Jinzhousaurus yangi

Norman, David B., 2015, On the history, osteology, and systematic position of the Wealden (Hastings group) dinosaur Hypselospinus fittoni (Iguanodontia: Styracosterna), Zoological Journal of the Linnean Society 173 (1), pp. 92-189 : 151

JINZHOUSAURUS YANGI WANG & XU, 2001

This taxon is based upon the nearly complete skull and postcranial skeleton of an ornithopod, of about 5 m body length, collected from the Yixian Formation of Liaoning Province, China, and dated as early Aptian ( Swisher et al., 1999). Following the initial brief description and naming of this specimen, two detailed papers describing the skull ( Barrett et al., 2009) and postcranial skeleton ( Wang et al., 2010) make this the best-illustrated and described Chinese derived ornithopod to date.

Teeth and jaws

Lateral crushing of the skull means that it is impossible to describe the structure of the lingual surface of individual dentary crowns. The lower jaw is robust and parallel-sided ( Barrett et al., 2009: fig. 1) and shows no indication of arching of its ventral margin as seen in Hy. fittoni .

Axial skeleton

The cervical and dorsal series are typical and in general conform to those of typical derived (non-camptosaurgrade) ornithopods. In particular there is no evidence of pronounced thickening of the articular margins of the centra as noted in Hy. fittoni and the neural spines ( Wang et al., 2010: figs 2, 3) are comparatively short and broad (and very distinct from the tall and slender form of spines described in Hy. fittoni ).

Appendicular skeleton

The pectoral girdle and forelimb ( Wang et al., 2010: figs 6–8) are similar in shape and proportions to those described for Hy. fittoni . The scapular blade appears to be more flared distally, but the sternals are very similar in shape and in both taxa there is a welldeveloped posteromedial apron on the blade; however, there is no indication of fusion or co-ossification of sternals in the skeleton of Jinzhousaurus ( Wang et al., 2010: fig. 6). The radius and ulna are robust in J. yangi and closely resemble those of Hy. fittoni . The carpus is partially fused, block-like, and incorporates metacarpal I, which thus sets digit I off at an acute angle from the palmar metacarpals (II−IV). The principal manus elements resemble those seen in Hy. fittoni : the pollex ungual is spine-like, curved along its length, and laterally compressed; it also appears to retain remnants of the claw grooves ( Wang et al., 2010: fig. 8). Metacarpals II−IV are subequal in length and appear closely appressed when articulated naturally. Digits II and III end in well-developed, flattened unguals (which are not present on digits IV and V). The pelvis and hindlimb are less well preserved and more difficult to interpret. The postacetabular process of the ilium bears a lateral ridge and brevis fossa that resembles that seen in Hy. fittoni . The ischium is robust and has a slightly curved shaft and modestly expanded ischiadic ‘boot’ at its distal end. The femur is also robustly constructed and, although crushed, the structure of the anterior and fourth trochanters and the form of the shaft are reminiscent of the structures seen in Hy. fittoni . Attention is drawn to the similarities between this taxon and Bolong (below).