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DINOSAURS

Chapter 5:

THE AMPHIBIOUS DINOSAURS,
BRONTOSAURUS, DIPLODOCUS, Etc.

Sub-Order Opisthocœlia (Cetiosauria or Sauropoda).


These were the Giant Reptiles par-excellence, for all of them were of enormous size, and some were by far the largest of all four-footed animals, exceeded in bulk only by the modern whales. In contrast to the carnivorous dinosaurs these are quadrupedal, with very small head, blunt teeth, long giraffe-like neck, elephantine body and limbs, long massive tail prolonged at the tip into a whip-lash as in the lizards. Like the elephant they have five short toes on each foot, probably buried in life in a large soft pad, but the inner digits bear large claws, blunt like those of turtles, one in the fore foot, three in the hind foot.

To this group belong the Brontosaurus and Diplodocus, the Camarasaurus, Morosaurus and other less known kinds. All of them lived during the late Jurassic and Comanchic ("Lower Cretaceous") and belong to the older of the two principal Dinosaur faunas. They were contemporaries of the Allosaurus and Megalosaurus, the Stegosaurus and Iguanodon, but unlike the Carnivorous and Beaked Dinosaurs they became wholly extinct before the Upper or true Cretacic, and left no relatives to take part in the final epoch of expansion and prosperity of the dinosaurian race at the close of the Reptilian era.

Fig. 20.: Skeletons of Brontosaurus (above) and

Fig. 20.—Skeletons of Brontosaurus (above) and Diplodocus (below) in the American Museum. The parts preserved in these specimens are shaded. Scale, 10 feet=1 inch.


BRONTOSAURUS.

The following description of the Brontosaurus skeleton in the American Museum was first published in the American Museum Journal of April, 1905:[11]

"The Brontosaurus skeleton, the principal feature of the hall, is sixty-six feet eight inches long. (The weight of the animal when alive is estimated by W.K. Gregory at 38 tons). About one-third of the skeleton including the skull is restored in plaster modelled or cast from other incomplete skeletons. The remaining two-thirds belong to one individual, except for a part of the tail, one shoulder-blade and one hind limb, supplied from another skeleton of the same species.

"The skeleton was discovered by Mr. Walter Granger of the Museum expedition of 1898, about nine miles north of Medicine Bow, Wyoming. It took the whole of the succeeding summer to extract it from the rock, pack it, and ship it to the Museum. Nearly two years were consumed in removing the matrix, piecing together and cementing the brittle and shattered petrified bone, strengthening it so that it would bear handling, and restoring the missing parts of the bones in tinted plaster. The articulation and mounting of the skeleton and modelling of the missing bones took an even longer time, so that it was not until February, 1905, that the Brontosaurus was at last ready for exhibition.

Fig. 21a.: Excavating the Brontosaurus skeleton.

Fig. 21b.: Excavating the Brontosaurus skeleton.

Fig. 21.—Excavating the Brontosaurus skeleton. The upper photograph shows the anterior ribs of one side still lying in position. The backbone is being prepared for removal, the sections each containing three vertebrae, partly cased in plaster and burlap (see chapter XI.) The lower photograph shows a later stage of progress, the blocks being undercut and nearly ready to turn over and incase the under side. Strips of wood have been pasted into each section to strengthen it.

"It will appear, therefore, that the collection, preparation and mounting of this gigantic fossil has been a task of extraordinary difficulty. No museum has ever before attempted to mount so large a fossil skeleton, and the great weight and fragile character of the bones made it necessary to devise especial methods to give each bone a rigid and complete support as otherwise it would soon break in pieces from its own weight. The proper articulating of the bones and posing of the limbs were equally difficult problems, for the Amphibious Dinosaurs, to which this animal belongs, disappeared from the earth long before the dawn of the Age of Mammals, and their nearest relatives, the living lizards, crocodiles, etc., are so remote from them in either proportions or habits that they are unsatisfactory guides in determining how the bones were articulated and are of but little use in posing the limbs and other parts of the body in positions that they must have taken during life. Nor among the higher animals of modern times is there one which has any analogy in appearance or habits of life to those which we have been obliged by the study of the skeleton to ascribe to the Brontosaurus.

"As far as the backbone and ribs were concerned, the articulating surfaces of the bones were a sufficient guide to enable us to pose this part of the skeleton properly. The limb joints, however, are so imperfect that we could not in this way make sure of having the bones in a correct position. The following method, therefore, was adopted.

"A dissection and thorough study was made by the writer, with the assistance of Mr. Granger, of the limbs of alligators and other reptiles, and the position, size and action of the principal muscles were carefully worked out. Then the corresponding bones of the Brontosaurus were studied, and the position and size of the corresponding muscles were worked out, so far as they could be recognized from the scars and processes preserved on the bone. The Brontosaurus limbs were then provisionally articulated and posed, and the position and size of each muscle were represented by a broad strip of paper extending from its origin to its insertion. The action and play of the muscles on the limb of the Brontosaurus could then be studied, and the bones adjusted until a proper and mechanically correct pose was reached. The limbs were then permanently mounted in these poses, and the skeleton as it stands is believed to represent, as nearly as study of the fossil enables us to know, a characteristic position that the animal actually assumed during life....

"In proportions and appearance the Brontosaurus was quite unlike any living animal. It had a long thick tail like the lizards and crocodiles, a long, flexible neck like an ostrich, a thick short, slab-sided body and straight, massive, post-like limbs suggesting the elephant, and a remarkably small head for the size of the beast. The ribs, limb-bones and tail-bones are exceptionally solid and heavy; the vertebrae of the back and neck, and the skull, on the contrary are constructed so as to combine the minimum of weight with the large surface necessary for the attachment of the huge muscles, the largest possible articulating surfaces, and the necessary strength at all points of strain. For this purpose they are constructed with an elaborate system of braces and buttresses of thin bony plates connecting the broad articulating surfaces and muscular attachments, all the bone between these thin plates being hollowed into a complicated system of air-cavities. This remarkable structure can be best seen in the unmounted skeleton of Camarasaurus, another Amphibious Dinosaur." (The scientific name Camarasaurus=chambered lizard, has reference to this peculiarity of construction.)

"The teeth of the Brontosaurus indicate that it was an herbivorous animal, feeding on soft vegetable food. Three opinions as to the habitat of Amphibious Dinosaurs have been held by scientific authorities. The first, advocated by Professor Owen, who described the first specimens found sixty years ago (1841-60) and supported especially by Professor Cope, has been most generally adopted. This regards the animals as spending their lives entirely in shallow water, partly immersed, wading about on the bottom, or perhaps occasionally swimming, but unable to emerge entirely upon dry land.[12] More recently, Professor Osborn has advocated the view that they resorted occasionally to the land for egg laying or other purposes, and still more recently the view has been taken by Mr. Riggs and the late Professor Hatcher that they were chiefly terrestrial animals. The writer inclines to the view of Owen and Cope, whose unequalled knowledge of comparative anatomy renders their opinion on this doubtful question especially authoritative.

Fig. 22.: Restoration of Brontosaurus by C.R. Knight, under direction of Professor Osborn.

After Osborn

Fig. 22.—Restoration of Brontosaurus by C.R. Knight, under direction of Professor Osborn.

"The contrast between the massive structure of the limb-bones, ribs and tail, and the light construction of the backbone, neck and skull, suggests that the animal was amphibious, living chiefly in shallow water, where it could wade about on the bottom, feeding upon the abundant vegetation of the coastal swamps and marshes, and pretty much out of reach of the powerful and active Carnivorous Dinosaurs which were its principal enemies. The water would buoy up the massive body and prevent its weight from pressing too heavily on the imperfect joints of the limb and foot bones, which were covered during life with thick cartilage, like the joints of whales, sea-lizards and other aquatic animals. If the full weight of the animal came on these imperfect joints the cartilage would yield and the ends of the bones would grind against each other, thus preventing the limb from moving without tearing the joint to pieces. The massive, solid limb and foot bones weighted the limbs while immersed in water, and served the same purpose as the lead in a diver's shoes, enabling the Brontosaurus to walk about firmly and securely under water. On the other hand, the joints of the neck and back are exceptionally broad, well fitting and covered with a much thinner surface of cartilage. The pressure was thus much better distributed over the joint, and the full weight of the part of the animal above water (reduced as it was by the cellular construction of the bones) might be borne on these joints without the cartilage giving way.

"Looking at the mounted skeleton we may see that if a line be drawn from the hip joint to the shoulder-blade, all the bones below this are massive, all above (including neck and head) are lightly constructed. This line may be taken to indicate the average water-line, so to speak, of this Leviathan of the Shallows. The long neck would enable the animal, however, to wade to a considerable depth, and it might forage for food either in the branches or the tops of trees, or more probably, among the soft succulent water-plants of the bottom. The row of short spoon-shaped stubby teeth around the front of the mouth would serve to bite or pull off soft leaves and water-plants, but the animal evidently could not masticate its food, and must have swallowed it without chewing as do modern reptiles and birds.

"The brain-case occupies only a small part of the back of the skull, so that the brain must have been small even for a reptile, and its organization (as inferred from the form of the brain-case) indicates a very low grade of intelligence. Much larger than the brain proper was the spinal cord, especially in the region of the sacrum, controlling most of the reflex and involuntary actions of the huge organism. Hence we can best regard the Brontosaurus as a great, slow-moving animal automaton, a vast storehouse of organized matter directed chiefly or solely by instinct, and to a very limited degree, if at all, by conscious intelligence. Its huge size and its imperfect organization, compared with the great quadrupeds of today, rendered its movements slow and clumsy; its small and low brain shows that it must have been automatic, instinctive and unintelligent."

Composition of the Brontosaurus Skeleton. "The principal specimen, No. 460, is from the Nine Mile Crossing of the Little Medicine Bow River, Wyoming. It consists of the 5th, 6th, and 8th to 13th cervical vertebrae, 1st to 9th dorsal and 3rd to 19th caudal vertebrae, all the ribs, both coracoids, parts of sacrum and ilia, both ischia and pubes, left femur and astragalus, and part of left fibula. The backbone and most of the neck of this specimen were found articulated together in the quarry, the ribs of one side in position, the remainder of the bones scattered around them, and some of the tail bones weathered out on the surface.

"From No. 222, found at Como Bluffs, Wyo., were supplied the right scapula, 10th dorsal vertebra, and right femur and tibia.

"No. 339, from Bone-Cabin Quarry, Wyoming, supplied the 20th to 40th caudal vertebrae, No. 592, from the same locality the metatarsals of the right hind foot; and a few toe bones are supplied from other specimens.

Fig. 23.: Skull of Diplodocus from Bone-Cabin Quarry,

Fig. 23.—Skull of Diplodocus from Bone-Cabin Quarry, north of Medicine Bow, Wyoming.

"The remainder of the skeleton is modelled in plaster, the scapula, humerus, radius and ulna from the skeleton in the Yale Museum, the rest principally from specimens in our own collections. The modelling of the skull is based partly upon specimens in the Yale Museum, but principally upon the complete skull of Morosaurus shown in another case.

"Mounted by A. Hermann, completed Feb. 10, 1905."


Diplodocus. The Diplodocus nearly equalled the Brontosaurus in bulk and exceeded it in length. A skeleton in the Carnegie Museum at Pittsburgh measures 87 feet in total length; although the mount is composed from several individuals these proportions are probably not far from correct. The skull is smaller and differently shaped and the teeth are of quite different type. In the American Museum of Natural History, a partial skeleton is exhibited in the wall case to the left of the entrance of the Dinosaur Hall, and in an A-case near by are skulls of Diplodocus and Morosaurus and a model of the skull of Brontosaurus. The Diplodocus skull is widely different from the other two in size and proportions and in the characters of teeth.

When the first remains of these amphibious Dinosaurs were found in the Oxford Clays of England, they were considered by Richard Owen to be related to the Crocodiles, and named Opisthocoelia. Subsequently the finding of complete skeletons in this country led Cope and Marsh to place them with the true Dinosaurs and the latter named them Sauropoda.[13] Remains of these animals have also been found in India, in German East Africa, in Madagascar, and in South America, so that they were evidently widely distributed. In the Northern world they survived until the Comanchic or Lower retaceous Period, but in the southern continents they may have lived on into the Upper Cretaceous or true Cretacic. Some of the remains recently found in German East Africa indicate an animal exceeding either Brontosaurus or Diplodocus in bulk.

Fig. 24.: The Largest Known Dinosaur. Sketch

Fig. 24.—The Largest Known Dinosaur. Sketch reconstruction of Brachiosaurus, from specimens in the Field Museum in Chicago, and the Natural History Museum in Berlin.

At the date of writing this handbook only preliminary accounts have been given of the marvellous finds made near Tendaguru by the expedition from Berlin. From these it appears that in length of neck and fore limb this East African Dinosaur greatly exceeded either Brontosaurus or Diplodocus. The hinder parts of the skeleton however, were relatively small. The proportions and measurements given tally closely with the American Brachiosaurus, a gigantic sauropod whose incomplete remains are preserved in the Field Museum in Chicago and to this genus the Berlin authorities now refer their largest and finest skeleton. If the Berlin specimens are correctly referred to Brachiosaurus they indicate an animal somewhat exceeding Diplodocus or Brontosaurus in total bulk but distinguished by much longer fore limbs and an immensely long neck—a giraffe-like wader adapted to take refuge in deeper waters, more out of reach of the fierce carnivores of the land.[14]


FOOTNOTES:

[11] The mounted Skeleton of Brontosaurus, by W.D. Matthew, Amer. Mus. Jour. Vol. v, pp. 63-70, figs. 1-5.

[12] Professor Williston makes the following criticism of this theory:

"I cannot agree with this view—the animals must have laid their eggs upon land—for the reason that reptile eggs cannot hatch in water. S.W.W."

 But with deference to Williston's high authority I may note that there is no evidence that the Sauropoda were egg-laying reptiles. They, or some of them, may have been viviparous like the Ichthyosaurus.

[13] European palaeontologists, especially Huxley and Seeley in England, had also recognized their true relationships, and Seeley's term Cetiosauria has precedence over Sauropoda, although the latter is in common use.

[14] It is of interest to observe that in this group of Sauropoda, the Brachiosauridæ, the neural spines of the vertebrae are much simpler and narrower than in the Brontosaurus and Diplodocus. The attachments were thus less extensive for the muscles of the back, indicating that these muscles were less powerful. This difference is correlated by Professor Williston with the longer fore limbs of the Brachiosaurus, as signifying that the animal was less able, as indeed he had less need, to rise up upon the hind limbs, in comparison with Diplodocus or Brontosaurus in which the fore limbs were relatively short.



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