Fig. 6 in New data on cranial anatomy of the ceratopsian dinosaur Psittacosaurus major

Fig. 6. The most parsimonious tree (length 58, consistency index 0.534, retention index 0.603) of Psittacosaurus obtained using the implicit enumeration option of the T.N.T. software (Goloboff et al. 2007). The data matrix of Averianov et al. (2006) was supplemented by coding 31 characters for Psittacosaurus major and P. lujiatunensis (see Appendix 1). P. xinjiangensis and Psittacosaurus specimen L0001 from the Yixian Formation of Liaoning (Xu and Wang 1998) were excluded due to large amount of missing data. Nodes are supported by the following unambiguous synapomorphies (in parenthesis are character numbers from Averianov et al.'s (2006) matrix). Node A: preorbital segment less than 40% of skull length (1), nasal extends ventrally beyond the external naris (5), ventral border of external naris is dorsal to the maxillary dorsal end (6), premaxillary teeth absent (8), and premaxillalacrimal contact present (9). Node B: lateral surface of the mandible straight (21). Node C: skull profile rounded (2). Node D: no synapomorphies. Node E: ventral margin of premaxilla−maxilla contact incised (11) and external mandibular fenestra present (20). Node F: "maxillary process" of maxilla present (14) and primary ridge on maxillary teeth caudoventrally angled (25). Node G: skull width exceeds skull length (3), premaxilla contacts jugal caudally (10), ventral postorbital horn present (15), rostral ramus of squamosal extends as far as to rostral wall of the supratemporal fenestra (17), quadrate shaft strongly arched in lateral view with caudal margin deeply excavated (19), and primary ridge on maxillary teeth weakly developed or absent (24). Node H: "maxillary process" of maxilla present (14) and denticles number on maxillary teeth equal to or more than 14 (26).