During Jurassic times all these orders of reptiles waxed prosperous and powerful, and branched out in many ways and in countless numbers; many new kinds of each appeared—the marine crocodiles, the quadrupedal dinosaurs, etc.—but no order or suborder, so far as we know, disappeared before its close. And this prosperity continued on into the Lower Cretaceous and for many even into the Upper Cretaceous. The largest dinosaurs disappeared in the Lower Cretaceous, so far as our knowledge goes, but the old-fashioned crocodiles continued on into the Upper, to give place to the new-fashioned kinds. The ichthyosaurs lingered on for a while on the western continent, but the mosasaurs appeared, and the plesiosaurs reached their highest evolution and continued to the end. The flying reptiles attained the zenith of their evolution, but disappeared before the close. The marine turtles attained the maximum of specialization and size. The upright-walking dinosaurs continued on unabated to the close of the period; and a new kind of dinosaurs appeared near the end. [Illustration: FIG. 28.—Restoration of _Dimetrodon_, a pelycosaur reptile from the Permian of Texas; about eight feet long.] With the opening of the next great era—the Cenozoic or Tertiary—the reptiles dwindled away to their present insignificant position, while the birds and mammals appeared in great numbers and varied forms. The Age of Reptiles was closed and the Age of Mammals had begun. The history of the reptiles during the Cenozoic is an uneventful one; they ceased their dominion upon land, in the water, and in the air. Their remains are scanty, for the most part, in the rocks of the Tertiary, and such as are known differ only in details from those now living. The land tortoises only, like the mammals of Oligocene and Miocene times, seized the opportunities of open prairies and prospered. A few of the late Mesozoic forms continued a short while into the Eocene. No new groups, perhaps few new families, came into existence during the greater part of this time; it was the age only of land tortoises and the poisonous snakes among reptiles. EXTINCT REPTILES OF NORTH AMERICA The oldest known fossil reptile of North America, or indeed of the world, is represented by a single specimen, lacking the skull, from black shales of Middle Pennsylvanian age overlying a coal seam at Linton, Ohio. The specimen was originally described as an amphibian, but was later recognized by Professor Cope as a true reptile. It was more fully described by the writer under the name _Eosauravus Copei_, who agreed with Cope as to its reptilian nature. Until the skull is discovered, however, the precise relationships of the animal must remain doubtful.