ORDER IX 



PTEROSAURIA 



251 



as many as three. In Bhamphorhyndms and Dimoiylioclon it was divaricated, 

 and doubtless assisted in the support of the patagium. The claws are usually 

 sharp and delicate, and during life were doubtless sheathed with horn. 



Sub-Order 1. PTERODERMATA. Seeley. 



Tail elongated ; wing metacarpal less than half the length of the hones of the 

 antebrachium ; fifth digit of pes with one to three phalanges. Jaivs dentigerous ; 

 external nares completely separated from antorhital vacuity. 



This group comprises the earlier and more generalised Pterosaurs, none of 

 which survived the Jurassic so far as known. Teeth are always present, 

 increasing in size posteriorly, but sometimes do not extend to the anterior 

 extremity of the jaws. The scapulae and coracoids are often fused proximally, 

 and the proximal tarsals are fused with the tibia. 



Family 1. Rhamphorhynchidae. 



Witli the characters of the sub-order, Jurassic. 



Dimorphodon, Owen (Fig. 357). Skull relatively very large, deepened in 

 form, and extremely light ; brain case unusually small. External narial 



• Fig. 357. 



Dimorplwdon maeronyx, Owen. Lower Lias ; Dorsetshire. Restoration of skeleton, Vr- 

 a, Antorbital vacuity ; n, External narial opening ; o, Orbit (from A. S. Woodward, after Owen). 



openings and antorbital vacuities very large. Jaws toothed to the extremity, 

 the anterior teeth very large and irregularly spaced ; mandibular suspensorium 



