Part 44

The English reader is chiefly indebted to the zeal and energy of Sir Woodbine Parish for the materials from which our naturalists have been enabled to re-construct the history of the Megatherium. The remains collected by him were found in the river Salado, which runs through the flat alluvial plains called Pampas to the south of the city of Buenos Ayres. A succession of three unusually dry seasons had lowered the waters to such a degree as to expose part of the pelvis to view, as the skeleton stood upright in the mud forming the bed of the river. Further inquiries led to the discovery of the remains of two other skeletons near the place where the first had been found; and with them an immense shell or carapace was met with, most of the bones associated with which crumbled to pieces on exposure to the air. The osseous structure of this enormous animal, as furnished by Mr. Clift, an eminent anatomist of the day, and under whose superintendence the skeleton was drawn, must have exceeded fourteen feet in length, and upwards of eight feet in height. The deeply shaded parts of the figure show the portions which are deficient in the Madrid skeleton.

Cuvier pointed out that the skull very much resembled that of the Sloths, but that the rest of the skeleton bore relationship, partly to the Sloths, and partly to the Anteaters.

The large bones, which descend from the zygomatic arch along the cheek-bones, would furnish a powerful means of attaching the motor muscles of the jaws. The anterior part of the muzzle is fully developed, and riddled with holes for the passage of the nerves and vessels which must have been there, not for a trunk, which would have been useless to an animal furnished with a very long neck, but for a snout analogous to that of the Tapir.

The jaw and dental apparatus cannot be exactly stated, because the number of teeth in the lower jaw is not known. The upper jaw, Professor Owen has shown, contained five molars on each side; and from comparison and analogy with the Scelidotherium it may be conjectured that the Megatherium had four on each side of the lower jaw. Being without incisors or canines, the structure of its eighteen molars proves that it was not carnivorous: they each resemble the composite molars of the Elephant.

The vertebræ of the neck (as exhibited in the foreshortened figure (Fig. 186), taken from the work of Pander and D’Alton, and showing nearly a front view of the head), as well as the anterior and posterior extremities of the Madrid skeleton, although powerful, are not to be compared in dimensions to those of the other extremity of the body; for the head seems to have been relatively light and defenceless. The lumbar vertebræ increase in a degree corresponding to the enormous enlargement of the pelvis and the posterior members. The vertebræ of the tail are enormous, as is seen in Fig. 187, which represents the bones of the pelvis and hind foot, discovered by Sir Woodbine Parish, and now in the Museum of the College of Surgeons. If we add to these osseous organs the muscles, tendons, and integuments which covered them, we must admit that the tail of the Megatherium could not be less than two feet in diameter. It is probable that, like the Armadillo, it employed the tail to assist in supporting the enormous weight of its body; it would also be a formidable defensive organ when employed, as is the case with the Pangolins and Crocodiles. The fore-feet would be about three feet long and one foot broad. They would form a powerful implement for excavating the earth, to the greatest depths at which the roots of vegetables penetrate. The fore-feet rested on the ground to their full length. Thus solidly supported by the two hind-feet and the tail, and in advance by one of the fore-feet, the animal could employ the fore-foot left at liberty in clearing away the earth, in digging up the roots of trees, or in tearing down the branches; the toes of the fore-feet were, for this purpose, furnished with large and powerful claws, which lie at an oblique angle relatively to the ground, much like the burrowing talons of the mole.

The solidity and size of the pelvis must have been enormous; its immense iliac bones are nearly at right angles with the vertebral column; their external edges are distant more than a yard and a half from each other when the animal is standing. The femur is three times the thickness of the thigh-bone of the Elephant, and the many peculiarities of structure in this bone appear to have been intended to give solidity to the whole frame, by means of its short and massive proportions. The two bones of the leg are, like the femur, short, thick, and solid; presenting proportions which we only meet with in the Armadilloes and Anteaters; burrowing animals with which, as we have said, its two extremities seem to connect it.

The anatomical organisation of these members denotes heavy, slow, and powerful locomotion, but solid and admirable combinations for supporting the weight of an enormous sedentary creature; a sort of excavating machine, slow of motion but of incalculable power for its own purposes. In short, the Megatherium exceeded in dimensions all existing Edentates. It had the head and shoulders of the Sloth, the feet and legs combined the characteristics of the Anteaters and Sloths, of enormous size, since it was at least twelve feet long when full grown, its feet armed with gigantic claws, and its tail at once a means of supporting its huge body and an instrument of defence. An animal built with such massive proportions could evidently neither creep nor run; its walk would be excessively slow. But what necessity was there for rapid movement in a being only occupied in burrowing under the earth, seeking for roots, and which would consequently rarely change its place? What need had it of agility to fly from its enemies, when it could overthrow the Crocodile with a sweep of its tail? Secure from the attacks of other animals, this robust herbivorous creature, of which Figure 188 is a restoration, must have lived peacefully and respected in the solitary pampas of America.

The immediate cause of the extinction of the Megatherium is, probably, to be found in causes which are still in operation in South America. The period between the years 1827 and 1830 is called the “gran seco,” or the great drought, in South America; and according to Darwin, the loss of cattle in the province of Buenos Ayres alone was calculated at 1,000,000 head. One proprietor at San Pedro, in the middle of the finest pasture-country, had lost 20,000 cattle previously to those years. “I was informed by an eyewitness,” he adds, “that the cattle, in herds of thousands, rushed into the Parana, and, being exhausted by hunger, they were unable to crawl up the muddy banks, and thus were drowned. The arm of the river which runs by San Pedro was so full of putrid carcases, that the master of a vessel told me that the smell rendered it quite impassable. All the small rivers became highly saline, and this caused the death of vast numbers in particular spots; for when an animal drinks of such water it does not recover. Azara describes the fury of the wild horses on a similar occasion: rushing into the marshes, those which arrived first being overwhelmed and crushed by those which followed.” The upright position in which the various specimens of Megatheria were found indicates some such cause of death; as if the ponderous animal, approaching the banks of the river, when shrunk within its banks, had been bogged in soft mud, sufficiently adhesive to hold it there till it perished.

“Journal of Researches,” &c., 2nd ed., p. 133. Charles Darwin.

Like the Megatherium, the Mylodon closely resembled the Sloth, and it belonged exclusively to the New World. Smaller than the Megatherium, it differed from it chiefly in the form of the teeth. These organs presented only molars with smooth surfaces, indicating that the animal fed on vegetables, probably the leaves and tender buds of trees. As the Mylodon presents at once hoofs and claws on each foot, it has been thought that it formed the link between the hoofed, or ungulated animals and the Edentates. Three species are known, which lived in the pampas of Buenos Ayres.

In consequence of some hints given by the illustrious Washington, Mr. Jefferson, one of his successors as President of the United States, discovered, in a cavern of Western Virginia, the bones of a species of gigantic Sloth, which he pronounced to be the remains of some carnivorous animal. They consisted of a femur, a humerus, an ulna, and three claws, with half a dozen other bones of the foot. These bones Mr. Jefferson believed to be analogous to those of the lion. Cuvier saw at once the true analogies of the animal. The bones were the remains of a species of gigantic Sloth; the complete skeleton of which was subsequently discovered in the Mississippi, in such a perfect state of preservation that the cartilages, still adhering to the bones, were not decomposed. Jefferson called this species the Megalonyx. It resembled in many respects the Sloth. Its size was that of the largest ox; the muzzle was pointed; the jaws were armed with cylindrical teeth; the anterior limbs much longer than the posterior; the articulation of the foot oblique to the leg; two great toes, short, and armed with long and very powerful claws; the index finger more slender, and armed also with a less powerful claw; the tail strong and solid: such were the salient points of the organisation of the Megalonyx, whose form was a little slighter than that of the Megatherium.

The country in which the Megatherium has been found is described by Mr. Darwin as belonging to the great Pampean formation, which consists partly of a reddish clay and in part of a highly calcareous marly rock. Near the coast there are some plains formed from the wreck of the upper plain, and from mud, gravel, and sand thrown up by the sea during the slow elevation of the land, as shown by the raised beds of recent shells. At Punta Alta there is a highly-interesting section of one of the later-formed little plains, in which many remains of these gigantic land-animals have been found. These were, says Mr. Darwin:--“First, parts of three heads and other bones of the Megatherium, the huge dimensions of which are expressed by its name. Secondly, the Megalonyx, a great allied animal. Thirdly, the Scelidotherium, also an allied animal, of which I obtained a nearly perfect skeleton: it must have been as large as a rhinoceros; in the structure of its head it comes, according to Professor Owen, nearest to the Cape Anteater, but in some other respects it approaches to the Armadilloes. Fourthly, the Mylodon Darwinii, a closely related genus, of little inferior size. Fifthly, another gigantic edental quadruped. Sixthly, a large animal with an osseous coat, in compartments, very like that of an armadillo. Seventhly, an extinct kind of horse. Eighthly, a tooth of a pachydermatous animal, probably the same with the Macrauchenia, a huge beast with a long neck like a camel. Lastly, the Toxodon, perhaps one of the strangest animals ever discovered; in size it equalled an Elephant or Megatherium, but the structure of its teeth, as Professor Owen states, proves indisputably that it was intimately related to the Gnawers, the order which, at the present day, includes most of the smallest quadrupeds; in many details it is allied to the pachydermata; judging from the position of its eyes, ears, and nostrils, it was probably aquatic, like the Dugong and Manatee, to which it is allied. How wonderfully are the different orders--at the present time so well separated--blended together in different points in the structure of the Toxodon!”

“Journal of Researches,” &c., by Charles Darwin, p. 81.

The remains on which our knowledge of the Scelidotherium is founded include the cranium, which is nearly entire, with the teeth and part of the os hyoides, seven cervical, eight dorsal, and five sacral vertebræ, both the scapulæ, and some other bones. The remains of the cranium indicate that its general form was an elongated slender compressed cone, beginning behind by a flattened vertical base, expanding slightly to the cheek-bone, and thence contracting to the anterior extremity. All these parts were discovered in their natural relative positions, indicating, as Mr. Darwin observes, that the gravelly formation in which they were discovered had not been disturbed since its deposition.

The lower jaw-bone of Mylodon, which Mr. Darwin discovered at the base of the cliff called Punta Alta, in Northern Patagonia, had the teeth entire on both sides; they are implanted in deep sockets, and only about one-sixth of the last molar projects above the alveolus, but the proportion of the exposed part increases gradually in the inner teeth (Fig. 191).

“The habits of life of these Megatheroid animals were a complete puzzle to naturalists, until Professor Owen solved the problem with remarkable ingenuity. The teeth indicate, by their simple structure, that these Megatheroid animals lived on vegetable food, and probably on the leaves and small twigs of trees; their ponderous forms and great strong curved claws seem so little adapted for locomotion, that some eminent naturalists have actually believed that, like the Sloths, to which they are intimately related, they subsisted by climbing back downwards, on trees, and feeding on the leaves. It was a bold, not to say preposterous idea to conceive even antediluvian trees with branches strong enough to bear animals as large as elephants. Professor Owen, with far more probability, believes that, instead of climbing on the trees, they pulled the branches down to them, and tore up the smaller ones by the roots, and so fed on the leaves. The colossal breadth and weight of their hinder quarters, which can hardly be imagined without having been seen, become, on this view, of obvious service instead of being an encumbrance; their apparent clumsiness disappears. With their great tails and their huge heels firmly fixed like a tripod in the ground, they could freely exert the full force of their most powerful arms and great claws. The Mylodon, moreover, was furnished with a long extensile tongue, like that of the giraffe, which by one of those beautiful provisions of Nature, thus reaches, with the aid of its long neck, its leafy food.”

“Journal of Researches,” &c., by Charles Darwin, 2nd ed., p. 81.

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Two gigantic birds seem to have lived in New Zealand during the Quaternary epoch. The Dinornis, which, if we may judge from the tibia, which is upwards of three feet long, and from its eggs, which are much larger than those of the Ostrich, must have been of most extraordinary size for a bird. In Fig. 192 an attempt is made to restore this fearfully great bird, the Dinornis. As to the Epiornis, its eggs only have been found.

On the opposite page (PLATE XXVIII.) an attempt is made to represent the appearance of Europe during the epoch we have under consideration. The Bear is seated at the mouth of its den--the cave (thus reminding us of the origin of its name of Ursus spelæus), where it gnaws the bones of the Elephant. Above the cavern the Hyæna spelæa looks out, with savage eye, for the moment when it will be prudent to dispute possession of these remains with its formidable rival. The great Wood-stag, with other great animals of the epoch, occupies the farthest shore of a small lake, where some small hills rise out of a valley crowned with the trees and shrubs of the period. Mountains, recently upheaved, rise on the distant horizon, covered with a mantle of frozen snow, reminding us that the glacial period is approaching, and has already begun to manifest itself.

All these fossil bones, belonging to the great Mammalia which we have been describing, are found in the Quaternary formation; but the most abundant of all are those of the Elephant and the Horse. The extreme profusion of the bones of the Mammoth, crowded into the more recently formed deposits of the globe, is only surpassed by the prodigious quantity of the bones of the Horse which are buried in the same beds. The singular abundance of the remains of these two animals proves that, during the Quaternary epoch, the earth gave nourishment to immense herds of the Horse and the Elephant. It is probable that from one pole to the other, from the equator to the two extremities of the axis of the globe, the earth must have formed a vast and boundless prairie, while an immense carpet of verdure covered its whole surface; and such abundant pastures would be absolutely necessary to sustain these prodigious numbers of herbivorous animals of great size.

The mind can scarcely realise the immense and verdant plains of this earlier world, animated by the presence of an infinity of such inhabitants. In its burning temperature, Pachyderms of monstrous forms, but of peaceful habits, traversed the tall vegetation, composed of grasses of all sorts. Deer of gigantic size, their heads ornamented with enormous horns, escorted the heavy herds of the Mammoth; while the Horse, small in size and compact of form, galloped and frisked round these magnificent horizons of verdure which no human eye had yet contemplated.

Nevertheless, all was not quiet and tranquil in the landscapes of the ancient world. Voracious and formidable carnivorous animals waged a bloody war on the inoffensive herds. The Tiger, the Lion, and the ferocious Hyæna; the Bear, and the Jackal, there selected their prey. On the opposite page an endeavour is made to represent the great animals among the Edentates which inhabited the American plains during the Quaternary epoch (PLATE XXIX). We observe there the Glyptodon, the Megatherium, the Mylodon, and, along with them, the Mastodon. A small Ape (the Orthopithecus), which first appeared in the Miocene period, occupies the branch of a tree in the landscape. The vegetation is that of tropical America at the present time.

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The deposits of this age, which are of later date than the Crag, and of earlier date than the Boulder Clay, with its fragments of rocks frequently transported from great distances, are classed under the term “pre-glacial.”

After the deposition of the Forest Bed, which is seen overlying the Crag for miles between high and low-water mark, on the shore west of Cromer, in Norfolk, there was a general reduction of temperature, and a period of intense cold, known as the “glacial period,” seems to have set in, during which a great part of what is now the British Islands was covered with a thick coating of ice, and probably united with the Continent.

At this time England south of the Bristol Channel (the estuary of the Severn), and the Thames, appears to have been above water. The northern part of the country, and the high-ground generally of Britain and Ireland were covered with gliding glaciers, by whose grinding action the whole surface became moulded and worn into its present shape, while the floating icebergs which broke off at the sea-side from these glaciers, conveyed away and dropped on the bed of the sea those fragments of rocks and the gravel and other earthy materials which are now generally recognised as glacial accumulations.

In all directions, however, proofs are being gradually obtained that, about this period, movements of submersion under the sea were in progress, all north of the Thames.