Scelidosaurus, Owen, 1859

SCELIDOSAURUS : HISTORICAL CONTEXT

The coincidence in timing of the discovery of the near complete scelidosaur skeleton (NHMUK R1111) in relation to the gradual unfolding of an understanding of the anatomy and relationships of dinosaurs was remarkable ( Norman, 2000b, 2001). The year 1858 coincided with Joseph Leidy’s preliminary study of the partial remains of the dinosaur Hadrosaurus foulkii ( Leidy 1859a, b), which was to challenge the early Victorian (Owen-inspired) conception of the appearance of dinosaurs ( Desmond, 1975). Until Leidy’s work was published, the dominant interpretation of the appearance and characteristics of dinosaurs was that created by Richard Owen (1842). Initially his concept of pillar-limbed, giant land reptiles was a purely intellectual exercise but, somewhat later, it was given presence and form (and popularized) through the creation of life-sized, iron-framed, concrete and tiled models for the landscaped gardens of the Crystal Palace Park that was created in 1853–54 ( Desmond, 1975; Norman, 1985, 1992, 2017; Wilford, 1985; Rudwick, 1992; Cadbury, 2000).

Leidy (1859a, b) described Hadrosaurus as an altogether taller, more upright (bipedal) animal with a somewhat kangaroo-like stance and appearance. This alternative view of dinosaurs became prevalent in the USA and contrasted strikingly with Owen’s original models of dinosaurs: it, in effect, constituted a profound ‘Old World’ vs. ‘New World’ divergence in interpretation and understanding ( Norman, 2000b, 2001). However, just as Leidy was describing his ‘New World’ Hadrosaurus, Richard Owen was presented with the nearly complete, articulated skeleton of a large, armoured (and perforce scaly), pillar-limbed and apparently quadrupedal ‘Old World’ dinosaur. Scelidosaurus represented (or so it seems from the perspective of the present day) an indisputable vindication of Owen’s (1842) inductive method (based as it was upon incomplete and extremely fragmentary fossil evidence), insofar as dinosaur anatomy and possible appearance were concerned. It is interesting to observe that neither Owen’s 1861 nor his 1863 monograph dwells on the posture or reconstruction of this dinosaur. Indeed, Owen’s remarks show considerable ambivalence with regard to the habits and mode of life of this new dinosaur. It seems probable that Owen had been strongly influenced (albeit unacknowledged) by Leidy’s reasoning in respect of the habits of Hadrosaurus ( Norman, 2000b, 2001). Leidy interpreted his New Jersey dinosaur as amphibious in habit, because its bones had been collected from marine rocks, and because it had short forelimbs, long hind limbs and a deep (scull-like) tail.

In the first of his two monographs, Owen constructed a convoluted argument concerning the likely habits of scelidosaurs from comparisons with what he knew of the skeleton of Iguanodon and the small skeletal bones of the supposed juvenile Scelidosaurus . He noted the comparatively small size of the forelimb of Iguanodon (as had been argued by Mantell in 1852) and related this to the swimming abilities of ‘the living land lizard of the Gallopagos [sic] Islands, called Amblyrhynchus ’ ( Owen, 1861: 6). These squamates hold their shorter forelimbs against the sides of their bodies, while swimming by undulating their flattened tail. Owen also posited that the collection of small skeletal bones of the scelidosaur may have belonged to a ‘neonate’. The ‘parent’ of the smaller individual, he suggested, might have been represented by the larger skeleton whose skull he had just described. He envisaged these two individuals swimming in shallow water before perishing and becoming buried on the sea floor. Owen also used the known habits of living armoured crocodiles in order to subtly reinforce his line of reasoning. Having established that scelidosaurs had an ‘aptitude for swimming’ ( Owen, 1863: 12), he allowed himself to conclude, in his second monograph, that the skeleton was designed ‘for terrestrial rather than aquatic life, or at least for amphibious habits on the margins of a river rather than for pursuit of food in the open sea’ ( Owen, 1863: 26). It would seem that the combination of the crocodile-like armour plating that covered the body of the scelidosaur, combined with the longer and more dinosaurian hindlimb and sacrum of this animal, persuaded Owen that it was, on balance, terrestrial in habit but could, at times, swim like a crocodile. A little later in the same concluding paragraph he, disconcertingly, refers to the forelimbs of Scelidosaurus as ‘paddles’.

Scientifically and historically, Owen’s reporting of Scelidosaurus represents a curious mixture of intensely technical anatomical description mixed with classically Owen-style sophistry. It is surprising (in retrospect) that Owen did not consider it necessary to demonstrate the validity of his inductive reasoning of 1842 (regarding the anatomical construction of dinosaurs) and its ‘proof’ in the form of Scelidosaurus ( Norman, 2000b, 2001). The similarity between the new, nearly complete dinosaur skeleton from Dorset and Owen’s model of Hylaeosaurus ( Fig. 6 View Figure 6 ) – based as it was upon the incomplete armoured dinosaur skeleton ( Mantell, 1833) – for the new Crystal Palace Park, is striking indeed ( Norman, 2000b, 2001). Owen allied Scelidosaurus and Hylaeosaurus in both structure and inferred habits ( Owen, 1863: 12) but left it to the reader to draw the necessary inferences. What seems particularly unfortunate, from both anatomical and systematic perspectives, is that since the time of Owen’s monographs there has never been a serious review of, or supplement to, his work.