Paleozoic

“ The great thickness of the strata, combined with the facts that the fossils show that many marvelous, mostly progressive, changes took place among living things, that seas came and went repeatedly over many parts of the continent, and that great changes took place in the configuration of the land, force us to conclude that Paleozoic time must have lasted for many millions of years. ”

“ And should such an hypothesis eventually be proved to be true, in the only way in which it can be demonstrated, viz. by observation and experiment upon the existing forms of life, the conclusion will inevitably present itself, that the Paleozoic, Mesozoic, and Cainozoic faunae and florae, taken together, bear somewhat the same proportion to the whole series of living beings which have occupied this globe, as the existing fauna and flora do to them. ”

“ That the sea was of very early Paleozoic (i.e., Cambrian) age has been proved by fossils in associated strata. Long after their deep burial and consolidation within the earth, the strata were subjected to tremendous mountain-making pressure, notably altered to a rock called “Quartzite,” raised high above sea level, and tilted almost vertically. Then through long ages (millions of years) overlying rocks of great thickness have been cut away (eroded) by weathering and stream action, laying bare the ledge as we see it to-day. ”

“ The earth’s crust is believed to be at least 31⁄4 billion years old. In order to deal with this vast stretch of time, geologists have divided the billions of years into various time units and have given each unit a name. The great divisions of geologic time, called eras, are Early Precambrian, Late Precambrian, Paleozoic, Mesozoic, and Cenozoic. ”

“ There must have existed great masses of the crude material, stored up in the rocks and in the waters of the sea, to provide with coverings all the testacea of every age, and to furnish the thousands of feet thickness of the Eozoic, Paleozoic, and Mesozoic limestones. ”

“ Toward the close of the Paleozoic era, changing climatic conditions caused the death of many forms of life upon the earth, and the development of new and hardier types. With these, in the Mesozoic era, came the new lords of the earth, the reptiles. ”

“ Where the lost or unknown parts belong, the largest divisions may be made, and possibly such may have been epochs of unusual activity, of diastrophic changes which greatly accelerated organic evolution. No one can say just where the dividing line should be drawn between the rocks of Paleozoic and Mesozoic age, or between the Mesozoic and Cenozoic, for there is none; the most that we can hope for is to make the divisions everywhere in the world conform to those first made for local reasons. ”

“ The primitive animals that evolved in the sea during the vast Precambrian Era left few traces in the rocks because they had not developed hard parts such as shells, but hard shells or skeletal parts became abundant during and after the Paleozoic Era. ”

“ When you were a tadpole and I was a fish
In the Paleozoic time
And side by side on the sluggish tide
We sprawled through the ooze and slime,
Or skittered with many a caudal flip
Through the depths of the Cambrian fen
My heart was rife with the joy of life,
For I loved you even then. ”

“ The Palæozoic was an immense period during which life abounded in the seas,—numberless species of mollusca, crustaceans, corals, fish are found,—and there were great forests, which have formed the coal measures, on land,—forests of strange primeval vegetation, but in which beautiful ferns, large and small, flourished in great numbers. The Secondary Era may be called the age of reptiles. To this era all the rocks we have so far studied belong. Now we come to the last era, the Tertiary, the age of the mammals. Instead of reptiles on land, in sea and air, we find a complete change. ”

“ There are no signs whatever of land life of any sort, plant or animal; there are no fishes nor any vertebrated creatures in this part of the record. Essentially all the plants and creatures which have left us their traces from this period of the earth's history, are shallow-water and intertidal beings. If we wished to parallel the flora and fauna of the Lower Palaeozoic rocks on the earth to-day, we should do it best, except in the matter of size, by taking a drop of water from a rock pool or scummy ditch and examining it under a microscope. ”

“ The older the rock, the simpler the plant and animal life it contains. Thus fossils can give a clue to the age of the rock strata.
Fossils can teach history. They tell us about plants and animals that are now extinct—the dinosaur, for example. They can also tell of ancient climates. Coral found in rocks in Greenland suggests it must have once been warm. Remains of fir and spruce trees have been found in the tropics.
How are fossils formed? Teeth, bone and wood don't last long in their original state. However, buried materials decompose, leaving a film of carbon as a fossil. ”

“ And thus ends a long era of world evolution, extending from the early appearance of land life down to the more recent times of the immediate ancestors of the human species and its collateral branches. This, the Cretaceous age, covers fifty million years and brings to a close the premammalian era of land life, which extends over a period of one hundred million years and is known as the Mesozoic. ”

“ The remarkable fossil remains and impressions of extinct animals and plants give us directly the historical evidence we need to understand the successive appearance and disappearance of the various species and groups. Geology has firmly established the chronological order of the sedimentary rocks, which have been successively formed of mud at the floor of the ocean, and has deduced their age from the thickness of the strata, and determined the relative date of their formation. The vast period during which organic life has been developing on the earth runs to many million years. ”

“ The periods we have already covered—the Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian—form the Primary or Palaeozoic Era, to which the earlier Archaean rocks were prefixed as a barren and less interesting introduction. The stretch of time on which we now enter, at the close of the Permian, is the Secondary or Mesozoic Era. It will be closed by a fresh upheaval of the earth and disturbance of life-conditions in the Chalk period, and followed by a Tertiary Era, in which the earth will approach its modern aspect. ”

“ Palæontology: The science of fossil organisms.
Palæozoic: A term applied to the second group of fossiliferous rocks, following the earliest, or Proterozoic, group, and preceding the Mesozoic group. It comprises the Cambrian, Ordovician, Devonian, Silurian, and Carboniferous systems, and its sediments are the first that contain well-preserved fossils.
Parasitism: A condition in which one organism (the parasite) residing in, or upon, another species of organism (the host) lives at its expense, the relation being detrimental to the latter. ”

“ If we take the Azoic period of the earth’s crust, and search through the granitic rocks of Scotland, Wales, or Cornwall; or if we pass on to the Palæozoic period, and examine the Old Red Sandstone, the Carboniferous system, or other formations; or, extending our researches, investigate the secondary formations, the Lias, the Oolite, and the Chalk, and so on until we arrive at the Tertiary period of the earth’s history; all the testimony is one; there is no contradiction; there are no fossil boats or sofas; no fossil beds or books; no fossil boys and girls; no fossil knives and forks ”

“ The three broad divisions—Palaeozoic, Mesozoic, Cainozoic—which are employed by geologists to mark three stages in the development of life on the earth, are based primarily upon the fossil contents of the strata which, at one time or another, have been continuously forming since the earliest times. ”

“ Now we can easily see how the remains of organic bodies, growing at the time of the formation of these beds, should be preserved in a fossil form. Limestone rocks are thickly studded in places with all sorts of marine formations. Coal fields reveal wonders of early vegetative growth. From sandstone rocks, and shaly beds, we learn strange stories of animal life at the time they were forming. From a careful study of these remains together with the formation in which they occur, not only in one locality but all over the earth, geologists have gradually unfolded the history of life on the globe. ”

“ Nevertheless, much interest is attached to the organic remains, as marking a kind of transition-period between the Palæozoic and Mesozoic epochs.
The plants of the Permian period, as a whole, have a distinctly Palæozoic aspect, and are far more nearly allied to those of the Coal-measures than they are to those of the earlier Secondary rocks; though the Permian species are mostly distinct from the Carboniferous, and there are some new genera. Thus, we find species of Lepidodendron, Calamites, Equisetites, Asterophyllites, Annularia, and other highly characteristic Carboniferous genera. ”

“ Paleontology, therefore, is not a mere branch of geology, but the foundation on which that science mainly rests. This fact is a sufficient excuse, if one were wanting, for noting the early opinions in regard to the changes of the earth's surface, as these changes were first studied to explain the position of fossils. The investigation of the latter first led to theories of the earth's formation, and thus to geology. When speculation replaced observation, fossils were discarded, and for a time the mineral characters of strata were thought to be the key to their position and age. ”

“ Thus in the whole of the great Palæozoic period, both in its fauna and flora, we have a continuity and similarity of a most marked character.
There is, indeed, nothing to preclude the supposition that many forms reckoned as species are really only race modifications. My own provisional conclusion, based on the study of Palæozoic plants, published many years ago,93 is that the general law will be found to be the existence of distinct specific types independent of each other, but liable in geological time to minor modifications, which have often been regarded as distinct species. ”

“ Time has approved of this sagacious anticipation, and we can now maintain with serene confidence that the four great Eozoic periods—Laurentian, Labrador, Atlantic or Montalban, and Huronian—were all enlivened by the existence of both vegetable and animal life. And Eozoic life had its peculiar characteristics just as much as the Silurian or Carboniferous. This life has appeared in consonance with the general principles of evolution as announced by our most learned sages. ”

“ Proofs from fossils in secondary and still older strata.—A great interval of time appears to have elapsed between the formation of the secondary strata, which constitute the principal portion of the elevated land in Europe, and the origin of the eocene deposits. If we examine the rocks from the chalk to the new red sandstone inclusive, we find many distinct assemblages of fossils entombed in them, all of unknown species, and many of them referable to genera and families now most abundant between the tropics. Among the most remarkable are reptiles of gigantic size ”

“ On the Third Day were created plants and trees; on the Fifth, reptiles, fish, and birds; on the Sixth, cattle, and the beasts of the earth, and, toward the end, man himself. Geologists, on the other hand, not influenced in the least degree by the Scripture narrative, but guided chiefly by the remains of animal and vegetable life which are preserved in the Crust of the Earth, have established three leading divisions of Geological time; the Palæozoic, or first age of organic life, the Mesozoic, or second great age of organic life, and the Kainozoic, or third great age of organic life. ”

“ The Palæozoic series is more than five times as thick as the Mesozoic, and these two taken together are twenty times the thickness of the Tertiary. Each series is divided by geologists into a series of systems, distinguished by the fossils they contain, which, on the whole, indicate animals of a higher degree of evolution as we ascend the series. ”

“ Unquestionably the oldest land-areas are represented by the disturbed Archæan and Palæozoic rocks of the Atlantic sea-board and central Europe. Examination of those tracts shows that they have experienced excessive denudation. The Archæan and Palæozoic masses, distributed along the margin of the Atlantic, are the mere wrecks of what, in earlier ages, must have been lofty regions, the mountain-chains of which may well have rivalled or even exceeded in height the Alps of to-day. They, together with the old disturbed rocks of central Europe, formed for a long time the only land in our area. ”

“ It is nevertheless remarkable, that on the continent of Europe, as in England, the fossil remains of mammalia belong almost exclusively to those of the Newer Pliocene and Post-Pliocene periods, and not to the Miocene or Eocene epochs, and when they are accompanied by land or river shells, these agree in great part, or entirely, with recent species. ”

“ This underground circulation of mineral matter in a dissolved condition explains the occurrence of fossils in land areas which have not necessarily been submerged during any great length of time, for it is well known that plant and animal remains are not invariably washed into lakes or seas, and that all sedimentary deposits have not been built up in large bodies of water. Here we are dealing with what is known as the continental type of sedimentation and such fossils as dinosaurs, mastodons, three-toed horses, and other former inhabitants of land areas. ”

“ How fossils tell of the geography of the past. Fossils are used not only as a record of the development of life upon the earth, but also in testimony to the physical geography of past epochs. They indicate whether in any region the climate was tropical, temperate, or arctic. Since species spread slowly from some center of dispersion where they originate until some barrier limits their migration farther, the occurrence of the same species in rocks of the same system in different countries implies the absence of such barriers at the period. ”