Apart from the pattern of dentary foramina, the distinction concerning the straightness of the dentary ramus relies upon an alleged association of another partial skeleton (NHMUK R1834) to the taxon B. dawsoni. The latter includes the anterior portion of an eroded dentary that appears to be arched, rather than straight. Unfortunately, NHMUK R1834 was incorrectly assigned to the taxon B. dawsoni by McDonald et al. (2010); it can be referred, quite unambiguously (Norman, 2010, in press), to the Valanginian taxon Hypselospinus fittoni (Lydekker, 1889) on the basis of detailed shared similarities between the ilium of the holotype of H. fittoni and that of NHMUK R1834 (Norman, in press). At present, K. tilgatensis comprises just the dentary of a large neoiguanodontian that is considered to be a nomen dubium and to be potentially referable to the contemporary large, robust neoiguanodontian taxon Barilium dawsoni. Furthermore, the dentary teeth are very similar in form to those of NHMUK R2358, which have been referred to B. dawsoni. Carpenter and Ishida (2010) proposed, in October of that year, a new taxonomic combination Torilion dawsoni (Fig. 2.2) for the holotype material named Iguanodon dawsoni; this proposal can be suppressed, because it is a junior objective synonym of Barilium dawsoni (Lydekker, 1888). Furthermore, Carpenter and Ishida proposed a new genus and species (Sellacoxa pauli) on the basis of a photograph of the right side of a large partial skeleton (NHMUK R3788) collected by Charles Dawson from Old Roar Quarry, near Hastings (Norman, 2011a). Naish and Martill (2008), using appropriately cautious remarks, suggested that its anatomy was unusual and perhaps indicative of a new species. The description by Carpenter and Ishida (2010) is erroneous (Norman, 2011a, 2011b) because these authors had evidently not examined the specimen closely and therefore failed to recognize preservational anomalies, missing pieces, or additional anatomical features visible on the other (left) side of the specimen (Norman, 2011a). Sellacoxa pauli (NHMUK R3788) is considered to be a nomen dubium (its diagnosis is incorrect), and this articulated partial skeleton is considered to be referable to the hypodigm of B. dawsoni (as originally argued by Norman, 1977, 2010, 2011a; Blows, 1998). The taxon Sellacoxa pauli Carpenter and Ishida, 2010, has been proposed to be a nomen dubium and that it can be relegated into synonym with Barilium dawsoni (Norman, 2011a; Fig. 2.2).
2.3. Barilium dawsoni. Preliminary skeletal reconstruction based upon the holotype and referred material (from Norman, 2011a).
Description
Craniodental Anatomy The dentary is robust and has parallel upper and lower edges and an elevated coronoid process that arises from a shelf lateral to the most posterior alveoli. The large, and visibly crushed, replacement dentary tooth crown preserved in NHMUK OR28660 generally resembles those seen in another referred specimen (NHMUK R2358) that comprises part of a robust dentary with three embedded teeth; these are of additional interest because they resemble the morphology seen in the lectotype tooth (I. anglicus: Norman, 2011b:fig. 27.23A).
Vertebrae Dorsal vertebrae are notable for having very tall, deep, and slightly inclined spines; anterior dorsals have slightly waisted, cylindrical vertebral centra; posterior dorsals become more axially compressed and develop everted edges. Sacrals are very poorly known, while the caudals are distinctive: those nearest the sacrum are squat, subrectangular in axial view, and somewhat inclined forward (Norman, 2011a:fig. 6); these are succeeded by deeper-bodied, hexagonal (more typical iguanodont) caudals, whereas the caudals toward the tip of the tail tend to have very angular sides and their articular faces tend to be deeply concave (Norman, 2011a:fig. 7).
Girdles and Limbs The pectoral (shoulder) girdle and forelimb are robust. The scapula (based upon the referred specimen NHMUK R2848) is long, curved, and expands towards its upper end. The coracoid is notably broad and dished, and has a prominent and completely enclosed coracoid foramen near the suture with the scapula (Norman, 2011a:fig. 17A). One specimen (NHMUK R2357) includes the “handle” portion of a hatchet-shaped sternal bone (Norman, 2011a:fig. 17B). The principal forearm bones (radius and ulna) are very robust; the carpals and metacarpal I cap the ends of the ulna and radius and are fused into a solid block that supports a fused, squat pollex. The form of the remaining bones of the hand is unknown. The hip (pelvic) bones include a very distinctive ilium, which has a long, robust, preacetabular process that is twisted along its length and bears a large rib facet near its base. The main body of the ilium is slab sided, thick along its dorsal edge with minimal lateral swelling and an inflection along its upper edge (posterodorsal to the ischiadic peduncle). The postacetabular process is deep and rounded in profile, and does not develop a ventrolateral ridge that delimits a vaulted brevis fossa; a well-developed brevis fossa is present in all other Wealden iguanodonts. The shape of the shaft of the ischium is unknown, but proximally the external surface of the shaft adjacent to the obturator process displays a pronounced vertical ridge that runs along the ischial shaft (NHMUK R2357) rather than forming a flat, rugose facet seen typically in this area in specimens attributable to H. fittoni; and the pubis appears to develop a thick, deep, and slightly upwardly curved prepubic process and the dorsoventrally compressed (strap-like) pubic shaft is unlikely to have extended to the end of the ischial shaft. The hindlimb is poorly known (Norman, 2011a).
2.4. Hypselospinus cf. fittoni, NHMUK R1831. Dentary (right) with teeth preserved in situ. (A) medial; (B) lateral; (C) dorsal views. Abbreviations: am, alveolar margin; br, badly broken portion of the dentary; cp, coronoid process; ds, dentary symphysis; m, matrix; mgr, Meckelian groove; pr, anterior lateral process of the dentary; sl, “slot-and-lip” portion of the dentary symphysis; tf, tooth fragments in alveolar bone; vc, vascular channel. Scale bar equals 10 cm (from Norman, in press).
Reconstruction of Barilium
The composite reconstruction of the skeleton (Fig. 2.3) suggests that this dinosaur was likely to have been at least facultatively quadrupedal, and it may in fact have been an obligate quadruped.
HYPSELOSPINUS Norman, 2010 HYPSELOSPINUS FITTONI (Lydekker, 1889)
Taxonomic Discussion
Lydekker (1889) described some portions of a skeleton recovered from the same quarry near Hastings that produced the type material of Barilium dawsoni. The type material was redescribed by Norman (2010, 2011b, in press) and on the basis of distinctive features of the holotype ilium, which was supplemented by better-preserved referred material – including specimens that were previously attributed to Iguanodon hollingtoniensis Lydekker, 1889. I. hollingtoniensis is now regarded as a junior subjective synonym of Hypselospinus fittoni (Norman, 2010). Iguanodon fittoni was rediagnosed and renamed as a new nomenclatural combination: Hypselospinus fittoni. This