REPTILES RE-CONQUER THE SEA.
The sea, as we have seen, was the metropolis of primitive life. Then
came the amphibia, and the scene of animal activities was partially
transferred to land, while with the coming of reptiles the abandoning
of the sea by the higher forms of life seemed to be insured. Yet the
change did not come so rapidly as one might think, for the reptiles
after having begun their conquest of the land sent not less than three
great branches back to the water, and one of these, at least, extended
its domain around the world, from the islands of the South Seas to what
are now the plains of North America.
During the latter part of the Age of Reptiles a great island sea
spread over a large part of this continent, while other portions of
the world were similarly inundated. Almost everywhere on the expanse
of the shallow Cretaceous waters might have been seen the forms of
huge, snake-like reptiles, the Elasmosaurs, whose arrow-shaped heads,
poised on long necks rose from ten to twenty feet above the surface
as they swam about searching for food or avoiding enemies. When the
prey was located, the reptiles dived to capture it; when an enemy
approached they swam away with almost incredible swiftness. Their
long necks were attached to large, thick bodies which ended in long,
tapering tails. The legs were modified to form broad paddles, of great
value in swimming; the front pair, perhaps, were used in seizing prey.
Being carnivorous, the Elasmosaur ate whatever it could catch, and
Elasmosaur bones are commonly found along with those of creatures on
which they fed. Not uncommonly large quantities of rounded pebbles
are found with the remains of these reptiles, sometimes a peck of
them in a single deposit. These stones filled the same purpose as do
the “gizzard stones” found in the stomachs of modern birds. Evidently
the Elasmosaurs and their allies did not tear or bite their food into
small bits, but relied on the action of their stomachs, assisted by
these stones, to do the work.
[Illustration: PLATE VIII. An Elasmosaur swimming, as drawn by
Williston.]
But, remarkable though these reptiles may seem, they were by no means
the rulers of the Mesozoic oceans and seas. The great Mosasaurs were
not only the giants of those waters, but were far more numerous and
wide-spread than their less hardy and prolific contemporaries.
We may quite properly call these animals great, for so they were. But
it is well to remember that among the lower animals as among men there
are degrees of greatness; moreover there is a general desire on the
part of men to magnify the animals of the past, and consider them as
being far larger than any that live today. Few people, when thinking of
ancient creatures, stop to recollect that the whales of today are by
far the largest animals that ever lived on the earth, just as modern
shellfish compare very favorably with those of past ages. True, there
are no reptiles today that compare with the largest of the Dinosaurs,
but by no means all of the Dinosaurs were giants. A few Mosasaurs
attained a length of forty feet--some even forty-five--but most of them
were less than twenty. Among modern reptiles, the Mugger, or Man-eating
Crocodile of Africa grows, if allowed to live long enough, to a length
of twenty-five or thirty feet, and therefore exceeds in measurements as
well as weight the average Mosasaur.
The Mosasaurs were elongated and gracefully fish-like in form. Their
heads were large, flattened, and conical; the eyes were placed on
the sides rather than the top of the skull. Their tails were long,
with flattened, fin-like extensions that assisted the four broad,
powerful flippers when the creatures were swimming. Like their distant
relatives, the snakes, they possessed four rows of teeth on the roof
of the mouth. These teeth were valueless for chewing, but were of
utmost service in holding the prey, which was swallowed entire. The
probability is that the tongue was long and forked, while the structure
of the throat and windpipe indicates that the mighty Mosasaur’s only
call was a serpent-like hiss.
The first Mosasaur was discovered in the quarries beneath St. Peter’s
Mount, near Maestritch, Germany, some ninety feet below the surface.
Immediately on finding the specimen the workmen informed Dr. Hoffman,
the surgeon of the local forces, and an ardent collector of fossils.
He labored with the quarrymen for two weeks, and was rewarded by an
almost perfect specimen which he took to his home and cleaned with
great care and success. The fossil was so unusual, and was made the
basis of so many papers, illustrations, and discussions, that the canon
of the cathedral which stands on St. Peter’s decided that he should
own the specimen. Dr. Hoffman refused to give it up, and Canon Goddin
instituted a long, expensive, and harassing law-suit, making certain
feudal rights the basis of his claim. The whole chapter, of course,
stood with their reverend brother, and the decree went against the
surgeon, who was forced to give up his specimen and pay the costs of
the trial. For several years the skull remained in the possession of
the clergyman, and Hoffman died without regaining it. Finally, during
the French revolution, Maestritch was bombarded and captured. During
the attack, the artillerymen had not been allowed to shoot into that
part of the city where the fossil was known to be. The canon, guessing
the reason for this particular favor, hid the skull in a vault, but was
forced to give it up when the city was plundered. The French, who did
not hesitate to appropriate anything of value in either science or art,
bore the famous Mosasaur off to Paris, and put it in the museum at the
Jardin des Planes, where it still remains.
[Illustration: PLATE IX.
A Mosasaur swimming.]
The first American Mosasaur discovery took place in 1820, at Great
Bend, Mo. Major O’Fallon, an Indian agent, found a fine specimen which
he took to his home in the town of St. Louis. A few years later the
relic was taken to Germany by Prince Maximilian of Wied, after his
famous trip through the United States in search of natural history
specimens and information. Since that time hundreds, even thousands,
of specimens have been collected and described from the Cretaceous
rocks of this country. The shallow seas that covered Kansas were the
headquarters of the Mosasaurs, and their skeletons are abundant in the
chalk cliffs of the district.
Among the fishes which were the prey of the Mosasaurs was the great
Portheus, or Bulldog fish, whose long, sharp teeth and powerful body
indicate that it often evened matters by capturing smaller mosasaurs.
The head of this monster was twice as large as that of a grizzly bear,
while the muzzle was stouter and deeper than that of a bulldog. Some
of the teeth projected as much as three inches above the gums, sinking
a full inch into the pits--as long as the fangs of a tiger, but more
slender. Two pairs of these deadly teeth crossed each other on either
side of the snout, and were re-enforced by numerous other long, conical
teeth farther back on the jaw.
Above the water soared or flew--it is not yet decided which--the great
Pterosaurs, or winged reptiles. According to the current conception,
these great beasts flew above the water, swooping down to snatch fishes
and smaller mosasaurs, on which they fed. Some of the Pterosaurs had
wing spreads of eighteen to twenty feet, and if they actually did fly,
were without doubt the largest of all denizens of the air. At night and
while resting they clung to cliffs and rocks by means of the long claws
with which their wings were equipped.
While we do not know whether or not the Mosasaurs fed upon turtles,
there were plenty from which they might have made their choice. One of
them, at least, was of gigantic size, having a flipper spread of at
least fifteen feet. The skin was smooth and leathery, that over the
back being strengthened by several ridges of stiffer integument. The
back flippers were relatively small, while the front ones were very
broad and without an armor of claws.
* * * * *
Gradually, after countless centuries of relative quiet, the earth
began to re-shape its surface. Mountains, plains, and plateaus arose,
leaving those sea-dwellers that could not swim or crawl to perish
in the hot suns of a new time. The once broad seas grew smaller and
smaller, were divided into lakes and basins, continued shrinking. The
sea-dwellers were imprisoned in these basins, where they preyed upon
each other with greater ease than had been possible in the open waters
of earlier times, while the fishes died from the constant freshening
of the water. The stronger gorged upon the weaker until they were left
stranded on the ever rising bars, with no food but their kindred,
and little strength to either attack or escape. At the last they may
have made desperate attempts to escape by land, or else lay starving
in the shallow, muddy pools. Perhaps as the waters shrank a few of
the great saurians fed with them, eventually making their way into
the new sea and ocean areas. But in all probability any such refugees
were so beaten and starved that they had but little chance for success
in life under their new environment. By the time of the great uplift
which proved their undoing, the Mosasaurs and their allies were an
old race,[8] and had little vitality left with which to cope with
new situations. They died, leaving no descendants,[9] and only the
scattered remains in Cretaceous rocks remain to tell of the once mighty
hordes.
FOOTNOTES:
[8] For a discussion of the age of groups, life cycle of species, etc.,
see the author’s booklet, “Animals of Ancient Seas,” No. 47 of this
Series.
[9] Rumors of Paleozoic monsters living in remote portions of the earth
appear constantly, but without foundation in fact. Just this year
(1922) newspapers and some magazines have made a great to-do about a
Plesiosaur that was supposed to be living in a South American lake.
The Plesiosaurs, aside from being as ancient as the Mosasaurs, were
exclusively marine; therefore, a report of one of them in a lake is
utterly absurd.