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It had two pairs of paddles so that the name of sea-serpent is very imperfectly applicable and four rows of formidable teeth on the roof of its mouth. Like the Deinosaurs and Pterosaurs, the order was doomed to be entirely extinguished after a brief supremacy in its environment.
The grains and fruits of the Angiosperms and the vast swarms of insects provided immense stores of food; the annihilation of the Pterosaurs left a whole stratum of the earth free for their occupation.
the first sentence smote him "Paleontologically the periods are characterized by absence of the large marine saurians, Dinosaurs and Pterosaurs " "eh?" gasped Barton. "Why, of course!" called Edgarton, a bit impatiently, from the window. Laboriously Barton went back and reread the phrase to himself. "Oh oh, yes," he conceded lamely. "Paleontologically," he began all over again.
Pterosaurs, winged reptiles, whose whole organism was adapted for flight through the air, appeared in the Jurassic and passed off the stage of existence before the end of the Cretaceous. The bones were hollow, as are those of birds. The sternum, or breastbone, was given a keel for the attachment of the wing muscles.
Then the saturnine groom took her to the airport to watch the airplanes come and go. They looked through the glass cages at these volant pterosaurs with American Airlines branded on their skins.
In the course of time they lose the teeth an advantage in the distribution of the weight of the body while flying and develop horny beaks. In the gradual shaping of the breast-bone and head, also, they illustrate the evolution of the bird-form. But the birds were meantime developing from a quite different stock, and would replace the Pterosaurs at the first change in the environment.
"Oh, dear, no!" he interrupted himself. "I was farther along than that! Absence of marine saurians? Oh, yes! "Absence of marine saurians," he resumed glibly, "Dinosaurs and Pterosaurs so abundant in the in the Cretaceous of Ammonites and Belemnites," he persisted heroically.
Small Pterosaurs continue throughout the period, but from these bat-like creatures we rise until we come to such dragons as the American Pteranodon, with a stretch of twenty-two feet between its extended wings and jaws about four feet long. In the earlier part of the period they all have the heavy jaws and numerous teeth of the reptile, with four or five well-developed fingers on the front limbs.
On the physical side it includes a very considerable rise of the land over the greater part of the globe, and the formation of lofty chains of mountains; on the botanical side it means the reduction of the rich Mesozoic flora to a relatively insignificant population, and the appearance and triumphant spread of the flowering plants, on the zoological side it witnesses the complete extinction of the Ammonites, Deinosaurs, and Pterosaurs, an immense reduction of the reptile world generally, and a victorious expansion of the higher insects, birds, and mammals; on the climatic side it provides the first definite evidence of cold zones of the earth and cold seasons of the year, and seems to represent a long, if irregular, period of comparative cold.
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