ORDER VIII 



DIXOSAURIA 



239 



i; 



ramus composed of six pieces, and with slender coronoid process. There are 

 ten cervical, eighteen dorso-lumbar, four to six sacral, and forty to fifty caudal 

 vertebrae. All the presacral vertebrae except the atlas and a few lumbars 



bear ribs, as do also the thirteen 

 anterior caudals. Ossified tendons 

 frequently observed a Ion- the neural 

 spines of the back and tail. Scapula 

 very long and slender ; coracoid 

 small and rounded, notched or per- 

 forate at its articular border ; 

 supposed pair of sternal bones 



Fig. 341. 



Iguanodon mantdli, Owen. Wealden ; Isle of Wight. 

 Inner (A), and posterior (B) aspects of mandibular tooth 

 (after Mantell). 



triangular. Manus 

 pentadactyl, the 

 pollex reduced to a 

 single spur-like 

 phalanx ; the others 

 having a formula of 

 3, 3, 3, 4. Ilium 

 greatly extended on 

 either side of the 

 acetabulum. Post- 

 pubis process slender 

 and rod-like, shorter 



than thp isrhinm Iguanodon bemissartensis, Boul. Wealden ; Bernissart, Belgium. Complete 



Liicvn uiic inoiiium. skeletoH) i /go ,. 0; coracoid; is, Ischium; p, Pubis; pp, Postpubic process 



Femur Scarcely Scapula ; 1— V, Digits (after Dollo). 



longer than the cms, 



and with prominent pendent inner trochanter. This, according to Dollo, is 

 distinct from the third trochanter of mammals, and indicates a powerful caudo- 

 femoral musculature, as in birds. Metatarsal Xo. I rudimentary, No. V wanting ; 

 the three ungual phalanges broad and claw-shaped ; formula of pes, 0, 3, 4, 5, 0. 

 Iguanodon is known by numerous complete skeletons from the "Wealden of 

 Bernissart, near Mons, Belgium, as many as twenty-three being exhibited in the 

 Brussels Museum. Fragmentary remains occur also in the English Wealden. 

 Lower Greensand, Purbeckian, and perhaps also in the Kimmeridge Clay. The 

 typical species, /. mantelli, Owen, from the Wealden of England, attains a total 

 length of 6 m., and /. Ijernissartensis, Boulenger ( = 1. seeleyi, Hulke), is between 

 8 and 10 m. long. As proved by its three-toed footmarks, the animal walked 

 on its hind feet in a kangaroo- like attitude, thus leaving the hands free for 

 prehension. 



