THE JURASSIC PERIOD. 101 



food in the small mammals and reptiles frequenting the shores of the 

 estuaries. Primitive lizards were doubtless abundant, but because of their 

 terrestrial habits and small size, very few if any have been discovered. 



The advent of aerial life; the pterosaurs. — It has already been 

 noted that the crowding of the land may have led some reptiles to 

 take to the sea. The same influence may have forced others to take 

 to the air, and thereby escape the monsters of the swamps, jungles, 

 and forests. Whatever the cause, the most unique feature of the 

 period was the development of flying reptiles. Appearing at the 

 very close of the Trias in a few yet imperfectly known forms, they 

 presented themselves at the very opening of the Jurassic period (Lower 

 Lias), as fully developed flying animals in the genus Dimorphodon, 

 and later formed a diversified group embracing long-tailed forms, as 



Fig. 374. — A flying saurian, Rhampkorhynchus phyllurus Marsh, in which the wing 

 membranes are preserved; about one-fourth natural size. The rod-like bones 

 that support the wing membranes are the extended fifth phalanges; the caudal 

 oar and the elongate skull are also well shown. From the lithographic stone at 

 Eichstadt, Bavaria. 



Rhampkorhynchus, and short-tailed forms, as Pterodactylus. With little 

 doubt they sprang from some agile, hollow-boned saurian, more or 

 less remotely akin to the slender, leaping dinosaurs. Between the 

 ponderous brontosaurs (Fig. 372) and the airy pterodactyls (Fig. 374), 

 the Jurassic suarians present the strangest of contrasts. The Jurassic 

 pterosaurs were small, but their successors attained a wing-spread of 

 nearly a score of feet. They were curiously composite in structure 

 and adaptation. Their bones were hollow, their fore limbs modified 



