Abstract New morphometric methods of analysis of phylliform ornithischian teeth provide the opportunity to study clade associations of ankylosaurs of ambiguous taxonomy that include dental material. With recent extensive sampling of ex situ/in situ dentition of ankylosaurs, we present new dental characters for phylogenetic analyses of Thyreophora that we use in seven phylogenetic analyses of both parsimony and Bayesian methods. Our analyses do not recover the previously proposed clades of Panoplosauridae, Polacanthidae, and Struthiosauridae. Prior dental characters that have been used as unambiguous synapomorphies to define Struthiosauridae suffered from vague descriptions that are not accurate portrayals of ankylosaur tooth morphology; therefore, these characters are not useful for thyreophoran phylogenetic analyses. Our phylogenetic analysis results suggest a large degree of homoplasy and support the need for a systematic revision of Nodosauridae. Tooth morphometrics supplement the placement of taxa in phylogenetic analyses and allow clade-level classification of taxa solely or primarily based upon tooth material. We identify clade associations of enigmatic ankylosaur taxa, such as Peloroplites with Panoplosauridae, Aletopelta with Nodosauridae/Panoplosauridae, and Priconodon with Nodosauridae, through a combination of morphometrics and phylogenetics, with implications for palaeobiogeography.
Cross et al. (Thu,) studied this question.