THE AMPHIBIOUS DINOSAURS, BRONTOSAURUS, DIPLODOCUS, ETC.
SUB-ORDER OPISTHOCOELIA (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.
[Illustration: 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.
[Illustration: 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.
[Illustration: Fig. 22.--RESTORATION OF BRONTOSAURUS BY C.R.
KNIGHT, UNDER DIRECTION OF PROFESSOR OSBORN. _After 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.
[Illustration: 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 Cretaceous 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.
[Illustration: 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:
[Footnote 11: The mounted Skeleton of Brontosaurus, by W.D. Matthew,
Amer. Mus. Jour. Vol. v, pp. 63-70, figs. 1-5.]
[Footnote 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.]
[Footnote 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.]
[Footnote 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.]