ANKYLOPOLLEXIA Sereno, 1986

Phylogenetic definition. The least inclusive clade containing Camptosaurus dispar (Marsh, 1879), Uteodon aphanoecetes (Carpenter and Wilson 2008), and Parasaurolophus walkeri Parks, 1922 (emended from Sereno, 1986).

Unambiguous synapomorphies. Ankylopollexia is characterized by nine unambiguous synapomorphies: deltoid ridge of the scapula close to parallel to the long axis of the scapula (198.0), humerus with a well-developed deltopectoral crest (212.0), ulna with a flange on the proximal end that wraps around the lateral edge of the radius (219.1) some fusion of the carpals (227.1), manual digit I oriented at least 45 degrees from the antebrachial axis (232.1), metacarpal I short and block-like (233.1), ungual of manual digit I subconical (241.1), brevis fossa of ilium not well defined by a lateral lip (259.0), ossified epaxial and hypaxial tendons arranged in a double-layered lattice (323.1).

Topology. This is a well-supported clade, with a Jackknife value of 35 and Bremer support of 6 in the parsimony analysis (Figure 7), and a posterior probability of 0.91 in the Bayesian tree (Figure 8). In both topologies, the most basally branching taxon is Uteodon, and Camptosaurus is recovered as the sister to Styracosterna. These two genera are the only non-styracosternan ankylopollexians.