CHAPTER II.. The Dinosaurs.

THE DINOSAURS.

The continent of North America during that portion of the earth’s history which we may call the Age of Reptiles would have seemed to our eyes like another world. The present coastal outlines, mountain chains, valleys, rivers, lakes, and plains have, with few exceptions, come into being long since that time. During the early part of the age there were high mountains in the eastern part of the continent, which sent strong, muddy streams flowing to the Atlantic. California, on the other hand, was under the Pacific; the Sierra Nevada region was a great trough, while throughout that region which is now eastern Colorado, Utah, western Texas, and Arizona there lay a belt of broad, shallow lakes.

The plant life of those times differed as much from that of previous ages as from those that were to follow. The great Pennsylvanian coal forests of lepidodendrons, sigillarias, and their allies, had almost completely vanished from the earth. The higher lands were clothed with cone-bearers, such as the Aurucarian pines of present day Australia. Thick, gloomy forests of tree ferns covered the moist regions, while great “canebrakes” of horsetail reeds whose stems reached four or five inches in thickness bordered the bayous and marshes. Cycads, trees which, though related to the pines and spruces, look like palms, were abundant in the forests of this time.

During the middle portion of the Age of Reptiles conditions, both in geography and in plant life, underwent no striking change. But in the late Mesozoic, the Cretaceous period, there were many changes. The Atlantic Ocean encroached on the eastern part of the continent, while the Gulf of Mexico extended as far north as Illinois, and reached westward over Texas. A broad mediterranean sea stretched from the Gulf to the Arctic Ocean, and from Iowa to Utah, with the Colorado Mountains rising from it as a chain of islands. West of the sea was a broad belt of swamp land which extended from northern Alberta almost to Mexico.

The plants of the Cretaceous changed with the geography. The Cycads, so abundant in the early Mesozoic, became rare in most regions. The highest types of flowering plants gained an almost complete ascendancy, and forests of a decidedly modern appearance covered the continent from the Gulf of Mexico to the Arctic Ocean. “Among the kinds of forest trees whose remains are found in the continental deposits of the Cretaceous are the magnolia, the myrtle, the laurel, the fig, the tulip tree, the chestnut, the oak, beech, elm, poplar, willow, birch and maple. Forests of Eucalyptus grew along the coast of New England, and palms on the Pacific shores of British Columbia. Sequoias of many varieties ranged far into northern Canada. In northern Greenland there were luxuriant forests of magnolias, figs, and cycads; and a similar flora has been disinterred from the Cretaceous rocks of Alaska and Spitsbergen. Evidently the lands within the Arctic Circle enjoyed a warm and genial climate, as they had done during the Paleozoic. Greenland had the temperature of Cuba and southern Florida, and the time was yet far distant when it was to be wrapped in glacier ice.”

Such were the conditions under which flourished the mightiest race of animals that has ever lived upon land. The Dinosaurs not only were the dominant animals of their time, but they reached sizes so great that they have been rivalled by but one group of mammals--the whales. They maintained their supremacy throughout a long period of time estimated at from nine to one hundred millions of years; they survived important changes in geography and climate, and became extinct through a combination of causes which are yet only half known. Perhaps the great changes in life conditions at the end of the Cretaceous had much to do with their disappearance, as may also have been true of other reptiles living at the same time. Not improbably, too, the rise of egg-eating mammals, more intelligent and active than the dinosaurs, was a factor; and last of all, there remains the ever ready and ever probable hypothesis of racial old age.

The Dinosaurs were descended, in the opinion of those who have studied them, from primitive, lizard-like reptiles with fairly long limbs, long tails, five toes on each foot, and a complete series of sharp pointed teeth. In all probability, according to Dr. W. D. Matthew, this ancestor was fully capable of living on dry land, and was more or less in the habit of walking on its hind legs alone.

One of the most striking things about the Dinosaurs is their notable lack of brain power. In man, a creature weighing anywhere from one hundred twenty to two hundred pounds, on the average, the weight of a normal brain is about three pounds. The smallest brain that can exist and possess reasoning powers is about two pounds, while the smallest human brain known to be fitted for life alone weighs just a little more than ten ounces.

We can readily see that if conditions were proportionate among the Dinosaurs the size of the brain would be almost unbelievable. Instead, the reptile Claosaurus, which once inhabited the valleys of Maryland, and was twenty-five feet long and more than twelve feet high, had a brain so small that it must have weighed less than one pound. Brachiosaurus, probably the biggest beast that ever walked, was not much better equipped, while Triceratops, a Dinosaur having more than twice the bulk of the average elephant, possessed a brain weighing about two pounds. Truly they who are prone to refer to the “brainlessness” of human beings should consider the Dinosaurs before they speak! These great beasts must have known just about enough to rest when they were tired and eat when they were hungry; “coming in out of the rain” doubtless was an idea altogether too complicated for them to grasp.

But, as Lucas and others have emphasized, intelligence is one thing and living another and a very different one. The poor, weak brains of the Dinosaurs doubtless had but little to do with the primary functions of life; the spinal cord took care of them. In some of the beasts, notably in the armored giant Stegosaurus, the spinal cord possessed a sacral enlargement that was twenty times as large as the brain. This remarkable fact, when announced by Professor Marsh, attracted great attention, and was made the subject of much newspaper writing. Thousands of people who would never recognize the name Stegosaur are familiar with the marvelous character of that beast as he is described in this catchy though fanciful poem:

The armored giant Stegosaurus.]

THE DINOSAUR.

Behold the mighty dinosaur, Famous in prehistoric lore, Not only for his weight and strength But for his intellectual length. You will observe by these remains The creature had two sets of brains-- One in his head (the usual place), The other at his spinal base. Thus he could reason a priori As well as a posteriori. No problem bothered him a bit: He made both head and tail of it. So wise he was, so wise and solemn, Each thought just filled a spinal column. If one brain found the pressure strong It passed a few ideas along; If something slipt his forward mind ’Twas rescued by the one behind; And if in error he was caught He had a saving afterthought. As he thought twice before he spoke He had no judgments to revoke; For he could think without congestion, Upon both sides of every question. O’ gaze upon this model beast, Defunct ten million years at least!

The Dinosaurs, like all other groups of animals, may be divided into sub-groups, depending on habits, structure, etc. The commonest classification separates them into three divisions: the carnivorous, the amphibious, and the beaked. One of the most remarkable of the flesh-eating species, though not the largest, is Allosaurus, a powerful reptile that once roamed over the western part of North America. He walked by means of his hind legs only, using his long tail as a balance for his body. The huge head, armed with long, sharp teeth, was set on a heavy, short neck; casts of the brain indicate that it was of much the same type as that of the modern alligator, but considerably less effective.

One of the greater carnivorous dinosaurs, showing the large head, long teeth, tiny fore limbs and ponderous walking legs typical of the group. (Modified after Lull.) ]

Allosaurus lived upon dry land, seldom venturing into the great Mesozoic swamps. He was predaceous, attacking his prey in swift, mighty rushes, tearing it with the jaws and occasionally striking it with the powerful tail. Anything like the elaborate stalking of game such as we see in the tiger and lion of today was impossible to the Dinosaur; he simply lay in wait until the close approach of prey stimulated him to his tremendous but half instinctive rush. The kill was torn to pieces and swallowed without chewing, as is the case with the alligator of today.

The amphibious Dinosaurs, which must have provided much of the food for Allosaurus and his kin, were characterized by blunt teeth and claws, strong, elephant-like legs and feet, long neck, and small head. They attained very great size, some of them, as we have said, being the largest of land animals. They may well be typified by Brontosaurus, the Thunder Lizard, which though not the longest, was one of the largest of his kind. The skeleton which is mounted in the American Museum is sixty-six feet long, the animal when alive having weighed about thirty-eight tons. The body was large and rather short; the neck long, and the head small. The tail was long and thick, and the legs massive and post-like. The bones of the legs were very long and heavy, the thigh bones being from five to six feet long--the largest single bones so far discovered. The vertebrae, or “backbones,” were as much as four and one-half feet high, being larger than those of the whale.

The teeth and general structure of Brontosaurus give fairly reliable evidence as to the habits of the animal. It spent its life in the shallow water of lagoons, feeding upon the succulent water plants. There is no evidence that it swam very much; probably its principal mode of progression was wading, with the immense body partly supported by the water. Perhaps the beast occasionally left the water for the purpose of laying eggs, as is shown in Knight’s oft-printed restoration. It appears, however, that Brontosaurus was not built for land travel; that his joints were so imperfectly formed that he could not have moved on land without tearing those of the leg to pieces. Dr. Matthew thinks that the species of this genus bore their young alive, as do certain modern reptiles, and therefore had no need to leave the swamps and bayous at any time during their lives.

Within the last few years there have come sketchy preliminary accounts of a mammoth find near Tendaguru, Africa, by an expedition sent out from Germany. They announce the discovery of a Dinosaur whose neck and fore limbs far exceeded those of Brontosaurus, although the hinder parts of the skeleton were relatively small. It appears that this giant, which the German savants appropriately named Gigantosaurus, is identical with the American form Brachiosaurus, whose fragmentary remains are on exhibit at the Field Museum of Chicago. It is, without question the largest known Dinosaur, so far as weight goes--a long-necked wading creature that lived much as did Brontosaurus but was capable of going into considerably deeper waters, quite beyond reach of the fierce carnivorous giants of the land.

Fig. 1--Diplodocus, the longest Dinosaur known.

Fig. 2--Brontosaurus, the giant that could not walk except in water, because of his great weight and feeble joints.]

The distinctive character of the third group of Dinosaurs is the possession of a horny beak or bill, much like that of modern birds. Indeed, there are many features in the anatomy of these reptiles that indicate their relationship to the birds, and it is probable that the remote ancestors of the two groups were very closely connected--perhaps identical. But the ancestral birds developed feathers and took to flying, while the ancestral beaked Dinosaurs (Predentates) specialized in the direction of land life, and in their later development became even more widely diversified in form than did their feathered relatives.

The beaked Dinosaurs lived entirely upon vegetable food. The best known of them, Triceratops or “He-of-the-three-horned-head,” looked more like a gigantic, long-tailed rhinoceros than a reptile. Above each eye was a long, sharp horn which extended forward; the bony cores which remain in the fossils are as much as thirty-three inches long, and during life the horny covering must have lengthened them by six inches to a foot. The horn above the nose was considerably shorter, yet would have compared favorably with that of many rhinoceroses.

“Standing before the skull of Triceratops,” says Dr. Lucas, “... one notices in front of each eye a thick guard of projecting bone, and while this must have interfered with vision directly ahead it must have also furnished protection for the eye. So long as Triceratops faced an adversary he must have been practically invulnerable, but as he was the largest animal of his time, upward of twenty-five feet in length, it is probable that his combats were mainly with those of his own kind and the subject of dispute some fair female upon whom two rival suitors had cast covetous eyes. What a sight it would have been to have seen two of these big brutes in mortal combat as they charged upon each other with all the impetus to be derived from ten tons of infuriate flesh! We may picture to ourselves horn clashing upon horn, or glancing from each bony shield until some skilful stroke or unlucky slip placed one combatant at the mercy of the other, and he went down before the blows of his adversary ‘as falls on Mount Alvernus a thunder-smitten oak?’”

Two Triceratops horns in the possession of the United States National Museum bear the marks of such an encounter as that described by Dr. Lucas, for one of them is broken about half way between the tip and the base, and the stump is healed and rounded over. Evidently their owner was not seriously injured in the fight, but lived to a ripe old age in spite of his infirmity.

Triceratops had a number of relatives, at least one of which is even more famous than himself. This is Stegosaurus, the great Armored Dinosaur that possessed the remarkable enlargement of the spinal cord. Like his three-horned relative, Stegosaurus was a land dweller that walked upon four legs. His head was very small, as were his fore limbs; his body was very large, and his tail long and powerful. Along his back ran two rows of bony plates, some of which were four inches thick at the base, and two and one-half feet high. The tail bore, near the tip, two pairs of spines which were almost as long as the back plates, and half again as thick. The hind limbs were long and straight, in marked contrast with the front ones, so that the creature when walking must have appeared to be in constant danger of turning a somersault.

Stegosaurus was a contemporary of Brontosaurus and the carnivorous Allosaurus. Like the former, he was a peaceful plant feeder, but unlike him, did not flee to the shallows in order to avoid his flesh-eating relatives. For this great armor, although undoubtedly developed in the interests of peace, was hardly designed with any consideration for the Hebrew creed of turning one cheek when the other is smitten. Stegosaurus was too brainless and to clumsy to go about seeking trouble, but to those creatures foolhardy enough to attack him he could offer stiff resistance. A few blows of the huge spiked tail, more powerful than the club of the mightiest ogre of mythology, would be quite enough for even such giants as Allosaurus. Stegosaurus, like the rhinoceros of modern Africa, probably went his way unharming and unharmed.

* * * * *

The Dinosaurs first appeared during the Triassic period when they roamed through the valleys of eastern North America in great numbers, leaving their footprints on the soft, fine mud of the valley flats. The succeeding period, the Jurassic, was their Golden Age--the age of Brontosaurus, Allosaurus, Stegosaurus, Diplodocus and other monsters. During the Comanchean and Cretaceous periods the larger Dinosaurs became extinct, and were supplanted by the smaller beaked forms, such as Triceratops. At the end of the Cretaceous period, which was also the end of the Age of Reptiles, the Dinosaurs became almost totally extinct. Perhaps a few of them survived in specially favored localities, for Dinosaur bones are found in rocks which a number of geologists refer to the beginning of the Age of Mammals. But such survivals were of small importance, and had little effect on the general annihilation. The Dinosaurs were unable to meet the demands of a dry-land environment, and joined the great hosts of creatures that at various times have held the earth in their sway and then, defeated by causes at which we can only guess, have passed into extinction.

FOOTNOTES:

The Mesozoic Era, or Age of Reptiles, is divided into four periods--Triassic, Jurassic, Comanchean, and Cretaceous. The first two are here referred to as the “early” part of the age; the third as the “middle,” and the fourth as the “late.”

The Eucalyptus is now common in Australia, while the Sequoia is the “Big Tree” of California.

Norton, Elements of Geology, 1st Ed., p. 378.

Dr. Matthew, curator of vertebrate paleontology at the American Museum of Natural History, is one of the authorities on Dinosaurs. His book, “Dinosaurs,” published by the Museum, has afforded much of the material to be found in this chapter.