224 



KNOWLEDGE 



[October 1, 1890. 



teeth to the very much smaller ones of an American 

 lizard known as the Iguana, Dr. Man tell proposed to call 

 the huge Wealden monster the Iguana-toothed Reptile, or, 

 technically, the Iguanodon. In the course of time 

 numerous more or less nearly entire bones of this creature 

 were obtained, when it was found that the thigh-bone of 

 some specimens considerably exceeded a yard in length. 

 This at once gave a clue to the enormous bulk of these 

 reptiles, since the corresponding bone of the largest 

 existing crocodile scarcely exceeds a foot in length. 

 Finally, it was estimated that the Iguanodon was a 

 creature about 30 feet in length, with a body as large as 

 that of an elephant, and that it walked on all four feet 

 like a crocodile. Accordingly, many years ago a restora- 

 tion of the Iguanodon was set up in the gardens of the 

 Crystal Palace, when the creature was modelled some- 

 what after the fashion of a large-bodied and short-tailed 

 crocodile. After Mantell's death other earnest investigators 

 occupied themselves with the structure of the skeleton of 

 this creature, and finally arrived at the unexpected con- 

 clusion that in many respects — more especially as regards 

 the structure of the haunch -bones and limbs — the skeleton 

 made a very curious approximation to that of birds, and 

 was quite unlike that of living reptiles. 



As we all know, all things come to those who wait, and 

 the above conclusions were triumphantly supported by the 

 discovery, some few years ago in the Weaklen deposits of 

 lU'lgium, of a number of nearly perfect, although much 

 cnisJicd, skeletons of the Iguanodon. These wonderful 

 discoveries enabled the Belgian naturalists to moimt two 

 entire skeletons in the Brussels Museum, in the court- 

 yard of which they now stand as the most marvellous 

 restorations of extinct animals of the Secondary epoch yet 

 known in Europe. Fig. 2 gives a greatly reduced 

 representation of the larger of these two skeletons, of 

 which the total length is about 38 feet. It wiD be seen 

 from this figure that the creature habitually walked on its 

 hind legs, doubtless partly supported by its powerful tail, 

 in a bird-like attitude. The fore limbs were considerably 

 shorter than the hind ones ; and the hands were extremely 

 powerful, and probably served to assist the creature in 

 bringing to its mouth the leaves and fruits upon which 

 we may assume it subsisted. There was a long series of 

 teeth, similar to the one represented in Fig. 1, on the sides 

 of both jaws ; but the muzzle was quite tootliless, and 

 may perhaps have been sheathed in horn, like the beak of 

 turtles. The extreme shortness of the fore limbs is of 

 itself sufficient to indicate that the Iguanodons really 

 walked on their hmd legs like birds ; but if we reijuire 

 further evidence on this point it is ready to our hand. 

 Thus in the Wealden sandstones of Hastings there have 

 been found numerous series of impressions of huge three- 

 toed hind feet, which correspond exactly in size with the 

 three-toed feet of the Iguanodon ; and, since there are no 

 impressions of the smaller fore feet among these tracks, 

 the bipedal gait of the Iguanodon is again proved from an 

 independent line of evidence. The three toes of the 

 Iguanodon, it may be observed, were terminated by broad 

 and flattened bones more like hoofs than claws, thus again 

 indicating the herbivorous nature of these reptUes. 



The description of the details in which the skeleton of 

 the Iguanodon approximates to that of birds would involve 

 too many abstruse anatomical points to be given in these 

 pages. It may be observed, however, that all the bones 

 of the limbs were hollow, as in birds, while those of all 

 living reptiles are solid. Then the two long and rod-like 

 bones descending from the haunches behind the thigh- 

 bone are essentially bird-like in form and position, and 

 difl'er totally from the corresponding bones of crocodiles 



and lizards. Again, the reduction of the number of hind 

 toes to three, and the close relationship of the upper bones 

 of the ankk^ to those of the leg arc strong points of resent- 

 lilance to birds. .It is true, indeed, that in birds the three 

 parallel long bones of the foot found immediately below 

 the ankle in the Iguanodon are fused into a single bone, 

 while the ankle-bones are respectively united with the 

 latter and the bones of the leg ; but in a fossil reptile from 

 the chalk of the United States, which may be regarded as 

 a distant cousin of our Iguanodon, the arrangement of 

 these bones is so like that obtaining in birds that the 

 difference is merely one of the degree to which specialisa- 

 tion (as naturalists call these peculiar modifications from 

 the ordinary type) has been carried. 



Indeed, to those who believe in the evolution of organized 

 nature (and there are very few competent to express 

 an opinion on the subject who do not hold this belief), it 

 now appears to be (|uite evident that birds have originally 



Fig. 2. — Restokation of the Skeleton of the Iguanodon. 

 About njlj the natural size. 



taken their origin from some kind of extinct reptile more 

 or less closely allied to the ancestors of the Iguanodon. 



From the absence of any trace of bony plates, like those 

 found in the skin of linng crocodiles, accompanying the 

 skeletons of the Iguanodon, we may safely infer that these 

 creatures had an entirely naked skin. In regard to their 

 food, we know that palms and cycads grew abundantly in 

 England during the Wealden period, and it is hence 

 highly probable that the fruits of these plants formed a 

 considerable part of the nutriment of these ancient 

 reptiles. 



The sight of a herd of these giant Iguanodons. many of 

 which stood over 20 feet in height, stalking on their hind 

 limbs among the old Wealden forests and overtopping 

 many of its trees, must have been a spectacle in compari- 

 son to which a drove of elephants in an Indian jungle 

 would be scarcely worth a moment's attention. 



A totally different type of Giant Land Reptile from the 

 Sussex ^^'ealden was first indicated to Mautell by a huge 

 bone of the upper arm, or humerus as it is anatomically 

 termed. This stupendous bone, which is now in the 

 British Museum, has a length of upwards of fifty-four 

 inches ; it approximates in form to the corresponding bone 

 of the crocodiles, being solid throughout, and is thus 

 totally different from the very much smaller arm-bone of 

 the Iguanodon. As being the largest form with which he 

 was acquainted, Mantell proposed to call the reptile repre- 

 sented by this bone the Pelorosaur, from the Greek jirlumx, 



