Equijubus

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 : 156

EQUIJUBUS NORMANI YOU, LUO, SHUBIN, WITMER,

TANG & TANG, 2003b ( MCDONALD ET AL., 2014)

Equijubus was collected from the ‘Middle Grey Unit’, Xinminpu Group (Albian: Tang et al., 2001), Gongpoquan Basin, Gansu Province, China ( You et al., 2003b). The specimen consists of a nearly complete skull and a very incomplete postcranial skeleton comprising a series of articulated cervical and dorsal vertebrae, as well as some pectoral, pelvic, and hindlimb fragments ( McDonald et al., 2014).

Teeth and jaws

The dentary teeth are broad and shield-shaped and similar in general outline to those of Hy. fittoni in having a distally offset primary ridge (but this is generally rather less prominent and poorly developed compared with Hy. fittoni ), an indistinct secondary ridge, and multiple strand-like accessory ridges. The dentary crowns have a narrower coronal margin and a less pronounced mesial ‘shoulder’ than seen in Hy. fittoni . The marginal denticles form simple conical structures, but those found on the mesial and distal edges of the crown form curved ledges that wrap around these edges and are mammillate. Although two replacement crowns were reported to be present beneath each functional tooth ( You et al., 2003b), this seems to be contradicted by McDonald et al. (2014) and a single replacement crown seems to have been present, as in Hy. fittoni (NHMUK R1831) .

Axial skeleton

The cervicals and dorsals show no particularly distinguishing characters. The bases of some neural spines suggest that the neural spines were thick and robust, and not narrow and elongate as in Hy. fittoni .

Appendicular skeleton

The sternal resembles that of Mantellisaurus in having an elongate, dorsoventrally compressed ‘handle’ and a relatively small ‘blade’ and small posterior process (unlike that of Hy. fittoni ). The incomplete ilium is attached to the sacrum. In general outline the preserved central portion resembles, in its proportions, that of Hy. fittoni but the brevis fossa appears to be absent and there is a more strongly everted facet on the dorsal margin of the blade, posterodorsal to the ischiadic peduncle. A fragment of the prepubic process is preserved and this suggests that this bone formed a laterally compressed plate with a pronounced distal expansion. The remnants of the femur indicate that the extensor intercondylar groove was completely enclosed and the distal portion of the femoral shaft was probably straight, rather than bowed.