The era of exclusive marine life has ended. Land elevation, cooling crust and cooling oceans, sea restriction and consequent deepening, together with a great increase of land in northern latitudes, all conspired greatly to change the world’s climate in all regions far removed from the equatorial zone.
The closing epochs of the preceding era were indeed the age of frogs, but these ancestors of the land vertebrates were no longer dominant, having survived in greatly reduced numbers. Very few types outlived the rigorous trials of the preceding period of biologic tribulation. Even the spore-bearing plants were nearly extinct.
THE EARLY REPTILIAN AGE
The erosion deposits of this period were mostly conglomerates, shale, and sandstone. The gypsum and red layers throughout these sedimentations over both America and Europe indicate that the climate of these continents was arid. The arid districts were subjected to great erosion from the violent and periodic cloudbursts on the surrounding highlands.
Few fossils are to be found in these layers, but numerous sandstone foot- prints of the land reptiles may be observed. In many regions, the one thousand feet of red sandstone deposit of this period contains no fossils. The life of land animals was continuous only in certain parts of Africa.
These deposits vary in thickness from 3,000 to 10,000 feet, even being 18,000 on the Pacific coast. Lava was later forced in between many of these layers. The Palisades of the Hudson River were formed by the extrusion of basalt lava between these Triassic strata. Volcanic action was extensive in different parts of the world.
Over Europe, especially Germany and Russia, may be found deposits of this period. In England, the New Red Sandstone belongs to this epoch. Limestone was laid down in the southern Alps as the result of a sea invasion and may now be seen as the peculiar dolomite limestone walls, peaks, and pillars of those regions. This layer is to be found all over Africa and Australia. The Carrara marble comes from such modified limestone.
Nothing of this period will be found in the southern regions of South America as that part of the continent remained down and hence presents only a water or marine deposit continuous with the preceding and succeeding epochs.
150,000,000 years ago, the early land-life periods of the world’s history began. Life, in general, did not fare well but did better than at the strenuous and hostile close of the marine-life era.
As this era opens, the eastern and central parts of North America, the northern half of South America, most of Europe, and all of Asia are well above water. North America for the first time is geographically isolated, but not for long as the Bering Strait land bridge soon again emerges, connecting the continent with Asia.
Great troughs developed in North America, paralleling the Atlantic and Pacific coasts. The great Eastern-Connecticut fault appeared, one side eventually sinking two miles. Many of these North American troughs were later filled with erosion deposits, as also were many of the basins of the fresh-water and salt-water lakes of the mountain regions. Later on, these filled land depressions were greatly elevated by lava flows which occurred underground. The petrified forests of many regions belong to this epoch.
The Pacific coast, usually above water during the continental sub- mergences, went down excepting the southern part of California and a large island which then existed in what is now the Pacific Ocean. This ancient California sea was rich in marine life and extended eastward to connect with the old sea basin of the midwestern region.
140,000,000 years ago, suddenly and with only the hint of the two pre- reptilian ancestors that developed in Africa during the preceding epoch, the reptiles appeared in full-fledged form. They developed rapidly, soon yielding crocodiles, scaled reptiles, and eventually both sea serpents and flying reptiles. Their transition ancestors speedily disappeared.
These rapidly evolving reptilian dinosaurs soon became the monarchs of this age. They were egg layers and are distinguished from all animals by their small brains, having brains weighing less than one pound to control bodies later weighing as much as forty tons. But earlier reptiles were smaller, carnivorous, and walked kangaroolike on their hind legs. They had hollow avian bones and subsequently developed only three toes on their hind feet, and many of their fossil footprints have been mistaken for those of giant birds. Later on, the herbivorous dinosaurs evolved. They walked on all fours, and one branch of this group developed a protective armor.
Several million years later the first mammals appeared. They were non-placental and proved a speedy failure; none survived. This was an experimental effort to improve mammalian types, but it did not succeed here on Urantia.
The marine life of this period was meager but improved rapidly with the new invasion of the sea, which again produced extensive coast lines of shallow waters. Since there was more shallow water around Europe and Asia, the richest fossil beds are to be found about these continents. Today, if you would study the life of this age, examine the Himalayan, Siberian, and Mediterranean regions, as well as India and the islands of the southern Pacific basin. A prominent feature of the marine life was the presence of hosts of the beautiful ammonites, whose fossil remains are found all over the world.
130,000,000 years ago, the seas had changed very little. Siberia and North America were connected by the Bering Strait land bridge. A rich and unique marine life appeared on the Californian Pacific coast, where over one thousand species of ammonites developed from the higher types of cephalopods. The life changes of this period were indeed revolutionary notwithstanding that they were transitional and gradual.
This period extended over twenty-five million years and is known as the Triassic.
THE LATER REPTILIAN AGE
120,000,000 years ago, a new phase of the reptilian age began. The great event of this period was the evolution and decline of the dinosaurs. Land- animal life reached its greatest development, in point of size, and had virtually perished from the face of the earth by the end of this age. The dinosaurs evolved in all sizes from a species less than two feet long up to the noncarnivorous dinosaurs, seventy-five feet long, that have never since been equaled in bulk by any living creature.
The largest of the dinosaurs originated in western North America. These monstrous reptiles are buried throughout the Rocky Mountain regions, along the whole of the Atlantic coast of North America, over western Europe, South Africa, and India, but not in Australia.
These massive creatures became less active and strong as they grew larger and larger; but they required such an enormous amount of food and the land was so overrun by them that they literally starved to death and became extinct – they lacked the intelligence to cope with the situation.
By this time most of the eastern part of North America, which had long been elevated, had been leveled down and washed into the Atlantic Ocean so that the coast extended several hundred miles farther out than now. The western part of the continent was still up, but even these regions were later invaded by both the northern sea and the Pacific, which extended eastward to the Dakota Black Hills Region.
This was a fresh-water age characterized by many inland lakes, as is shown by the abundant fresh-water fossils of the so-called Morrison beds of Colorado, Montana, and Wyoming. The thickness of these combined salt-water and fresh-water deposits varies from 2,000 to 5,000 feet; but very little limestone is present in these layers.
The same polar sea that extended so far down over North America likewise covered all of South America except the soon appearing Andes Mountains. Most of China and Russia was inundated, but the water invasion was greatest in Europe. It was during this submergence that the beautiful lithographic stone of southern Germany was laid down, those strata in which fossils, such as the most delicate wings of olden insects, are preserved as of but yesterday.
The flora of this age was much like that of the preceding. Ferns persisted, while conifers and pines became more and more like the present- day varieties. Some coal was still being formed along the northern Mediterranean shores.
The return of the seas improved the weather. Corals spread to European waters, testifying that the climate was still mild and even, but they never again appeared in the slowly cooling polar seas. The marine life of these times improved and developed greatly, especially in European waters. Both corals and crinoids temporarily appeared in larger numbers than heretofore, but the ammonites dominated the invertebrate life of the oceans, their average size ranging from three to four inches, though one species attained a diameter of eight feet. Sponges were everywhere, and both cuttlefish and oysters continued to evolve.
110,000,000 years ago, the potentials of marine life were continuing to unfold. The sea urchin was one of the outstanding mutations of this epoch. Crabs, lobsters and the modern types of crustaceans matured. Marked changes occurred in the fish family, a sturgeon type first appearing, but the ferocious sea serpents, descended from the land reptiles, still infested all the seas, and they threatened the destruction of the entire fish family.
This continued to be, pre-eminently, the age of the dinosaurs. They so overran the land that two species had taken to the water for sustenance during the preceding period of sea encroachment. These sea serpents represent a backward step in evolution. While some new species are progressing, certain strains remain stationary and others gravitate backward, reverting to a former state. And this is what happened when these two types of reptiles forsook the land.
As time passed, the sea serpents grew to such size that they became very sluggish and eventually perished because they did not have brains large enough to afford protection for their immense bodies. Their brains weighed less than two ounces notwithstanding the fact that these huge ichthyosaurs sometimes grew to be fifty feet long, the majority being over thirty-five feet in length. The marine crocodilians were also a reversion from the land type of reptile, but unlike the sea serpents, these animals always returned to the land to lay their eggs.
Soon after two species of dinosaurs migrated to the water in a futile attempt at self-preservation, two other types were driven to the air by the bitter competition of life on land. But these flying pterosaurs were not the ancestors of the true birds of subsequent ages. They evolved from the hollow-bone leaping dinosaurs, and their wings were of batlike formation with a spread of twenty to twenty-five feet. These ancient flying reptiles grew to be ten feet long, and they had separable jaws much like those of modern snakes. For a time, these flying reptiles appeared to be a success, but they failed to evolve along lines which would enable them to survive as air navigators. They represent the non-surviving strains of bird ancestry.
Turtles increased during this period, first appearing in North America. Their ancestors came over from Asia by way of the northern land bridge.
One hundred million years ago the reptilian age was drawing to a close. The dinosaurs, for all their enormous mass, were all but brainless animals, lacking the intelligence to provide sufficient food to nourish such enormous bodies. And so, did these sluggish land reptiles perish in ever-increasing numbers. Henceforth, evolution will follow the growth of brains, not physical bulk, and the development of brains will characterize each succeeding epoch of animal evolution and planetary progress.
This period, embracing the height and the beginning decline of the reptiles, extended nearly twenty-five million years and is known as the Jurassic.
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