Scelidosaurus harrisonii, OWEN, 1861

SCELIDOSAURUS HARRISONII OWEN, 1861

Lectotype: NHMUK R1111 ( Charig & Newman, 1992; BZN, 1994). The remains of a medium-sized (4.4 m long), armoured ornithischian dinosaur, comprising the skull, lower jaws (missing only the rostral portion of the snout) and most of the articulated postcranial skeleton (missing portions of the cervical series and distal portions of both forelimbs).

Derivation of name: From the Greek skelos (σκέλος) = limb or leg and sauros (σαυρος) = lizard/ reptile. The epithet harrisonii refers to belonging to James Harrison, the collector.

The generic name was probably chosen to distinguish this terrestrial (or amphibious) taxon from the paddle-limbed reptiles that predominate the Liassic beds of the Charmouth/Lyme Regis area.

Stratigraphic range: Charmouth Mudstone Formation (Upper Sinemurian), Black Ven Marl Member, Asteroceras obtusum Zone, Obtusum Subzone ( Hesselbo & Jenkyns, 1995) . The nodule-bearing beds that occasionally reveal these remains are referred to locally as the Topstones Bed and there have been reports of scelidosaur remains occurring in the Stonebarrow Flatstones Bed (see Fig. 7 View Figure 7 ).

An additional report ( Ensom, 1987) records scelidosaur remains as having been collected from the lower Pliensbachian (Belemnite Marl Member, Uptonia jamesoni Zone ) at Seatown (on the coast east of Charmouth). These specimens are considered likely to have been derived from Charmouth.

Locality: Cliff exposures on The Spittles-Black Ven between Charmouth and Lyme Regis, Dorset. Weathered nodules containing bones and isolated eroded bones are found occasionally on the foreshore beneath these cliffs ( Fig. 1 View Figure 1 ) .

Diagnosis: (Cranial only – the equivalent Diagnosis in the second part of this monograph series will add autapomorphies identified in the postcranial endoskeleton. The third part will provide a synthetic Diagnosis based on the total anatomy of this taxon). Rugose, mound-shaped projection on the premaxillae supports a small, keratinous beak; facet for the posteromedial process of the premaxilla positioned on the laterodorsal surface of the nasal; small, beanshaped, shallow antorbital fossa delimited by a sharp edge ventrally; the sagittal crest comprises two parallel crests separated by a narrow midline trough; localized exostosis restricted largely to the angular on the mandible (no osteoderm present); epivomer plates form part of the roof of the nasal chambers; epipterygoid bone forms a small, vertically oriented, conical structure with a laterally flattened base applied to the dorsolateral surface of the pterygoid; large oblique facets on the ventrolateral wall of the basioccipital; expanded and ventrally faceted pedicle on the opisthotic; elongate epistyloid bones project obliquely (posteroventrally) from the skull; spur-like structure on the dorsal edge of the paroccipital encloses the post-temporal fenestra; a pair of large curved osteodermal horns are sutured to the posterodorsal surface of the occiput.