The head is only two feet long, and is, therefore, small out of all proportion to the great body. The neck measures twenty-one feet four inches, and is by far the longest and largest neck known in any animal living or extinct. The back is relatively very short, measuring ten feet eight inches. The vertebrae of the hip measure two feet and three inches. The tail measures from thirty-two to forty feet. We thus obtain, as a moderate estimate of the total length of the animal, sixty-eight to seventy feet. The restored skeleton, published by Mr.
J.B. Hatcher in July, 1901, and partly embodying our results, gave to science the first really accurate knowledge of the length of these animals, which hitherto had been greatly overestimated. The highest point in the body was above the hips; here in fact, was the center of power and motion, because, as observed above, the tail fairly balanced the anterior part of the body.
The restoration by Mr. Knight is drawn from a very careful model made under my direction, in which the proportions of the animal are precisely estimated. It is, I think, accurate--for a restoration--as well as interesting and up-to-date. These restorations are the "working hypotheses" of our science; they express the present state of our knowledge, and, being subject to modification by future discoveries, are liable to constant change.
By contrast, the second type of giant dinosaur, the _Brontosaurus_, or "thunder saurian" of Marsh, as shown in the restoration (fig. 22), was far more ma.s.sive in structure and relatively shorter in body. Five more or less complete skeletons are now to be seen in the Yale, American, Carnegie, and Field Columbian museums. In 1898 we discovered in the bluffs, about three miles west of the Bone-Cabin Quarry, the largest of these animals which has yet been found; it was worked out with great care and is now being restored and mounted complete in the American Museum. The thigh-bone is enormous, measuring five feet eight inches in length, and is relatively of greater ma.s.s than that of _Diplodocus_. The neck, chest, hips, and tail are correspondingly ma.s.sive. The neck is relatively shorter, however, measuring eighteen feet, while in _Diplodocus_ it measures over twenty-one feet. The total length of this ma.s.sive specimen is estimated at sixty-three feet, or from six to eight feet less than the largest "long-limbed"
dinosaur. The height of the skeleton at the hips is fifteen feet.
There is less direct evidence that the "thunder saurian" had the power of raising its fore quarters in the air than in the case of the "light-limbed saurian," because no bend or supporting point in the tail has been distinctly observed.
The third type of giant dinosaur is the less completely known "chambered saurian," the _Camarasaurus_ of Cope or _Morosaurus_ of Marsh, an animal more quadrupedal in gait or walking more habitually on all fours, like the great _Cetiosaurus_, or "whale saurian,"
discovered near Oxford, England. With its shorter tail and heavier fore limbs, it is still less probable that this animal had the power of raising the anterior part of its body from the ground. Of a related type, perhaps, is the largest dinosaur ever found; this is the _Brachiosaurus_, limb-bones of which were discovered in central Colorado in 1901 and are now preserved in the Field Columbian Museum of Chicago. Its thigh-bone is six feet eight inches in length, and its upper arm-bone, or humerus, is even slightly longer.
_Feeding Habits of the Giant Dinosaurs._ We still have to solve one of the most perplexing problems of fossil physiology; how did the very small head, provided with light jaws, slender and spoon-shaped teeth confined to the anterior region, suffice to provide food for these monsters? I have advanced the idea that the food of _Diplodocus_ consisted of some very abundant and nutritious species of water-plant; that the clawed feet were used in uprooting such plants, while the delicate anterior teeth were employed only for drawing them out of the water; that the plants were drawn down the throat in large quant.i.ties without mastication, since there were no grinding or back teeth whatever in this animal. Unfortunately for this theory, it is now found that the front feet were not provided with many claws, there being only a single claw on the inner side. Nevertheless by some such means as this, these enormous animals could have obtained sufficient food in the water to support their great bulk.
_The Carnivorous Dinosaurs._ Mingling with the larger bones in the quarry are the more or less perfect remains of swamp turtles, of dwarf crocodiles, of the entirely different group of plated dinosaurs, or _Stegosauria_, but especially of two entirely distinct kinds of large and small flesh-eating dinosaurs. The latter rounded out and gave variety to the dinosaur society, and there is no doubt that they served the savage but useful purpose, rendered familiar by the doctrine of Malthus, of checking overpopulation. These fierce animals had the same remote ancestry as the giant dinosaurs, but had gradually acquired entirely different habits and appearance.
Far inferior in size, they were superior in agility, exclusively bipedal, with very long, powerful hind limbs, upon which they advanced by running or springing, and with short fore limbs, the exact uses of which are difficult to ascertain. Both hands and feet were provided with powerful tearing claws. On the hind foot is the back claw, so characteristic of the birds, which during the Tria.s.sic period left its faint impression almost everywhere in the famous Connecticut valley imprints of these animals. That the fore limb and hand were of some distinct use is proved by the enormous size of the thumb-claw; while the hand may not have conveyed food to the mouth, it may have served to seize and tear the prey. As to the actual pose in feeding, there can be little doubt as to its general similarity to that of the _Raptores_ among the birds, as suggested to me by Dr. Wortman (see fig. 10); one of the hind feet rested on the prey, the other upon the ground, the body being further balanced or supported by the vertebrae of the tail. The animal was thus in a position to apply its teeth and exert all the power of its very powerful arched back in tearing off its food. That the gristle of the bone or cartilage was very palatable is attested not only by the toothmarks upon these bones, but by many similar markings found in the Bone-Cabin Quarry.
_The Bird-Catching Dinosaur._ Of all the bird-like dinosaurs which have been discovered, none possesses greater similitude to the birds than the gem of the quarry, the little animal about seven feet in length which we have named _Ornitholestes_, or the "bird-catching dinosaur." It was a marvel of speed, agility, and delicacy of construction. Externally its bones are simple and solid-looking, but as a matter of fact they are mere sh.e.l.ls, the walls being hardly thicker than paper, the entire interior of the bone having been removed by the action of the same marvelous law of adaptation which sculptured the vertebrae of its huge contemporaries. There is no evidence, however, that these hollow bones were filled with air from the lungs, as in the case of the bones of birds. The foot is bird-like; the hand is still more so; in fact, no dinosaur hand has ever before been found which so closely mimics that of a bird in the great elongation of the first or index-finger, in the abbreviation of the thumb and middle finger, and in the reduction of the ring-finger.
These fingers, with sharp claws, were not strong enough for climbing, and the only special fitness we have been able to imagine is that they were used for the grasping of a light and agile prey (see figs. 17, 18.)
Another reason for the venture of designating this animal as the "bird-catcher" is that the Jura.s.sic birds (not thus far discovered in America, but known from the _Archaeopteryx_ of Germany) were not so active or such strong fliers as existing birds; in fact, they were not unlike the little dinosaur itself. They were toothed, long-tailed, short-armed, the body was feathered instead of scaled; they rose slowly from the ground. This renders it probable that they were the prey of the smaller pneumatic-built dinosaurs such as the present animal.
This hypothetical bird-catcher seems to have been designed to spring upon a delicately built prey, the structure being the very antipode of that of the large carnivorous dinosaurs. A difficulty in the bird-catching theory, namely, that the teeth are not as sharp as one would expect to find them in a flesh-eater, is somewhat offset by the similarity of the teeth to those of the bird-eating monitor lizards (_Vara.n.u.s_), which are not especially sharp.
_The Great Yield of the Quarry._ Our explorations in the quarry began in the spring of 1898, and have continued ever since during favorable weather. The total area explored at the close of the sixth year was seven thousand two hundred and fifty square feet. Not one of the twelve-foot squares into which the quarry was plotted lacked its covering of bones, and in some cases the bones were two or three deep.
Each year we have expected to come to the end of this great deposit, but it still yields a large return, although we have reason to believe that we have exhausted the richest portions.
We have taken up four hundred and eighty-three parts of animals, some of which may belong to the same individuals. These were packed in two hundred and seventy-five boxes, representing a gross weight of nearly one hundred thousand pounds. Reckoning from the number of thigh-bones, we reach, as a rough estimate of the total, seventy-three animals of the following kinds: giant herbivorous dinosaurs, 44; plated herbivorous dinosaurs, or stegosaurs, 3; iguanodonts or smaller herbivorous dinosaurs, 4; large carnivorous dinosaurs, 6; small carnivorous dinosaurs, 3; crocodiles, 4; turtles, 5. But this represents only a part of the whole deposit, which we know to be of twice the extent already explored, and these figures do not include the bones which were partly washed out and used in the construction of the Bone-Cabin. The grand total would probably include parts of over one hundred giant dinosaurs.
_The Struggle for Existence Among the Dinosaurs._ Never in the whole history of the world as we now know it have there been such remarkable land scenes as were presented when the reign of these t.i.tanic reptiles was at its climax. It was also the prevailing life-picture of England, Germany, South America, and India. We can imagine herds of these creatures from fifty to eighty feet in length, with limbs and gait a.n.a.logous to those of gigantic elephants, but with bodies extending through the long, flexible, and tapering necks into the diminutive heads, and reaching back into the equally long and still more tapering tails. The four or five varieties which existed together were each fitted to some special mode of life; some living more exclusively on land, others for longer periods in the water.
The compet.i.tion for existence was not only with the great carnivorous dinosaurs, but with other kinds of herbivorous dinosaurs (the iguanodonts), which had much smaller bodies to sustain and a much superior tooth mechanism for the taking of food.
The cutting off of this giant dinosaur dynasty was nearly if not quite simultaneous the world over. The explanation which is deducible from similar catastrophes to other large types of animals is that a very large frame, with a limited and specialized set of teeth fitted only to a certain special food, is a dangerous combination of characters.
Such a monster organism is no longer adaptable; any serious change of conditions which would tend to eliminate the special food would also eliminate these great animals as a necessary consequence.
[Ill.u.s.tration: Fig. 46.--Badlands on the Red Deer River in Alberta. This region is the richest known collecting ground for cretacic dinosaurs.]
There is an entirely different cla.s.s of explanations, however, to be considered, which are consistent both with the continued fitness of structure of the giant dinosaurs themselves and with the survival of their especial food; such, for example, as the introduction of a _new enemy_ more deadly even than the great carnivorous dinosaurs. Among such theories the most ingenious is that of the late Professor Cope, who suggested that some of the small, inoffensive, and inconspicuous forms of Jura.s.sic mammals, of the size of the shrew and the hedgehog, contracted the habit of seeking out the nests of these dinosaurs, gnawing through the sh.e.l.ls of their eggs, and thus destroying the young. The appearance, or evolution, of any egg-destroying animals, whether reptiles or mammals, which could attack this great race at such a defenseless point would be rapidly followed by its extinction.
We must accordingly be on the alert for all possible theories of extinction; and these theories themselves will fall under the universal principle of the survival of the fittest until we approximate or actually hit upon the truth.
FOSSIL HUNTING BY BOAT IN CANADA.
_By Barnum Brown._
"How do you know where to look for fossils?" is a common question. In general it may be answered that the surface of North America has been pretty well explored by government surveys and scientific expeditions and the geologic age of the larger areas determined. Most important in determining the geologic sequence of the earth"s strata are the fossil remains of animal and plant life. A grouping of distinct species of fossils correlated with stratigraphic characters in the rocks determines these subdivisions. When a collection of fossils is desired to represent a certain period, exploring parties are sent to these known areas. Sometimes however, chance information leads up to most important discoveries, such as resulted from the work of the past two seasons in Alberta, Canada.
A visitor to the Museum, Mr. J.L. Wagner, while examining our mineral collections saw the large bones in the Reptile Hall and remarked to the Curator of Mineralogy that he had seen many similar bones near his ranch in the Red Deer Canon of Alberta. After talking some time an invitation was extended to the writer to visit his home and prospect the canon. Accordingly in the fall of 1909 a preliminary trip was made to the locality.
From Didsbury, a little town north of Calgary, the writer drove eastward ninety miles to the Red Deer River through a portion of the newly opened grain belt of Alberta, destined in the near future to produce a large part of the world"s bread. Near the railroad the land is mostly under cultivation and comfortable homes and bountiful grain fields testify to the rich nature of the soil. A few miles eastward the brushland gives way to a level expanse of gra.s.s-covered prairie dotted here and there by large and small lakes probably of glacial origin. Mile after mile the road follows section lines and one is rarely out of sight of the house of some "homesteader." It is through this level farm land that the Red Deer River wends its way flowing through a canon far below the surface. Near Wagner"s ranch the canon was prospected and so many bones found that it appeared most desirable to do extended searching along the river.
Usually fossils are found in "bad lands," where extensive areas are denuded of gra.s.s and the surface eroded into hills and ravines. A camp is located near some spring or stream and collectors ride or walk over miles of these exposures in each direction till the region is thoroughly explored. Quite different are conditions on the Red Deer River. Cutting through the prairie land the river had formed a canon two to five hundred feet deep and rarely more than a mile wide at the top. In places the walls are nearly perpendicular and the river winds in its narrow valley, touching one side then crossing to the other so that it is impossible to follow up or down its course any great distance even on horseback.
It was evident that the most feasible way to work these banks was from a boat; consequently in the summer of 1910 our party proceeded to the town of Red Deer, where the Calgary-Edmonton railroad crosses the river. There a flatboat, twelve by thirty feet in dimension, was constructed on lines similar to a western ferry boat, having a carrying capacity of eight tons with a twenty-two foot oar at each end to direct its course. The rapid current averaging about four miles per hour precluded any thought of going up stream in a large boat, so it was constructed on lines sufficiently generous to form a living boat as well as to carry the season"s collection of fossils.
Supplied with a season"s provisions, lumber for boxes, and plaster for encasing bones, we began our fossil cruise down a canon which once echoed songs of the _Bois brule_, for this was at one time the fur territory of the great Hudson Bay Company.
[Ill.u.s.tration: Fig. 47.--American Museum Expedition on the Red Deer River. Fossils secured along the banks were packed and loaded aboard the large scow and floated down the river to the railway station.]
No more interesting or instructive journey has ever been taken by the writer. High up on the plateau, buildings and haystacks proclaim a well-settled country, but habitations are rarely seen from the river and for miles we floated through picturesque solitude unbroken save by the roar of the rapids.
Especially characteristic of this canon are the slides where the current setting against the bank has undermined it until a mountain of earth slips into the river, in some cases almost choking its course.
A continual sorting thus goes on, the finer material being carried away while the boulders are left as barriers forming slow moving reaches of calm water and stretches of rapids difficult to navigate during low water. In one of these slides we found several small mammal jaws and teeth not known before from Canada, a.s.sociated with fossil clam sh.e.l.ls of Eocene age.
The long midsummer days in lat.i.tude 52 gave many working hours, but with frequent stops to prospect the banks we rarely floated more than twenty miles per day. An occasional flock of ducks and geese were disturbed as our boat approached and bank beaver houses were frequently pa.s.sed, but few of the animals were seen during the daytime. Tying the boat to a tree at night we would go ash.o.r.e to camp among the trees where after dinner pipes were smoked in the glow of a great camp fire. Only a fossil hunter or a desert traveler can fully appreciate the luxury of abundant wood and running water. In the stillness of the night the underworld was alive and many little feet rustled the leaves where daylight disclosed no sound. Then the beaver and muskrat swam up to investigate this new intruder, while from the tree-tops came the constant query, "Who! Who!"
For seventy miles the country is thickly wooded with pine and poplar, the stately spruce trees silhouetted against the sky adding a charm to the ever changing scene. Nature has also been kind to the treeless regions beyond, for underneath the fertile prairie, veins of good lignite coal of varying thickness are successively cut by the river.
In many places these are worked in the river banks during winter. One vein of excellent quality is eighteen feet thick, although usually they are much thinner. The government right has been taken to mine most of this coal outcropping along the river.
[Ill.u.s.tration: Fig. 48.--Locality of Ankylosaurus skull in Edmonton formation in Red Deer River. The skull is in the rock just above the pick, about the center of the photograph.]
Along the upper portion of the stream are banks of Eocene age, from which sh.e.l.ls and mammal jaws were secured, but near the town of Content where the river bends southward, a new series of rocks appeared and in these our search was rewarded by finding dinosaur bones similar to those seen at Wagner"s ranch. Specimens were found in increasing numbers as we continued our journey, and progress down the river was necessarily much slower. Frequently the boat would be tied up a week or more at one camp while we searched the banks, examining the cliffs layer by layer that no fossil might escape observation.
With the little dingey the opposite side of the river was reached so that both sides were covered at the same time from one camp. As soon as a mile or more had been prospected or a new specimen secured, the boat was dropped down to a new convenient anchorage. Box after box was added to the collection till scarcely a cubit"s s.p.a.ce remained unoccupied on board our fossil ark.
Where prairie badlands are eroded in innumerable b.u.t.tes and ravines it is always doubtful if one has seen all exposures, so there was peculiar satisfaction in making a thorough search of these river banks knowing that few if any fossils had escaped observation. On account of the heavy rainfall and frequent sliding of banks new fossils are exposed every season so that in a few years these same banks can again be explored profitably. This river will become as cla.s.sic hunting ground for reptile remains as the Badlands of South Dakota are for mammals.
Although the summer days are long in this lat.i.tude the season is short and thousands of geese flying southward foretell the early winter.
Where the temperature is not infrequently forty to sixty degrees below zero in winter, it is difficult to think of a time when a warm climate could have prevailed, yet such condition is indicated by the fossil plants.
When the weather became too cold to work with plaster, the fossils were shipped from a branch railroad forty-five miles distant, the camp material was stored for the winter and with block and tackle the big boat was hauled up on sh.o.r.e above the reach of high water.
In the summer of 1911 the boat was recalked and again launched when we continued our search from the point at which work closed the previous year. During the summer we were visited by the Museum"s President, Prof. Henry Fairfield Osborn, and one of the Trustees, Mr. Madison Grant. A canoeing trip, one of great interest and pleasure, was taken with our visitors covering two hundred and fifty miles down the river from the town of Red Deer, during which valuable material was added to the collection and important geological data secured.
As a result of the Canadian work the Museum is enriched by a magnificent collection of Cretaceous fossils some of which are new to science.
FOOTNOTES:
[Footnote 19: Transactions Kansas Academy of Science, p. 43.]
[Footnote 20: From Fossil Wonders of the West. Century Magazine 1904, vol. lxviii, pp. 680-694. Reprinted by permission.]
[Footnote 21: At this time the Union Pacific Railroad directly pa.s.sed the bluffs; in the recent improvement of the grade the main line has been moved to the south.--H.F.O.]
[Footnote 22: A different interpretation of this contraction is given upon p. 68.]