The announcement of the discovery
of the ornithischian, Sanxiasaurus (Ning et al. 2019; Fig. 1) calls into question the topology of the Ornithischia. What are the outgroup taxa and clades? Which are the basalmost taxa?
The trouble is
Ning et al. failed to include a long list of outgroup and basal taxa (Figs. 1, 2). So, what are the ramifications?
topologies can change when you add pertinent taxa and delete irrelevant taxa. You can only know which is which when you start with a wide enough gamut cladogram. Only then can you have confidence that your subsets are indeed monophyletic.
Ning Li, et al. (11 co-authors) 2019. A neornithischian dinosaur from the Middle Jurassic Xintiangou Formation of Yunyang, Chongqing, China: the earliest record in Asia. Historical Biology (advance online publication)