Earlier a skull only taxon, Auroraceratops, nested with a skull-less taxon, Stenopelix in the Ornithischia. Such non-overlapping trait pairings cannot be resolved. Does one nest basal to another? Or vice versa? Do they nest together? The cladogram cannot tell you, so you end up with 3 possible trees. Sometimes that happens.
What helps is taxon addition.
Here Leptoceratops (Fig. 1), known from complete material (skull + post-crania) is added to the LRT and returns the basal ceratopsian node to resolution.
Leptoceratops gracilis (Brown 1914; Latest Cretaceous; 2m long) is a late surviving member of an early radiation of bipedal ceratopsians that probably browsed while quadrupedal. The ventral maxilla was convex. The skull was narrower than most. The ribs appear to have flared widely, not deeply, creating a horned-lizard-like torso.
Brown B 1914. Leptoceratops, a new genus of Ceratopsia from the Edmonton Cretaceous of Alberta. Bulletin of the AMNH 33, article 36.
Dr. David Unwin reports
the untimely death of Dr. Lü Junchang, author and co-author of dozens of publications coming out of China. I met Dr. Lü long ago when he was working in Texas, early in his career and studies. The pterosaur, Beipiaopterus, was the subject of an early paper in 2002. He was kind enough to send PDFs on his work at every request.