RHABDODONTIDAE

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 : 162-163

RHABDODONTIDAE (E.G. WEISHAMPEL ET AL., 2003;

BUTLER ET AL., 2008; GODEFROIT, CODREA & WEISHAMPEL, 2009; OSI ET AL., 2012)

Rhabdodontids are medium−large (3−8 m long) basal ornithopods (sensu amplo). The best-preserved and described examples of these taxa are Zalmoxes robustus ( Weishampel et al., 2003) and the contemporary Zalmoxes shquiperorum ( Weishampel et al., 2003; Godefroit et al., 2009) from the lower Maastrichtian of Romania. Rhabdodontids, as a group, appear to be restricted to the late Cretaceous but range geographically across western Eurasia: Rhabdodon spp. France ( Matheron, 1869; Buffetaut & Le Loeuff, 1991); Mochlodon spp. Hungary ( Osi et al., 2012) and Austria ( Seeley, 1881). Related taxa also occur in the late Lower Cretaceous of Australia ( Muttaburrasaurus Bartholomai & Molnar, 1981 , and pers. observ. 1978) and South Africa ( Kangnasaurus : ( Cooper, 1985, and pers. observ. 1993) and the Late Cretaceous of Antarctica (unnamed taxon – A. C. Milner & P. M. Barrett, unpubl. data and pers. observ. 2005).

Teeth and jaws

The dentary teeth are unusually large, shieldshaped, and the lingual enamelled surface of the crown differs considerably in detail from that seen in Hy. fittoni . The dentary and maxillary crowns are typically clypeodont ( Norman, 2014) in that they exhibit a very prominent primary ridge, flanked upon either side by divergent sets of accessory ridges, whereas the maxillary crowns lack a prominent primary ridge labially and have a tightly packed array of apicobasally orientated accessory ridges. This general crown morphology is common to a range of basal ornithopod (clypeodont) taxa: Hypsilophodon spp. , Muttaburrasaurus langdoni, Rhabdodon spp., Zalmoxes spp. , Mochlodon suessi , Mochlodon vorosi , Kangnasaurus coetzeei , Tenontosaurus spp. , and the unnamed Antarctic taxon (A. C. Milner & P. M. Barrett, unpubl. data). The lower jaw is dominated by a robust dentary with a complex predentary suture that is not seen in Hy. fittoni ; however, the coronoid process of the dentary is comparatively short and reclines at an obtuse angle to the long axis of the dentary, similar to that in Hy. fittoni .

Axial skeleton

The neural spines of the dorsal series are comparatively low and rectangular in lateral view, and are readily distinguished from the narrow and extremely elongate spines seen in Hy. fittoni .

Appendicular skeleton

The pectoral girdle, forelimb, pelvis, and hindlimb differ in detail from the comparable elements of Hy. fittoni ( Weishampel et al., 2003; Godefroit et al., 2009).