The Story of the Earth and Man

by Sir John William Dawson

The data for such calculations are very uncertain, and three elements of additional uncertainty closely related to each other must also be noticed. The first is the unknown length of the intervals in which no deposition whatever may have been taking place over the areas open to our investigation. The second is the varying amounts in which material once deposited may have been swept away by water. The third is the amount of difference that may have resulted from the progressive change of the geographical features of our continents. These uncertainties would all tend to diminish our estimate of the relative length of the Mesozoic. Lastly, the changes that have taken place in living beings, though a good measure of the lapse of time, cannot be taken as a criterion here, since there is much reason to believe that more rapid changes of physical conditions act as an inducing cause of rapid changes of life.

On the whole, then, taking such facts as we have, and making large deductions for the several causes tending to exaggerate our conception of Palæozoic time, we can scarcely doubt that the Palæozoic may have been three times as long as the Mesozoic. If so, the continental pulsations, and the changes in animal and vegetable life, must have gone on with accelerated rapidity in the later period,—a conclusion to which we shall again have occasion to refer when we arrive at the consideration of the Tertiary or Neozoic time, and the age of man, and the probable duration of the order of things under which we live.

I have given this preliminary sketch of the whole Mesozoic time, because we cannot here, as in the Palæozoic, take up each age separately; and now we must try to picture to ourselves the life and action of these ages. In doing so we may look at, first, the plant life of this period; second, animal life on the land; and third, animal life in the waters and in the ocean depths.

The Mesozoic shores were clothed with an abundant flora, which changed considerably in its form during the lapse of this long time; but yet it has a character of its own distinct from that of the previous Palæozoic and the succeeding Tertiary. Perhaps no feature of this period is more characteristic than the great abundance of those singular plants, the cycads, which in the modern flora are placed near to the pines, but in their appearance and habit more resemble palms, and which in the modern world are chiefly found in the tropical and warm temperate zones of Asia and America. No plants certainly of this order occur in the Carboniferous, where their nearest allies are perhaps some of the Sigillarise; and in the modern time the cycads are not so abundant, nor do they occur at all in climates where their predecessors appear to have abounded. In the quarries of the island of Portland, we have a remarkable evidence of this in beds with numerous stems of cycads still in situ in the soil in which they grew, and associated with stumps of pines which seem to have flourished along with them. In further illustration of this point, I may refer to the fact that Carruthers, in a recent paper, catalogues twenty-five British species belonging to eight genera—a fact which markedly characterizes the British flora of the Mesozoic period. These plants will therefore occupy a prominent place in our restoration of the Mesozoic landscape, and we should give especial prominence to the beautiful species Williamsonia gigas, discovered by the eminent botanist whose name it bears, and restored in his paper on the plant in the “Linnæan Transactions.” These plants, with pines and gigantic equisetums, prevailed greatly in the earlier Mesozoic flora, but as the time wore on, various kinds of endogens, resembling the palms and the screw-pines of the tropical islands, were introduced, and toward its close some representatives of the exogens very like our ordinary trees. Among these we find for the first time in our upward progress in the history of the earth, species of our familiar oaks, figs, and walnut, along with some trees now confined to Australia and the Cape of Good Hope, as the banksias and “silver-trees,” and their allies. In America a large number of the genera of the modern trees are present, and even some of those now peculiar to America, as the tulip-trees and sweet-gums. These forests of the later Mesozoic must therefore have been as gay with flowers and as beautiful in foliage as those of the modern world, and there is evidence that they swarmed with insect life. Further, the Mesozoic plants produced in some places beds of coal comparable in value and thickness to those of the old coal formation. Of this kind are the coal beds of Brora in Sutherlandshire, those of Richmond in Virginia, and Deep River in N. Carolina, those of Vancouver’s Island, and a large part of those of China. To the same age have been referred some at least of the coal beds of Australia and India. So important are these beds in China, that had geology originated in that country, the Mesozoic might have been our age of coal.

If the forests of the Mesozoic present a great advance over those of the Palæozoic, so do the animals of the land, which now embrace all the great types of vertebrate life. Some of these creatures have left strange evidence of their existence in their footprints on the sand and clay, now cemented into beds of hard rock excavated by the quarryman. If we had landed on some wide muddy Mesozoic shore, we might have found it marked in all directions with animal footprints. Some of these are shaped much like a human hand. The creature that made this mark was a gigantic successor of the crocodilian newts or labyrinthodonts of the Carboniferous, and this type seems to have attained its maximum in this period, where one species, Labyrinthodon giganteus, had great teeth three or four inches in length, and presenting in their cross section the most complicated foldings of enamel imaginable. But we may see on the shores still more remarkable footprints. They indicate biped and three-toed animals of gigantic size, with a stride perhaps six feet in length. Were they enormous birds? If so, the birds of this age must have been giants which would dwarf even our ostriches. But as we walk along the shore we see many other impressions, some of them much smaller and different in form. Some, again, very similar in other respects, have four toes; and, more wonderful still, in tracing up some of the tracks, we find that here and there the creature has put down on the ground a sort of four-fingered hand, while some of these animals seem to have trailed long tails behind them. What were these portentous creatures—bird, beast, or reptile? The answer has been given to us by their bones, as studied by Yon Meyer and Owen, and more recently by Huxley and Cope. We thus have brought before us the Dinosaurs—the terrible Saurians—of the Mesozoic age, the noblest of the Tanninim of old. These creatures constitute numerous genera and species, some of gigantic size, others comparatively small;—some harmless browsers on plants, others terrible renders of living flesh; but all remarkable for presenting a higher type of reptile organization than any now existing, and approaching in some respects to the birds and in others to the mammalia. Let us take one example of each of the principal groups. And first marches before us the Iguanodon or his relation Hadrosaurus—a gigantic biped, twenty feet or more in height, with enormous legs shaped like those of an ostrich, but of elephantine thickness. It strides along, not by leaps like a kangaroo, but with slow and stately tread, occasionally resting, and supporting itself on the tripod formed by its hind limbs and a huge tail, like the inverted trunk of a tree. The upper part of its body becomes small and slender, and its head, of diminutive size and mild aspect, is furnished with teeth for munching the leaves and fruits of trees, which it can easily reach with its small fore-limbs, or hands, as it walks through the woods. The outward appearance of these creatures we do not certainly know. It is not likely that they had bony plates like crocodiles, but they may have shone resplendent in horny scale armour of varied hues. But another and more dreadful form rises before us. It is Megalosaurus or perhaps Lælaps. Here we have a creature of equally gigantic size and biped habits; but it is much more agile, and runs with great swiftness or advances by huge leaps, and its feet and hands are armed with strong curved claws; while its mouth has a formidable armature of sharp-edged and pointed teeth. It is a type of a group of biped bird-like lizards, the most terrible and formidable of rapacious animals that the earth has ever seen. Some of these creatures, in their short deep jaws and heads, resembled the great carnivorous mammals of modern times, while all in the structure of their limbs had a strange and grotesque resemblance to the birds. Nearly all naturalists regard them as reptiles; but in their circulation and respiration they must have approached to the mammalia, and their general habit of body recalls that of the kangaroos. They were no doubt oviparous; and this, with their biped habit, seems to explain the strong resemblance of their hind quarters to those of birds. Had we seen the eagle-clawed Lælaps rushing on his prey; throwing his huge bulk perhaps thirty feet through the air, and crushing to the earth under his gigantic talons some feebler Hadrosaur, we should have shudderingly preferred the companionship of modern wolves and tigers to that of those savage and gigantic monsters of the Mesozoic.

We must not leave the great land-lizards of the reptilian age, without some notice of that Goliath of the race which, by a singular misnomer, has received the appellation of Ceteosaurus or “Whale-Saurian.” It was first introduced to naturalists by the discovery of a few enormous vertebrae in the English Oolite; and as these in size and form seemed best to fit an aquatic creature, it was named in accordance with this view. But subsequent discoveries have shown that, incredible though this at first appeared, the animal had limbs fitted for walking on the land. Professor Phillips has been most successful in collecting and restoring the remains of Ceteosaurus, and devotes to its history a long and interesting section of his “Geology of Oxford.” The size of the animal may be estimated, from the fact that its thigh-bone is sixty-four inches long, and thick in proportion. From this and other fragments of the skeleton, we learn that this huge monster must have stood ten feet high when on all fours, and that its length, could not have been less than fifty feet; perhaps much more. From a single tooth, which has been found, it seems to have been herbivorous; and it was probably a sort of reptilian Hippopotamus, living on the rich herbage by the sides of streams and marshes, and perhaps sometimes taking to the water, where the strokes of its powerful tail would enable it to move more rapidly than on the land. In structure, it seems to have been a composite creature, resembling in many points the contemporary Dinosaurs; but in others, approaching to the crocodiles and the lizards.

But the wonders of Mesozoic reptiles are not yet exhausted. While noticing numerous crocodiles and lizard: like creatures, and several kinds of tortoises, we are startled by what seems a flight of great bats, wheeling and screaming overhead, pouncing on smaller creatures of their own kind, as hawks seize sparrows and partridges, and perhaps diving into the sea for fish. These were the Pterodactyles, the reptile bats of the Mesozoic. They fly by means of a membrane stretched on a monstrously enlarged little finger, while the other fingers of the fore limb are left free to be used as hands or feet. To move these wings, they had large breast-muscles like those of birds. In their general structure, they were lizards, but no doubt of far higher organization than any animals of this order now living; and in accordance with this, the interior of their skull shows that they must have had a brain comparable with that of birds, which, they rivalled in energy and intelligence. Some of them were larger than the largest modern birds of prey, others were like pigeons and snipes in size. Specimens in the Cambridge Museum indicate one species twenty feet in the expanse of its wings. Cope has recently described an equally gigantic species from the Mesozoic of Western America, and fragments of much larger species are said to exist.[AE] Imagine such a creature, a flying dragon, with vast skinny wings, its body, perhaps, covered with scales, both wings and feet armed with strong claws, and with long jaws furnished with sharp teeth. Nothing can be conceived more strange and frightful. Some of them had the hind limbs long, like wading birds. Some had short, legs, adapted perhaps for perching. They could probably fold up their wings, and walk on all fours. Their skeleton, like that of birds, was very light, yet strong; and the hollow bones have pores, which show that, as in birds, air could be introduced into them from the lungs. This proves a circulation resembling that of birds, and warm blood. Indeed, in many respects, these creatures bridge over the space between the birds and the reptiles. “That they lived,” says Seeley, "exclusively upon land or in the air is improbable, considering the circumstances under which their remains are found. It is likely that they haunted the sea-shores; and while sometimes rowing themselves over the water with their powerful wings, used the wing membrane, as does the bat, to encloses the prey and bring it to the mouth. The large Pterodactyles probably pursued a more substantial prey than dragon-flies. Their teeth were well suited for fish; but probably fowl and small mammal, and even fruits, made a variety in their food. As the lord of the cliff, it may be supposed to have taken toll of all animals that could be conquered with tooth and nail. From its brain, it might be regarded as an intelligent animal. The jaws present indications of having been sheathed with a horny covering, and some species show a rugose anterior termination of the snout, suggestive of fleshy lips like those of the bat, and which may have been similarly used to stretch and clean the wing-membrane."

[AE] Seeley: “Ornithosauria.”

Here, however, perched on the trees, we see true birds. At least they have beaks, and are clothed with feathers. But they have very strange wings, the feathers all secondaries, without any large quills, and several fingers with claws at the angle of the wing, so that though less useful as wings, they served the double purpose of wing and hand. More strange still, the tail was long and flexible, like that of a lizard, with the feathers arranged in rows along its sides. If the lizards of this strange and uncertain time had wings like bats, the birds had tails and hands like lizards. This was in short the special age of reptiles, when animals of that class usurped the powers which rightfully belonged to creatures yet in their nonage, the true birds and mammals of our modern days, while the birds were compelled to assume some reptilian traits.