486 PTEROSAURIA 



from the acetabulum. The whole arrangement resembles that of 

 the Crocodilian pelvis. The hind-limbs are bird-like in so far as 

 the fibulae are reduced to splints, and attached to the proximal 

 halves of the long and slender tibiae. The feet contain five 

 separate toes with rather long metatarsals and short claws. 

 Many of the bones are hollow. 



The Pterosauria have no relationship with the birds, in spite 

 of the number of apparently striking resemblances (e.g. choanae, 

 pre-orbital foramina, brain, scapula, fibula, cervical vertebrae), 

 which are, however, coincidences, cases of convergence, in con- 

 formity with the aerial life. The totally different plan of the 

 wings is sufficient to show this. On the other hand, the real 

 affinities of this group of flying reptiles are unknown. They 

 turn up " fully fledged " in the Lower Lias, and they reach their 

 highest specialisation in the Upper Cretaceous epoch, with which 

 they have died out. In fact we do not know any forms through 

 which to connect them with other extinct reptiles. The skull 

 shows some Rhynchocephalian features ; the pelvis, Crocodilian 

 features ; and this combination points back a long way. 



Order PTEROSAURI. 



Sub-Order 1. Pterodactyl!, with alveolar teeth in the upper 

 and lower jaws. Imperfect remains, impressions of phalanges of 

 the long patagial finger, are known from the Rhaetic of Wiirt- 

 emberg. The oldest well-known genus is Dimorphodon, Lower 

 Lias of Lyme Eegis. D. macronyx. Total length between 3 

 and 4 feet, of which the large light skull takes up about 9 

 inches, and the long thin tail about 2 feet. The patagial finger 

 is about 20 inches, the whole wing about 28 inches long, 

 Rliamphorhynclius longicaudatus of the Upper Oolite of Germany 

 is remarkable for the long slender teeth, which are directed 

 forwards and separated by wide spaces from each other. The 

 nine or ten cervical vertebrae are elongated. R. phyllurus of the 

 same geological age has left impressions of the flying membranes. 

 They extend from the whole length of the wing and the 

 sides of the trunk to the thigh as far as the knee, and from the 

 inside of the hind-limbs to the tail. The end of the tail 

 carries a spatulate membrane. Allied is Ornithocheirus, with 

 many species in the English Wealden and Greensand. Ptero- 



