Here is a cladogram from "The phylogeny of the ornithischian dinosaurs", Butler, Upchurch, & Norman, Journal of Systematic Palaeontology (2008):
Of these, :
lived during the Jurassic.
The synopsis explains well why this classification is subject to adjustment, and why you may have seen contradictory models in your research:
SYNOPSIS Ornithischia is a familiar and diverse clade of dinosaurs whose global phylogeny has
remained largely unaltered since early cladistic analyses in the mid 1980s. Current understanding of
ornithischian evolution is hampered by a paucity of explicitly numerical phylogenetic analyses that
consider the entire clade. As a result, it is difficult to assess the robustness of current phylogenetic
hypotheses for Ornithischia and the effect that the addition of new taxa or characters is likely to have
on the overall topology of the clade.
The new phylogenetic analysis presented here incorporates a range of new basal taxa and characters
in an attempt to rigorously test global ornithischian phylogeny. Parsimony analysis is carried out
with 46 taxa and 221 characters. Although the strict component consensus tree shows poor resolution
in a number of areas, application of reduced consensus methods provides a well-resolved picture
of ornithischian interrelationships. Surprisingly, Heterodontosauridae is placed as the most basal
group of all well-known ornithischians, phylogenetically distant from a stem-defined Ornithopoda,
creating a topology that is more congruent with the known ornithischian stratigraphical record. There
is no evidence for a monophyletic ‘Fabrosauridae’, and Lesothosaurus (the best-known ‘fabrosaur’)
occupies an unusual position as the most basal member of Thyreophora. Other relationships within
Thyreophora remain largely stable. The primitive thyreophoran Scelidosaurus is the sister taxon of
Eurypoda (stegosaurs and ankylosaurs), rather than a basal ankylosaur as implied by some previous
studies.
The taxonomic content of Ornithopoda differs significantly from previous analyses and basal
relationships within the clade are weakly supported, requiring further investigation. ‘Hypsilophodontidae’
is paraphyletic, with some taxa (Agilisaurus, Hexinlusaurus, Othnielia) placed outside
of Ornithopoda as non-cerapodans. Ceratopsia and Pachycephalosauria are monophyletic and are
united as Marginocephalia; however, the stability of these clades is reduced by a number of poorly
preserved basal taxa.
This analysis reaffirms much of the currently accepted ornithischian topology. Nevertheless, instability
in the position and content of several clades (notably Heterodontosauridae and Ornithopoda)
indicates that considerable future work on ornithischian phylogeny is required and causes problems
for several current phylogenetic definitions.
