. The origin and evolution of life, on the theory of action, reaction and interaction of energy. he ancient Rocky Mountain region. While the continental seas of Jurassic time were favorableto this remarkable aquatic marine phase of the reptiles, stillgreater inundations both of North America and of Europeoccurred during Upper Cretaceous time. This was the periodof the maximum evolution of the sea reptiles, the ultimatefood supply of which was the surface life of the oceans, the Fig. 82. Restorations of Two Ich-thyosaurs. Cymhospcmdylns, a primitive ichthyosaurfrom the Triassic seas of Nevada (
. The origin and evolution of life, on the theory of action, reaction and interaction of energy. he ancient Rocky Mountain region. While the continental seas of Jurassic time were favorableto this remarkable aquatic marine phase of the reptiles, stillgreater inundations both of North America and of Europeoccurred during Upper Cretaceous time. This was the periodof the maximum evolution of the sea reptiles, the ultimatefood supply of which was the surface life of the oceans, the Fig. 82. Restorations of Two Ich-thyosaurs. Cymhospcmdylns, a primitive ichthyosaurfrom the Triassic seas of Nevada (afterMerriam), and the highly speciahzedBaptanodon, a Cretaceous ichthyosaurof the seas of that period in the regionof Wyoming, in which the teeth aregreatly reduced. Restorations for theauthor by W. K. Gregory and RichardDeckert. 2o6 THE ORIGIN AND EVOLUTION OF LIFE marine Protozoa, skeletons of which were depositing the greatchalk beds of Europe and of western North America. The Plesiosaurs had begun their invasion of the sea duringUpper Triassic time, as shown in the primitive half-lizard. Fig. 83. North America in Upper Cretaceous Time. The great inland continental sea extending from the Gulf to the Arctic Ocean, was favor-able to the evolution of the mosasaurs, plesiosaurs, and giant sea turtles (Airhelon).This period is marked by the greatest inundation of North America during Mesozoictime, by mountains slowly rising along the Pacific coast from Mexico to Alaska, and byvolcanic activity in Antillia. Detail from the globe model in the American Museum byChester A. Reeds and George Robertson, after Schuchert. Lariosaurus, discovered in northern Italy, which still retainsits original lacertilian appearance, due to the fact that thelimbs and feet are not as yet transformed into paddles. Inthe subsequent evolution of paddles the number of digits re-mains the same, namely, five, but the number of the phalangeson each digit is greatly increased through the process knownas hyperph
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