PAST DISTRIBUTION OF ANIMALS 515 



but ganoids and lungfishes existed in great variety in the Devonian, 

 which is known as the age of fishes. The more modern fishes, the 

 teleosts, were not known until the Jurassic and are represented now by the 

 greatest number and diversity of species they have ever possessed. A 

 footprint from the Devonian is the earhest trace of an amphibian. There 

 were giant armored amphibians, the Stegocephala, in the Pennsylvanian 

 and Permian periods. These reached a maximum length of 15 to 20 

 feet in the Triassic, when they became extinct. The reptiles appeared 

 about the time of the amphibians but did not become dominant until 

 the Mesozoic, which was the age of reptiles; they reached their highest 

 development during the Jurassic. The aquatic and marine types 

 attained a length of 40 feet; a flying pterodactyl had a wing spread of 25 

 feet; and the gigantic dinosaurs reached 100 feet in length. These 

 giants suddenly became extinct in the Cretaceous. 



Fossil remains of the earliest bird, Archaeo'ptenjx (Fig. 271), have been 

 found in the Jurassic slates of Bavaria, and a number of other birds 

 are known from the Cretaceous. The earliest mammalian remains are 

 from the upper Triassic, and many types are known from the Creta- 

 ceous. IVIammals have been dominant since the beginning of the Cenozoic 

 era. Human origins have already been discussed. Steps in the devel- 

 opment of other mammalian types will be referred to in the next chapter, 

 on evolution. 



