SAUROLOPHIDAE

Prieto-Márquez, Albert, 2010, Global phylogeny of Hadrosauridae (Dinosauria: Ornithopoda) using parsimony and Bayesian methods, Zoological Journal of the Linnean Society 159 (2), pp. 435-502 : 461

SAUROLOPHIDAE

This clade is defined as the last common ancestor of Saurolophus osborni Brown, 1913 , Lambeosaurus lambei Parks, 1923 , and all of its descendants (definition emended from Wagner, 2001; Prieto-Marquez, 2008). This clade represents the major split within Hadrosauridae into the hollow-crested lambeosaurines and all other forms that include flat-headed and solid-crested species. This split occurred no later than the Santonian, according to the time-calibrated phylogram based on the strict reduced consensus tree derived from the parsimony analysis ( Fig. 10 ). Saurolophidae was supported by four unambiguous synapomorphies: presence of sinuous primary ridge in dentary tooth crowns [7(1), reversed in saurolophines except in the Brachylophosaurus clade and Gryposaurus latidens Horner, 1992 ]; long deltopectoral crest, with the ratio between the proximodistal length of the crest and the proximodistal length of the humerus greater than 0.55 [219(2), reversed in saurolophines except the Salitral Moreno OTU, Saurolophus , Edmontosaurus , and Shantungosaurus giganteus ]; deltopectoral crest of the humerus extending abruptly from the humeral shaft to give a distinct angular profile [221(1)]; and caudodorsally oriented dorsal margin of the postacetabular proces of the ilium, rising dorsally relative to the acetabular margin [248(1), reversed in the Big Bend UTEP saurolophine].

Numerous ambiguous synapomorphies also supported Saurolophidae under DELTRAN, which are not documented because of poor preservation in the most immediate outgroup taxa, Claosaurus agilis , Lophorhothon atopus , and Hadrosaurus foulkii : three functional teeth throughout most of the dental battery, gradually decreasing to two near the rostral and caudal ends of the dentary [3(2)]; 33–44 tooth positions in the maxilla [15(1), convergent in Protohadros byrdi ]; two functional teeth throughout most of the dental battery length, gradually changing to one near the rostral and caudal ends of the maxilla [17(2)]; predentary with an angle between its rostral surface and the dorsal margin of the lateral process of 40–55° [24(2), reversed in Gryposaurus monumentensis Gates & Sampson, 2007 , Kritosaurus navajovius , and Edmontosaurus ); subrectangular to rectangular predentary denticles [25(1), reversed in Gryposaurus notabilis ]; predentary denticles limited to the rostral margin [28(1), convergent in Bactrosaurus johnsoni ]; dorsal keel-like process of the predentary with welldeveloped ridge on the lingual surface of the rostral segment of the predentary, from which the former extends further caudally to lie dorsal to the dentary symphysis [31(1), convergent in Protohadros byrdi ]; angle between the dentary symphysis and the lateral side of the rostral half of the dentary up to 15° [39(1), convergent in P. byrdi ); dentary coronoid process rostrally inclined with an angle up to 68° [42(2)]; well-developed expansion of both the caudal and, especially, the rostral margin of the dorsal region of the coronoid process of the dentary [43(1)]; welldeveloped expansion of the lateral side of the dentary ventral to the coronoid process, with an angle between the lateral surface of the dentary and that of the region caudoventral to the coronoid process up to 165° [46(1)]; longitudinal axis of the dentary occlusal plane axis parallel with the lateral side of the dentary [47(1)]; caudal end of the dental battery located posterior to the caudal edge of the coronoid process [49(2)]; rostrodorsal process of the surangular reduced in thickness rostrocaudally, strap-like, and wedging dorsally into a thin sliver that becomes concealed in lateral view by the dorsal half of the caudal margin of the coronoid process [51(1)]; convex side of the lateral lap and the lateroventral surface of the main body of the surangular facing more ventrally than laterally [54(1)]; premaxillary oral margin very strongly deflected ventrally, so that, approximately, the dorsoventral distance between the occlusal plane and the level of the premaxillary oral margin is equal to or larger than the mean depth of the dentary [61(1), convergent in P. byrdi ]; premaxillary oral margin with a ‘double layer’ morphology consisting of an external denticle-bearing layer and an internal layer of thickened bone set back slightly from the oral margin, and separated from the denticular layer by a deep sulcus bearing vascular foramina [63(1), convergent in Bactrosaurus johnsoni ]; subtriangular articular surface for the jugal that is more laterally than dorsally facing, with a lateroventrally-directed pointed corner that is located adjacent and slightly dorsal to the proximal end of the lateral ridge of the ectopterygoid shelf [92(2)]; six or less maxillary foramina ventral and rostral to the jugal articulation (excluding large rostrodorsal or rostrolateral foramen) [94(1)]; dorsoventrally deep, with the caudodorsal margin of the rostral process of the jugal about 60–90% as deep as the rostral jugal constriction, dorsally or slightly recurved caudodorsally, and forming the rostroventral corner of the orbital rim [104(1), convergent in P. byrdi ]; medial articular surface of the rostral process of the jugal facing medially, being bounded only caudally by a rim of bone [107(1)]; elongated orbit, dorsoventrally deeper than it is wide [188(1)]; subtriangular occiput, with the quadrates laterally splayed distally [196(1)]; 12 or more cervical vertebrae [199(1)]; eight or more co-ossified vertebrae in the sacrum [202(1), convergent in Iguanodon bernissartensis ]; coracoid reduced in size relative to the scapula [205(1)]; concave craniomedial margin of the coracoid, with a relatively large and lateroventrally-projected biceps tubercle [208(1)]; recurved ventral process of the coracoid, so that it is caudoventrally directed [210(1), reversed in Shantungosaurus giganteus ]; curved dorsal margin of the scapula, dorsally convex, with the curvature originating at the level of the dorsal margin of the pseudoacromion process, most pronounced over the dorsoventral constriction [211(1), convergent in Tanius sinensis and reversed in the Sabinas saurolophine]; relatively long scapula, ratio between its anteroposterior length and the depth of the proximal region greater than 4 [212(1), reversed in the Secernosaurus – Gryposaurus clade and in S. giganteus ]; ratio between the depth of the distal end of the scapular blade and the depth of the proximal region of the scapula, 1 or greater [213(1), convergent in B. johnsoni and reversed in the Secernosaurus – Gryposaurus clade and S. giganteus ]; number of carpal bones reduced to a maximum of two unfused elements [225(1)]; absence of manual digit I [226(1)]; elongation of metacarpal V, so that it is more than twice as long as it is proximally wide [228(1), reversed in the Charonosaurus – Parasaurolophus clade]; and absence of distal tarsals II and III [280(1)]. Under ACCTRAN, Saurolophidae was also supported by an ambiguous synapomorphy: the presence of dentary marginal denticles with three or more indentations at the apex [10(0)].

Figures

Figure 10. Time-calibrated phylogram based on the strict reduced consensus tree derived from maximum parsimony analysis of hadrosaurid relationships. The geochronological ages are taken from Gradstein, Ogg & Smith (2004).