side was thought to belong to a fish._
The next birds that we know are from our own country, and although
separated by an interval of thousands of years from the Jurassic
Archaeopteryx, time enough for the members of one group to have quite
lost their wings, they still retain teeth, and in this respect the most
bird-like of them is quite unlike any modern bird. These come from the
chalk beds of western Kansas, and the first specimens were obtained by
Professor Marsh in his expeditions of 1870 and 1871, but not until a few
years later, after the material had been cleaned and was being studied,
was it ascertained that these birds were armed with teeth. The smaller
of these birds, which was apparently not unlike a small gull in general
appearance, was, saving its teeth, so thoroughly a bird that it may be
passed by without further notice, but the larger was remarkable in many
ways. Hesperornis, the western bird, was a great diver, in some ways the
greatest of the divers, for it stood higher than the king penguin,
though more slender and graceful in general build, looking somewhat like
an overgrown, absolutely wingless loon.
The penguins, as everyone knows, swim with their front limbs--we can't
call them wings--which, though containing all the bones of a wing, have
become transformed into powerful paddles; Hesperornis, on the other
hand, swam altogether with its legs--swam so well with them, indeed,
that through disuse the wings dwindled away and vanished, save one bone.
This, however, is not stating the theory quite correctly; of course the
matter cannot be actually proved. Hesperornis was a large bird, upwards
of five feet in length, and if its ancestors were equally bulky their
wings were quite too large to be used in swimming under water, as are
those of such short-winged forms as the Auks which fly under the water
quite as much as they fly over it. Hence the wings were closely folded
upon the body so as to offer the least possible resistance, and being
disused, they and their muscles dwindled, while the bones and muscles
of the legs increased by constant use. By the time the wings were small
enough to be used in so dense a medium as water the muscles had become
too feeble to move them, and so degeneration proceeded until but one
bone remained, a mere vestige of the wing that had been. The penguins
retain their great breast muscles, and so did the Great Auk, because
their wings are used in swimming, since it requires even more strength
to move a small wing in water than it does to move a large wing in the
thinner air. As for our domesticated fowls--the turkeys, chickens, and
ducks--there has not been sufficient lapse of time for their muscles to
dwindle, and besides artificial selection, the breeding of fowls for
food has kept up the mere size of the muscles, although these lack the
strength to be found in those of wild birds.
As a swimming bird, one that swims with its legs and not with its wings,
Hesperornis has probably never been equalled, for the size and
appearance of the bones indicate great power, while the bones of the
foot were so joined to those of the leg as to turn edgewise as the foot
was brought forward and thus to offer the least possible resistance to
the water. It is a remarkable fact that the leg bones of Hesperornis are
hollow, remarkable because as a rule the bones of aquatic animals are
more or less solid, their weight being supported by the water; but those
of the great diver were almost as light as if it had dwelt upon the dry
land. That it did not dwell there is conclusively shown by its build,
and above all by its feet, for the foot of a running bird is modified in
quite another way.
The bird was probably covered with smooth, soft feathers, something like
those of an Apteryx; this we know because Professor Williston found a
specimen showing the impression of the skin of the lower part of the leg
as well as of the feathers that covered the "thigh" and head. While such
a covering seems rather inadequate for a bird of such exclusively
aquatic habits as Hesperornis must have been, there seems no getting
away from the facts in the case in the shape of Professor Williston's
specimen, and we have in the Snake Bird, one of the most aquatic of
recent birds, an instance of similarly poor covering. As all know who
have seen this bird at home, its feathers shed the water very
imperfectly, and after long-continued submersion become saturated, a
fact which partly accounts for the habit the bird has of hanging itself
out to dry.
[Illustration: Fig. 16.--Hesperornis, the Great Toothed Diver. _From a
drawing by J. M. Gleeson._]
The restoration which Mr. Gleeson has drawn differs radically from any
yet made, and is the result of a careful study of the specimen belonging
to the United States National Museum. No one can appreciate the
peculiarities of Hesperornis and its remarkable departures from other
swimming birds who has not seen the skeleton mounted in a swimming
attitude. The great length of the legs, their position at the middle of
the body, the narrowness of the body back of the hip joint, and the
disproportionate length of the outer toe are all brought out in a manner
which a picture of the bird squatting upon its haunches fails utterly to
show. As for the tail, it is evident from the size and breadth of the
bones that something of the kind was present; it is also evident that it
was not like that of an ordinary bird, and so it has been drawn with
just a suggestion of Archaeopteryx about it.
The most extraordinary thing about Hesperornis, however, is the position
of the legs relative to the body, and this is something that was not
even suspected until the skeleton was mounted in a swimming attitude. As
anyone knows who has watched a duck swim, the usual place for the feet
and legs is beneath and in a line with the body. But in our great
extinct diver the articulations of the leg bones are such that this is
impossible, and the feet and lower joint of the legs (called the tarsus)
must have stood out nearly at right angles to the body, like a pair of
oars. This is so peculiar and anomalous an attitude for a bird's legs
that, although apparently indicated by the shape of the bones, it was at
first thought to be due to the crushing and consequent distortion to
which the bones had been subjected, and an endeavor was made to place
the legs in the ordinary position, even though this was done at the
expense of some little dislocation of the joints. But when the mounting
of the skeleton had advanced further it became more evident that
Hesperornis was not an ordinary bird, and that he could not have swum in
the usual manner, since this would have brought his great knee-caps up
into his body, which would have been uncomfortable. And so, at the cost
of some little time and trouble,[7] the mountings were so changed that
the legs stood out at the sides of the body, as shown in the picture.
[7] _The mounting of fossil bones is quite a different matter from the
wiring of an ordinary skeleton, since the bones are not only so hard
that they cannot be bored and wired like those of a recent animal, but
they are so brittle and heavy that often they will not sustain their own
weight. Hence such bones must be supported from the outside, and to do
this so that the mountings will be strong enough to support their
weight, allow the bones to be removed for study, and yet be
inconspicuous, is a difficult task._
A final word remains to be said about toothed birds, which is, that the
visitor who looks upon one for the first time will probably be
disappointed. The teeth are so loosely implanted in the jaw that most of
them fall out shortly after death, while the few that remain are so
small as not to attract observation.
By the time the Eocene Period was reached, even before that, birds had
become pretty much what we now see them, and very little change has
taken place in them since that time; they seem to have become so exactly
adapted to the conditions of existence that no further modification has
taken place. This may be expressed in another way, by saying that while
the Mammals of the Eocene have no near relatives among those now living,
entire large groups having passed completely out of existence, the few
birds that we know might, so far as their appearance and affinities go,
have been killed yesterday.
Were we to judge of the former abundance of birds by the number we find
in a fossil state, we should conclude that in the early days of the
world they were remarkably scarce, for bird bones are among the rarest
of fossils. But from the high degree of development evidenced by the few
examples that have come to light, and the fact that these represent
various and quite distinct species,[8] we are led to conclude that
birds were abundant enough, but that we simply do not find them.
[8] _But three birds, besides a stray feather or two, are so far known
from the Eocene of North America. One of these is a fowl not very unlike
some of the small curassows of South America; another is a little bird,
supposed to be related to the sparrows, while the third is a large bird
of uncertain relationships._
Several eggs, too--or, rather, casts of eggs--have lately been found in
the Cretaceous and Miocene strata of the West; and, as eggs and birds
are usually associated, we are liable at any time to come upon the bones
of the birds that laid them.
To the writer's mind no thoroughly satisfactory explanation has been
given for the scarcity of bird remains; but the reason commonly advanced
is that, owing to their lightness, dead birds float for a much longer
time than other animals, and hence are more exposed to the ravages of
the weather and the attacks of carrion-feeding animals. It has also been
said that the power of flight enabled birds to escape calamities that
caused the death of contemporary animals; but all birds do not fly; and
birds do fall victims to storms, cold, and starvation, and even perish
of pestilence, like the Cormorants of Bering Island, whose ranks have
twice been decimated by disease.
It is true that where carnivorous animals abound, dead birds do
disappear quickly; and my friend Dr. Stejneger tells me that, while
hundreds of dead sea-fowl are cast on the shores of the Commander
Islands, it is a rare thing to find one after daylight, as the bodies
are devoured by the Arctic foxes that prowl about the shores at night.
But, again, as in the Miocene of Southern France and in the Pliocene of
Oregon, remains of birds are fairly numerous, showing that, under proper
conditions, their bones are preserved for future reference, so that we
may hope some day to come upon specimens that will enable us to round
out the history of bird life in the past.
_REFERENCES_
_The first discovered specimen of Archaeopteryx, Archaeopteryx macrura, is
in the British Museum, the second more complete example is in the Royal
Museum of Natural History, Berlin. The largest collection of toothed
birds, including the types of Hesperornis, Ichthyornis and others, is in
the Yale University Museum, at New Haven. The United States National
Museum at Washington has a fine mounted skeleton of Hesperornis, and the
State University of Kansas, at Lawrence, has the example showing the
impressions of feathers._
_For scientific descriptions of these birds the reader is referred to
Owen's paper "On the Archaeopteryx of von Meyer, with a Description of
the Fossil Remains, etc.," in the "Transactions of the Philosophical
Society of London for 1863," page 33, and "Odontornithes, a Monograph of
the Extinct Toothed Birds of North America," by O. C. Marsh. Much
popular and scientific information concerning the early birds is to be
found in Newton's "Dictionary of Birds," and "The Story of Bird Life,"
by W. P. Pycraft; the "Structure and Life of Birds," by F. W. Headley;
"The Story of the Birds," by J. Newton Baskett._
[Illustration: Fig. 17.--Archaeopteryx as Restored by Mr. Pycraft.]
VI
THE DINOSAURS
"_Shapes of all sorts and sizes, great and small._"
A few million years ago, geologists and physicists do not agree upon the
exact number, although both agree upon the millions, when the Rocky
Mountains were not yet born and the now bare and arid western plains a
land of lakes, rivers, and luxuriant vegetation, the region was
inhabited by a race of strange and mighty reptiles upon whom science has
bestowed the appropriate name of Dinosaurs, or terrible lizards.
Our acquaintance with the Dinosaurs is comparatively recent, dating from
the early part of the nineteenth century, and in America, at least, the
date may be set at 1818, when the first Dinosaur remains were found in
the Valley of the Connecticut, although they naturally were not
recognized as such, nor had the term been devised. The first Dinosaur
to be formally recognized as representing quite a new order of reptiles
was the carnivorous Megalosaur, found near Oxford, England, in 1824.
[Illustration: Fig. 18.--Thespesius. A Common Herbivorous Dinosaur of
the Cretaceous. _From a drawing by Charles R. Knight._]
For a long time our knowledge of Dinosaurs was very imperfect and
literally fragmentary, depending mostly upon scattered teeth, isolated
vertebrae, or fragments of bone picked up on the surface or casually
encountered in some mine or quarry. Now, however, thanks mainly to the
labors of American palaeontologists, thanks also to the rich deposits of
fossils in our Western States, we have an extensive knowledge of the
Dinosaurs, of their size, structure, habits, and general appearance.
There are to-day no animals living that are closely related to them;
none have lived for a long period of time, for the Dinosaurs came to an
end in the Cretaceous, and it can only be said that the crocodiles, on
the one hand, and the ostriches, on the other, are the nearest existing
relatives of these great reptiles.
For, though so different in outward appearance, birds and reptiles are
structurally quite closely allied, and the creeping snake and the bird
on which it preys are relatives, although any intimate relationship
between them is of the serpent's making, and is strongly objected to by
the bird.
But if we compare the skeleton of a Dinosaur with that of an ostrich--a
young one is preferable--and with those of the earlier birds, we shall
find that many of the barriers now existing between reptiles and birds
are broken down, and that they have many points in common. In fact, save
in the matter of clothes, wherein birds differ from all other animals,
the two great groups are not so very far apart.
The Dinosaurs were by no means confined to North America, although the
western United States seem to have been their headquarters, but ranged
pretty much over the world, for their remains have been found in every
continent, even in far-off New Zealand.
In point of time they ranged from the Trias to the Upper Cretaceous,
their golden age, marking the culminating point of reptilian life, being
in the Jurassic, when huge forms stalked by the sea-shore, browsed amid
the swamps, or disported themselves along the reedy margins of lakes
and rivers.
They had their day, a day of many thousand years, and then passed away,
giving place to the superior race of mammals which was just springing
into being when the huge Dinosaurs were in the heyday of their
existence.
And it does seem as if in the dim and distant past, as in the present,
brains were a potent factor in the struggle for supremacy; for, though
these reptiles were giants in size, dominating the earth through mere
brute force, they were dwarfs in intellect.
The smallest human brain that is thought to be compatible with life
itself weighs a little over ten ounces, the smallest that can exist with
reasoning powers is two pounds; this in a creature weighing from 120 to
150 pounds.
What do we find among Dinosaurs? Thespesius, or Claosaurus, which may
have walked where Baltimore now stands, was twenty-five feet in length
and stood a dozen feet high in his bare feet, had a brain smaller than a
man's clenched fist, weighing less than one pound.
Brontosaurus, in some respects the biggest brute that ever walked, was
but little better off, and Triceratops, and his relatives, creatures
having twice the bulk of an elephant, weighing probably over ten tons,
possessed a brain weighing not over two pounds!
How much of what we term intelligence could such a creature
possess--what was the extent of its reasoning powers? Judging from our
own standpoint and the small amount of intellect apparent in some humans
with much larger brains, these big reptiles must have known just about
enough to have eaten when they were hungry, anything more was
superfluous.
However, intelligence is one thing, life another, and the spinal cord,
with its supply of nerve-substance, doubtless looked after the mere
mechanical functions of life; and while even the spinal cord is in many
cases quite small, in some places, particularly in the sacral region, it
is subject to considerable enlargement. This is notably true of
Stegosaurus, where the sacral enlargement is twenty times the bulk of
the puny brain--a fact noted by Professor Marsh, and seized upon by the
newspapers, which announced that he had discovered a Dinosaur with a
brain in its pelvis.
In their great variety of size and shape the Dinosaurs form an
interesting parallel with the Marsupials of Australia. For just as these
are, as it were, an epitome of the class of mammals, mimicking the
herbivores, carnivores, rodents and even monkeys, so there are
carnivorous and herbivorous Dinosaurs--Dinosaurs that dwelt on land and
others that habitually resided in the water, those that walked upright
and those that crawled about on all fours; and, while there are no hints
that any possessed the power of flight, some members of the group are
very bird-like in form and structure, so much so that it has been
thought that the two may have had a common ancestry.
The smallest of the Dinosaurs whose acquaintance we have made were
little larger than chickens; the largest claim the distinction of being
the largest known quadrupeds that have walked the face of the earth, the
giants not only of their day, but of all time, before whose huge frames
the bones of the Mammoth, that familiar byword for all things great,
seem slight.
For Brontosaurus, the Thunder Lizard, beneath whose mighty tread the
earth shook, and his kindred were from 40 to 60 feet long and 10 to 14
feet high, their thigh bones measuring 5 to 6 feet in length, being the
largest single bones known to us, while some of the vertebrae were 4-1/2
feet high, exceeding in dimensions those of a whale.
[Illustration: Fig. 19--A Hind Leg of the Great Brontosaurus, the
Largest of the Dinosaurs.]
The group to which Brontosaurus belongs, including Diplodocus and
Morosaurus, is distinguished by a large, though rather short, body,
very long neck and tail, and, for the size of the animal, a very small
head. In fact, the head was so small and, in the case of Diplodocus, so
poorly provided with teeth that it must have been quite a task, or a
long-continued pleasure, according to the state of its digestive
apparatus, for the animal to have eaten its daily meal.
[Illustration: Fig. 20.--A Single Vertebra of Brontosaurus.]
An elephant weighing 5 tons eats 100 pounds of hay and 25 pounds of
grain for his day's ration; but, as this food is in a comparatively
concentrated form, it would require at least twice this weight of green
fodder.
It is a difficult matter to estimate the weight of a live Diplodocus or
a Brontosaurus, but it is pretty safe to say that it would not be far
from 20 tons, and that one would devour at the very least something over
700 pounds of leaves or twigs or plants each day--more, if the animal
felt really hungry.
But here we must, even if reluctantly, curb our imagination a little and
consider another point: the cold-blooded, sluggish reptiles, as we know
them to-day, do not waste their energies in rapid movements, or in
keeping the temperature of their bodies above that of the air, and so by
no means require the amount of food needed by more active, warm-blooded
animals. Alligators, turtles, and snakes will go for weeks, even months,
without food, and while this applies more particularly to those that
dwell in temperate climes and during their winter hibernation
practically suspend the functions of digestion and respiration, it is
more or less true of all reptiles. And as there is little reason for
supposing that reptiles behaved in the past any differently from what
they do in the present, these great Dinosaurs may, after all, not have
been gifted with such ravenous appetites as one might fancy. Still, it
is dangerous to lay down any hard and fast laws concerning animals, and
he who writes about them is continually obliged to qualify his
remarks--in sporting parlance, to hedge a little, and in the present
instance there is some reason, based on the arrangement of vertebrae and
ribs, to suppose that the lungs of Dinosaurs were somewhat like those of
birds, and that, as a corollary, their blood may have been better
aerated and warmer than that of living reptiles. But, to return to the
question of food.
From the peculiar character of the articulations of the limb-bones, it
is inferred that these animals were largely aquatic in their habits, and
fed on some abundant species of water plants. One can readily see the
advantage of the long neck in browsing off the vegetation on the bottom
of shallow lakes, while the animal was submerged, or in rearing the head
aloft to scan the surrounding shores for the approach of an enemy. Or,
with the tail as a counterpoise, the entire body could be reared out of
water and the head be raised some thirty feet in the air.
Triceratops, he of the three-horned face, had a remarkable skull which
projected backward over the neck, like a fireman's helmet, or a
sunbonnet worn hind side before, while over each eye was a massive horn
directed forward, a third, but much smaller horn being sometimes present
on the nose.
The little "Horned Toad," which isn't a toad at all, is the nearest
suggestion we have to-day of Triceratops; but, could he realize the
ambition of the frog in the fable and swell himself to the dimensions of
an ox, he would even then be but a pigmy compared with his ancient and
distant relative.
So far as mere appearance goes he would compare very well, for while so
much is said about the strange appearance of the Dinosaurs, it is to be
borne in mind that their peculiarities are enhanced by their size, and
that there are many lizards of to-day that lack only stature to be even
more _bizarre_; and, for example, were the Australian Moloch but big
enough, he could give even Stegosaurus "points" in more ways than one.
Standing before the skull of Triceratops, looking him squarely in the
face, 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."
[Illustration: Fig. 21.--Moloch. A Modern Lizard that Surpasses the
Stegosaurs in All but Size. _From a drawing by J. M. Gleeson._]