HADROSAURIDAE

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 : 457-461

HADROSAURIDAE

This study followed Cope’s (1870) original concept of Hadrosauridae , where Hadrosaurus foulkii is the type genus and species of the family. Thus, Hadrosauridae was here redefined as the last common ancestor of Hadrosaurus foulkii Leidy, 1858 , Edmontosaurus regalis Lambe, 1917b , Saurolophus osborni Brown, 1913 , and Lambeosaurus lambei Parks, 1923 , and all of its descendants (definition emended from Sereno, 1998; Wagner, 2001; Prieto-Marquez, 2008). According to the time-calibrated phylogram based on the strict reduced consensus tree derived from the parsimony analysis, hadrosaurids appeared no later than the Santonian ( Fig. 10 ). Hadrosauridae was supported by four unambiguous synapomorphies: loss of all but the primary ridge of dentary tooth crowns [5(3), convergent in Eolambia caroljonesa ]; ilium with ventralmost margin of the supra-acetabular process located anterodorsally relative to the caudoventral margin of the lateral ridge of the caudal protuberance of the ischial peduncle [235(1)]; short supraacetabular process of the ilium, ratio between the breadth of the process across its dorsal region, and the craniocaudal length of the central iliac blade less than 0.55 [237(3), reversed in Gryposaurus , the Secernosaurus clade, the Sabinas saurolophine, the Prosaurolophus clade, Brachylophosaurus canadensis Sternberg, 1953 , and Maiasaura peeblesorum Horner & Makela, 1979 ]; and ilium with lateral margin of the iliac peduncle progressively disappearing ventrally into the lateral surface of the region adjacent to the acetabular margin [257(1)].

Because the cranium of Hadrosaurus foulkii remains unknown (aside from a handful of teeth and a pair of poorly preserved maxillary fragments), numerous additional synapomorphies that might also ·

be diagnostic for hadrosaurids could only be ambiguously reconstructed. When the accelerated transformation option (ACCTRAN) was applied to the ancestral state reconstructions the following characters also became synapomorphic for Hadrosauridae : up to 32 tooth positions in the maxillary tooth row [15(1), convergent in Protohadros byrdi ]; relatively elevated lateral surface of the rostrodorsal region of the maxilla [89(1), reversed in the Brachylophosaurus clade]; anterior apex of the rostral process of the jugal wedge-shaped, pointed, but not excessively elongated, with the dorsal magin of the apex forming a relatively steep angle with the horizontal [103(1), reversed in the Brachylophosaurus clade]; caudodorsal margin of the rostral process of the jugal that is 60–90% as deep as the rostral jugal constriction, and dorsally or slightly recurved caudodorsally, forming the rostroventral corner of the orbital rim [104(1)]; caudoventral apex of the rostral jugal process located ventral to the caudal margin of the lacrimal process (106[1], reversed in all saurolophines except the Brachylophosaurus clade); medial articular surface of the rostral process of the jugal facing medially, the articular surface is bounded only caudally by a rim of bone [107(1)]; squamosal buttress on the caudal margin of the dorsal end of the quadrate absent or poorly developed as a gentle convexity [120(0)]; extensive intersquamosal joint present at the midline, parietal completely excluded from the sagittal plane of the skull at that particular spot (in adults) [136(2)]; absence of frontal fontanelle [139(0), convergent in Iguanodon bernissartensis , Mantellisaurus atherfieldensis , and Equijubus normani ]; coracoid reduced in size relative to the scapula [205(1)]; angle between the lateral margins of the facet for scapular articulation and the glenoid up to 115° [207(1), reversed in Secernosaurus koerneri , the Salitral Moreno OTU, Tsintaosaurus spinorhinus , and Pararhabdodon isonensis ); concave anteromedial margin of the coracoid, associated with a relatively large and lateroventrallyprojected biceps tubercle [208(1)]; moderately long ‘hook-like’ ventral process of the coracoid, ratio between the dorsoventral depth and the breadth of the process between 0.65 and 0.80 [209(1)]; recurved and caudoventrally directed ventral process of the coracoid [210(1), reversed in Shantungosaurus giganteus ); curved and dorsally convex dorsal margin of the scapula, curvature originating at the level of the dorsal margin of the pseudoacromion process, and being most pronounced over the dorsoventral constriction [211(1), convergent in Tanius sinensis Wiman, 1929 , and reversed in the Sabinas OTU]; relatively long scapula, ratio between its anteroposterior length and the dorsoventral depth of its proximal end greater than 4 [212(1), reversed in the Kritosaurus navajovius clade and S. giganteus ); elongation of metacarpal V, so that it is more than twice as long as it is proximally wide [228(1), reversed in

TURONIAN SANTONIAN APTIAN ALBIAN CENOMANIAN CONIACIAN CAMPANIAN MAASTRICHTIAN 125.0 112.0 99.6 93.5 89.3 85.8 83.5 70.6 65.5 million years B.P.

Charonosaurus jiayinensis Godefroit et al., 2000 and Parasaurolophus ]; and mediolaterally broad and proximodistally shortened pedal unguals, rounded shield or hoof-like shaped, with reduced or absent claw grooves [285(1), convergent in Bactrosaurus johnsoni ). On the other hand, the following ambiguous synapomorphy also supported Hadrosauridae when the delayed transformation option (DELTRAN) was applied to the ancestral state reconstructions: dorsoventrally thick and continuous lateral emargination of the ectopterygoid shelf, gradually thicker caudally than rostrally [99(2)].

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).