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Journal of Paleontology 90(1):133–146
(Brett-Surman and Wagner, 2007). The distal surface of this process is abraded, and the ventral tip has been eroded away.
Phylogenetic analysis
The phylogenetic position of the CCQ saurolophine material was inferred via maximum parsimony analysis. The taxonomic sample included 60 iguanodontian species (14 hadrosaurid outgroups, 23 Saurolophinae, and 21 Lambeosaurinae). The data set consisted of 273 equally weighted morphological characters (189 cranial and 84 postcranial; see Supplemental Data 1 and 2). Multistate characters containing states that are not mutually exclusive and following a natural morphocline were ordered. This criterion allows for ‘crediting’ shared intermediate states. An example of such characters is the position of the large maxillary foramen (character 85) that includes three states: exposed laterally and opening ventral to the mid-depth of the premaxillary shelf (0); exposed laterally and opening near the dorsal margin of the premaxillary shelf (1); not exposed laterally and opening on the dorsal surface of the premaxillary shelf (2). The optimal tree(s) search was conducted in TNT version 1.1 (Goloboff et al., 2008). A heuristic search of 10,000 replicates using random additional sequences was performed, followed by branch swapping by tree-bisection-reconnection holding ten trees per replicate. Decay indices (Bremer support) and Bootstrap proportions were computed using TNT. The Bootstrap analysis was set for 5,000 replicates using heuristic searches, in which each search was conducted using random additional sequences with branch-swapping by subtree pruning and regrafting and 25 replicates. The analysis resulted in 116 most parsimonious trees
(C.I. = 0.42; R.I. = 0.77; Fig. 7.1), with a score of 934 steps that was hit 8,968 times out of the 10,000 replicates. Exclusion of ANSP 17730-17731 from the data set reduced the number of most parsimonious trees to 16 (C.I. = 0.43; R.I. = 0.77; Fig. 7.2), with a score of 934 steps that was hit 9,853 times out of the 10,000 replicates. The CCQsaurolophine is deeply nested within Kritosaurini forming a polytomy with species of Gryposaurus and Rhinorex condrupus. It shares the following ambiguous synapomorphy with other kritosaurins except Naashoibitosaurus ostromi Hunt and Lucas, 1993: lacrimal with convex ventral margin rostral to the jugal notch (convergent in Saurolophini and unknown in the Secernosaurus clade). The CCQ taxon also shares a broad supraacetabular crest being between 70% and 85% of the length of the iliac plate with all kritosaurines excluding N. ostromi and Kritosaurus (ilium not preserved in the latter two taxa). Characters shared with Gryposaurus and Rhinorex condrupus are (1) extension of the caudal ramus of the postorbital that overlaps the laterodorsal surface of the squamosal rostral to quadrate cotylus (postorbital not preserved in the Secernosaurus clade) and (2) ratio between the craniocaudal length of the postacetabular process and the craniocaudal length of the central plate of the ilium greater than 1.1 (convergent in Saurolophini). Inclusion ofANSP 17730 and 17729within Saurolophinae is
supported by the following synapomorphies: (1) absent or poorly demarcated caudodorsal margin of the lateroventral rim of the supraacetabular process and (2) supraacetabular crest at least slightly wider than half the width of the central iliac plate.
In addition, nesting of this individual within saurolophines to the exclusion of Brachylophosaurini is supported by the possession of a relatively shallow iliac plate, with a ratio between this and the distance between the pubic peduncle and the caudodorsal prominence of the ischiadic peduncle less than 0.80. Finally, placement of the specimen within Kritosaurini is supported by a supraacetabular crest with a breadth lying between 70% and 85% of the width of the iliac plate; this condition is shared with the Gryposaurus and Secernosaurus clades.
Remarks.—All three currently recognized species of the genus Gryposaurus lived in Laramidia (present-day western North America) during Campanian times (Fig. 8). The oldest of these species is G. latidens, from lower Campanian (about 80 Ma; Horner et al., 2001) deposits of lithofacies 3 in the lower Two Medicine Formation of northwestern Montana, USA (Prieto-Márquez, 2012). Lithofacies 3 is alluvial in nature and its fauna diversified in the context of an expanding coastal plain (Horner et al., 2001). The other two species, G. notabilis and G. monumentensis Gates and Sampson, 2007, are late Campa- nian in age. In particular, G. notabilis came from the lower Dinosaur Park Formation of southern Alberta, Canada (Evans 2007; Prieto-Márquez, 2010c). The lower Dinosaur Park Formation was deposited in fluvial systems developed in allu- vial wetland environments of a coastal plain influenced by a subtropical to warm-temperate monsoonal climate (Eberth and Currie, 2005). G. monumentensis was recorded in the Kaiparowits Formation of southern Utah (USA) corresponding to a humid alluvial plain containing marshes and other wetlands adjacent to rivers and streams (Gates and Sampson, 2007). A fourth integrant of the Gryposaurus clade recovered in our consensus tree (Fig. 7) is Rhinorex condrupus from late Campanian (74.5–75.2 Ma) strata of the Neslen Formation in east-central Utah (Gates and Scheetz, 2015; Fig. 8). These strata document a marine-influenced environment (Gates and Scheetz, 2015). It is most parsimonious to consider that the CCQ
kritosaurin material may represent stratigraphical extensions of the fossil record of either G. latidens or G. notabilis (mainly due to geographical proximity compared to the other members of the clade) or a new species of Gryposaurus. In the absence of more diagnostic material, we tentatively refer the more informative bulk of the kritosaurin material from CCQ to ?Gryposaurus sp. The aforementioned paleoenvironemnts posited for the Gryposaurus species offer no additional clues for refining our identification of the CCQ kritosaurin in terms of potential habitat preferences as they all indicate similar depositional settings among known Gryposaurus and between these and the CCQ specimens.
Observations on hadrosaurid ontogenetic variation
The hadrosaurid sample collected at CCQ includes a number of relatively small juvenile elements, of which we were able to observe a dentary, a scapula, two humeri, and a tibia (Fig. 3; Table 3). Comparisons between the dimensions of these elements and those of commonly large hadrosaurid specimens (Fig. 3) indicate that the CCQ juveniles are no larger than one- third of typical adult size. The absence of diagnostic characters
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