THE DINOSAURS.
The continent of North America during that portion of the earth’s
history which we may call the Age of Reptiles would have seemed to our
eyes like another world. The present coastal outlines, mountain chains,
valleys, rivers, lakes, and plains have, with few exceptions, come
into being long since that time. During the early part[4] of the age
there were high mountains in the eastern part of the continent, which
sent strong, muddy streams flowing to the Atlantic. California, on the
other hand, was under the Pacific; the Sierra Nevada region was a great
trough, while throughout that region which is now eastern Colorado,
Utah, western Texas, and Arizona there lay a belt of broad, shallow
lakes.
The plant life of those times differed as much from that of previous
ages as from those that were to follow. The great Pennsylvanian coal
forests of lepidodendrons, sigillarias, and their allies, had almost
completely vanished from the earth. The higher lands were clothed with
cone-bearers, such as the Aurucarian pines of present day Australia.
Thick, gloomy forests of tree ferns covered the moist regions, while
great “canebrakes” of horsetail reeds whose stems reached four or five
inches in thickness bordered the bayous and marshes. Cycads, trees
which, though related to the pines and spruces, look like palms, were
abundant in the forests of this time.
During the middle portion of the Age of Reptiles conditions, both in
geography and in plant life, underwent no striking change. But in the
late Mesozoic, the Cretaceous period, there were many changes. The
Atlantic Ocean encroached on the eastern part of the continent, while
the Gulf of Mexico extended as far north as Illinois, and reached
westward over Texas. A broad mediterranean sea stretched from the Gulf
to the Arctic Ocean, and from Iowa to Utah, with the Colorado Mountains
rising from it as a chain of islands. West of the sea was a broad belt
of swamp land which extended from northern Alberta almost to Mexico.
The plants of the Cretaceous changed with the geography. The Cycads,
so abundant in the early Mesozoic, became rare in most regions. The
highest types of flowering plants gained an almost complete ascendancy,
and forests of a decidedly modern appearance covered the continent from
the Gulf of Mexico to the Arctic Ocean. “Among the kinds of forest
trees whose remains are found in the continental deposits of the
Cretaceous are the magnolia, the myrtle, the laurel, the fig, the tulip
tree, the chestnut, the oak, beech, elm, poplar, willow, birch and
maple. Forests of Eucalyptus grew along the coast of New England,[5]
and palms on the Pacific shores of British Columbia. Sequoias of many
varieties ranged far into northern Canada. In northern Greenland there
were luxuriant forests of magnolias, figs, and cycads; and a similar
flora has been disinterred from the Cretaceous rocks of Alaska and
Spitsbergen. Evidently the lands within the Arctic Circle enjoyed
a warm and genial climate, as they had done during the Paleozoic.
Greenland had the temperature of Cuba and southern Florida, and the
time was yet far distant when it was to be wrapped in glacier ice.”[6]
Such were the conditions under which flourished the mightiest race of
animals that has ever lived upon land. The Dinosaurs not only were the
dominant animals of their time, but they reached sizes so great that
they have been rivalled by but one group of mammals--the whales. They
maintained their supremacy throughout a long period of time estimated
at from nine to one hundred millions of years; they survived important
changes in geography and climate, and became extinct through a
combination of causes which are yet only half known. Perhaps the great
changes in life conditions at the end of the Cretaceous had much to do
with their disappearance, as may also have been true of other reptiles
living at the same time. Not improbably, too, the rise of egg-eating
mammals, more intelligent and active than the dinosaurs, was a factor;
and last of all, there remains the ever ready and ever probable
hypothesis of racial old age.
The Dinosaurs were descended, in the opinion of those who have studied
them, from primitive, lizard-like reptiles with fairly long limbs, long
tails, five toes on each foot, and a complete series of sharp pointed
teeth. In all probability, according to Dr. W. D. Matthew,[7] this
ancestor was fully capable of living on dry land, and was more or less
in the habit of walking on its hind legs alone.
One of the most striking things about the Dinosaurs is their notable
lack of brain power. In man, a creature weighing anywhere from one
hundred twenty to two hundred pounds, on the average, the weight of a
normal brain is about three pounds. The smallest brain that can exist
and possess reasoning powers is about two pounds, while the smallest
human brain known to be fitted for life alone weighs just a little more
than ten ounces.
We can readily see that if conditions were proportionate among
the Dinosaurs the size of the brain would be almost unbelievable.
Instead, the reptile Claosaurus, which once inhabited the valleys of
Maryland, and was twenty-five feet long and more than twelve feet
high, had a brain so small that it must have weighed less than one
pound. Brachiosaurus, probably the biggest beast that ever walked,
was not much better equipped, while Triceratops, a Dinosaur having
more than twice the bulk of the average elephant, possessed a brain
weighing about two pounds. Truly they who are prone to refer to the
“brainlessness” of human beings should consider the Dinosaurs before
they speak! These great beasts must have known just about enough to
rest when they were tired and eat when they were hungry; “coming in out
of the rain” doubtless was an idea altogether too complicated for them
to grasp.
But, as Lucas and others have emphasized, intelligence is one thing and
living another and a very different one. The poor, weak brains of the
Dinosaurs doubtless had but little to do with the primary functions
of life; the spinal cord took care of them. In some of the beasts,
notably in the armored giant Stegosaurus, the spinal cord possessed
a sacral enlargement that was twenty times as large as the brain.
This remarkable fact, when announced by Professor Marsh, attracted
great attention, and was made the subject of much newspaper writing.
Thousands of people who would never recognize the name Stegosaur are
familiar with the marvelous character of that beast as he is described
in this catchy though fanciful poem:
[Illustration: PLATE IV.
The armored giant Stegosaurus.]
THE DINOSAUR.
Behold the mighty dinosaur,
Famous in prehistoric lore,
Not only for his weight and strength
But for his intellectual length.
You will observe by these remains
The creature had two sets of brains--
One in his head (the usual place),
The other at his spinal base.
Thus he could reason a priori
As well as a posteriori.
No problem bothered him a bit:
He made both head and tail of it.
So wise he was, so wise and solemn,
Each thought just filled a spinal column.
If one brain found the pressure strong
It passed a few ideas along;
If something slipt his forward mind
’Twas rescued by the one behind;
And if in error he was caught
He had a saving afterthought.
As he thought twice before he spoke
He had no judgments to revoke;
For he could think without congestion,
Upon both sides of every question.
O’ gaze upon this model beast,
Defunct ten million years at least!
The Dinosaurs, like all other groups of animals, may be divided
into sub-groups, depending on habits, structure, etc. The commonest
classification separates them into three divisions: the carnivorous,
the amphibious, and the beaked. One of the most remarkable of the
flesh-eating species, though not the largest, is Allosaurus, a powerful
reptile that once roamed over the western part of North America. He
walked by means of his hind legs only, using his long tail as a balance
for his body. The huge head, armed with long, sharp teeth, was set on
a heavy, short neck; casts of the brain indicate that it was of much
the same type as that of the modern alligator, but considerably less
effective.
[Illustration: PLATE V.
One of the greater carnivorous dinosaurs, showing the large head,
long teeth, tiny fore limbs and ponderous walking legs typical of the
group. (Modified after Lull.)
]
Allosaurus lived upon dry land, seldom venturing into the great
Mesozoic swamps. He was predaceous, attacking his prey in swift, mighty
rushes, tearing it with the jaws and occasionally striking it with the
powerful tail. Anything like the elaborate stalking of game such as we
see in the tiger and lion of today was impossible to the Dinosaur; he
simply lay in wait until the close approach of prey stimulated him to
his tremendous but half instinctive rush. The kill was torn to pieces
and swallowed without chewing, as is the case with the alligator of
today.
The amphibious Dinosaurs, which must have provided much of the food for
Allosaurus and his kin, were characterized by blunt teeth and claws,
strong, elephant-like legs and feet, long neck, and small head. They
attained very great size, some of them, as we have said, being the
largest of land animals. They may well be typified by Brontosaurus, the
Thunder Lizard, which though not the longest, was one of the largest
of his kind. The skeleton which is mounted in the American Museum
is sixty-six feet long, the animal when alive having weighed about
thirty-eight tons. The body was large and rather short; the neck long,
and the head small. The tail was long and thick, and the legs massive
and post-like. The bones of the legs were very long and heavy, the
thigh bones being from five to six feet long--the largest single bones
so far discovered. The vertebrae, or “backbones,” were as much as four
and one-half feet high, being larger than those of the whale.
The teeth and general structure of Brontosaurus give fairly reliable
evidence as to the habits of the animal. It spent its life in the
shallow water of lagoons, feeding upon the succulent water plants.
There is no evidence that it swam very much; probably its principal
mode of progression was wading, with the immense body partly supported
by the water. Perhaps the beast occasionally left the water for
the purpose of laying eggs, as is shown in Knight’s oft-printed
restoration. It appears, however, that Brontosaurus was not built for
land travel; that his joints were so imperfectly formed that he could
not have moved on land without tearing those of the leg to pieces. Dr.
Matthew thinks that the species of this genus bore their young alive,
as do certain modern reptiles, and therefore had no need to leave the
swamps and bayous at any time during their lives.
Within the last few years there have come sketchy preliminary accounts
of a mammoth find near Tendaguru, Africa, by an expedition sent out
from Germany. They announce the discovery of a Dinosaur whose neck and
fore limbs far exceeded those of Brontosaurus, although the hinder
parts of the skeleton were relatively small. It appears that this
giant, which the German savants appropriately named Gigantosaurus,
is identical with the American form Brachiosaurus, whose fragmentary
remains are on exhibit at the Field Museum of Chicago. It is,
without question the largest known Dinosaur, so far as weight goes--a
long-necked wading creature that lived much as did Brontosaurus but was
capable of going into considerably deeper waters, quite beyond reach of
the fierce carnivorous giants of the land.
[Illustration: PLATE VI.
Fig. 1--Diplodocus, the longest Dinosaur known.
Fig. 2--Brontosaurus, the giant that could not walk except in water,
because of his great weight and feeble joints.]
The distinctive character of the third group of Dinosaurs is the
possession of a horny beak or bill, much like that of modern birds.
Indeed, there are many features in the anatomy of these reptiles that
indicate their relationship to the birds, and it is probable that the
remote ancestors of the two groups were very closely connected--perhaps
identical. But the ancestral birds developed feathers and took to
flying, while the ancestral beaked Dinosaurs (Predentates) specialized
in the direction of land life, and in their later development became
even more widely diversified in form than did their feathered relatives.
The beaked Dinosaurs lived entirely upon vegetable food. The best known
of them, Triceratops or “He-of-the-three-horned-head,” looked more like
a gigantic, long-tailed rhinoceros than a reptile. Above each eye was
a long, sharp horn which extended forward; the bony cores which remain
in the fossils are as much as thirty-three inches long, and during
life the horny covering must have lengthened them by six inches to a
foot. The horn above the nose was considerably shorter, yet would have
compared favorably with that of many rhinoceroses.
“Standing before the skull of Triceratops,” says Dr. Lucas, “... 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?’”
Two Triceratops horns in the possession of the United States National
Museum bear the marks of such an encounter as that described by Dr.
Lucas, for one of them is broken about half way between the tip and the
base, and the stump is healed and rounded over. Evidently their owner
was not seriously injured in the fight, but lived to a ripe old age in
spite of his infirmity.
Triceratops had a number of relatives, at least one of which is even
more famous than himself. This is Stegosaurus, the great Armored
Dinosaur that possessed the remarkable enlargement of the spinal cord.
Like his three-horned relative, Stegosaurus was a land dweller that
walked upon four legs. His head was very small, as were his fore limbs;
his body was very large, and his tail long and powerful. Along his back
ran two rows of bony plates, some of which were four inches thick at
the base, and two and one-half feet high. The tail bore, near the tip,
two pairs of spines which were almost as long as the back plates, and
half again as thick. The hind limbs were long and straight, in marked
contrast with the front ones, so that the creature when walking must
have appeared to be in constant danger of turning a somersault.
[Illustration: PLATE VII. Triceratops, the Three Horned Reptile.]
Stegosaurus was a contemporary of Brontosaurus and the carnivorous
Allosaurus. Like the former, he was a peaceful plant feeder, but unlike
him, did not flee to the shallows in order to avoid his flesh-eating
relatives. For this great armor, although undoubtedly developed in
the interests of peace, was hardly designed with any consideration
for the Hebrew creed of turning one cheek when the other is smitten.
Stegosaurus was too brainless and to clumsy to go about seeking
trouble, but to those creatures foolhardy enough to attack him he
could offer stiff resistance. A few blows of the huge spiked tail,
more powerful than the club of the mightiest ogre of mythology, would
be quite enough for even such giants as Allosaurus. Stegosaurus, like
the rhinoceros of modern Africa, probably went his way unharming and
unharmed.
* * * * *
The Dinosaurs first appeared during the Triassic period when they
roamed through the valleys of eastern North America in great numbers,
leaving their footprints on the soft, fine mud of the valley flats.
The succeeding period, the Jurassic, was their Golden Age--the age of
Brontosaurus, Allosaurus, Stegosaurus, Diplodocus and other monsters.
During the Comanchean and Cretaceous periods the larger Dinosaurs
became extinct, and were supplanted by the smaller beaked forms,
such as Triceratops. At the end of the Cretaceous period, which was
also the end of the Age of Reptiles, the Dinosaurs became almost
totally extinct. Perhaps a few of them survived in specially favored
localities, for Dinosaur bones are found in rocks which a number of
geologists refer to the beginning of the Age of Mammals. But such
survivals were of small importance, and had little effect on the
general annihilation. The Dinosaurs were unable to meet the demands of
a dry-land environment, and joined the great hosts of creatures that at
various times have held the earth in their sway and then, defeated by
causes at which we can only guess, have passed into extinction.
FOOTNOTES:
[4] The Mesozoic Era, or Age of Reptiles, is divided into four
periods--Triassic, Jurassic, Comanchean, and Cretaceous. The first two
are here referred to as the “early” part of the age; the third as the
“middle,” and the fourth as the “late.”
[5] The Eucalyptus is now common in Australia, while the Sequoia is the
“Big Tree” of California.
[6] Norton, Elements of Geology, 1st Ed., p. 378.
[7] Dr. Matthew, curator of vertebrate paleontology at the American
Museum of Natural History, is one of the authorities on Dinosaurs. His
book, “Dinosaurs,” published by the Museum, has afforded much of the
material to be found in this chapter.