128 FROM FISH TO PHILOSOPHER 



mals, but the somewhat smaller AUosaurus, which had 

 a length of only 30 feet, and the httle Compsognathus, 

 only 2V2 feet long, had developed carnivorous habits 

 and probably preyed upon their less agile fellows. In 

 well-preserved fossils of Jurassic ichthyosaurs, imbom 

 young have been found inside the body, showing that 

 as an adaptation to their marine habitat they had be- 

 come ovoviviparous, a notable adaptation since all recent 

 aquatic reptiles come ashore to lay their eggs. (Rattle- 

 snakes and a few other recent reptiles are ovoviviparous, 

 but not in adaptation to a marine habitat. ) 



In the Cretaceous, when reptilian evolution reached 

 its peak, Tyrannosaurus rex, the mightiest flesh-eater 

 ever to live on earth, stretched 47 feet from nose to tip 

 of tail and, erect on his massive hind legs, his head tow- 

 ered 20 feet above the ground. The duckbilled dinosaur, 

 Trachodon mirabilis, was almost as large, while some of 

 the Ceratopsia or homed dinosaurs were twice as bulky 

 as the greatest living rhinoceros. In the sea some of the 

 plesiosaurs reached a length of 40 to 50 feet, and com- 

 peted with marine turtles 1 1 feet long and with a newly 

 evolved group, the mosasam-s, which had taken to car- 

 nivorous piracy in the water. The pterodactyls, though 

 less numerous than in the Jurassic, also went in for size: 

 Pteranodon, for example, had a wingspread of 25 feet, 

 exceeding any other winged creature of all time and 

 truly meriting the title of winged dragon. It is believed 

 that this creature, like the flying reptiles of the Jurassic, 

 lived on fish, which it possibly caught in the salt marshes 

 by diving from high cliffs, but how it got on to the cliffs 

 and how it got out of the water remain a mystery. 



The transition from the Mesozoic to the Cenozoic has 

 been called 'the time of the great dying.' Every one of 

 the terrestrial and aquatic dinosaurs went down to ex- 

 tinction, leaving of the great Age of Reptiles only the 

 turtles, snakes, lizards, crocodilians, and the primitive 

 lizard, Sphenodon, to survive in the modem world. No 



