THE MOST ANCIENT BIRDS.
When and how the first bird came into being is one of the undiscovered
secrets of paleontology. The probability is that at some time during
the late Triassic--the first division of the Mesozoic, or “Middle Life”
era--a little reptile somewhat like the smallest of the bird-like
dinosaurs developed feathers and began to make short flights through
the air. Whether this reptile, which actually may have been a dinosaur,
developed wings on his forelegs and rose from the ground, or whether he
developed feathers on both front and hind legs and began by gliding,
is a matter of theory. Just now the latter view seems to be the more
elaborately worked out, and therefore the more widely accepted. But
there is fashion in theories just as there is in dress, and some new
discovery may easily render the supposed four-winged ancestor passe.
But, uncertain though the origin of birds may be, there is little
doubt regarding the most ancient known member of the class. It is the
famous Archeopteryx, found in the equally noted lithographic quarries
at Solenhofen, Bavaria. This ancient bird, for all practical purposes
the starting point in the history of the feathered animals,[10] was
considerably smaller than a crow, and possessed a short, strong beak
which was armed with sharp, reptile-like teeth. The wings were short
and broad, while the tail was considerably longer than the rest of the
body, and was of very remarkable construction. As everyone who has ever
shot sparrows or plucked a chicken knows, the tail of a modern bird is
made up very much like a feather fan, and closes up like one, with the
bony part very short and broad. In the Archeopteryx, however, the tail
was long and lizard-like, with the feathers placed in pairs, one pair
to each tail joint. Thus the creature when flying must have looked much
like an undersized crow dragging after him a palm leaf instead of a
tail.
As may be inferred from the foregoing description, the feathers of
Archeopteryx are well preserved in the two fossils which have been
found. However, they are shown only on certain parts of the body,
and from this some scientists have concluded that the bird possessed
feathers on only the wings, tail, and thighs. There seems, however,
to be little ground for this conclusion, and restorations of the
creature showing it as a bird-like lizard with a few tufts of feathers
are hardly to be relied upon. It is very improbable that such highly
developed feathers as those which are preserved should have been
present without the more primitive ones being found on the back,
breast, and neck. Also, since the feathers of the latter type are
smaller and more easily destroyed than those of the wings and tail,
it is quite natural that they should fail to be preserved in the old
Jurassic sediments.
[Illustration: PLATE X.
The fossil remains of Archeopteryx.]
The Archeopteryx lived during the period when the Dinosaurs were in the
height of their glory. Whether or not he was descended from any of the
birds who, without much question, left tracks in the Connecticut valley
during the preceding age cannot be determined. Doubtless those ancient
forms would hardly have been recognizable as birds, yet inasmuch as
they wore feathers they may properly be placed in that group. For
we may both concisely and accurately define birds as animals with
feathers, for feathers are possessed by every bird that lives, and are
possessed by no creatures other than birds. Flight, as we shall see in
the next chapter, is a characteristic that is by no means universal in
the bird world, but even the flightless birds, such as the ostrich and
the Apteryx, are covered with feathers. True, in the penguins, birds
that spend most of their time on and under the water, the feathers
have been changed so that they are hardly recognizable, yet a closer
examination shows the essential structure to be there, and our
definition is upheld.
[Illustration: PLATE XI.
Hesperornis swimming beneath the water.
(After Lucas.)]
The next birds of which we have relics were inhabitants of the western
part of our own country, and although separated by tens or hundreds of
thousands of years from the Jurassic Archeopteryx, they still possessed
teeth--a characteristic that separates them sharply from all modern
birds. They were first collected during the years 1870-71 by Professor
O. C. Marsh, who was at that time exploring the chalk beds of western
Kansas. It was not until 1873, however, that Marsh was able to give his
specimens a thorough laboratory examination and discovered that the
jaws were set with teeth, thus establishing a new and most important
fact in evolution.[11] Previous to this men had been quite willing
to believe that birds were descended from toothed animals, for all
the creatures from which they might have come were toothed, but not a
few hesitated to acknowledge that birds themselves possessed similar
equipment. But with Marsh’s discovery the case was proved, and “scarce
as hen’s teeth” ceased to be a joke, at least so far as fossils are
concerned.
The larger of the two species of birds found in Kansas was a truly
remarkable creature, in some ways the most astonishing bird that has
ever lived. Hesperornis (western bird) looked much like an overgrown,
wingless loon, or “hell diver,” and was quite as much at home in the
water as is that bird. Instead of swimming with the wings, as does
the penguin of Antarctic regions, Hesperornis swam with its legs and
feet, and did it so successfully that the wings disappeared, with
the exception of a single bone. At the same time, the muscles of the
breast, which are used in moving the wings, dwindled away, so that
Hesperornis, although some five feet in length, was remarkably slender
and torpedo-shaped.
Concerning its habits and probable appearance during life Dr. Lucas
says: “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 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 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 is
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....
“The restoration which Mr. Gleeson has drawn[12] differs radically
from any yet made, and is the result of 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, the
mountings were so changed that the legs stood out at the sides of the
body, as shown in the picture.”[13]
The birds progressed while their kindred and ancestors, the reptiles,
were declining. By the dawn of the Eocene, the first period of the Age
of Mammals, the birds were very much like those of modern times, and
in the last three million years or more very little change has taken
place. However, there were a number of bizarre and gigantic forms which
arose during the later ages of bird ascendancy, and those we shall
consider in the following chapter.
One who has observed the great abundance of birds today might well
conclude that bird remains should be among the commonest of the
vertebrate fossils. Exactly the opposite, however, is true, for bird
bones are among the rarest finds of the paleontological collector.
Bones of the wings and legs, and occasional skulls, go to make up the
bulk of the finds, with smaller bones, and impressions of the feathers
turning up just often enough to keep the collector in a constant state
of anticipation. A few eggs, also, have been found in the strata of
western United States, but as yet the birds that laid them are unknown.
The scarcity of bird fossils is a problem to which no satisfactory
answer has yet been given. The commonest theory is that dead birds,
because of their very light weight, float for long periods of time,
and are thus exposed to the attacks of weather, bacteria, and carrion
feeding birds and animals. The bones, too, are light and easily broken,
so that they will not stand the wear as will the heavier remains of
mammals and sea-dwelling shellfish. Yet, in certain formations of
France and Oregon, where conditions are not notably different from
those of other and barren strata, remains of birds are fairly common.
This proves that under proper conditions, whatever they may have been,
bird bones did fossilize--a fact which holds out the hope that some day
a fortunate collector will unearth a large and varied deposit, and will
then be able to fill out some of the greater gaps in the history of
feathered creatures.
FOOTNOTES:
[10] That is, until a more ancient specimen is discovered. One must
always be prepared for new discoveries in paleontology, just as in
other sciences.
[11] Although the first specimen of Archeopteryx had been found several
years before, it was too poorly preserved to show the teeth. It was not
until 1877 that the famous Berlin specimen, which shows the teeth and
feathers so admirably, was discovered.
[12] This restoration served as the copy for the accompanying plate.
[13] Animals of the Past, 1st Ed., pp. 83-85.