We shall now consider the next higher group of Vertebrates, the amphibians, which breathe by gills when young and later develop lungs. Many live both on land and in water like the frogs. Unlike fishes they have legs with toes and not fins. Beginning probably in the Devonian as a branch of the fishes, amphibians showed a marvelous development during later Paleozoic and very early Mesozoic times when they reached their climax, after which they fell off remarkably, being now relatively unimportant like the frogs and salamanders. They are of special significance because they were the first of all the back-boned animals (Vertebrates) to inhabit the land which they dominated only until the great rise of reptiles of Mesozoic time. The reptiles in fact evolved from the amphibians in the late Paleozoic when many transition forms occurred. (Plate 15.) During those ancient days the numerous and very diversified amphibians were like giant salamanders, commonly five to eight feet long, with one Triassic form fifteen to twenty feet long, and with heavily armored skulls two to four feet long. Turning now to the reptiles we find that they are much more distinctly land animals than the preceding types of Vertebrates. Reptilian life of the earth began in late Paleozoic time as an evolutionary branch of the amphibians. The earliest forms were in many ways much like the amphibians, but gradually they diversified and progressed so that before the close of the Mesozoic era, which has long been called the "Age of Reptiles," they were the rulers of the world. "They covered the land with gigantic herbivorous and carnivorous forms; they swarmed in the sea, and, as literal dragons, they dominated the air." (Scott.) Mesozoic reptiles are of special interest and significance not only in themselves, but also because from one of their branches the birds were evolved, and from another the mammals. "In advancing from the amphibian to the reptile the evolution of the Vertebrates was far from finished. The cold-blooded, clumsy and sluggish, small-brained and unintelligent reptile is as far inferior to the higher mammals, whose day was still to come, as it is superior to the amphibian and the fish." (Norton.)