only a few synapomorphies (Sereno 1986). Some recent cladistic analyses, in contrast, have challenged hypsilophodontid monophyly (e.g. Winkler et al. 1998, Weishampel et al. 2003). Norman et al. (2004), for example, found traditional hypsilophodontids to represent a paraphyletic grade basal to Iguanodontia. The name is probably best defined as it is here, to include any taxxa most closely related to the nominotypical genus
, however that may sort out in future analyses.
Inactive Taxon Status
Current Age Range
Bathoniaan-Callovian (165 Ma)
Maastrichtian (66 Ma)
Basis for Range
The earliest record is based on
from the Bathonian-Callovian-age Lower Shaximiao Formation in China. The latest records are several genera from Maastrichtian-age formations in western North America. Dates are rounded to the nearest million, the earliest from the beginning of the stage and the latest from the end of the stage (Gradstein et al. 2004).
Definitional History #1
All euornithopods closer to