THE EMPIRE OF THE GREAT REPTILES.
Had we lived in the Carboniferous period, we might have supposed that
the line of the great Labyrinthodont Batrachians would have been
continued onward and elevated, perhaps, in the direction of the
Mammalia, to which some features of their structure point. But we should
have been mistaken in this. The Labyrinthodonts, it is true, extend into
the Trias; but there is perhaps a sign of their coming degradation in
the appearance in the Permian of the first known mud-eel, a humble
Batrachian form allied to the Newts and Water-lizards.[62] Their special
peculiarities are dropped in the Mesozoic in favour of those of certain
small and feeble lizard-like animals, appearing first in the
Carboniferous, and more manifestly in the Permian, and which are the
true forerunners, though they can scarcely be the ancestors, of the
magnificent reptilian species of the Mesozoic, which have caused this
period to be called aEurooethe age of reptiles.aEuroŁ
The leading reptilian animal from the European Permian has long been the
_Proterosaurus_, from the copper slates of Thuringia (Fig. 141), a
reptile of lizard-like form, with well-developed limbs, and attaining a
length of three or four feet. It resembles more nearly those large
modern lizards known as aEurooeMonitors,aEuroŁ than any other existing form. The
fore-limb represented in the figure foreshadows very closely the bones
of the human arm and hand. Besides this we find in the Permian certain
lizards (_Theriodonts_ of Owen) which present the remarkable and
advanced peculiarity already predicted by some Carboniferous
Microsauria,[63] of having distinct canine teeth, producing a division
into incisors, canines, and molars, in the manner of the Carnivorous
quadrupeds, which they seem also to have resembled in some other parts
of their skeletons. It is not impossible that the footprints in the
Permian sandstones of Scotland, which have been referred to tortoises,
were those of animals of this type. Cope has recently described from the
Permian of Texas a number of reptiles which have the complex dentition
of the Theriodonts, and others which simulate that of Herbivorous
mammals, by the possession of flat grinding teeth supposed to be adapted
to vegetable food.[64] The teeth of all these Permian reptiles were set
in sockets, also an advanced peculiarity. Thus already in the Permian,
before the final decadence of the Carboniferous flora, and while the
PalA|ozoic invertebrates still lingered in the sea, the age of reptiles
dawned, and gave promise of its future greatness by the assumption on
the part of reptilian species of structures now limited to the Mammalia.
[Illustration: FIG. 141.aEuro"Arm of _Proterosaurus Speneri_. Reduced.
Permian.]
But the great Mesozoic reptiles were not fully enthroned, till the
Permian, an unsettled and disturbed age, characterised by great earth
movements, had passed away, and until that period of continental
elevation, with local deserts and desiccation, and much volcanic action,
which we call the Trias, had also passed.
Then in the Jurassic and early Cretaceous the reptiles culminated, and
presented features of magnitude and structural complexity unrivalled in
later times. At the same time the Labyrinthodonts disappear, or are
degraded into the humble stations which the modern Batrachians now
occupy.
To understand the reptiles of this age, it will be necessary to notice
the subdivisions of their modern representatives. The true reptiles now
existing constitute the following orders:aEuro"1, the Turtles and Tortoises
(_Chelonia_); 2, the Snakes (_Ophidia_); 3, the Lizards (_Lacertilia_);
4, the Crocodiles and Alligators (_Crocodilia_). All of these, except
the snakes, are well represented among Mesozoic fossils; but we have in
this middle age of the earthaEuro(TM)s geological history to add to them from
five to seven orders now altogether extinct, and these not of low and
inferior organisation, but including species far in advance of any now
existing both in elevation and magnitude, and constituting the veritable
aristocracy of the reptile race. It will best serve our purpose here to
consider chiefly these perished orders and their history, and then to
notice very shortly those that now survive.
[Illustration: FIG. 142.aEuro"Skeleton of _Ichthyosaurus_. Lias. England.]
The first of the extinct orders is that of the great Sea-lizards,[65] of
which the now familiar _Ichthyosaurus_ and _Plesiosaurus_ of the English
seas, to be seen in all museums and text-books, are the types (Figs.
142, 142_a_ and 142_b_). These were marine animals of large size, but
not fishes or amphibians. They were true air-breathing reptiles, but
with paddles for swimming instead of feet, and some of them with long
flattened tails for steering and propulsion. They bore, in short,
precisely the same relation to the other members of the class Reptilia
which the Whales and Porpoises bear to the ordinary quadrupeds. Some of
these animals are believed to have been fifty or sixty feet in length,
thus rivalling the Whales, while others were of smaller dimensions, like
the Porpoises and Dolphins. Some, like the _Ichthyosaurus_ and
_Pliosaurus_ (Fig. 142_a_), were strongly built and powerful swimmers,
and able to destroy the largest fishes, while others, like
_Plesiosaurus_, had the body short and compact, the head small, and the
neck long and flexible, and probably preyed on small animals near the
borders of the waters. Catalogues of British fossils alone include about
thirty species of Enaliosaurs, which haunted the coasts of Mesozoic
Europe, a wonderful fact, when we consider the absence of these
creatures from the modern seas, and the probability that only a fraction
of the species are yet known to us.
[Illustration: FIG. 142_a_.aEuro"Head of _Pliosaurus_. Jurassic. Much
reduced.]
[Illustration: FIG. 142_b_.aEuro"Paddle of _Plesiosaurus Oxoniensis_.
Jurassic.aEuro"After Phillips. One-tenth natural size.]
Another remarkable group is that to which Cope has given the name of
_Pythonomorpha_, and which he regards as allied to the serpents, or as
gigantic sea-serpents provided with swimming paddles, but which Owen
considers more nearly connected with the lizards. In either case they
constitute a group by themselves, remarkable not only on account of
their anatomical affinities with animals so unlike them in general port,
but also for their enormously extended length and formidable dentition
(Fig. 143). Such animals as the _Mososaurus_ of Maestricht and
_Clidastes_ of Western America may have exceeded in length the largest
Ichthyosaurs and the most bulky of living Cetaceans, though their
slender forms and numerous vertebrA| remind one of the semi-fabulous
sea-serpent, rather than of any known animal of our modern age. They
were characteristic of the Later Mesozoic, more especially of the
Cretaceous period, and must have been formidable enemies to the fishes
of their time.
Owen has formed two orders[66] for the reception of some remarkable
extinct reptiles of this age, found especially in South Africa and
India, but also in Europe and America. The first includes large
lizard-like animals having horny jaws like those of turtles, and in some
of the species with great defensive tusks (Fig. 144). Their mode of life
is not well known, but they may have been peaceable and harmless
vegetable feeders. The second has been already referred to, in
connection with the Permian, where it first appears, though it is
continued in the Trias (Fig. 145). The resemblance of the skulls of
these creatures to those of Carnivorous mammals is very striking, and
nothing can be more singular than their early appearance and their
decadence before the advent of those Tertiary mammals which in more
modern times occupy their place.
[Illustration: FIG. 143.aEuro"Skeleton of _Clidastes_. A great Mososauroid
Sea Reptile of the Cretaceous.aEuro"After Cope, much reduced.]
[Illustration: FIG. 144.aEuro"An Anomodont Reptile of the Trias (_Dicynodon
lacerticeps_, Owen). Reduced.]
[Illustration: FIG. 145.aEuro"A Theriodont Reptile of the Trias
(_Lycosaurus_).aEuro"After Owen. Reduced.]
[Illustration: FIG. 146.aEuro"Skeleton of _Pterodochylus crassirostris_.
Jurassic of Solenhofen. Reduced.]
[Illustration: FIG. 147.aEuro"Restoration of _Rhamphorhyncus Bucklandi_.
Jurassic of England.aEuro"After Phillips.
_a_, One of the teeth. Natural size.]
Perhaps the most extraordinary of all the Mesozoic modifications of the
reptilian type was that of the flying reptiles, or _Pterodactyls_.
These were, in short, lizards modified for flight, somewhat in the same
manner with the bats among the mammals. If the bat may be likened to a
flying shrew-mouse, a Pterodactyl may in like manner be compared to a
flying lizard; but the modification in the latter case is by much the
more remarkable, inasmuch as the lizard is a cold-blooded animal, and
far less likely to be endowed with the active circulation and muscular
power necessary to flight than is the mouse. In point of fact, there can
be no doubt that the Pterodactyls must have been provided with some
approach to a mammalian or ornithic heart, as they certainly were with
great breast-muscles attached to a keel in the breast-bone for working
their large membranous wings. These wings were also somewhat original in
their construction. They were not furnished with pinions, like those of
the bird, but with a membrane like that of the bat, and this, instead of
being stretched over four enormously lengthened fingers, as in that
quadruped, was supported on a single elongated finger, corresponding,
singularly enough, to the little finger, which usually inconspicuous
member constituted in some of these strange creatures a limb longer than
the whole body (Figs. 146, 147.) The other fingers of the hand were left
free for walking or grasping. They are thus believed to have been able
to walk as well as to fly, and even in case of need, to swim; while
they could probably perch like birds on rocks and trees. Their heads,
though very lightly framed, were large and reptilian in aspect, and
furnished with sharp teeth, and sometimes probably with a beak as well.
Few creatures of the old world are of more hideous and sinister aspect.
Yet some of them must have been as light and graceful on the wing as
swallows or sea-gulls. There are many species, most of them small, but
some of those in the later Mesozoic attained to so great a size that the
expanse of their wings must have exceeded twenty feet, making them
veritable flying dragons, probably formidable to all the smaller animals
of their time. Though these animals were strictly reptiles, they
combined in their structures contrivances for aA"rial locomotion now
distributed between the bats and the birds. They had bat-like wings and
bird-like chests. Some had horny beaks. All had hollow limb bones, and
air cavities to give lightness to the skull. Their brains approach to
those of birds, and, as already stated, their respiration and
circulation must have been of a high order. These facts are very
suggestive, and perhaps in no point is the imagination or the faith of
the devout evolutionist more severely tested than in realising the
spontaneous assumption of these characters by reptiles, and their
subsequent distribution between the very dissimilar types in which they
are now continued.
[Illustration: FIG. 148.aEuro"A Jurassic Bird (_ArchA|opteryx
macroura_).aEuro"After Owen.]
[Illustration: FIG. 149.aEuro"Jaw of a Cretaceous Toothed Bird (_Ichthyornis
dispar_).aEuro"After Marsh. Natural size.]
The approximation of the winged reptiles to the birds is further
increased by the facts that in the Jurassic and Cretaceous periods there
were birds having reptilian tails and probably toothed jaws
(_ArchA|opteryx macroura_, Fig. 148). The species just named, while in
its limbs, trunk, and feathers a veritable perching bird, resembles a
reptile in its head and tail. In the Cretaceous of Western America,
Marsh has recently discovered two distinct types of toothed birds, one
having the teeth in regular sockets, the other having them implanted in
a groove in the jaw. One of these birds (_Ichthyornis dispar_, Fig. 149)
was larger than a pigeon, with powerful wings constructed like those of
ordinary birds. It had also the curious and old-fashioned peculiarity of
biconcave vertebrA|, like those of fishes and some reptiles. Another
(_Hesperornis regalis_) stood five or six feet high, and had rudimentary
wings like those of the Penguins. These toothed birds extend into the
Eocene Tertiary, where the _Odontopteryx_ of Owen has been known for
some time. In the Eocene, however, this toothed bird is associated with
others of ordinary types, allied closely to the Ostriches, the Pelicans,
the Ibis, the Woodpeckers, the Hawks, the Owls, the Vultures, and the
ordinary perching birds. In the Later Mesozoic, indeed, some reptiles
became so bird-like that they nearly approached the earliest birds; but
this was a final and futile effort of the reptile to obtain in the air
that supremacy which it had long enjoyed in earth and water; and its
failure was immediately succeeded in the Eocene by the appearance of a
cloud of true birds, representing all the existing orders of the class.
[Illustration: FIG. 150.aEuro"Jaw of _Bathygnathus borealis_ (Leidy). A
Triassic Dinosaur from Prince Edward Island.
_a_, Cross section of second tooth, natural size. _b_, Fifth tooth,
natural size.]
We may close our notice of the winged reptiles of the Mesozoic by
quoting from Phillips his summary of the characters of _Rhamphorhyncus_
(Fig. 147)[67]: aEurooeGifted with ample means of flight, able at least to
perch on rocks and scuffle along the shore, perhaps competent to dive,
though not so well as a palmiped bird, many fishes must have yielded to
the cruel beak and sharp teeth of the _Rhamphorhyncus_. If we ask to which
of the many families of birds the analogy of structure and probable way
of life would lead us to assimilate _Rhamphorhyncus_, the answer must
point to the swimming races, with long wings, clawed feet, hooked beak,
and habits of violence and voracity; and for preference, the shortness
of the legs and other circumstances may be held to claim for the
Stonesfield fossil a more than fanciful similitude to the groups of
Cormorants and other marine divers which constitute an effective part of
the picturesque army of robbers of the sea.aEuroŁ
[Illustration: FIG. 151.aEuro"_Hadrosaurus Foulkii_ (Cope). An Herbivorous
Dinosaur, 28 feet long.aEuro"After HawkinsaEuro(TM)s restoration.]
Lastly, the reptiles, in this age of their imperial sway, culminated in
the _Dinosaurians_, animals far above any modern Reptilia in the
perfection of their organisation, and many of them of gigantic size.
Just as the Pterosaurs filled the place now occupied by the birds, so
the Dinosaurs filled that represented by the mammals, or rather they
took up a place holding some close relations with both the birds and the
mammals. There were thus reptilian animals which on the one hand were
the elephants and lions of their time, and on the other bore a grotesque
resemblance to creatures so unlike these as the Ostriches, in so far as
their anatomical structure was concerned; while it is evident that their
whole organisation places them in the highest position possible within
the reptilian class. Some of them must have been herbivorous, and
probably slow in movement and quiet in nature. Others were carnivorous
and of terrible energy, while furnished with the most destructive
weapons (Figs. 152, 153). Many had the power of erecting themselves on
their hind-feet and walking as bipeds; and to adapt them to this end
their hinder limbs were very large and strong, and they had long
pillar-like tails, while their fore-feet were comparatively small, and
used perhaps mainly for prehension (Figs. 151, 154).
[Illustration: FIG. 152.aEuro"Jaws of _Megalosaurus_.aEuro"After Phillips.
One-tenth natural size.]
The size of some of these creatures was stupendous. The _Hadrosaurus_ of
New Jersey, an Herbivorous species (Fig. 151), when erected on its hind
limbs and tail, must have stood more than twenty feet in height.
_Megalosaurus_ and _Iguanodon_, of the English Jurassic and Wealden,
must have been of still more gigantic size. The former was a carnivorous
animal, its head (Fig. 152) four or five feet in length, armed with
teeth, sabre-shaped, sharp and crenate on the edges (Fig. 153), its hind
limbs of enormous power, so that if our imagination does not fail us in
the attempt to realise such a wonder, we may even suppose this huge
animal, much larger than the largest elephant, springing like a tiger on
its prey, a miracle of terrible strength and ferocity, before which no
living thing could stand. Its companion, _Iguanodon_, was, on the
contrary, a harmless herbivorous creature, using its great strength and
stature as a means of obtaining leaves and fruits for food, and perhaps
falling a prey to the larger Carnivorous Dinosaurs its contemporaries. A
still more bulky animal was the _Ceteosaurus_, so admirably described by
Phillips. Its thigh-bone measures more than five feet in length and a
foot in diameter; and it must have stood ten feet high when on all
fours, while its length must have reached forty or fifty feet. It seems
from the forms of its bones to have been able to walk on land, but
probably spent most of its time in the water, where it may be compared
to a huge reptilian hippopotamus. Very recently some bones found in
rocks, possibly of Wealden age, in Western America, and described by
Cope and by Marsh, indicate that even _Ceteosaurus_ had not attained to
the maximum of Dinosaurian dimensions. These new animals have vertebrA|
twenty inches in length and from twelve inches to thirteen inches in the
diameter of their bodies, while their lateral processes stretched three
and a half feet. The shoulder-blade of one species is five feet in
length, and its thigh-bone is six feet long. From these measurements
Cope concludes that, unlike most other Dinosaurs, it had the fore-feet
larger in proportion than the hind-feet, so as to have somewhat the
appearance of a large giraffe. The bones of the back have a remarkable
cavernous structure, which Cope interprets as indicating air cavities,
to give lightness, as in the case of the bones of birds; but Owen
suggests that the cavities were filled with cartilage, and that the
animals were aquatic in their habits. Evidently in point of size the
Dinosaurs had a better claim than even Behemoth to be called the aEurooechief
of the ways of God.aEuroŁ Some of them, however, were of small size, and
probably active and bird-like in their movements. One of these is the
animal represented in Fig. 154, a species from the lithographic
limestone of Solenhofen.[68]
[Illustration: FIG. 153.aEuro"Tooth of _Megalosaurus_. Natural size.
_a_, Cross section. _b_, Crenellation of edges. Enlarged.]
Nothing in the life of the Mesozoic has so seized on the imagination of
evolutionists as the links of connection between birds and reptiles,
which has even been introduced by Huxley into the classification of
animals, by his grouping these heretofore very distinct classes in one
gigantic and comprehensive class of _Sauropsida_. It is necessary,
therefore, to glance at these connections, and if possible to arrive at
some conception of their true value. The links which connect the
reptiles and the birds are twofold. First, that between the Dinosaurs
and the ostrich tribe,[69] and, secondly, that between the Pterodactyls
and their allies, and the peculiar Mesozoic birds, such as
_ArchA|opteryx_. The first would serve to account for the few exceptional
Struthious birds of the modern world. The second would account for the
Passerine and other more ordinary birds; and thus, according to
evolution, the now somewhat homogeneous class of birds would have a
double, or more probably multiple, origin from several lines of
reptilian ancestors. This, no doubt, greatly complicates the links of
connection, whether these be supposed to indicate derivation or not.
[Illustration: FIG. 154.aEuro"_Compsognathus._ One of the smaller
Dinosaurs.aEuro"After Wagner.]
If we inquire as to the first connection above stated, we may define it
briefly in the words of Prof. Phillips, with reference to
_Megalosaurus_, which aEurooewas not a ground-crawler, like the alligator, but
moving with free steps, chiefly, if not solely, on the hind limbs, and
claiming a curious analogy, if not some degree of affinity, with the
ostrich.aEuroŁ[70] But the question arises, Was this resemblance merely that
of two oviparous bipeds, or anything more? and when we set off, against
the resemblance in haunch bones and hind limbs, the entire dissimilarity
in head, in fore limbs, in vertebrA|, in tail, and probably in external
covering, we are disposed to agree with Huxley in his statement, with
respect to the Struthious birds, that their aEurooetotal amount of
approximation to the reptilian type is but small; and the gap between
reptiles and birds is but very slightly narrowed by their existence.aEuroŁ
There is therefore here a great gap, even in the linking together of the
types, independently of any question of derivation.
The second line of connection appears at first sight more promising.
_ArchA|opteryx_ has a reptilian tail, and claws on the wing; and, as it had
toothed jaws, like some of the birds in the Cretaceous, must have
altogether made a much nearer approach to a reptile than any modern bird
does. The remarkable aEurooefish-birdaEuroŁ (_Ichthyornis_) of Marsh is also very
reptilian in some of its characters. But when we compare these reptilian
birds with the Pterodactyls and their allies, a vast gap at once becomes
apparent. Disregarding the external clothing, we find the wing in the
two groups entirely dissimilar in details of construction, and this
dissimilarity extends to the hind limbs as well, so that the
Pterodactyls resemble bats rather than birds.
Without committing ourselves to any doctrine of development, we might
have rejoiced if our geological discoveries had established a continuous
chain, or two continuous chains, of being between the reptiles and the
birds; but this end is evidently still far from being attained, though
some approximation has undoubtedly been made. To quote again the
admission of Huxley: aEurooeBirds are no more modified reptiles than reptiles
are modified birds, the reptilian and ornithic types being both in
reality somewhat different superstructures, raised upon one and the same
ground-planaEuroŁaEuro"that ground-plan being the idea of the air-breathing
oviparous vertebrate, and the reptile representing the less specialized
and less ornate building. As yet the origin of that idea, and the mode
of carrying it out to completion, remain unknown, except to the
Architect and Builder, who may reveal them to earnest seekers for truth
in His own good time.
As to links of connection with the Mammalia, these are still more
obscure. In the Mesozoic the mammals are represented as yet only by a
few small species allied to the pouched (Marsupial) and insectivorous
quadrupeds of Australia, and these are closely linked with some of the
smaller carnivorous Mammalia of the early Tertiary; but neither approach
very closely to any known reptilian types. Nor have we yet any
connecting links between the great marine reptiles and the Cetaceans and
Sirenians which in the Tertiary take their place in the sea.
It is an interesting fact, to come before us in our next chapter, that
the great land reptiles of the Mesozoic survived long enough to become
contemporary with the introduction and first luxuriance of the modern
types of vegetation in the later Cretaceous. It would be natural to
suppose that access to these great supplies of better food would have
stimulated the increase and development of the herbivorous species, and
would have indirectly had the same effect on those that were
carnivorous; but the opposite result seems to have followed, and in the
next period the reptiles altogether gave place to the mammals, unless,
indeed, they were themselves by some mysterious and comparatively rapid
process transformed into Mammalia, to suit them to the better conditions
of an improved world.
So far as yet known, the reign of reptiles was world-wide in its time;
and the imagination is taxed to conceive of a state of things in which
the seas swarmed with great reptiles on every coast, when the land was
trodden by colossal reptilian bipeds and quadrupeds, in comparison with
some of which our elephants are pygmies, and when the air was filled
with the grotesque and formidable Pterodactyls. Yet this is no fancy
picture. It represents a time which actually existed, when that
comparatively low, brutal, and insensate type of existence represented
by the modern crocodiles and alligators was supreme in the world. The
duration of these creatures was long, and in watching the progress of
creation, they would have seemed the permanent inhabitants of the earth.
Yet all have perished, and their modern successors, except a few large
species existing in the warmer climates, have become subject to the more
recently introduced Mammalia.
How did the ancient reptile aristocracy perish? We are ignorant of the
details of the catastrophe, but their final disappearance and
replacement by the more modern fauna was connected with a great
continental subsidence in the Cretaceous age, and with changes of
climate and conditions preceding and subsequent to it. Yet the struggle
for continued dominion was hard and protracted; and toward its close
some of the champions of the reign of reptiles were the greatest and
most magnificent examples of the type; as if they had risen in their
might to defy approaching ruin. Thus some of the most stupendous forms
appear in the later Cretaceous, after the great subsidence had made
progress and almost attained its consummation. Like the antediluvian
giants, they were undismayed even when the land began to sink beneath
their feet; and for them there was no ark of deliverance.
[Illustration: LOWER CRETACEOUS LEAVES. REDUCED IN SIZE.aEuro"After
Lesquereux.
_a_, _Aralia Saporteana_. _b_, _Sassafras araliopsis_. _c_, _Quercus
primordialis_. _d_, _Fagus polyclada_. _e_, _Salix proteA|folia_. _f_,
_Laurus proteA|folia_.]