Phylogeny of iguanodontian dinosaurs and the evolution of quadrupedality Author Poole, Karen E. text Palaeontologia Electronica 2016 a 30 25 3 1 65 http://dx.doi.org/10.26879/702 journal article 10.26879/702 1094-8074 11063310 RHABDODONTIDAE Weishampel, Jianu, Csiki, and Norman, 2003 Phylogenetic definition. A node-based taxon consisting of the most recent common ancestor of Zalmoxes robustus and Rhabdodon priscus and all the descendants of this common ancestor ( Weishampel et al., 2003 ). Unambiguous synapomorphies. Rhabdodontidae is characterized by the presence of apicobasally extending ridges on the cutting surfaces of unworn cheek teeth (lingual surface of maxillary teeth, labial surface of dentary teeth) (138.1), acromion process of scapula does not extend beyond the edge of the coracoid (196.0), medial condyle of the humerus transversely wider than the lateral (216.2), proximal flange present on the ulna (219.1), preacetabular process of the ilium twisted around its long axis (249.1), pubic peduncle of the ischium dorsoventrally compressed (280.1), and distal condyles of the femur expanded both cranially and caudally (304.1), metatarsal V absent (320.1). Topology. This small clade contains two genera, Zalmoxes and Rhabdodon , both known from the Late Cretaceous of Europe. This clade is recovered in the parsimony analysis with a jackknife value of 81 and a Bremer support of 4, and in the Bayesian analysis with a posterior probability of 1. DRYOMORPHA Sereno, 1986 Phylogenetic definition. The most inclusive clade containing Dryosaurus altus ( Marsh, 1878 ) and Parasaurolophus walkeri Parks, 1922 ( Sereno, 2005 ). Unambiguous synapomorphies. In both parsimony and Bayesian analyses, Dryomorpha is characterized by a premaxilla with a posterolateral process that contacts the lacrimal (6.1), a maxilla with a rostrolateral process (18.1), a lacrimal that fits into a slot in the dorsal process of the maxilla (27.1), a quadratojugal that lacks a dorsal process (57.1), a coronoid process with subequal craniocaudal widths of dentary and surangular (109.1), cheek teeth with secondary ridges that are thin and formed only from enamel (145.1), a radius that is triangular in distal view (224.1), and an ischium with the obturator process within the proximal 25% of the ischium (287.1). In the parsimony analysis, Dryomorpha is further supported by a maxillary tooth row that is medially bowed in ventral view (26.0), a jugal that is excluded from the antorbital fenestra by lacrimal-maxilla contact (47.0), a quadratojugal that lacks a foramen through the center of the element (58.0), and absent ossified hypaxial tendons on the caudal vertebrae (322.0). In the Bayesian analysis, Dryomorpha is also supported by the presence of a quadrate buttress or "hamular process" (63.1), presence of a quadrate (or paraquadratic) foramen or notch on the boundary between the quadrate and quadratojugal (65.1), and presence of a short midline process of the predentary dorsal to the dentary symphysis (90.1) Topology. In both parsimony and Bayesian analyses ( Figure 6 ), Dryomorpha contains two sister clades: Dryosauridae and Ankylopollexia. Support for this node is moderate (jackknife=19, Bremmer support=4, PP=0.27).