Caudal Vertebrae There are six caudal vertebrae: two proximal caudals represent the first, and second or third caudals; several middle to distal caudals are present; there are multiple fragmentary centra. In the proximal caudals the centra are round, amphiplatyan, and longitudinally compressed (Fig. 5.8A, B, D, E). The dorsal surface is defined by broad, triangular neural arches. The prezygapophyses are small, ovoid facets that project obliquely while the postzygapophyses are ventrolaterally directed, oblong facets attached to the posterior edge of the neural spine. The neural spines are rectangular in lateral view, tall (>30 cm long), relatively narrow, and deflected distally by ~45° to 60° (Fig. 5.8B, E). The neural spine is three times the length of the centrum and unexpanded distally. Its cranial edge is relatively straight, except for a slight convexity, similar to Eolambia (McDonald et al., 2012). The transverse processes are broken, but are attached at the base of the neural arch. In the middle caudal series, the centrum is heart shaped and the ventral surface is rounded, with a pronounced ventrally deflected hemapophysis for a chevron (hemal arch; Fig. 5.8G, I). Prezygapophyses are prominent while the postzygapophyses project ventrolaterally from the neural arch, with ovoid articular facets visible in lateral view. The neural spine is deflected distally, but at a greater angle (~60°) than proximal caudals. The opening for the neural canal is small and circular. Transverse processes are present and extend laterally with an oval cross section. The remaining middle to distal caudals are incomplete; all have heart-shaped centra and lack neural spines and zygapophyses. Transverse processes become less prominent in more distal caudals. The distal-most caudals have more elongate centra in lateral view.
Ossified Tendons Ossified tendon fragments were recovered but found isolated away from the caudal vertebrae. None were recovered on or associated with the caudal series. They are thin, cylindrical elements, pencil like in appearance. They are thicker along the proximal surface and thin distally.
Scapula The left scapula is a broad, robust element 356 mm in length from the ventral margin to the mid-shaft (Fig. 5.9A–C). The blade of the specimen was damaged during excavation, and is incomplete. The partial blade is straight in lateral aspect and oval in cross section, with no proximal constriction and a mild medial curvature to accommodate the ribcage. The cranial edge of the blade rises gently into the pseudoacromion process, which is a convex, rounded ridge that thins cranially, similar to that of Eolambia (McDonald et al., 2012) and it is gently inclined laterally toward the coracoid suture, as in Probactrosaurus (Norman, 2002). The pseudoacromion process curves ventrally into the coracoid suture. A low deltoid ridge is present, extending caudally as a low prominence from the pseudoacromion process. The coracoid suture is convex and bi-faceted into two thick, prominent surfaces in cranioventral view, similar to Camptosaurus and Mantellisaurus (Paul, 2007; Carpenter and Wilson, 2008). The coracoid suture is thick (94 mm) and curves into the scapular part of the glenoid. The proximal blade expands ventrally to produce a deep, pronounced (60 mm wide × 150 mm long) arched depression that terminates in a broad laterally projected buttress. It is similar in form to the iguanodontians Camptosaurus and Iguanodon and the hadrosauroid Probactrosaurus (Norman, 1986, 2002, 2004; Carpenter and Wilson, 2008). The angle of ascent of the scapula labrum away from the shaft is steep and similar in form to Eolambia (McDonald et al., 2012).
Coracoid The left coracoid is 200 mm long, slightly convex in lateral view, and concave in medial view (Fig. 5.9C–E). A large, elliptical coracoid foramen occurs near the caudal margin at the scapular contact. The glenoid surface is found along the caudoventral margin and is roughly equal in size to its counterpart on the scapula. The scapular suture is elongate and rugose at the glenoid contact, and tapers into a thin and blade-like ridge dorsocranially. The coracoid ridge is present on the cranial margin, forming a low, rounded prominence. Along the cranioventral margin is the base of the sternal process, which is broken and thus its exact shape cannot be determined. Overall the morphology of the coracoid strongly resembles that of Eolambia and Probactrosaurus (Norman, 2002; McDonald et al., 2012).
Ilium The left ilium has a vertical height of 212 mm and a total length of 604 mm, as preserved. The preacetabular process is incomplete missing its distal end (Fig. 5.10). The preserved portion of the preacetabular process is stout and rounded dorsally with a thin ventral margin, giving the process a nearly triangular cross section. It is gently deflected ventrolaterally and contains a well-developed medial shelf, similar to Eolambia and Probactrosaurus, (Norman, 2002; McDonald et al., 2012). The preacetabular notch is open. The pubic peduncle is short (36 mm) and subrounded with a slight inclination cranially, similar to Bactrosaurus, Probactrosaurus, Tethyshadros, and Eolambia (Godefroit et al., 1998; Norman, 2002; Dalla Vecchia, 2009; McDonald et al., 2012). The broad ischial peduncle is 176 mm in length and rectangular. The acetabular margin is 93 mm in length and relatively shallow.
The dorsal edge of the ilium underwent some postburial distortion, displacing the suprailiac crest dorsally (Fig. 5.10A, C). Its dorsal margin caudal to the pubic peduncle was likely straight or slightly convex in lateral view, and sigmoidal in dorsal view. The suprailiac crest begins as a narrow ridge just caudal to the pubic peduncle and it widens caudally, producing a thick (20 mm) curved ridge that deflects caudoventrally, and ends just caudal to the ischial peduncle, where it grades into the postacetabular process. This more cranial position of the suprailiac crest (“antitrochanter”) is distinctive of early hadrosaurids (Brett-Surman and Wagner, 2007). The postacetabular process is broad and triangular in lateral view, as is typical of derived iguanodontids and basal hadrosauroids (Norman, 2004; Brett-Surman and Wagner, 2007). A medial brevis shelf is absent. The medial surface of the ilium is concave, with the deepest portion overlying the ischial peduncle. Multiple facets for sacral rib attachment are visible (Fig. 5.10B). The ilium fits well into the first iliac morphotype recognized by Chapman and Brett-Surman (1990) and bears a strong resemblance to the ilium of Claosaurus (Prieto-Márquez, 2011).
5.9. Pectoral girdle of UTA-AASO-2003. (A) left scapula in lateral view; (B) medial view of same; (C) anterior view of same; (D) left coracoid in lateral view; (E) medial view of same; (F) posterior view of same.
5.10. Left ilium of UTA-AASO-2003. (A) lateral view; (B) medial view; (C) dorsal view.
5.11. Pelvic elements of UTA-AASO-2003. (A) left