THE INHABITANTS
Any segment of land—the moon, for example—can be interesting of itself, but its greater significance must always lie in the life it sustains.
Toward dusk on a spring evening one hundred and thirty-six million years ago a small furry animal less than four inches long peered cautiously from low reeds which grew along the edge of a tropical lagoon that covered much of what was to be Colorado. It was looking across the surface of the water as if waiting for some creature to emerge from the depths, but nothing stirred.
From among the fern trees to the left there was movement, and for one brief instant the little animal looked in that direction. Shoving its way beneath the drooping branches and making considerable noise as it awkwardly approached the lagoon for a drink of water, came a medium-sized dinosaur, walking on two legs and twisting its short neck from side to side, as if on the watch for larger animals that might attack.
It was about three feet tall at the shoulders and not more than six feet in length. Obviously a land animal, it edged up to the water carefully, constantly jerking its short neck in probing motions. In paying so much attention to the possible dangers on land, it overlooked the real danger that waited in the water, for as it reached the lagoon and began lowering the forepart of its body so that it could drink, a fallen log which had lain inconspicuously half in the water, half out sprang into action.
It was a crocodile, well armored in heavy skin and possessed of powerful jaws lined with piercing teeth. It made a lunge at the drinking dinosaur, but it had moved too soon. Its well-calculated grab at the reptile’s right foreleg missed by a fraction, for the dinosaur managed to withdraw so speedily that the great snapping jaw closed not on the bony leg, as intended, but only upon the soft flesh covering it.
There was a ripping sound as the crocodile tore off a strip of flesh, and a sharp guttural click as the wounded dinosaur responded to the pain. Then peace returned. The dinosaur could be heard for some moments retreating. The disappointed crocodile swallowed the meager meal it had caught, then returned to its log-like camouflage, and the furry little animal returned to its earlier preoccupation of staring at the surface of the lagoon.
Its attention was poorly directed, for as it watched, it became aware, with a sense of terrible panic, of wings in the darkening sky, and at the very last moment of safety it threw itself behind the trunk of a ginkgo tree, flattened itself out, and held its breath as a large flying reptile swooped down, its gaping, sharp-toothed mouth open, and just missed its target.
Still flat against the moist earth, the little animal watched in terror as the huge reptile banked low over the lagoon and returned in what under other circumstances might have been a beautiful flight. This time it came straight at the crouching animal, but then, abruptly, had to swerve away because of the ginkgo roots. Dipping one wing, it turned gracefully in the air, then swooped down on another small creature hiding near the crocodile, unprotected by any tree.
Deftly the flying reptile snapped its beak and caught its prey, which uttered high shrieks as it was carried aloft. For some moments the little animal hiding in the ginkgo watched the flight of its enemy as the reptile dipped and swerved through the sky like a falling feather, finally vanishing with its catch.
The little watcher could breathe again. It was unlike the great reptiles, for they were cold-blooded and it was warm. They raised their babies from hatching eggs, while its came from the mother’s womb. It was a pantothere, one of the earliest mammals and progenitor of later types like the opossum, and it had scant protection in the swamp. Watching cautiously lest the flying hunter return, it ventured forth to renew its inspection of the lagoon, and after a pause, spotted what it had been looking for.
About ninety feet out into the water a small knob had appeared on the surface. It was only slightly larger than the watching animal itself, about six inches in diameter. It seemed to be floating on the surface, unattached to anything, but actually it was the unusual nose of an animal that had its nostrils on top of its head. The beast was resting on the bottom of the lagoon and breathing in this inventive manner.
Now, as the watching animal expected, the floating knob began slowly to emerge from the waters. It was attached to a head, not extraordinarily large but belonging obviously to an animal markedly bigger than either the first dinosaur or the crocodile. It was not a handsome head, nor graceful either, but what happened next displayed each of those attributes.
For the head continued to rise from the lagoon, higher and higher and higher in one long beautiful arch, until it stood twenty-five feet above the water, suspended at the end of a long and most graceful neck. It was like a ball extended endlessly upward on a frail length of wire, and when it was fully aloft, with no body visible to support it, the head turned this way and that in delicate motion, as if surveying the total world that lay below.
The small head and enormous neck remained in this position for some minutes, sweeping in lovely arcs of exploration. Apparently the small eyes which stood on either side of the projecting nose at the top of the skull were reassured by what they saw, for now a new kind of motion ensued.
From the surface of the lake an enormous construction began slowly to appear, an inch at a time, muddy waters falling from it as it rose. Slowly, slowly the thing in the lagoon came into view, until it disclosed a monstrous prism of dark flesh to which the prehensile neck was attached.
The body of the great reptile looked as if it were about twelve feet tall, but how far into the water it extended could not be discerned; it surely went very deep. Now, as the furry animal on shore watched, the massive body began to move, slowly and rhythmically. Where the neck joined the great dark bulk of the body, little waves broke and slid along the flanks of the beast. Water dripped from the upper part of the body as it moved ponderously through the swamp.
The reptile appeared to be swimming, its neck probing in sweeping arcs, but actually it was walking on the bottom, its huge legs hidden by water. And then, as it drew closer to shore and entered shallower water, there occurred a moment of marked grace and beauty. From the water trailing behind the animal, an enormous tail emerged. Longer than the neck and disposed in more delicate lines, it extended forty-four feet, swaying slightly on the surface of the lagoon. From head to tip of tail, the reptile measured eighty-seven feet.
Up to now it had looked like a long snake, floundering through the lagoon, but the truth was about to be revealed, for as the reptile advanced, the massive legs which had been supporting it became visible. They were enormous, four pillars of great solidity attached to the torso by joints of such crude construction that although the creature was amphibious, she could not easily support herself on dry land, where water did not buoy her up.
With slow, lumbering strides the reptile moved toward a clear river that emptied into the swamp, and now its total form was visible. Its head reared thirty-five feet; its shoulders were thirteen feet high; its tail dragged aft some fifty feet; it weighed nearly thirty tons.
It was diplodocus, not the largest of the dinosaurs and certainly not the most fearsome. This particular specimen was a female, seventy years old and in the prime of life. She lived exclusively on vegetation, which she now sought among the swamp waters. Moving her small head purposefully from one kind of plant to the next, she cropped off such food as she could find. This was not an easy task, for she had an extremely small mouth studded with minute peg-like front teeth and no back ones for chewing. It seems incomprehensible that with such trivial teeth she could crop enough food to nourish her enormous body, but she did. It was this problem of chewing that had brought her toward the shore, this and one other strange impetus that she could not yet identify. She attended first to the chewing.
After finishing with such plants as were at hand, she moved into the channel. The mammal, still crouching among the roots of the ginkgo tree, watched with satisfaction as she moved past. It had been afraid that she might plant one of her massive feet on its nest, as another dinosaur had
done, obliterating both the nest and its young. Indeed, diplodocus left underwater footprints so wide and so deep that fish used them as nests. One massive footprint might be many times as wide as the mammal was long.
And so diplodocus moved away from the lagoon and the apprehensive watcher. As she went she was one of the most totally lovely creatures so far seen on earth, a perfect poem of motion. Placing each foot carefully and without haste, and assuring herself that at least two were planted solidly on the bottom at all times, she moved like some animated mountain, keeping the main bulk of her body always at the same level, while her graceful neck swayed gently and her extremely long tail remained floating on the surface.
The various motions of her great body were always harmonious; even the plodding of the four gigantic feet had a captivating rhythm. But when the undulating grace of the long neck and the longer tail was added, this large reptile epitomized the beauty of the animal kingdom as it then existed.
She was looking for a stone. For some time she had instinctively known that she lacked a major stone, and this distressed her. She had become agitated about the missing stone and now proposed settling the matter. Keeping her head low, she scanned the bottom of the stream but found no suitable stones.
This forced her to move upstream, the delicate motion of her body conforming to the shifting bottom as it rose slightly before her. Now she came upon a wide selection of stones, but prudence warned her that they were too jagged for her purpose, and she ignored them. Once she stopped, turned a stone over with her blunt nose and scorned it. Too many cutting edges.
Her futile search made her irritable and she failed to notice the approach of a rather large land-based dinosaur that walked on two legs. He did not come close to approaching her in size, but he was quicker of motion, and had a large head, gaping mouth and a ferocious complement of jagged teeth. He was a meat-eater, always on the watch for the giant water-based dinosaurs who ventured too close to land. He was not large enough to tackle a huge animal like diplodocus if she was in her own element, but he had found that usually when the large reptiles came into the stream, there was something wrong with them, and twice he had been able to hack one down.
He approached diplodocus from the side, stepping gingerly on his two powerful hind feet, keeping his two small front feet ready like hands to grasp her should she prove to be in weakened condition. He was careful to keep clear of her tail, for this was her only weapon.
She remained unaware of her would-be attacker, and continued to probe the river bottom for the right stone. The carnivorous dinosaur interpreted her lowered head as a sign of weakness. He lunged at the spot where her vulnerable neck joined the torso, only to find that she was in no way incapacitated, for when she saw him coming she twisted adroitly, and presented the attacker with the broad and heavy side of her body. This repulsed him, and he stumbled back. As he did so, diplodocus stepped forward, and slowly swung her tail in a mighty arc, hitting him with such force that he was thrown off his feet and sent crashing into the brush.
One of his small front feet was broken by the blow and he uttered a series of awk-awks, deep in his throat, as he shuffled off. Diplodocus gave him no more attention and resumed her search for the right stone.
Finally she found what she wanted. It weighed about three pounds, was flattish on the ends and both smooth and rounded. She nudged it twice with her snout, satisfied herself that it was suited to her purposes, then lifted it in her mouth, raised her head to its full majestic height, swallowed the stone and allowed it to slide easily down her long neck into her gullet and from there into her grinding gizzard, where it joined six smaller stones that rubbed together gently and incessantly as she moved. This was how she chewed her food, the seven stones serving as substitutes for the molars she lacked.
With awkward yet attractive motions she adjusted herself to the new stone, and could feel it find its place among the others. She felt better all over and hunched her shoulders, then twisted her hips and flexed her long tail.
Night was closing in. The attack by the smaller dinosaur reminded her that she ought to be heading back toward the safety of the lagoon, back where fourteen other reptiles formed a protective herd, but she was kept in the river by a vague longing which she had experienced several times before, but which she could not remember clearly. She had, like all members of the diplodocus family, an extremely small brain, barely large enough to send signals to the various remote parts of her body. For example, to activate her tail became a major tactical problem, for any signal originating in her distant head required some time to reach the effective muscles of the tail. It was the same with the ponderous legs; they could not be called into instant action.
Her brain was too small and too undifferentiated to permit reasoning or memory; habit ingrained warned her of danger, and only the instinctive use of her tail protected her from the kind of assault she had just experienced. As for explaining in specific terms the gnawing agitation she now felt, and which had been the major reason for her leaving the safety of the herd, her small brain could give her no help.
She therefore walked with splashing grace toward a spot some distance upstream. How beautiful she was as she moved through the growing darkness! All parts of her great body seemed to relate to one central impulse, gently twisting neck stalwart central structure, slow-moving mighty legs and delicate tail extending almost endlessly behind and balancing the whole. It would require far more than a hundred million years of experiment before her equal would be seen again.
She was moving toward a white chalk cliff which she had known before. It stood some distance in from the lagoon, sixty feet higher than the river at its feet. Here, back eddies had formed a swamp, and as she approached this protected area diplodocus became aware of a sense of security. She hunched her shoulders again and adjusted her hips. Moving her long tail in graceful arcs, she tested the edge of the swamp with one massive forefoot. Liking what she felt, she moved slowly forward, sinking deeper and deeper into the dark waters until she was totally submerged, except for the knobby tip of her head which she left exposed so that she could breathe.
She did not fall asleep, as she should have done. The gnawing insatiety kept her awake, even though she could feel the new stone working on the foliage she had consumed that day and even though the buzzing of the day insects had ceased, indicating that night was at hand. She wanted to sleep but could not, so after some hours the tiny brain sent signals along the extended nerve systems and she pulled herself through the swamp with noisy sucking sounds. Soon she was back in the main channel, still hunting vaguely for something she could neither define nor locate. And so she spent the long tropical night.
Diplodocus was able to function as capably as she did for three reasons. When she was in the swamp at the foot of the cliff, an area that would have meant death for most animals, she was able to extricate herself because her massive feet had a curious property; although they made a footprint many inches across as. they flattened out in mud, they could, when it came time to withdraw them from the clinging muck, compress to the width of the foreleg; so that for diplodocus to pull her huge leg and foot from mud was as simple as pulling a reed from the muck at the edge of the swamp; there was nothing for the mud to cling to, and the leg pulled free with a swooshing sound.
Diplodocus, ‘double beams,’ was so named because sixteen of her tail vertebrae—twelve through twenty-seven behind the hips—were made with paired flanges to protect the great artery that ran along the underside of the tail. But the vertebrae had another channel topside, and it ran from the base of the head to the strongest segment of the tail. In this channel lay a powerful and very thick sinewy which was anchored securely at shoulder and hip and which could be activated from either position. Thus the long neck and the sweeping tail were the progenitors of the crane, which in later time would lift extremely heavy objects by the clever device of running a cable over a pulley and counterbalancing the whole. The pulley used by diplodocus was the channel made by the pair
ed flanges of the vertebrae; her cable was the powerful sinew of neck and tail; her counterbalance was the bulk of her torso, and all functioned with an almost divine simplicity. Had she had powerful teeth, her neck was so excellently balanced that she could have lifted into the air the dinosaur that attacked her in the way the claw of a well-designed crane can lift an object many times its own apparent weight. Without this advanced system of cable and pulley, diplodocus could have activated neither her neck nor her tail, and she could not have survived. With it, she was a sophisticated machine, as well adapted to her mode of life as any animal which might succeed her in generations to come.
The third advantage she had was remarkable, and raises questions as to how it could have developed. The powerful bones of her legs, which were under water most of the time, were of the most heavy construction, thus providing her with necessary ballast, but those that were higher in her body were of successively lighter bulk, not only in sheer weigh but also in actual bone composition, and this delicate construction buoyed up her body, permitting it almost to float.
That was not all. Many fenestrations, open spaces like windows. perforated the vertebrae of her neck and tail, thus reducing their weight. These intricate bones, with their channels top and bottom, were so exquisitely engineered that they can be compared only to the arches and windows of a Gothic cathedral. Bone was used only where it was required to handle stress. No shred was left behind to add its weight if it could be dispensed with, yet every arch required for stability was in place. The joints were articulated so perfectly that the long neck could twist in any direction, yet the flanges within which the sinews rode were so strong that they would not be damaged if a great burden was placed on neck or head.
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