Animals of the Past

VI

Our acquaintance with the Dinosaurs is comparatively recent, dating from the early part of the nineteenth century, and in America, at least, the date may be set at 1818, when the first Dinosaur remains were found in the Valley of the Connecticut, although they naturally were not recognized as such, nor had the term been devised. The first Dinosaur to be formally recognized as representing quite a new order of reptiles was the carnivorous Megalosaur, found near Oxford, England, in 1824.

For a long time our knowledge of Dinosaurs was very imperfect and literally fragmentary, depending mostly upon scattered teeth, isolated vertebræ, or fragments of bone picked up on the surface or casually encountered in some mine or quarry. Now, however, thanks mainly to the labors of American palæontologists, thanks also to the rich deposits of fossils in our Western States, we have an extensive knowledge of the Dinosaurs, of their size, structure, habits, and general appearance.

There are to-day no animals living that are closely related to them; none have lived for a long period of time, for the Dinosaurs came to an end in the Cretaceous, and it can only be said that the crocodiles, on the one hand, and the ostriches, on the other, are the nearest existing relatives of these great reptiles.

For, though so different in outward appearance, birds and reptiles are structurally quite closely allied, and the creeping snake and the bird on which it preys are relatives, although any intimate relationship between them is of the serpent's making, and is strongly objected to by the bird.

But if we compare the skeleton of a Dinosaur with that of an ostrich—a young one is preferable—and with those of the earlier birds, we shall find that many of the barriers now existing between reptiles and birds are broken down, and that they have many points in common. In fact, save in the matter of clothes, wherein birds differ from all other animals, the two great groups are not so very far apart.

The Dinosaurs were by no means confined to North America, although the western United States seem to have been their headquarters, but ranged pretty much over the world, for their remains have been found in every continent, even in far-off New Zealand.

In point of time they ranged from the Trias to the Upper Cretaceous, their golden age, marking the culminating point of reptilian life, being in the Jurassic, when huge forms stalked by the sea-shore, browsed amid the swamps, or disported themselves along the reedy margins of lakes and rivers.

They had their day, a day of many thousand years, and then passed away, giving place to the superior race of mammals which was just springing into being when the huge Dinosaurs were in the heyday of their existence.

And it does seem as if in the dim and distant past, as in the present, brains were a potent factor in the struggle for supremacy; for, though these reptiles were giants in size, dominating the earth through mere brute force, they were dwarfs in intellect.

The smallest human brain that is thought to be compatible with life itself weighs a little over ten ounces, the smallest that can exist with reasoning powers is two pounds; this in a creature weighing from 120 to 150 pounds.

What do we find among Dinosaurs? Thespesius, or Claosaurus, which may have walked where Baltimore now stands, was twenty-five feet in length and stood a dozen feet high in his bare feet, had a brain smaller than a man's clenched fist, weighing less than one pound.

Brontosaurus, in some respects the biggest brute that ever walked, was but little better off, and Triceratops, and his relatives, creatures having twice the bulk of an elephant, weighing probably over ten tons, possessed a brain weighing not over two pounds!

How much of what we term intelligence could such a creature possess—what was the extent of its reasoning powers? Judging from our own standpoint and the small amount of intellect apparent in some humans with much larger brains, these big reptiles must have known just about enough to have eaten when they were hungry, anything more was superfluous.

However, intelligence is one thing, life another, and the spinal cord, with its supply of nerve-substance, doubtless looked after the mere mechanical functions of life; and while even the spinal cord is in many cases quite small, in some places, particularly in the sacral region, it is subject to considerable enlargement. This is notably true of Stegosaurus, where the sacral enlargement is twenty times the bulk of the puny brain—a fact noted by Professor Marsh, and seized upon by the newspapers, which announced that he had discovered a Dinosaur with a brain in its pelvis.

In their great variety of size and shape the Dinosaurs form an interesting parallel with the Marsupials of Australia. For just as these are, as it were, an epitome of the class of mammals, mimicking the herbivores, carnivores, rodents and even monkeys, so there are carnivorous and herbivorous Dinosaurs—Dinosaurs that dwelt on land and others that habitually resided in the water, those that walked upright and those that crawled about on all fours; and, while there are no hints that any possessed the power of flight, some members of the group are very bird-like in form and structure, so much so that it has been thought that the two may have had a common ancestry.

The smallest of the Dinosaurs whose acquaintance we have made were little larger than chickens; the largest claim the distinction of being the largest known quadrupeds that have walked the face of the earth, the giants not only of their day, but of all time, before whose huge frames the bones of the Mammoth, that familiar byword for all things great, seem slight.

Fig. 19—A Hind Leg of the Great Brontosaurus, the Largest of the Dinosaurs.

For Brontosaurus, the Thunder Lizard, beneath whose mighty tread the earth shook, and his kindred were from 40 to 60 feet long and 10 to 14 feet high, their thigh bones measuring 5 to 6 feet in length, being the largest single bones known to us, while some of the vertebræ were 4-1/2 feet high, exceeding in dimensions those of a whale.

The group to which Brontosaurus belongs, including Diplodocus and Morosaurus, is distinguished by a large, though rather short, body, very long neck and tail, and, for the size of the animal, a very small head. In fact, the head was so small and, in the case of Diplodocus, so poorly provided with teeth that it must have been quite a task, or a long-continued pleasure, according to the state of its digestive apparatus, for the animal to have eaten its daily meal.

Fig. 20.—A Single Vertebra of Brontosaurus.

An elephant weighing 5 tons eats 100 pounds of hay and 25 pounds of grain for his day's ration; but, as this food is in a comparatively concentrated form, it would require at least twice this weight of green fodder.

It is a difficult matter to estimate the weight of a live Diplodocus or a Brontosaurus, but it is pretty safe to say that it would not be far from 20 tons, and that one would devour at the very least something over 700 pounds of leaves or twigs or plants each day—more, if the animal felt really hungry.

But here we must, even if reluctantly, curb our imagination a little and consider another point: the cold-blooded, sluggish reptiles, as we know them to-day, do not waste their energies in rapid movements, or in keeping the temperature of their bodies above that of the air, and so by no means require the amount of food needed by more active, warm-blooded animals. Alligators, turtles, and snakes will go for weeks, even months, without food, and while this applies more particularly to those that dwell in temperate climes and during their winter hibernation practically suspend the functions of digestion and respiration, it is more or less true of all reptiles. And as there is little reason for supposing that reptiles behaved in the past any differently from what they do in the present, these great Dinosaurs may, after all, not have been gifted with such ravenous appetites as one might fancy. Still, it is dangerous to lay down any hard and fast laws concerning animals, and he who writes about them is continually obliged to qualify his remarks—in sporting parlance, to hedge a little, and in the present instance there is some reason, based on the arrangement of vertebræ and ribs, to suppose that the lungs of Dinosaurs were somewhat like those of birds, and that, as a corollary, their blood may have been better aërated and warmer than that of living reptiles. But, to return to the question of food.

From the peculiar character of the articulations of the limb-bones, it is inferred that these animals were largely aquatic in their habits, and fed on some abundant species of water plants. One can readily see the advantage of the long neck in browsing off the vegetation on the bottom of shallow lakes, while the animal was submerged, or in rearing the head aloft to scan the surrounding shores for the approach of an enemy. Or, with the tail as a counterpoise, the entire body could be reared out of water and the head be raised some thirty feet in the air.

Triceratops, he of the three-horned face, had a remarkable skull which projected backward over the neck, like a fireman's helmet, or a sunbonnet worn hind side before, while over each eye was a massive horn directed forward, a third, but much smaller horn being sometimes present on the nose.

The little "Horned Toad," which isn't a toad at all, is the nearest suggestion we have to-day of Triceratops; but, could he realize the ambition of the frog in the fable and swell himself to the dimensions of an ox, he would even then be but a pigmy compared with his ancient and distant relative.

So far as mere appearance goes he would compare very well, for while so much is said about the strange appearance of the Dinosaurs, it is to be borne in mind that their peculiarities are enhanced by their size, and that there are many lizards of to-day that lack only stature to be even more bizarre; and, for example, were the Australian Moloch but big enough, he could give even Stegosaurus "points" in more ways than one.

Standing before the skull of Triceratops, looking him squarely in the face, 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."

A pair of Triceratops horns in the National Museum bears witness to such encounters, for one is broken midway between tip and base; and that it was broken during life is evident from the fact that the stump is healed and rounded over, while the size of the horns shows that their owner reached a ripe old age.

For, unlike man and the higher vertebrates, reptiles and fishes do not have a maximum standard of size which is soon reached and rarely exceeded, but continue to grow throughout life, so that the size of a turtle, a crocodile, or a Dinosaur tells something of the duration of its life.

Before quitting Triceratops let us glance for a moment at its skeleton. Now among other things a skeleton is the solution of a problem in mechanics, and in Triceratops the head so dominates the rest of the structure that one might almost imagine the skull was made first and the body adjusted to it. The great head seems made not only for offence and defence; the spreading frill serves for the attachment of muscles to sustain the weight of the skull, while the work of the muscles is made easier by the fact that the frill reaches so far back of the junction of head with neck as to largely counterbalance the weight of the face and jaws. When we restored the skull of this animal it was found that the centre of gravity lay back of the eye. Several of the bones of the neck are united in one mass to furnish a firm attachment for the muscles that support and move the skull, but as the movements of the neck are already restricted by the overhanging frill, this loss of motion is no additional disadvantage.

To support all this weight of skull and body requires very massive legs, and as the fore legs are very short, this enables Triceratops to browse comfortably from the ground by merely lowering the front of the head.

These forms we have been considering were the giants of the group, but a commoner species, Thespesius, though less in bulk than those just mentioned, was still of goodly proportions, for, as he stalked about, the top of his head was twelve feet from the ground.

Thespesius and his kin seem to have been comparatively abundant, for they have a wide distribution, and many specimens, some almost perfect, have been discovered in this country and abroad. No less than twenty-nine Iguanodons, a European relative of Thespesius, were found in one spot in mining for coal at Bernissart, Belgium. Here, during long years of Cretaceous time, a river slowly cut its way through the coal-bearing strata to a depth of 750 feet, a depth almost twice as great as the deepest part of the gorge of Niagara, and then, this being accomplished, began the work of filling up the valley it had excavated.

It was then a sluggish stream with marshy borders, a stream subject to frequent floods, when the water, turbid with mud and laden with sand, overflowed its banks, leaving them, as the waters subsided, covered thickly with mud. Here, amidst the luxuriant vegetation of a semi-tropical climate, lived and died the Iguanodons, and here the pick of the miner rescued them from their long entombment to form part of the treasures of the museum at Brussels.

Like other reptiles, living and extinct, Thespesius was continually renewing his teeth, so that as fast as one tooth was worn out it was replaced by another, a point wherein Thespesius had a decided advantage over ourselves. On the other hand, as there was a reserve supply of something like 400 teeth in the lower jaw alone, what an opportunity for the toothache!

And then we have a multitude of lesser Dinosaurs, including the active, predatory species with sharp claws and double-edged teeth. Megalosaurus, the first of the Dinosaurs to be really known, was one of these carnivorous species, and from our West comes a near relative, Ceratosaurus, the nose-horned lizard, a queer beast with tiny fore legs, powerful, sharp-clawed hind feet, and well-armed jaws. A most formidable foe he seems, the more that the hollow bones speak of active movements, and Professor Cope pictured him, or a near relative, vigorously engaged in combat with his fellows, or preying upon the huge but helpless herbivores of the marshes, leaping, biting, and tearing his enemy to pieces with tooth and claw.

Professor Osborn, on the other hand, is inclined to consider him as a reptilian hyena, feeding upon carrion, although one can but feel that such an armament is not entirely in the interests of peace.

Last, but by no means least, are the Stegosaurs, or plated lizards, for not only were they beasts of goodly size, but they were among the most singular of all known animals, singular even for Dinosaurs. They had diminutive heads, small fore legs, long tails armed on either side near the tip, with two pairs of large spines, while from these spines to the neck ran series of large, but thin, and sharp-edged plates standing on edge, so that their backs looked like the bottom of a boat provided with a number of little centreboards. Just how these plates were arranged is not decided beyond a peradventure, but while originally figured as having them in a single series down the back it seems much more probable that they formed parallel rows.

The largest of these plates were two feet in height and length, and not more than an inch thick, except at the base, where they were enlarged and roughened to give a firm hold to the thick skin in which they were imbedded. Be it remembered, too, that these plates and spines were doubtless covered with horn, so that they were even longer in life than as we now see them. The tail spines varied in length, according to the species, from eight or nine inches to nearly three feet, and some of them have a diameter of six inches at the base. They were swung by a tail eight to ten feet long, and as a visitor was heard to remark, one wouldn't like to be about such an animal in fly time.

Such were some of the strange and mighty animals that once roamed this continent from the valley of the Connecticut, where they literally left their footprints on the sands of time, to the Rocky Mountains, where the ancient lakes and rivers became cemeteries for the entombment of their bones.

The labor of the collector has gathered their fossil remains from many a Western canyon, the skill of the preparator has removed them from their stony sepulchres and the study of the anatomist has restored them as they were in life.

REFERENCES.

Most of our large museums have on exhibition fine specimens of many Dinosaurs, comprising skulls, limbs, and large portions of their skeletons. The American Museum of Natural History, New York, has the largest and finest display. The first actual skeleton of a Dinosaur to be mounted in this country was the splendid Claosaurus at the Yale University Museum, where other striking pieces are also to be seen. The mounting of this Claosaurus, which is 29 feet long and 13 feet high, took an entire year. The United States National Museum is particularly rich in examples of the great, horned Triceratops, while the Carnegie Museum, Pittsburgh, has the best Diplodocus. The Field Columbian Museum and the Universities of Wyoming and Colorado all have good collections.

The largest single bone of a Dinosaur is the thigh bone of a Brontosaurus in the Field Columbian Museum, this measuring 6 feet 8 inches in length. The height of a complete hind leg in the American Museum of Natural History is 10 feet, while a single claw measures 6 by 9 inches. The skeleton of Triceratops restored in papier-maché for the Pan-American Exposition measured 25 feet from tip of nose to end of tail and was 10 feet 6 inches to the top of the backbone over the hips, this being the highest point. The head in the United States National Museum used as a model is 5 feet 6 inches long in a straight line and 4 feet 3 inches across the frill. There is a skull in the Yale University Museum even larger than this.

Articles relating to Dinosaurs are mostly technical in their nature and scattered through various scientific journals. The most accessible probably is "The Dinosaurs of North America," by Professor O. C. Marsh, published as part of the sixteenth annual report of the United States Geological Survey. This contains many figures of the skulls, bones, and entire skeletons of many Dinosaurs.

VII

There was a time, not so very long ago, when fossils were looked upon as mere sports of Nature, and little attention paid to them; later their true nature was recognized, though they were merely gathered haphazard as occasion might offer. But now, and for many years past, the fossil-bearing rocks of many parts of the world have been systematically worked, and from the material thus obtained we have acquired a great deal of information regarding the inhabitants of the ancient world. This is particularly true of our own western country, where a vast amount of collecting has been done, although very much remains to be done in the matter of perfecting this knowledge, and hosts of new animals remain to be discovered. For this information we are almost as much indebted to the collector who has gathered the needed material, and the preparator whose patience and skill have made it available for study, as to the palæontologist who has interpreted the meaning of the bones.

To collect successfully demands not only a knowledge of the rocks in which fossils occur and of the localities where they are best exposed to view, but an eye quick to detect a piece of bone protruding from a rock or lying amongst the shale, and, above all, the ability to work a deposit to advantage after it has been found. The collector of living animals hies to regions where there is plenty for bird and beast to eat and drink, but the collector of extinct animals cares little for what is on the surface of the earth; his great desire is to see as much as possible of what may lie beneath. So the prospector in search of fossils betakes himself to some region where the ceaseless warfare waged by water against the dry land has seamed the face of the earth with countless gullies and canyons, or carved it into slopes and bluffs in which the edges of the bone-bearing strata are exposed to view, and along these he skirts, ever on the look-out for some projecting bit of bone. The country is an almost shadeless desert, burning hot by day, uncomfortably cool at night. Water is scarce, and when it can be found, often has little to commend it save wetness; but the collector is buoyed up through all this with the hope that he may discover some creature new to science that shall not only be bigger and uglier and stranger than any heretofore found, but shall be the long-sought form needed for the solution of some difficult problem in the history of the past.

Now collecting is a lottery, differing from most lotteries, however, in that while some of the returns may be pretty small, there are few absolute blanks and some remarkably large prizes, and every collector hopes that it may fall to his lot to win one of these, and is willing to work long and arduously for the chance of obtaining it.

It may give some idea of the chances to say that some years ago Dr. Wortman spent almost an entire season in the field without success, and then, at the eleventh hour, found the now famous skeleton of Phenacodus, or that a party from Princeton actually camped within 100 yards of a rich deposit of rare fossils and yet failed to discover it.

Let us, however, suppose that the reconnaissance has been successful, and that an outcrop of bone has been found, serving like a tombstone carven with strange characters to indicate the burial-place of some primeval monster. Possibly Nature long ago rifled the grave, washing away much of the skeleton, and leaving little save the fragments visible on the surface; on the other hand, these pieces may form part of a complete skeleton, and there is no way to decide this important question save by actual excavation. The manner of disinterment varies, but much depends on whether the fossil lies in comparatively loose shale or is imbedded in the solid rock, whether the strata are level or dip downward into the hillside. If, unfortunately, this last is the case, it necessitates a careful shoring up of the excavation with props of cotton-wood or such boards as may have been brought along to box specimens, or it may even be necessary to run a short tunnel in order to get at some coveted bone. Should the specimen lie in shale, as is the case with most of the large reptiles that have been collected, much of that work may be done with pick and shovel; but if it is desirable or necessary to work in firm rock, drills and hammers, wedges, even powder, may be needed to rend from Nature her long-kept secrets. In any event, a detailed plan is made of the excavation, and each piece of bone or section of rock duly recorded therein by letter and number, so that later on the relation of the parts to one another may be known, or the various sections assembled in the work-room exactly as they lay in the quarry. Bones which lie in loose rock are often, one might say usually, more or less broken, and when a bone three, four, or even six feet long, weighing anywhere from 100 to 1,000 pounds, has been shattered to fragments the problem of removing it is no easy one. But here the skill of the collector comes into play to treat the fossil as a surgeon treats a fractured limb, to cover it with plaster bandages, and brace it with splints of wood or iron so that the specimen may not only be taken from the ground but endure in safety the coming journey of a thousand or more miles. For simpler cases or lighter objects strips of sacking, or even paper, applied with flour and water, suffice, or pieces of sacking soaked in thin plaster may be laid over the bone, first covering it with thin paper in order that the plaster jacket may simply stiffen and not adhere to it. Collecting has not always been carried on in this systematic manner, for the development of the present methods has been the result of years of experience; formerly there was a mere skimming-over of the surface in what Professor Marsh used to term the potato-gathering style, but now the effort is made to remove specimens intact, often imbedded in large masses of rock, in order that all parts may be preserved.

We will take it for granted that our specimens have safely passed through all perils by land and water, road and rail; that they have been quarried, boxed, carted over a roadless country to the nearest railway, and have withstood 2,000 miles of jolting in a freight-car. The first step in reconstruction has been taken; the problem, now that the boxes are reposing on the work-room floor, is to make the blocks of stone give up the secrets they have guarded for ages, to free the bones from their enveloping matrix in order that they may tell us something of the life of the past. The method of doing this varies with the conditions under which the material has been gathered, and if from hard clay, chalk, or shale, the process, though tedious enough at best, is by no means so difficult as if the specimens are imbedded in solid rock. In this case the fragments from a given section of quarry must be assembled according to the plan which has been carefully made as the work of exhumation progressed, all pieces containing bone must be stuck together, and weak parts strengthened with gum or glue. Now the mass is attacked with hammer and chisel, and the surrounding matrix slowly and carefully cut away until the contained bone is revealed, a process much simpler and more expeditious in the telling than in the actuality; for the preparator may not use the heavy tools of the ordinary stone-cutter: sometimes an awl, or even a glover's needle, must suffice him, and the chips cut off are so small and such care must be taken not to injure the bone that the work is really tedious. This may, perhaps, be better appreciated by saying that to clean a single vertebra of such a huge Dinosaur as Diplodocus may require a month of continuous labor, and that a score of these big and complicated bones, besides others of simpler structure, are included in the backbone. The finished specimen weighs over 120 pounds, while as originally collected, with all the adherent rock, the weight was twice or thrice as great. Such a mass as this is comparatively small, and sometimes huge blocks are taken containing entire skulls or a number of bones, and not infrequently weighing a ton. The largest single specimen is a skull of Triceratops, collected by Mr. J. B. Hatcher, which weighed, when boxed, 3,650 pounds.

Or, as the result of some mishap, or through the work of an inexperienced collector, a valuable specimen may arrive in the shape of a box full of irregular fragments of stone compared with which a dissected map or an old-fashioned Chinese puzzle is simplicity itself, and one may spend hours looking for some piece whose proper location gives the clew to an entire section, and days, even, may be consumed before the task is completed. While this not only tries the patience, but the eyes as well, there is, nevertheless, a fascination about this work of fashioning a bone out of scores, possibly hundreds, of fragments, and watching the irregular bits of stone shaping themselves into a mosaic that forms a portion of some creature, possibly quite new to science, and destined to bear a name as long as itself. And thus, after many days of toil, the bone that millions of years before sank into the mud of some old lake-bottom or was buried in the sandy shoals of an ancient river, is brought to light once more to help tell the tale of the creatures of the past.

One bone might convey a great deal of information; on the other hand it might reveal very little; for, while it is very painful to say so, the popular impression that it is possible to reconstruct an animal from a single bone, or tell its size and habits from a tooth is but partially correct, and sometimes "the eminent scientist" has come to grief even with a great many bones at his disposal. Did not one of the ablest anatomists describe and figure the hip-bones of a Dinosaur as its shoulder-blade, and another, equally able, reconstruct a reptile "hind side before," placing the head on the tail! This certainly sounds absurd enough; but just as absurd mistakes are made by men in other walks of life, often with far more deplorable results.

Before passing to the restoration of the exterior of animals it may be well to say something of the manner in which the skeleton of an extinct animal may be reconstructed and the meaning of its various parts interpreted. For the adjustment of the muscles is dependent on the structure of the skeleton, and putting on the muscles means blocking out the form, details of external appearance being supplied by the skin and its accessories of hair, scales, or horns. Let us suppose in the present instance that we are dealing with one of the great reptiles known as Triceratops whose remains are among the treasures of the National Museum at Washington, for the reconstruction of the big beast well illustrates the methods of the palæontologist and also the troubles by which he is beset. Moreover, this is not a purely imaginary case, but one that is very real, for the skeleton of this animal which was shown at Buffalo was restored in papier-maché in exactly the manner indicated. We have a goodly number of bones, but by no means an entire skeleton, and yet we wish to complete the skeleton and incidentally to form some idea of the creature's habits. Now we can interpret the past only by a knowledge of the present, and it is by carefully studying the skeletons of the animals of to-day that we can learn to read the meaning of the symbols of bones left by the animals of a million yesterdays. Thus we find that certain characters distinguish the bone of a mammal from that of a bird, a reptile, or a fish, and these in turn from one another, and this constitutes the A B C of comparative anatomy. And, in a like manner, the bones of the various divisions of these main groups have to a greater or less extent their own distinguishing characteristics, so that by first comparing the bones of extinct animals with those of creatures that are now living we are enabled to recognize their nearest existing relative, and then by comparing them with one another we learn the relations they bore in the ancient world. But it must be borne in mind that some of the early beasts were so very different from those of to-day that until pretty much their entire structure was known there was nothing with which to compare odd bones. Had but a single incomplete specimen of Triceratops come to light we should be very much in the dark concerning him; and although remains of some thirty individuals have been discovered, these have been so imperfect that we are very far from having all the information we need. A great part of the head, with its formidable looking horns, is present, and although the nose is gone, we know from other specimens that it, too, was armed with a knob, or horn, and that the skull ended in a beak, something like that of a snapping turtle, though formed by a separate and extra bone; similarly the end of the lower jaw is lacking, but we may be pretty certain that it ended in a beak, to match that of the skull. The large leg-bones of our specimen are mostly represented, for these being among the more solid parts of the skeleton are more frequently preserved than any others, and though some are from one side and some from another, this matters not. If the hind legs were disproportionately long it would indicate that our animal often or habitually walked erect, but as there is only difference enough between the fore and hind limbs to enable Triceratops to browse comfortably from the ground we would naturally place him on all fours, even were the skull not so large as to make the creature too top-heavy for any other mode of locomotion. Were the limbs very small in comparison with the other bones, it would obviously mean that their owner passed his life in the water. For a skeleton has a twofold meaning, it is the best, the most enduring, testimony we have as to an animal's place in nature and the relationships it sustains to the creatures that lived with it, before it, and after it. More than this, a skeleton is the solution of a problem in mechanics, the problem of carrying a given weight and of adaptation to a given mode of life. Thus the skeleton varies according as a creature dwells on land, in the water, or in the air, and according as it feeds on grass or preys upon its fellows.

And so the mechanics of a skeleton afford us a clew to the habits of the living animal. Something, too, may be gathered from the structure of the leg-bones, for solid bones mean either a sluggish animal or a creature of more or less aquatic habits, while hollow bones emphatically declare a land animal, and an active one at that; and this, in the case of the Dinosaurs, hints at predatory habits, the ability to catch and eat their defenceless and more sluggish brethren. A claw, or, better yet, a tooth, may confirm or refute this hint; for a blunt claw could not be used in tearing prey limb from limb, nor would a double-edged tooth, made for rending flesh, serve for champing grass.

But few bones of the feet, and especially the fore feet, are present, these smaller parts of the skeleton having been washed away before the ponderous frame was buried in the sand, and the best that can be done is to follow the law of probabilities and put three toes on the hind foot and five on the fore, two of these last without claws. The single blunt round claw among our bones shows, as do the teeth, that Triceratops was herbivorous; it also pointed a little downward, and this tells that in the living animal the sole of the foot was a thick, soft pad, somewhat as it is in the elephant and rhinoceros, and that the toes were not entirely free from one another. There are less than a dozen vertebræ and still fewer ribs, besides half a barrelful of pieces, from which to reconstruct a backbone twenty feet long. That the ribs are part from one side and part from another matters no more than it did in the case of the leg-bones; but the backbone presents a more difficult problem, since the pieces are not like so many checkers—all made after one pattern—but each has an individuality of its own. The total number of vertebræ must be guessed at (perhaps it would sound better to say estimated, but it really means the same), and knowing that some sections are from the front part of the vertebral column and some from the back, we must fill in the gaps as best we may. The ribs offer a little aid in this task, giving certain details of the vertebræ, while those in turn tell something about the adjoining parts of the ribs. We finish our Triceratops with a tail of moderate length, as indicated by the rapid taper of the few vertebræ available, and from these we gather, too, that in life the tail was round, and not flattened, and that it neither served for swimming nor for a balancing pole. And so, little by little, have been pieced together the fragments from which we have derived our knowledge of the past, and thus has the palæontologist read the riddles of the rocks.

To make these dry bones live again, to clothe them with flesh and reconstruct the creature as he was or may have been in life, is, to be honest, very largely guesswork, though to make a guess that shall come anywhere near the mark not only demands a thorough knowledge of anatomy—for the basis of all restoration must be the skeleton—but calls for more than a passing acquaintance with the external appearance of living animals. And while there is nothing in the bones to tell how an animal is, or was, clad, they will at least show to what group the creature belonged, and, that known, there are certain probabilities in the case. A bird, for example, would certainly be clad in feathers. Going a little farther, we might be pretty sure that the feathers of a water-fowl would be thick and close; those of strictly terrestrial birds, such as the ostrich and other flightless forms, lax and long. These as general propositions; of course, in special cases, one might easily come to grief, as in dealing with birds like penguins, which are particularly adapted for an aquatic life, and have the feathers highly modified. These birds depend upon their fat, and not on their feathers, for warmth, and so their feathers have become a sort of cross between scales and hairs. Hair and fur belong to mammals only, although these creatures show much variety in their outer covering. The thoroughly marine whales have discarded furs and adopted a smooth and slippery skin,[9] well adapted to movement through the water, relying for warmth on a thick undershirt of blubber. The earless seals that pass much of their time on the ice have just enough hair to keep them from absolute contact with it, warmth again being provided for by blubber. The fur seals, which for several months in the year dwell largely on land, have a coat of fur and hair, although warmth is mostly furnished, or rather kept in, by fat.

No reptile, therefore, would be covered with feathers, neither, judging from those we know to-day, would they be clad in fur or hair; but, such coverings being barred out, there remain a great variety of plates and scales to choose from. Folds and frills, crests and dewlaps, like beauty, are but skin deep, and, being thus superficial, ordinarily leave no trace of their former presence, and in respect to them the reconstructor must trust to his imagination, with the law of probabilities as a check rein to his fancy. This law would tell us that such ornaments must not be so placed as to be in the way, and that while there would be a possibility—one might even say probability—of the great, short-headed, iguana-like Dinosaurs having dewlaps, that there would be no great likelihood of their possessing ruffs such as that of the Australian Chlamydosaurus (mantled lizard) to flap about their ears. Even Stegosaurus, with his bizarre array of great plates and spines, kept them on his back, out of the way. Such festal ornamentation would, however, more likely be found in small, active creatures, the larger beasts contenting themselves with plates and folds.

Spines and plates usually leave some trace of their existence, for they consist of a super-structure of skin or horn, built on a foundation of bone; and while even horn decomposes too quickly to "petrify," the bone will become fossilized and changed into enduring stone. But while this affords a pretty sure guide to the general shape of the investing horn, it does not give all the details, and there may have been ridges and furrows and sculpturing that we know not of.

Knowing, then, what the probabilities are, we have some guide to the character of the covering that should be placed on an animal, and if we may not be sure as to what should be done, we may be pretty certain what should not.

For example, to depict a Dinosaur with smooth, rubbery hide walking about on dry land would be to violate the probabilities, for only such exclusively aquatic creatures as the whales among mammals, and the salamanders among batrachians, are clothed in smooth, shiny skin. There might, however, be reason to suspect that a creature largely aquatic in its habits did occasionally venture on land, as, for instance, when vertebræ that seem illy adapted for carrying the weight of a land animal are found in company with huge limb-bones and massive feet we may feel reasonably certain that their owner passed at least a portion of his time on terra firma.

So much for the probabilities as to the covering of animals known to us only by their fossil remains; but it is often possible to go beyond this, and to state certainly how they were clad. For while the chances are small that any trace of the covering of an extinct animal, other than bony plates, will be preserved, Nature does now and then seem to have relented, and occasionally some animal settled to rest where it was so quickly and quietly covered with fine mud that the impression of small scales, feathers, or even smooth skin, was preserved; curiously enough, there seems to be scarcely any record of the imprint of hair. Then, too, it is to be remembered that while the chances were very much against such preservation, in the thousands or millions of times creatures died the millionth chance might come uppermost.

Silhouettes of those marine reptiles, the Ichthyosaurs, have been found, probably made by the slow carbonization of animal matter, showing not only the form of the body and tail, but revealing the existence of an unsuspected back fin. And yet these animals were apparently clad in a skin as thin and smooth as that of a whale. Impressions of feathers were known long before the discovery of Archæopteryx; a few have been found in the Green River and Florissant shales of Wyoming, and a Hesperornis in the collection of the State University of Kansas shows traces of the existence of long, soft feathers on the legs and very clear imprints of the scales and reticulated skin that covered the tarsus. From the Chalk of Kansas, too, came the example of Tylosaur, showing that the back of this animal was decorated with the crest shown in Mr. Knight's restoration, one not unlike that of the modern iguana. From the Laramie sandstone of Montana Mr. Hatcher and Mr. Butler have obtained the impressions of portions of the skin of the great Dinosaur, Thespesius, which show that the covering of this animal consisted largely, if not entirely, of small, irregularly hexagonal horny scutes, slightly thickened in the centre. The quarries of lithographic stone at Solenhofen have yielded a few specimens of flying reptiles, pterodactyls, which not only verify the correctness of the inference that these creatures possessed membranous wings, like the bats, but show the exact shape, and it was sometimes very curious, of this membrane. And each and all of these wonderfully preserved specimens serve both to check and guide the restorer in his task of clothing the animal as it was in life.

And all this help is needed, for it is an easy matter to make a wide-sweeping deduction, apparently resting on a good basis of fact, and yet erroneous. Remains of the Mammoth and Woolly Rhinoceros, found in Siberia and Northern Europe, were thought to indicate that at the period when these animals lived the climate was mild, a very natural inference, since the elephants and rhinoceroses we now know are all inhabitants of tropical climes. But the discovery of more or less complete specimens makes it evident that the climate was not particularly mild; the animals were simply adapted to it; instead of being naked like their modern relatives, they were dressed for the climate in a woolly covering. We think of the tiger as prowling through the jungles of India, but he ranges so far north that in some localities this beast preys upon reindeer, which are among the most northern of large mammals, and there the tiger is clad in fairly thick fur.

When we come to coloring a reconstructed animal we have absolutely no guide, unless we assume that the larger a creature the more soberly will it be colored. The great land animals of to-day, the elephant and rhinoceros, to say nothing of the aquatic hippopotamus, are very dully colored, and while this sombre coloration is to-day a protection, rendering these animals less easily seen by man than they otherwise would be, yet at the time this color was developing man was not nor were there enemies sufficiently formidable to menace the race of elephantine creatures.

For where mere size furnishes sufficient protection one would hardly expect to find protective coloration as well, unless indeed a creature preyed upon others, when it might be advantageous to enable a predatory animal to steal upon its prey.

Color often exists (or is supposed to) as a sexual characteristic, to render the male of a species attractive to, or readily recognizable by, the female, but in the case of large animals mere size is quite enough to render them conspicuous, and possibly this may be one of the factors in the dull coloration of large animals.

So while a green and yellow Triceratops would undoubtedly have been a conspicuous feature in the Cretaceous landscape, from what we know of existing animals it seems best to curb our fancy and, so far as large Dinosaurs are concerned, employ the colors of a Rembrandt rather than those of a sign painter.

Aids, or at least hints, to the coloration of extinct animals are to be found in the coloration of the young of various living species, for as the changes undergone by the embryo are in a measure an epitome of the changes undergone by a species during its evolution, so the brief color phases or markings of the young are considered to represent the ordinary coloring of distant ancestors. Young thrushes are spotted, young ostriches and grebes are irregularly striped, young lions are spotted, and in restoring the early horse, or Hyracothere, Professor Osborn had the animal represented as faintly striped, for the reason that zebras, the wild horses of to-day, are striped, and because the ass, which is a primitive type of horse, is striped over the shoulders, these being hints that the earlier horse-like forms were also striped.

Thus just as the skeleton of a Dinosaur may be a composite structure, made up of the bones of a dozen individuals, and these in turn mosaics of many fragments, so may the semblance of the living animal be based on a fact, pieced out with a probability and completed by a bit of theory.

REFERENCES

There is a large series of restorations of extinct animals, prepared by Mr. Charles R. Knight, under the direction of Professor Osborn, in the Hall of Palæontology of the American Museum of Natural History, and these are later to be reproduced and issued in portfolio form.

Should the reader visit Princeton, he may see in the museum there a number of B. Waterhouse Hawkins's creations—creations is the proper word—which are of interest as examples of the early work in this line.

The "Report of the Smithsonian Institution for 1900" contains an article on "The Restoration of Extinct Animals," pages 479-492, which includes a number of plates showing the progress that has been made in this direction.