Batyrosaurus rozhdestvenskyi

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 : 159

BATYROSAURUS ROZHDESTVENSKYI GODEFROIT, ESCUILLIÉ, BOLOTSKY & LAUTERS, 2012

This taxon comprises a partial skeleton collected in Akkurgan, Kazakhstan, from the Bostobinskaya Svita (Santonian−Campanian).

Dentition, jaws, and cranium

Dentary crowns are broader than their maxillary counterparts and are broad and shield-like with a distally offset primary ridge, a well-defined secondary ridge, and a comparatively short tertiary (accessory) ridge that is present near the mesial edge of the crown; there is also a tertiary ridge on the distal portion of the crown. The structure of the crown suggests that a distinct mesial shoulder was present on the coronal margin. The marginal denticles form curved mammillated ledges down the sides of the crown, but are simple and coneshaped along the upper (coronal) margin). Tooth morphology is very similar to that described in Altirhinus ( Norman, 1998) . The dentary ramus is slightly arched anteriorly and comparatively narrow. The coronoid process is low and oblique and the alveolar trough is marked by tooth grooves that bear the remnant shape of broad tooth crowns (rather than parallel-sided slots). These structures are similar to those seen in Hy. fittoni . The alveolar trough extends medial to the coronoid process and may not have extended beyond the anterior margin of the base of that process (this is obscured by breakage). There is an abbreviated diastema and the predentary, which has a denticular oral margin and paired oblique vascular channels adjacent to the midline, also tapers anteriorly (in plan view) and resembles that which was described as a unique feature of Proa ( McDonald et al., 2012b) . A surangular foramen is present. The cranial roof is broad and flat, and the frontal forms a portion of the dorsal orbital rim. The quadrate has a narrow, semicircular embayment with facets, dorsally and ventrally, for the quadratojugal; this suggests that a paraquadrate foramen was present (this was also argued to be the pattern in Altirhinus , Probactrosaurus, Jayewati , Bactrosaurus , and Gilmoreosaurus – Godefroit et al., 2012). In most respects the anatomical similarities to those seen in the stratigraphically much earlier Hy. fittoni are close.

Postcranial skeleton

The sternal bones are hatchet-shaped with an elongate ‘handle’. The radius appears to be slender (and approximately of equal length to the humerus) although the distal articular end is dorsoventrally expanded. A somewhat eroded and conical (possible?) pollex ungual has been described ( Godefroit et al., 2012: fig. 20.11F).