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Maxillary teeth in the holotype of P. djadokhtaensis are not well preserved, but they are preserved in place and provide important information on the anatomy of individual teeth (Fig. 7.16). Unfortunately, the caudal end of the tooth row is not preserved and the total number of tooth positions is therefore unknown; however, the number of tooth positions in the maxillary tooth row is at least 20, with a single functional tooth and one replacement tooth per position. Each tooth is straight and symmetrical and has a well-developed primary carina on the buccal surface. Very slight secondary ridges are present on mesial and distal to the primary ridge on some, but not all, teeth.

7.15. Right surangular of Plesiohadros djadokhtaensis (MPC-D100/745) in (A) lateral; (B) dorsal; and (C) medial views. Scale bars equal 5 cm. Abbreviations: an.f, angular facet; ar.f, articular facet; cot, mandibular cotyle; ret, retroarticular process; spl.f, splenial facet.

The dentary tooth row, consisting of more than 22 tooth positions, is straight in occlusal view (Fig. 7.17). The dentary crowns are relatively broad and slightly asymmetrical in lingual view, and the mid-dentary tooth crown in Fig. 7.17 is approximately twice as tall as it is wide. The apex of each tooth is slightly offset mesially. Ornamentation on the enamel face of the crown consists of a primary ridge, and one or two accessory ridges mesial and distal to the primary ridge. The mesial secondary ridge occurs on most crowns, and is more prominent than the distal secondary ridge, when present, on the same tooth. Small denticles are present along the slightly raised mesial and distal margins of the tooth crown. At least one tooth is functional and there are at least two replacement teeth per tooth position, but precise counts of functional and replacement teeth are difficult determine due to poor preservation. The dentary teeth closely resemble those of Bactrosaurus johnsoni in terms of their overall proportions and ornamentation of the enamel face (Godefroit et al., 1998).

7.16. Left maxillary teeth of Plesiohadros djadokhtaensis (MPC-D100/745) in (A, B) lateral; and (C, D) medial views. (A, C) photographs and (B, D). interpretive line drawings. Scale bars equal 5 cm. Abbreviations: d.sh, distal shoulder; m.sh, mesial shoulder; oc.s, occlusal surfaces; pr, primary ridge; rep.cr, replacement maxillary crowns.

Hyoid The long slender right hyoid is slightly curved and twisted along its length (Fig. 7.18). Rostrally blunt, it gently flares into a plate-like caudal end.

7.17. Left dentary teeth of Plesiohadros djadokhtaensis (MPC-D100/745) in medial view. (A) photograph and (B) interpretive line drawing. Scale bar equals 5 cm. Abbreviations: pr, primary ridge; sr, secondary ridge.

7.18. Right hyoid of Plesiohadros djadokhtaensis (MPC-D100/745) in (A) dorsal; (B) lateral; and (C) medial views. Scale bars equal 10 cm.