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After the appearance of Archaeopteryx Lithographica, the first known bird, the myriad species descended from it. It is hard to isolate when the first owls evolved. The first owl may have come out of the Cenozoic era of 70 to 40 million years ago if not the latter part of the Mesozoic era, which was 135 to 70 million years ago.
Let us now study the history of the great river in the last days of the Cenozoic Time, and early days of the fifth and last great Geological Time, in which we are now living the Quaternary, or Age of Man an epoch which I have called the "Great River Age."
The progress of life is then described as the basis of subdivision into Geological Ages; and the subdivisions of geological time are presented as follows: I. Azoic Time or Age. II. Palaeozoic Time. 1. The Age of Mollusks, or Silurian. 2. The Age of Fishes, or Devonian. 3. The Age of Coal Plants, or Carboniferous. III. Mesozoic Time. 4. The Age of Reptiles. IV. Cenozoic Time. 5. The Age of Mammals.
In any case, the "historical period" is an insignificant quantity compared with the vast length of the preceding ages, in which there was no question of human existence on our planet. Even the important Cenozoic or Tertiary period, in which the first placentals or higher mammals appear, probably amounts to little over two per cent of the whole organic age.
The day of the ammonite and the belemnite also now drew to a close, and only a few of these cephalopods were left to survive the period. It is therefore at the close of the Cretaceous that the line is drawn which marks the end of the Middle Age of geology and the beginning of the Cenozoic era, the era of modern life, the Age of Mammals.
"They talk about their Atlantises, their submerged continents!" he exclaimed, with a sniff through his wide, hairy nostrils. "Why, Trednoke, do you realize that we are living literally at the bottom of a Mesozoic at any rate, Cenozoic sea?" The gentleman thus indignantly addressed contemplated his questioner with the serenity of one conscious of freedom from geologic responsibility.
The vegetable kingdom reached its culmination before the animal kingdom, and if the dividing line between the Mesozoic and the Cenozoic were drawn according to the progress of plant life, the Cretaceous instead of the Tertiary would be made the opening period of the modern era.
|Quaternary |Recent Cenozoic | |Pleistocene | |Tertiary |Pliocene |Miocene |Eocene |Cretaceous Mesozoic |Jurassic |Triassic |Permian |Carboniferous |Pennsylvanian | |Mississippian Paleozoic |Devonian |Silurian |Ordovician |Cambrian Algonkian Archean
But the height at which the Tertiary strata now stand five thousand feet above the sea at Denver, and twice that height in the plateaus of southern Utah proves that the plateaus of which the Tertiary strata form a part have been uplifted during the Cenozoic.
Disregarding some problematical five-toed forms like Phenacodus, the first type of undoubted relationship to modern horses is Hyracotherium, a little animal about three feet long that lived during the Eocene period of the Cenozoic epoch.
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