Barilium dawsoni (Norman, 2011)

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 : 147

BARILIUM DAWSONI (LYDEKKER, 1888A) NORMAN, 2010

Although a sympatric contemporary of Hypselospinus this taxon can be readily distinguished anatomically ( Norman, 2010, 2011a).

Teeth and jaws

The dentary teeth of Barilium have a simpler ridge pattern on the enamelled lingual surface of the crown ( Norman, 2011a: text-fig. 20): the primary and secondary ridges are clearly demarcated and subequal in size and there are very few strand-like accessory ridges The referred dentary of B. dawsoni (NHMUK OR28660 – see Kukufeldia tilgatensis below) is very large, robust, and straight and similar in shape to that seen in I. bernissartensis (see also discussion below), as noted by Lydekker (1888b), rather than being arched anteriorly as in the case of Hypselospinus .

Axial skeleton

The dorsal vertebrae of Barilium are large and cylindrical, and have wide and comparatively tall neural spines (when viewed laterally) compared with those of Hypselospinus ; the latter are more slender and taller. The anterior caudal vertebrae of Barilium are low and angular sided, whereas those of Hypselospinus are more cylindrical, axially compressed, and bear very elongate, narrow, neural spines; the more posterior caudals of Barilium tend to have strongly amphicoelous articular faces to the centrum.

Appendicular skeleton

The shoulder girdle and forelimb in these two taxa are very similar. However, the pollex spine of Barilium is short, blunt, and transversely compressed whereas that of Hypselospinus is tall, inclined, and pointed. The pelves have distinctive ilia: unlike Hypselospinus , Barilium has a thick, axially twisted preacetabular process, and the dorsal edge of the ilium is transversely thick and rounded. The postacetabular portion of the iliac blade has a deep, medially curving surface with a posterior margin that is rounded in lateral view; it also lacks the well-developed brevis fossa demarcated by a prominent lateral ridge that is present in ilia of Hy. fittoni ( Norman, 2010, 2011a). The hindlimb bones appear to be generally similar in these two taxa (although these elements are poorly represented in Barilium ).