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The atlas and the manus were found in direct association with the holotype skull, and are therefore interpreted as part of that individual. The articulated ankle and foot (MPC-D100/751) was found in that same formation at the same locality as the holotype, and it pertains to a similarly sized large hadrosauroid. MPC-D100/751 is referred to Plesiohadros djadokhtaensis on the basis of stratigraphic and geographic proximity to the holotype.

7.19. Atlas of Plesiohadros djadokhtaensis (MPC-D100/745) in (A) cranial; (B) caudal; (C) dorsal; (D) ventral; and (E) right lateral views. Scale bars equal 5 cm. Abbreviations: at.rf, atlantal rib facet; cc.j, craniocervical joint surface; ic, intercentrum; na, neural arch.

Atlas The atlas is complete, consisting of paired unfused pleurocentra and a single neurocentrum (Fig. 7.19). The pleurocentra form the lateral and dorsal margins of the neural canal; they meet, but do not fuse on the dorsal midline. The internal surface of the ventrally positioned neurocentrum marks where the dens of the axis articulates with the atlas. The atlantal rib (Fig. 7.20) widens proximally to articulate with the diapophysis of the atlas.

Manus The left manus of P. djadokhtaensis is preserved (Fig. 7.21). Digit I, including its metacarpal, is not known. Metacarpals II–V are slender and long (midshaft width < 0.15 length) and metacarpals II, III, and IV align with each other proximally. Metacarpal V is conical and appears to bear two phalanges. The penultimate phalanx of digit III is wedge shaped, and digit IV terminates in a hoof-shaped ungual.

Tibia All that is known of the tibia of P. djadokhtaensis is its distal quarter from the left side (Fig. 7.22). Here the medial malleolus and ventral surface articulate with the astragalus. The remainder of the cranial surface of the tibia forms the facet for the fibula.

7.20. Atlantal rib of Plesiohadros djadokhtaensis (MPC-D100/745) in (A) medial; and (B) lateral views. Scale bars equal 5 cm. Abbreviations: ct, merged capitulum and tuberculum.

Fibula Only the distal fibula is preserved. Medially, it forms an articular facet for the lateral malleolus of the tibia (Fig. 7.22). The distal end of the fibula appears to be only moderately expanded, as seen in most hadrosauroids, and does not exhibit the enlarged distal end as described for Parasaurolophus cyrtocristatus (Brett-Surman and Wagner, 2007).

Astragalus The astragalus was found in articulation with the distal tibia (Fig. 7.22). It is typically hadrosauroid in morphology, cupped proximally for the tibia and very broadly convex where it articulates with the metatarsus. The cranial ascending process is short and shifted to the medial side, as in hadrosaurids (Horner et al., 2004; Brett-Surman and Wagner, 2007).

Pes Three metatarsals and digits are preserved in the referred specimen of P. djadokhtaensis (Fig. 7.23). Metatarsal II is the most gracile; its proximal end wraps around that of metatarsal III. This distal end of metatarsal II is slightly twisted laterally and bears a facet to articulate with the first phalanx of digit I. Metatarsal III is the longest; its greatest width is at its proximal and distal ends; the latter forms an almost bicondylar condition for articulation with the first phalanx of digit III. Metatarsal IV is slim, has an axially long contact with metatarsal III, and forms a unicondylar contact with the first phalanx of digit IV. As in metatarsal II, the long axis of metatarsal IV is slightly divergent distally from that of digit III.

The pedal digital formula of P. djadokhtaensis is 0-3-4-4-0. The first phalanx of each digit is the largest, followed by relatively thin, wedge-shaped phalanges that terminate in a hoof-like ungual.