Footprints may aid greatly in determining the att.i.tude a.s.sumed by extinct animals, and in this way they have been of great service in furnishing proof that many of the Dinosaurs walked erect. The impressions on the sands of the old Connecticut estuary may be said to show this very plainly, but in England and Belgium is evidence still more conclusive, in the shape of tracks ascribed to the Iguanodon. These were made on soft soil into which the feet sank much more deeply than in the Connecticut sands, and the casts made in the natural moulds show the impression of toes very clearly. If the animals had walked flat-footed, as we do, the prints of the toes would have been followed by a long heel mark, but such is not the case; there are the sharply defined marks of the toes and nothing more, showing plainly that the Iguanodons walked, like birds, on the toes alone. More than this, had these Dinosaurs dragged their tails there would have been a continuous furrow between the footprints; but nothing of this sort is to be found; on the contrary, a fine series of tracks, uncovered at Hastings, England, made by several individuals and running for seventy-five feet, shows footprints only. Hence it may be fairly concluded that these great creatures carried their tails clear of the ground, as shown in the picture of _Thespesius_, the weight of the tail counterbalancing that of the body. Where crocodilians or some of the short-limbed Dinosaurs have crept along there is, as we should expect, a continuous furrow between the imprints of the feet. This is what footprints tell us when their message is read aright; when improperly translated they only add to the enormous bulk of our ignorance.
Some years ago we were treated to accounts of wonderful footprints in the rock of the prison-yard at Carson City, Nev., which, according to the papers, not only showed that men existed at a much earlier period than the scientific supposed, but that they were men of giant stature.
This was clearly demonstrated by the footprints, for they were such as _might_ have been made by huge moccasined feet, and this was all that was necessary for the conclusion that they _were_ made by just such feet. For it is a curious fact that the majority of mankind seem to prefer any explanation other than the most simple and natural, particularly in the case of fossils, and are always looking for a primitive race of gigantic men.
Bones of the Mastodon and Mammoth have again and again been eagerly accepted as those of giants; a salamander was brought forward as evidence of the deluge (_h.o.m.o diluvii testis_); ammonites and their allies pose as fossil snakes, and the "petrified man" flourishes perennially. However, in this case the prints were recognized by naturalists as having most probably been made by some great ground sloth, such as the Mylodon or Morotherium, these animals, though belonging to a group whose headquarters were in Patagonia, having extended their range as far north as Oregon. That the tracks seemed to have been made by a biped, rather than a quadruped, was due to the fact that the prints of the hind feet fell upon and obliterated the marks of the fore. Still, a little observation showed that here and there prints of the fore feet were to be seen, and on one spot were indications of a struggle between two of the big beasts. The mud, or rather the stone that had been mud, bears the imprints of opposing feet, one set deeper at the toes, the other at the heels, as if one animal had pushed and the other resisted. In the rock, too, are broad depressions bearing the marks of coa.r.s.e hair, where one creature had apparently sat on its haunches in order to use its fore limbs to the best advantage. Other footprints there are in this prison-yard; the great round "spoor" of the mammoth, the hoofs of a deer, and the paws of a wolf(?), indicating that hereabout was some pool where all these creatures came to drink. More than this, we learn that when these prints were made, or shortly after, a strong wind blew from the southeast, for on that face of the ridges bounding the margin of each big footprint, we find sand that lodged against the squeezed-up mud and stuck there to serve as a perpetual record of the direction of the wind.
_REFERENCES_
_Almost every museum has some specimen of the Connecticut Valley footprints, but the largest and finest collections are in the museums of Amherst College, Ma.s.s., and Yale University, although, owing to lack of room, only a few of the Yale specimens are on exhibition. The collection at Amherst comprises most of the types described by Professor E.
Hitchc.o.c.k in his "Ichnology of New England," a work in two fully ill.u.s.trated quarto volumes. Other footprints are described and figured by Dr. J. Deane in "Ichnographs from the Sandstone of the Connecticut River."_
[Ill.u.s.tration: Fig. 8.--The Track of a Three-toed Dinosaur.]
IV
RULERS OF THE ANCIENT SEAS
"_A time there was when the universe was darkness and water, wherein certain animals of frightful and compound mien were generated. There were serpents, and other creatures with the mixed shapes of one another...._"--_The Archaic Genesis._
History shows us how in the past nation after nation has arisen, increased in size and strength, extended its bounds and dominion until it became the ruling power of the world, and then pa.s.sed out of existence, often so completely that nothing has remained save a few mounds of dirt marking the graves of former cities. And so has it been with the kingdoms of nature. Just as Greece, Carthage, and Rome were successively the rulers of the sea in the days that we call old, so, long before the advent of man, the seas were ruled by successive races of creatures whose bones now lie scattered over the beds of the ancient seas, even as the wrecks of galleys lie strewn over the bed of the Mediterranean. For a time the armor-clad fishes held undisputed sway; then their reign was ended by the coming of the sharks, who in their turn gave way to the fish-lizards, the Ichthyosaurs and Plesiosaurs.
These, however, were rather local in their rule; but the next group of reptiles to appear on the scene, the great marine reptiles called Mosasaurs, practically extended their empire around the world, from New Zealand to North America.
We properly call these reptiles great, for so they were; but there are degrees of greatness, and there is a universal tendency to think of the animals that have become extinct as much greater than those of the present day, to magnify the reptile that we never saw as well as the fish that "got away," and it may be safely said that the greatest of animals will shrink before a two-foot rule. As a matter of fact, no animals are known to have existed that were larger than the whales; and, while there are now no reptiles that can compare in bulk with the Dinosaurs, there were few Mosasaurs that exceeded in size a first-cla.s.s Crocodile. An occasional Mosasaur reaches a length of forty feet, but such are rare indeed, and one even twenty-five feet long is a large specimen,[4] while the great Mugger, or Man-eating Crocodile, grows, if permitted, to a length of twenty-five or even thirty feet, and need not be ashamed to match his bulk and jaws against those of most Mosasaurs.
[4] _It is surprising to find Professor Cope placing the length of the Mosasaurs at 70, 80, or 100 feet, as there is not the slightest basis for even the lowest of these figures. Professor Williston, the best authority on the subject, states, in his volume on the "Cretaceous Reptiles of Kansas," that there is not in existence any specimen of a Mosasaur indicating a greater length than 45 feet._
The first of these sea-reptiles to be discovered has pa.s.sed into history, and now reposes in the Jardin des Plantes, Paris, after changing hands two or three times, the original owner being dispossessed of his treasure by the subtleties of law, while the next holder was deprived of the specimen by main force. Thus the story is told by M.
Faujas St. Fond, as rendered into English, in Mantell"s "Petrifactions and their Teachings": "Some workmen, in blasting the rock in one of the caverns of the interior of the mountain, perceived, to their astonishment, the jaws of a large animal attached to the roof of the chasm. The discovery was immediately made known to M. Hoffman, who repaired to the spot, and for weeks presided over the arduous task of separating the ma.s.s of stone containing these remains from the surrounding rock. His labors were rewarded by the successful extrication of the specimen, which he conveyed in triumph to his house. This extraordinary discovery, however, soon became the subject of general conversation, and excited so much interest that the canon of the cathedral which stands on the mountain resolved to claim the fossil, in right of being lord of the manor, and succeeded, after a long and hara.s.sing lawsuit, in obtaining the precious relic. It remained for years in his possession, and Hoffman died without regaining his treasure. At length the French Revolution broke out, and the armies of the Republic advanced to the gates of Maestricht. The town was bombarded; but, at the suggestion of the committee of savans who accompanied the French troops to select their share of the plunder, the artillery was not suffered to play on that part of the city in which the celebrated fossil was known to be preserved. In the meantime, the canon of St. Peter"s, shrewdly suspecting the reason why such peculiar favor was shown to his residence, removed the specimen and concealed it in a vault; but, when the city was taken, the French authorities compelled him to give up his ill-gotten prize, which was immediately transmitted to the Jardin des Plantes, at Paris, where it still forms one of the most interesting objects in that magnificent collection." And there it remains to this day.
[Ill.u.s.tration: Fig. 9.--A Great Sea Lizard, _Tylosaurus Dyspelor_. _From a drawing by J. M. Gleeson._]
The seas that rolled over western Kansas were the headquarters of the Mosasaurs, and hundreds--aye, thousands--of specimens have been taken from the chalk bluffs of that region, some of them in such a fine state of preservation that we are not only well acquainted with their internal structure, but with their outward appearance as well. They were essentially swimming lizards--great, overgrown, and distant relatives of the Monitors of Africa and Asia, especially adapted to a roving, predatory life by their powerful tails and paddle-shaped feet. Their cup-and-ball vertebrae indicate great flexibility of the body, their sharp teeth denote ability to capture slippery prey, and the structure of the lower jaw shows that they probably ate in a hurry and swallowed their food entire, or bolted it in great chunks. The jaws of all reptiles are made up of a number of pieces, but these are usually so spliced together that each half of the jaw is one inflexible, or nearly inflexible, ma.s.s of bone. In snakes, which swallow their prey entire, the difficulty of swallowing animals greater in diameter than themselves is surmounted by having the two halves of the lower jaw loosely joined at the free ends, so that these may spread wide apart and thus increase the gape of the mouth. This is also helped by the manner in which the jaw is joined to the head. The pelican solves the problem by the length of his mandibles, this allowing so much spring that when open they bow apart to form a nice little landing net. In the Mosasaurs, as in the cormorants, among birds, there is a sort of joint in each half of the lower jaw which permits it to bow outward when opened, and this, aided by the articulation of the jaw with the cranium, adds greatly to the swallowing capacity. Thus in nature the same end is attained by very different methods. To borrow a suggestion from Professor Cope, if the reader will extend his arms at full length, the palms touching, and then bend his elbows outward he will get a very good idea of the action of a Mosasaur"s jaw. The western sea was a lively place in the day of the great Mosasaurs, for with them swam the king of turtles, Archelon, as Mr. Wieland has fitly named him, a creature a dozen feet or more in length, with a head a full yard long, while in the shallows prowled great fishes with ma.s.sive jaws and teeth like spikes.
[Ill.u.s.tration: Fig. 10.--Jaw of a Mosasaur, Showing the Joint that Increased the Swallowing Capacity of that Reptile.]
There, too, was the great, toothed diver, Hesperornis (see page 83), while over the waters flew pterodactyls, with a spread of wing of twenty feet, largest of all flying creatures; and, not improbably--nay, very probably--fish-eaters, too; and when each and all of these were seeking their dinners, there were troublous times for the small fry in that old Kansan sea.
And then there came a change; to the south, to the west, to the north, the land was imperceptibly but surely rising, perhaps only an inch or two in a century, but still rising, until "The Ocean in which flourished this abundant and vigorous life was at last completely inclosed on the west by elevations of sea-bottom, so that it only communicated with the Atlantic and Pacific at the Gulf of Mexico and the Arctic Sea."
The continued elevation of both eastern and western sh.o.r.es contracted its area, and when ridges of the sea-bottom reached the surface, forming long, low bars, parts of the water-area were included, and connection with salt-water prevented. Thus were the living beings imprisoned and subjected to many new risks to life. The stronger could more readily capture the weaker, while the fishes would gradually perish through the constant freshening of the water. With the death of any considerable cla.s.s, the balance of food-supply would be lost, and many large species would disappear from the scene. The most omnivorous and enduring would longest resist the approach of starvation, but would finally yield to inexorable fate--the last one caught by the shifting bottom among shallow pools, from which his exhausted energies could not extricate him.[5]
[5] _Cope: "The Vertebrata of the Cretaceous Formations of the West," p.
50, being the "Report of the United States Geological Survey of the Territories," Vol. II._
Like the "Fossil man" the sea-serpent flourishes perennially in the newspapers and, despite the fact that he is now mainly regarded as a joke, there have been many attempts to habilitate this mythical monster and place him on a foundation of firm fact. The most earnest of these was that of M. Oudemans, who expressed his belief in the existence of some rare and huge seal-like creature whose occasional appearance in southern waters gave rise to the best authenticated reports of the sea-serpent. Among other possibilities it has been suggested that some animal believed to be extinct had really lived over to the present day.
Now there are a few waifs, spared from the wrecks of ancient faunas, stranded on the sh.o.r.es of the present, such as the Australian Ceratodus and the Gar Pikes of North America, and these and all other creatures that could be mustered in were used as proofs to sustain this theory.
If, it was said, these animals have been spared, why not others? If a fish of such ancient lineage as the Gar Pike is so common as to be a nuisance, why may there not be a few Plesiosaurs or a Mosasaur somewhere in the depths of the ocean? The argument was a good one, the more that we may "suppose" almost anything, but it must be said that no trace of any of these creatures has so far been found outside of the strata in which they have long been known to occur, and all the probabilities are opposed to this theory. Still, if some of these creatures _had_ been spared, they might well have pa.s.sed for sea-serpents, even though Zeuglodon, the one most like a serpent in form, was the one most remotely related to snakes.
Zeuglodon, the yoke-tooth, so named from the shape of its great cutting teeth, was indeed a strange animal, and if we wonder at the Greenland Whale, whose head is one-third its total length, we may equally wonder at Zeuglodon, with four feet of head, ten feet of body, and forty feet of tail. No one, seeing the bones of the trunk and tail for the first time, would suspect that they belonged to the same animal, for while the vertebrae of the body are of moderate size, those of the tail are, for the bulk of creature, the longest known, measuring from fifteen to eighteen inches in length, and weighing in a fossil condition fifty to sixty pounds. In life, the animal was from fifty to seventy feet in length, and not more than six or eight feet through the deepest part of the body, while the tail was much less; the head was small and pointed, the jaws well armed with grasping and cutting teeth, and just back of the head was a pair of short paddles, not unlike those of a fur seal. It is curious to speculate on the habits of a creature in which the tail so obviously wagged the dog and whose articulations all point to great freedom of movement up and down. This may mean that it was an active diver, descending to great depths to prey upon squid, as the Sperm-Whale does to-day, while it seems quite certain that it must have reared at least a third of its great length out of water to take a comprehensive view of its surroundings. And if size is any indication of power, the great tail, which obviously ended in flukes like those of a whale, must have been capable of propelling the beast at a speed of twenty or thirty miles an hour. Something of the kind must have been needed in order that the small head might provide food enough for the great tail, and it has been suggested that inability to do this was the reason why Zeuglodon became extinct. On the other hand, it has been ingeniously argued that the huge tail served to store up fat when food was plenty, which was drawn upon when food became scarce. The fur seals do something similar to this, for the males come on sh.o.r.e in May rolling in blubber, and depart in September lean and hungry after a three months" fast.
Zeuglodons must have been very numerous in the old Gulf of Mexico, for bones are found abundantly through portions of our Southern States; it was also an inhabitant of the old seas of southern Europe, but, as we shall see, it gave place to the great fossil shark, and this in turn pa.s.sed out of existence. Still, common though its bones may be, stories of their use for making stone walls--and these stories are still in circulation--resolve themselves on close scrutiny into the occasional use of a big vertebra to support the corner of a corn-crib.
The scientific name of Zeuglodon is _Basilosaurus cetoides_, the whale-like king lizard--the first of these names, _Basilosaurus_, having been given to it by the original describer, Dr. Harlan, who supposed the animal to have been a reptile. Now it is a primary rule of nomenclature that the first name given to an animal must stick and may not be changed, even by the act of a zoological congress, so Zeuglodon must, so far as its name is concerned, masquerade as a reptile for the rest of its paleontological life. This, however, really matters very little, because scientific names are simply verbal handles by which we may grasp animals to describe them, and Dr. Le Conte, to show how little there may be in a name, called a beetle Gyascutus. Owen"s name of Zeuglodon, although not tenable as a scientific name, is too good to be wasted, and being readily remembered and easily p.r.o.nounced may be used as a popular name.
[Ill.u.s.tration: Fig. 11.--Koch"s Hydrarchus, Composed of Portions of the Skeleton of Several Zeuglodons.]
One might think that a creature sixty or seventy feet long was amply long enough, but Dr. Albert Koch thought otherwise, and did with Zeuglodon as, later on, he did with the Mastodon, combining the vertebrae of several individuals until he had a monster 114 feet long! This he exhibited in Europe under the name of Hydrarchus, or water king, finally disposing of the composite creature to the Museum of Dresden, where it was promptly reduced to its proper dimensions. The natural make-up of Zeuglodon is sufficiently composite without any aid from man, for the head and paddles are not unlike those of a seal, the ribs are like those of a manatee, and the shoulder blades are precisely like those of a whale, while the vertebrae are different from those of any other animal, even its own cousin and lesser contemporary Dorudon. There were also tiny hind legs tucked away beneath skin, but these, as well as many other parts of the animal"s structure were unknown, until Mr. Charles Schuchert collected a series of specimens for the National Museum, from which it was possible to restore the entire skeleton. Owing to a rather curious circ.u.mstance the first attempt at a restoration was at fault; among the bones originally obtained by Mr. Schuchert there were none from the last half of the tail, an old gully having cut off the hinder portion of the backbone and destroyed the vertebrae. Not far away, however, was a big lump of stone containing several vertebrae of just the right size, and these were used as models to complete the papier-mache skeleton shown at Atlanta, in 1894. But a year after Mr. Schuchert collected a series of vertebrae, beginning with the tip of the tail, and these showed conclusively that the first lot of tail vertebrae belonged to a creature still undescribed and one probably more like a whale than Zeuglodon himself, whose exact relationships are a little uncertain, as may be imagined from what was said of its structure. Mixed with the bones of Zeuglodon was the sh.e.l.l of a turtle, nearly three feet long, and part of the backbone of a great water-snake that must have been twenty-five feet long, both previously quite unknown. One more curious thing about Zeuglodon bones remains to be told, and then we are done with him; ordinarily a fossil bone will break indifferently in any direction, but the bones of Zeuglodon are built, like an onion, of concentric layers, and these have a great tendency to peel off during the preparation of a specimen.
And now, as the wheels of time and change rolled slowly on, sharks again came uppermost, and the warmer Eocene and Miocene oceans appear to have fairly teemed with these sea wolves. There were small sharks with slender teeth for catching little fishes, there were larger sharks with saw-like teeth for cutting slices out of larger fishes, and there were sharks that might almost have swallowed the biggest fish of to-day whole, sharks of a size the waters had never before contained, and fortunately do not contain now. We know these monsters mostly by their teeth, for their skeletons were cartilaginous, and this absence of their remains is probably the reason why these creatures are pa.s.sed by while the adjectives huge, immense, enormous are lavished on the Mosasaurs and Plesiosaurs--animals that the great-toothed shark, _Carcharodon megalodon_, might well have eaten at a meal. For the gaping jaws of one of these sharks, with its hundreds of gleaming teeth must, at a moderate estimate, have measured not less than six feet across.
The great White Shark, the man-eater, so often found in story books, so rarely met with in real life, attains a length of thirty feet, and a man just makes him a good, satisfactory lunch. Now a tooth of this shark is an inch and a quarter long, while a tooth of the huge _Megalodon_ is commonly three, often four, and not infrequently five inches long.
Applying the rule of three to such a tooth as this would give a shark 120 feet long, bigger than most whales, to whom a man would be but a mouthful, just enough to whet his sharkship"s appet.i.te. Even granting that the rule of three unduly magnifies the dimensions of the brute, and making an ample reduction, there would still remain a fish between seventy-five and one hundred feet long, quite large enough to satisfy the most ambitious of _tuna_ fishers, and to have made bathing in the Miocene ocean unpopular. Contemporary with the great-toothed shark was another and closely related species that originated with him in Eocene times, and these two may possibly have had something to do with the extinction of Zeuglodon. This species is distinguished by having on either side of the base of the great triangular cutting teeth a little projection or cusp, like the "ear" on a jar, so that this species has been named _auriculatus_, or eared. The edges of the teeth are also more saw-like than in those of its greater relative, and as the species must have attained a length of fifty or sixty feet it may, with its better armature, have been quite as formidable. And, as perhaps the readers of these pages may know, the supply of teeth never ran short. Back of each tooth, one behind another arranged in serried ranks, lay a reserve of six or seven smaller, but growing teeth, and whenever a tooth of the front row was lost, the tooth immediately behind it took its place, and like a well-trained soldier kept the front line unbroken. Thus the teeth of sharks are continually developing at the back, and all the teeth are steadily pushing forward, a very simple mechanical arrangement causing the teeth to lie flat until they reach the front of the jaw and come into use.
Once fairly started in life, these huge sharks spread themselves throughout the warm seas of the world, for there was none might stand before them and say nay. They swarmed along our southern coast, from Maryland to Texas; they swarmed everywhere that the water was sufficiently warm, for their teeth occur in Tertiary strata in many parts of the world, and the deep-sea dredges of the Challenger and Albatross have brought up their teeth by scores. And then--they perished, perished as utterly as did the hosts of Sennacherib. Why? We do not know. Did they devour everything large enough to be eaten throughout their habitat, and then fall to eating one another? Again, we do not know. But perish they did, while the smaller white shark, which came into being at the same time, still lives, as if to emphasize the fact that it is best not to overdo things, and that in the long run the victory is not _always_ to the largest.
_REFERENCES_
_The finest Mosasaur skeleton ever discovered, an almost complete skeleton of Tylosaurus dyspelor, 29 feet in length, may be seen at the head of the staircase leading to the Hall of Paleontology, in the American Museum of Natural History, New York. Another good specimen may be seen in the Yale University Museum, which probably has the largest collection of Mosasaurs in existence. Another fine collection is in the Museum of the State University of Kansas, at Lawrence._
_The best Zeuglodon, the first to show the vestigial hind legs and to make clear other portions of the structure, is in the United States National Museum._
_The great sharks are known in this country by their teeth only, and, as these are common in the phosphate beds, specimens may be seen in almost any collection. In the United States National Museum, the jaws of a twelve-foot blue shark are shown for comparison. The largest tooth in that collection is 5-3/4 inches high and 5 inches across the base. It takes five teeth of the blue shark to fill the same number of inches._
_The Mosasaurs are described in detail by Professor S. W. Williston, in Vol. IV. of the "University Geological Survey of Kansas." There is a technical--and, consequently, uninteresting--account of Zeuglodon in Vol. XXIII. of the "Proceedings of the United States National Museum,"
page 327._
[Ill.u.s.tration: Fig. 12.--A Tooth of Zeuglodon, one of the "Yoke Teeth,"
from which it derives the name.]
V
BIRDS OF OLD
"_With head, hands, wings, or feet, pursues his way, And swims, or sinks, or wades, or creeps, or flies._"
When we come to discuss the topic of the earliest bird--not the one in the proverb--our choice of subjects is indeed limited, being restricted to the famous and oft-described Archaeopteryx from the quarries of Solenhofen, which at present forms the starting-point in the history of the feathered race. Bird-like, or at least feathered, creatures, must have existed before this, as it is improbable that feathers and flight were acquired at one bound, and this lends probability to the view that at least some of the tracks in the Connecticut Valley are really the footprints of birds. Not birds as we now know them, but still creatures wearing feathers, these being the distinctive badge and livery of the order. For we may well speak of the feathered race, the exclusive prerogative of the bird being not flight but feathers; no bird is without them, no other creature wears them, so that birds may be exactly defined in two words, feathered animals. Reptiles, and even mammals, may go quite naked or cover themselves with a defensive armor of bony plates or h.o.r.n.y scales; but under the blaze of the tropical sun or in the chill waters of arctic seas birds wear feathers only, although in the penguins the feathers have become so changed that their ident.i.ty is almost lost.