140


Journal of Paleontology 90(1):133–146


Table 2. Selected measurements (in millimeters) of CCQ saurolophid elements. All elements are referable to kritosaurin saurolophines, except the lambeosaurine ischium ANSP 17727.


Element


Prefrontal (ANSP 17692), preserved length Prefrontal (ANSP 17692), preserved width Lacrimal (ANSP 18328), preserved length


Lacrimal (ANSP 18328), preserved depth of caudal margin Postorbital (ANSP 18320), preserved length


Postorbital (ANSP 18320), depth across ventral process Squamosal (ANSP 18323), preserved length


Squamosal (ANSP 18323), preserved width quadrate cotylus to medial process


Humerus (ANSP 15981), length


Humerus (ANSP 15981), maximum width across deltopectoral crest


Ilium (ANSP 17729), preserved length


Ilium (ANSP 17729), maximum depth of iliac central plate Ilium (ANSP 17730), preserved length


Ilium (ANSP 17730), maximum depth of iliac central plate Ilium (ANSP 17731), preserved length


Ilium (ANSP 17731), maximum depth of iliac central plate Ischium (ANSP 17727), preserved length


Pubis (ANSP 17723), length from iliac process to preserved distal blade


Pubis (ANSP 17724), length from iliac process to preserved distal blade


Pubis (ANSP 17725), length from iliac process to preserved distal blade


Pubis (ANSP 17726), length from iliac process to preserved distal blade


Measurement (mm)


131 60


131 116 152 96


169 97


545 132


975 156 945 221 964 211 730 450


460 410 417


depression on the lateral surface of the main body of the squa- mosal that receives the head of the quadrate. The caudal wall of the quadrate cotylus is continuous caudally with the large postcotyloid process. This process is dorsoventrally compressed and hook-like, extending lateroventrally from the caudolateral corner of the squamosal. Its rugose recessed caudoventral sur- face would contact extensively the proximal region of the par- occipital process of the fused opisthotic-exoccipital. The medial process of the squamosal extends medially and slightly dorsally. Distally, this process curves rostromedially to form the caudo- medial corner of the supratemporal fenestra.


of narrow vertical indentations. The ventral process projects and wedges rostroventrally to meet the jugal, forming about half of the caudodorsal magin of the orbit. Caudodorsally, the caudal edge of the ventral process becomes continuous with that of the caudal process; both processes form an extremely wide rostrodorsal margin for the infratemporal fenestra. The caudal process of the postorbital is greatly compressed dorsoventrally and slightly inclined ventrally, so that its inner side faces ventromedially. The latter surface is excavated and would overlap part of the rostral process of the squamosal. The medio- ventral surface of the central body of the postorbital, dorsal to the ventral process, displays an eroded oval depression for reception of the lateral process of the laterosphenoid (Fig. 4.6).


Squamosal.—The squamosal consists of a thick curved lamina that is deeply concave ventrally. From it, three processes project medially, rostrally, and ventrolaterally. In the most complete of the available squamosals, ANSP 18324 (Fig. 4.10–4.12), the bone is missing the distal tip of the rostral process, portions of the medial margin of the main squamosal body, and the distal segment of the postcotyloid process. The rostral process forms a long wedge that is dorsoventrally compressed. Its dorsal surface, particularly the lateral extent, is occupied by a large recessed facet that receives the caudal process of the postorbital. A robust subconical precotyloid process extends lateroventrally adjacent and lateral to the proximal region of the rostral process. This process is nearly as long as the quadrate cotylus is wide. The triangular surface present between the rostral margin of the proximal region of the precotyloid process and the lateral edge of the proximal region of the postorbital process is smooth and gently concave. The caudal margin of the precotyloid process forms the rostral boundary of the quadrate cotylus. The cotylus consists of a dorsoventrally compressed but deep oval


Humerus.—The humerus ANSP 15981 combines relatively slender proportions with a substantially expanded dectopectoral crest (Fig. 5.1,5.2). Specifically, the length of the element is more than six times the width of the lateral surface of the proximal end. Among hadrosaurids, similarly elongate humeri are present in specimens of Gryposaurus notabilis (e.g., TMP 80.22.1) and Prosaurolophus maximus (e.g., MOR 454; Prieto- Márquez, 2008, fig. H.18). The deltopectoral crest comprises slightly more than half of the length of the humerus and projects lateroventrally from the proximal half of the humerus; the ratio between the maximum width of the crest and the minimum diameter of the humeral shaft is 1.80 in ANSP 15981. This combination of overall proportions and development of the deltopectoral crest is unlike that seen in lambeosaurines, in which the ratio of humerus length to proximal width tends to be less than 4.9 and the ratio of deltopectoral crest width to mini- mum humeral circumference is greater than 1.90 (Prieto- Márquez, 2008). The humeral shaft is elliptical in cross section and mediolaterally compressed. The distal end of the humerus is mediolaterally expanded to form the lateral ulnar and medial radial condyles. The radial condyle is wider and more cranio- caudally expanded than the ulnar condyle. Deep and wide depressions separate the two condyles on the cranial and caudal surfaces of the distal end of the humerus.


Pubis.—The pubis has a ventrally deflected subrectangular prepubic blade, with subparallel dorsal and ventral margins, and an angular craniodorsal corner (Fig. 5.3–5.6). This geometry is characteristic of kritosaurins such as Gryposaurus notabilis (e.g., ROM 764), Secernosaurus koerneri Brett-Surman, 1979 (e.g., MACN RN 2) and saurolophins such as Prosaurolophus maximus (e.g., MOR 454), and probably, Saurolophus spp. (Prieto-Márquez, 2008). The length of the proximal constriction is subequal to that of the prepubic blade. The tetrahedral iliac peduncle projects caudodorsally from the dorsal extent of the acetabular region of the pubis. The concave caudal surface of the iliac peduncle forms half of the acetabular margin of the pubis and is continuous with the ventral half of the proximal region of the ischiadic peduncle. The ischiadic peduncle is mediolaterally compressed and laterally offset relative to the proximal region of the postpubic process. The rod-like post- pubic process is relatively robust and projects caudoventrally forming a 115° angle with the long axis of the prepubic process.


Ilium.—ANSP 17729 (Fig. 5.7) is characterized by a remark- ably shallow iliac plate. Specifically, the maximum depth:


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