DINOSAURS (_continued_).
"Fossils have been eloquently and appropriately termed
'Medals of Creation.'"--Dr. Mantell.
When any tribe of plants or animals becomes very flourishing, and
spreads over the face of the earth, occupying regions far apart from
one another, where the geographical and other conditions, such as
climate, are unlike, its members will inevitably develop considerable
differences among themselves.
During the great Mesozoic period, Dinosaurs spread over a large part
of the world; they became very numerous and powerful. Just as the
birds and beasts (quadrupeds) of to-day show an almost endless
variety, according to the circumstances in which they are placed, so
that great and powerful order of reptiles we are now considering ran
riot, and gave rise to a variety of forms, or types. Those described
in the last chapter were heavy, slow-moving Dinosaurs, of great
proportions, and were all herbivorous creatures, apparently without
weapons of offence or defence.
The group Theropoda, or "beast-footed" Dinosaurs, that partly form the
subject of the present chapter, were all flesh-eating animals; and, as
we shall discover from their fossilised remains, were of less size,
and led active lives. In fact, they acted in their day the part played
by lions and tigers to-day.
In the year 1824 that keen observer and original thinker, the Rev. Dr.
Buckland, described to the Geological Society of London some remains
of a very strange and formidable reptile found in the Limestone of
Stonesfield, near Woodstock (about twelve miles from Oxford). This
rock, known as "Stonesfield slate" from its property of splitting up
into thin layers, has long been celebrated for its fossil remains, and
from it have also been obtained the bones of some early mammals. It is
a member of the Lower Oolitic group.
The portions of skeleton originally discovered consisted of part of a
lower jaw, with teeth, a thigh bone (femur), a series of vertebræ of
the trunk, a few ribs, and some other fragments. The name
Megalosaurus,[12] or "great lizard," suggested itself both to Dr.
Buckland and Baron Cuvier, because it was evident from the size of the
bones that the creature must have been very big. It is true these
bones were not found together in one spot; but Professor Owen came to
the conclusion that they all belonged to the same species.
[12] Greek--_megas_, great; _sauros_, lizard.
No entire skeleton of the Megalosaur has ever been found, but there
was enough material to enable Dr. Buckland, Professor Owen, and
Professor Phillips to form a very fair idea of its general structure.
It should be mentioned here that Dr. Mantell, the enthusiastic
geologist to whose labours palæontologists are greatly indebted, had
previously discovered similar teeth and bones in the Wealden strata of
Tilgate Forest. Sherborne, in Dorset, is another locality which has
yielded a fine specimen of parts of both jaws with teeth. A cast of
this may be seen in the geological collection at South Kensington. It
was found in the Inferior Oolite (Wall-case IV.); the original
specimen lies in the museum of Sherborne College. Remains of
Megalosaurus have also been found at the following places: Lyme-Regis
and Watchet (in the Lias); near Bridport (in Inferior Oolite); Enslow
Bridge (upper part of the Great Oolite and Forest Marble Beds);
Weymouth (in Oxford Clay); Cowley and Dry Sandford (in the Coral Rag);
Malton in Yorkshire (in Coralline Oolite); also in Normandy. They have
also been found in Wealden strata.
The portion of a lower jaw in the Oxford Museum is twelve inches long,
with a row of nine teeth, or sockets for teeth. The structure of the
teeth leaves no doubt as to the carnivorous habits of the creature.
With a length of perhaps thirty feet, capable of free and rapid
movement on land, with strong hind limbs, short head, with long
pointed teeth, and formidable claws to its feet, the Megalosaur must
have been without a rival among the carnivorous reptiles on this side
of the world. It probably walked for the most part on its hind legs,
as depicted in our illustration, and Professors Huxley and Owen, on
examining the bones in the Oxford Museum, were much impressed with the
bird-like character of some parts of the skeleton, showing an approach
to the ostrich type. The form of the teeth, as pointed out by Dr.
Buckland, exhibits a remarkable combination of contrivances. When
young and first protruding above the gum, the apex of the tooth
presented a double cutting edge of serrated enamel; but as it advanced
in growth its direction was turned backwards in the form of a pruning
knife, and the enamelled sawing edge was continued downwards to the
base of the inner and cutting side, but became thicker on the other
side, obtaining additional strength when it was no longer needed as a
cutting instrument (Fig. 12).
[Illustration: Fig. 12.--Lower jaw-bone of Megalosaurus, with teeth.]
The genus Megalosaurus--now rendered classic through the labours of
Professors Buckland, Phillips, and Owen--may be regarded as the type
of the carnivorous Dinosaurs; and it affords an excellent and
instructive instance of the gradual restoration of the skeleton of a
new monster from more or less fragmentary remains. Certain very
excusable errors were at first made in the restoration, but these
have since been rectified by a comparison with the allied American
forms, such as Allosaurus, of which nearly entire skeletons have of
late been discovered in strata of Jurassic age--in fact, the same rock
in Colorado as that in which the huge Atlantosaurus bones lay hid. The
accompanying woodcut (Fig. 13) shows how the skeleton has been
restored in the light of these later discoveries of Professor Marsh.
The large bones of the limbs of these formidable flesh-eating monsters
were hollow, and many of the vertebræ, as well as some of those of the
feet, contained cavities, or were otherwise lightened in order to give
the creature a greater power of rapid movement.
[Illustration: Fig. 13.--Skeleton of Megalosaurus, restored. (After
Meyer.)]
It is not very difficult to imagine a Megalosaur lying in wait for his
prey (perhaps a slender, harmless little mammal of the ant-eater type)
with his hind limbs bent under his body, so as to bring the heels to
the ground, and then with one terrific bound from those long legs
springing on to the prey, and holding the mammal tight in its clawed
fore limbs, as a cat might hold a mouse. Then the sabre-like teeth
would be brought into action by the powerful jaws, and soon the flesh
and bones of the victim would be gone! (See Plate VI.)
[Illustration: Plate VI.
A CARNIVOROUS DINOSAUR, MEGALOSAURUS BUCKLANDI.
Length about 25 feet.]
As we remarked before, the carnivorous Dinosaurs were the lions and
tigers of the Mesozoic era, and, what with small mammals and numerous
reptiles of those days, it would seem that they were not limited in
their choice of diet.
It is a question not yet decided whether Dinosaurs laid eggs as most
modern reptiles do, or were viviparous like quadrupeds; but Professor
Marsh thinks there are reasons for the latter supposition.
During the early part of the Mesozoic era, at the period known as the
Triassic (New Red Sandstone), Dinosaurs flourished vigorously in
America, developing a great variety of forms and sizes. Although but
few of their bones have as yet been discovered in those rocks, they
have left behind unmistakable evidence of their presence in the
well-known footprints and other impressions upon the shores of the
waters which they frequented.[13] The Triassic Sandstone of the
Connecticut Valley has long been famous for its fossil footprints,
especially the so-called "bird-tracks," which are generally supposed
to have been made by birds, the tracks of which they certainly appear
to resemble. But a careful investigation of nearly all the specimens
yet discovered has convinced Professor Marsh that these fossil
impressions were not made by birds (see Fig. 14). Most of the
three-toed tracks, he thinks, were made by Dinosaurs, who usually
walked upon their hind feet alone, and only occasionally put to the
ground their small fore limbs. He has detected impressions of the
latter in connection with nearly all the larger tracks of the hind
limbs. These double impressions are just such as Dinosaurs would make;
and, since the only characteristic bones yet found in the same rocks
belong to this order of reptiles, it is but fair to attribute all
these footprints to Dinosaurs, even where no impressions of fore feet
have been detected, _until_ some evidence of birds is forthcoming. The
size of some of these impressions, as well as the length of stride
they indicate, is against the idea of their having been made by birds.
Some of them, for instance, are twenty inches in length, and four or
five feet apart! The foot of the African ostrich is but ten inches
long, so we must fall back on the Dinosaurs for an explanation.
However, it is quite possible that some of the smaller impressions
were made by birds.
[13] Since the above was written, Professor Marsh has described, in
_The American Journal of Science_ for June, 1892, several more or less
complete skeletons of Triassic Dinosaurs, lately found, and now in the
Yale College Museum. This is an important discovery.
[Illustration: Fig. 14.--Portion of a slab of New Red Sandstone, from
Turner's Falls, Massachusetts, U.S., covered with numerous tracks,
probably of Dinosaurs. This specimen is now in the Natural History
Museum. The separate tracks are indicated by the numbers. (After
Hitchcock.)]
There is at South Kensington a fine series of these and other
specimens of fossil footprints (Gallery No. XI., Wall-cases 8-10). The
surface of one large slab in the geological collection is eight feet
by six feet, and bears upwards of seventy distinct impressions
disposed in several tracks, as shown in Fig. 14. The lines were added
by Dr. Hitchcock, who has published full descriptions in order to show
the direction and disposition of the tracks.
[Illustration: Fig. 15.--Portion of a slab, with tracks. (After
Hitchcock.)]
In a presidential address to the Geological Society, Sir Charles
Lyell, speaking of the Connecticut Sandstone and its impressions,
said, "When I first examined these strata of slate and sandstone near
Jersey City, in company with Mr. Redfield, I saw at once from the
ripple-marked surface of the slabs, from the casts of cracks, the
marks of rain-drops, and the embedded fragments of drift-wood, that
these beds had been formed precisely under circumstances most
favourable for the reception of impressions of the feet of animals
walking between high and low water. In the prolongation of the same
beds in the Valley of Connecticut, there have been found, according to
Professor Hitchcock, the footprints of no less than thirty-two species
of bipeds, and twelve of quadrupeds. They have been observed in more
than twenty localities, which are scattered over an area of nearly
eighty miles from north to south, in the States of Massachusetts and
Connecticut. After visiting several of these places, I entertained no
doubt that the sand and mud were deposited on an area which was slowly
subsiding all the while, so that at some points a thickness of more
than a thousand feet of superimposed strata had accumulated in very
shallow water, the footprints being repeated at various intervals on
the surface of the mud throughout the entire series of superimposed
beds." When Sir Charles Lyell first examined this region in 1842,
Professor Hitchcock had already seen two thousand impressions of feet!
It is not difficult to imagine the conditions under which such
impressions may have been preserved, for at the present day there are
to be seen, on some shores, illustrations of similar operations. Dr.
Gould, of Boston, U.S., was the first to call the attention of
naturalists to a very instructive example of such processes on the
shores of the Bay of Fundy, where the tide is said to rise in some
places seventy feet high. Here we have a very perfect surface for
receiving and retaining impressions. Vast are the numbers of wading
and sea-birds that course to and fro over the extensive tract of
plastic red surface left dry by the far retreat of the tide in the Bay
of Fundy. During the period that elapses between one spring tide and
the next, the highest part of the tidal deposit is exposed long enough
to receive and retain many impressions; even during the hours of hot
sunshine, to which, in the summer months, this so-trodden tract is
left exposed, the layer last deposited becomes baked hard and dry, and
before the returning tidal wave has power to break up the preceding
one, the impressions left on that stratum have received a deposit. A
cast is thus taken of the mould previously made, and each succeeding
tide brings another layer of deposit. We can easily imagine that in
succeeding ages the petrifying influences will consolidate the sandy
layers into a fossil rock. Such a rock would split in such a way,
along its natural layers of formation, as to show the old moulds on
one surface, and the casts on the other.
[Illustration: Fig. 16.--Limb-bones of _Allosaurus_. (After Marsh.)
1. Fore leg. 2. Hind leg.]
Professor Marsh has had the good fortune to discover a very peculiar
new form of carnivorous Dinosaur, to which he has given the name
Ceratosaurus,[14] because its skull supported a horn. But the horn is
not the only new feature presented by this interesting creature. Its
vertebræ are of a strange and unexpected type; and in the pelvis all
the bones are fused together, as in modern birds. Externally, also,
the Ceratosaurus differed from other members of the carnivorous group,
for its body was partly protected by long plates in the skin, such as
crocodiles have: these extended from the back of the head, along the
neck, and over the back. An almost complete skeleton was found which
indicates an animal about seventeen feet long. When alive it was
probably about half the bulk of the Allosaurus mentioned above. (See
Fig. 16.)
[14] Greek--_keras_, horn; _sauros_, lizard. Some authorities consider
it to be identical with Megalosaurus.
Seen from above, its skull resembles in general outline that of a
crocodile, the facial portion being elongated and gradually tapering
to the muzzle, with the nasal openings separate, and placed near the
end of the snout.
[Illustration: Fig. 17.--Skull of _Ceratosaurus_. Top view. (After
Marsh.)]
The teeth of this horned Dinosaur resemble those of the Megalosaur.
Its eyes were protected by protuberances of the skull just above the
cavity in which the eye was placed (see Figs. 17 and 18). The brain
was a good deal larger in proportion to the size of the animal than in
Brontosaurus and its allies; so perhaps we may infer that it was
endowed with greater intelligence, as it certainly was more active in
its habits. The fore limbs, as in Megalosaurus, were small, and some
of the fingers ended in powerful claws, which no doubt it used to good
purpose.
Perhaps the most remarkable of all the Dinosaurs was a diminutive
creature only two feet in length, which was related to those we have
just been considering, and whose skeleton has been found almost entire
in the now famous Lithographic Stone of Solenhofen in Bavaria. Of this
unique type, the Compsognathus, the skeleton of which is in many ways
so bird-like, Professor Huxley remarks, "It is impossible to look at
the conformation of this strange reptile and to doubt that it hopped,
or walked, in an erect or semi-erect position, after the manner of a
bird, to which its long neck, slight head, and small anterior limbs
must have given it an extraordinary resemblance." (See Fig. 19.)
[Illustration: Fig. 18.--Skull of _Ceratosaurus nasicornis_. (After
Marsh.)]
At the head of this chapter are placed the words of Dr. Mantell,
"Fossils have been eloquently and appropriately termed _Medals of
Creation_," and the eloquent passage by which those words are followed
may be transcribed here. He goes on to say, "For as an accomplished
numismatist, even when the inscription of an ancient and unknown coin
is illegible, can from the half-obliterated effigy, and from the style
of art, determine with precision the people by whom, and the period
when, it was struck: in like manner the geologist can decipher these
natural memorials, interpret the hieroglyphics with which they are
inscribed, and from apparently the most insignificant relics trace the
history of beings of whom no other records are extant, and ascertain
the forms and habits of unknown types of organisation whose races are
swept from the face of the earth, ere the creation of man, and the
creatures which are his contemporaries. Well might the illustrious
Bergman exclaim, "_Sunt instar nummorum memoralium quæ de præteritis
globi nostri fatis testantur, ubi omnia silent monumenta historica._""
[Illustration: Fig. 19.--Skeleton of _Compsognathus longipes_. (From
the Solenhofen limestone.)]
Geology owes a deep debt of gratitude to the late Dr. Gideon A.
Mantell, who, during the intervals of a laborious professional life,
collected and described the remains of several strange extinct
reptiles, and wrote a number of works on geology, such as served in
his day to advance the science to which he was so enthusiastically
devoted.
We propose to give a brief account of a wonderful group of Dinosaurs,
first introduced to the scientific world through Dr. Mantell's
labours.
The first of these monsters is the Iguanodon, the earliest known
individual of the "bird-footed" division (Ornithopoda). The history of
the gradual reconstruction of its skeleton is an instructive instance
of the results that may be obtained by a careful and patient study of
fragmentary remains. Through the labours of Dr. Mantell, in the first
half of this century, a considerable knowledge was acquired of the
greater part of the skeleton, but certain portions remained a puzzle;
these, however, were eventually explained by Professor Huxley and Mr.
Hulke, and a few years ago a series of complete skeletons were most
fortunately obtained in Belgium, so that now every part of the huge
framework of this monster is known to the palæontologist. Its history,
as a fossil, is a most interesting one, and furnishes one more example
of the marvellous insight into the nature of extinct animals displayed
by the illustrious Baron Cuvier. Let us begin with the teeth, since
they were the first part of the monster brought to light.
It is, perhaps, hardly necessary to remark that, to one thoroughly
acquainted with the structures of living animals, a tooth, or a series
of teeth, will furnish material from which important conclusions with
regard to the structure and habits of an extinct animal may be drawn.
So, also, with regard to some other parts, such as limb-bones, but
more especially the bones of which the backbone is composed (known as
vertebræ). These are very important. The veteran anatomist, Professor
Owen, has said, "If I were restricted to a single specimen on which to
deduce the nature of an extinct animal, I should choose a vertebra to
work out a reptile, and a tooth in the case of a mammal." Seven or
eight different "characters," he says, may be deduced from a reptilian
vertebra. It is, of course, impossible for any one to reconstruct an
entire animal from a single bone or a few teeth, yet such fragments
indicate in a general way the nature of a lost creation and its
position in the animal kingdom.
[Illustration: Fig. 20.--Tooth of Iguanodon, with the apex slightly
worn. (From the Wealden Beds of Tilgate Forest. Natural size.) 1.
Front aspect, showing the longitudinal ridges and serrated margins of
the crown. 2. View of the back, or inner surface of the tooth. _a._
Serrated margins. _b._ Apex of the crown worn by use.]
It is all the more important to give to the general reader this
warning, because an impression seems still to remain in the popular
mind that Owen could and did restore extinct types from a single bone
or a single tooth; but no anatomist would attribute to any mortal man
such superhuman power. Let us, therefore, while gratefully
acknowledging the debt we all owe to the great naturalist--who has
gone to his rest since our first edition appeared--not attribute to
him impossible things. Nor can it be denied that even he sometimes
fell into error, or drew conclusions not borne out by later
discoveries. It must also be confessed that in some respects he lagged
behind in the march of scientific progress. While on this subject we
cannot do better than quote some remarks of our friend, Mr. A. Smith
Woodward, of the Natural History Museum, in an able review of Sir
Richard's work on vertebrates.[15] He says, "Owen, in fact, was
Cuvier's direct successor, and, apart from his striking hypotheses
..., it is in this character that he has left the deepest impression
upon biological science. Extending and elaborating comparative anatomy
as understood by Cuvier, Owen concentrated his efforts on utilising
the results for the interpretation of the fossil remains--even
isolated bones and teeth--of extinct animals. He never hesitated to
deal with the most fragmentary evidence, having complete faith in the
principles established by Cuvier; and it is particularly interesting,
in the light of present knowledge, to study the long series of
successes and failures that characterise his work. However,
unwittingly, Owen may be said to have contributed most to the
demolition of the narrow Cuvierian views. When dealing with animals
closely related to those now living, his correctness of interpretation
was usually assured; when treating of more remote types, he could do
little more than guess, unless tolerably complete skeletons happened
to be at his disposal....
"In short, Owen's work on fragmentary fossils has demonstrated that
the principles of comparative anatomy are very different from those
inferred by Cuvier from his limited field of observation, and the
discoveries of Leidy, Marsh, Cope, Scott, and Osborn, in America, have
finally led to a new era that Owen only began to foresee clearly in
his later days."
[15] _Natural Science_, ii. p. 130. (Feb. 1893.)
The first specimens of teeth of the Iguanodon were found by Mrs.
Mantell, in 1822, in the coarse conglomerate of certain strata in
Tilgate Forest, belonging to the Cretaceous period (see Table of
Strata, Appendix I.). Dr. and Mrs. Mantell subsequently collected a
most interesting series of these remarkable teeth (which, for a time,
puzzled the most learned men of the day), from the perfect tooth of a
young animal, to the last stage, that of a mere long stump worn away
by mastication. In external form they bore a striking resemblance to
the grinders of herbivorous mammals, and were wholly unlike any that
had previously been known. Even the quarrymen, accustomed to collect
the remains of fishes, shells, and other objects embedded in the
rocks, had not observed fossils of this kind; and until Dr. Mantell
showed them his specimens, were not aware of the presence of such
teeth in the stone they were constantly breaking up for the roads. The
first specimen that arrested his attention was a large tooth, which,
from the worn surface of its crown, had evidently once belonged to
some herbivorous animal. In form it so entirely resembled the
corresponding part of an incisor tooth of a large pachydermatous
animal ground down by use, that Dr. Mantell was much embarrassed to
account for its presence in the ancient Wealden strata, in which,
according to all previous experience, no fossil remains of mammals
would be likely to occur. No reptiles of the present day are capable
of masticating their food; how, then, could he venture to assign it to
a reptile? Here was a puzzle to be solved, and in his perplexity he
determined to try whether the great naturalist at Paris would be able
to throw any light on the question. Through Sir Charles (then Mr.)
Lyell, this perplexing tooth was submitted to Baron Cuvier; and great
was the doctor's astonishment on hearing that it had been without
hesitation pronounced to be the upper incisor of a rhinoceros! The
same tooth, with some other specimens, had already been exhibited at a
meeting of the Geological Society, and shown to Dr. Buckland, Mr.
Conybeare, and others, but with no more satisfactory result. Worse
than that: Dr. Mantell was told that the teeth were of no particular
interest, and that, without doubt, they either belonged to some large
fish, or were the teeth of a mammal, and derived from some superficial
deposit of the "glacial drift," then called Diluvium.
There was one man, however, who foresaw the importance of Mantell's
discovery, and that was Dr. Wollaston. This distinguished philosopher,
though not a naturalist, supported the doctor's idea that the teeth
belonged to an unknown herbivorous reptile, and encouraged him to
continue his researches.
As if to add to the difficulty of solving the enigma, certain bones of
the fore limb, discovered soon after in the same quarry and forwarded
to Paris, were declared to belong to a species of hippopotamus!
Another very curious bone--of which we shall speak presently--was
declared to be the lesser horn of a rhinoceros! The famous Dr.
Buckland even went so far as to warn Dr. Mantell not to publish it
forth that these bones and teeth had been found in the Tilgate Forest
strata. To him it seemed incredible that such remains could have been
obtained from beds older than the superficial drift deposits of the
district. We must bear in mind that in those days palæontology, or the
knowledge of the world's former inhabitants, was a new science still
in its infancy, and the idea of mammals having existed so far back as
the Cretaceous period must have appeared incredible.
However, the workmen in the quarry were stimulated by suitable
rewards, and at length the doctor's efforts resulted in the discovery
of teeth which displayed the curious serrated edges, and the entire
form of the unused crown. Having forwarded specimens and drawings of
these to Paris, Dr. Mantell went to London, and ransacked all the
drawers in the Hunterian Museum that contained jaws and teeth of
reptiles, but without finding any that threw light on this subject.
Fortunately, Mr. Samuel Stuchbury, then a young man, was present, and
proposed to show him the skeleton of an Iguana, which he had himself
prepared from a specimen that had long been immersed in spirits. And
now the puzzle was in a fair way to being solved; for, to his great
delight, the doctor found that the minute teeth of that reptile bore a
closer resemblance in their general form to those from Tilgate Forest
than any others he had ever seen.
In spite of this fortunate discovery, however, others remained
obstinate and unconvinced; and it was not until he had collected a
series of specimens, exhibiting various stages of the teeth, that the
correctness of his opinion was admitted, either as to their true
interpretation, or the age of the strata in which they were imbedded.
And now there came good news from Paris. Cuvier, with the fresh
material submitted to him, had boldly renounced his previous opinion,
and gave the weight of his great authority to the view maintained by
the discoverer of these teeth. In a letter to the doctor he said that
such teeth were quite unknown to him, and that they belonged to some
reptile. He suggested that they implied the existence of a _new
animal_, a _herbivorous reptile_. Time would either confirm or
disprove the idea, and in the mean time he advised Dr. Mantell to seek
diligently for further evidence, and, if part of a jaw could be found
with teeth adhering, he believed he could solve the problem. In his
immortal work, _Ossemens Fossiles_, Cuvier generously admits his
former mistake, and said he was entirely convinced of his error.
Baron Cuvier alone amongst the doctor's friends or correspondents was
able to give any hint as to the character and probable relations of
the animal to which the recently discovered teeth belonged. Being
hampered by arduous professional duties in a provincial town, remote
from museums and libraries, Dr. Mantell transmitted to the Royal
Society figures and drawings of the specimens, and, at the suggestion
of the Rev. W. D. Conybeare, adopted the name Iguanodon (Iguana-tooth)
for the extinct reptile, a name which pointed to the resemblance of
its teeth to those of the modern iguana, a land-lizard inhabiting many
parts of America and the West Indies, and rarely met with north or
south of the tropics. These lizards are from three to five feet in
length, and perfectly harmless, feeding on insects and vegetables, and
climbing trees in quest of the tender leaves and buds, which they chip
off and swallow whole; they nestle in the hollows of rocks, and
deposit their eggs in the sands and banks of rivers.
In all living reptiles the insects or vegetables on which they feed
are seized by the tongue or teeth, and swallowed whole, so that a
movable covering to the jaws, similar to the lips and cheeks of the
mammalia, is not necessary, either for seizing and retaining food, or
for subjecting it by muscular movements to the action of the teeth. It
is the power of perfect mastication possessed by the Iguanodon that is
so strange, for it implies a most remarkable approach in extinct
reptiles to characters possessed now only by herbivorous mammalia,
such as horses, cows, deer, etc. From this and other strange
characters seen in the Dinosaurs, we learn that they in their day
played the part of our modern quadrupeds, whether carnivorous or
herbivorous, and showed a remarkable approach to the mammalian type,
which of course is a much higher one.
It is, therefore, not to be wondered at that Dr. Mantell's
contemporaries, with the exception of Cuvier, found in the teeth we
have described an awkward puzzle, and refused to believe that they
belonged to a reptile. Such a notion was at variance with all previous
experience, and we naturally form our conclusions to a large extent by
experience. Let us, then, beware lest we allow our ideas to be limited
by what after all is, as it were, only an expression of our ignorance.
The Hottentot who has never seen snow would refuse to believe that
rain can assume a solid form; and, in the same way, if we bind
ourselves down by experience, we might refuse to believe in some of
the still more wonderful dinosaurian types to be described in this
chapter, such as the Triceratops, with a pair of large horns, a skull
over six feet long, and limbs larger than those of the rhinoceros!
(see p. 117).
The strange vagaries of Dinosaurs have led Professor Marsh and other
authorities to exalt them, from their former position of a mere order
in the reptile class, to the dignity of a sub-class all to themselves;
and there is much to be said for this view. Compared with the
Marsupials, living and extinct, they show an equal diversity of
structure and variations in size from by far the largest land animals
known down to some of the smallest.[16]
[16] Bauer, after a full critical examination of the Dinosauria,
considers that one order is insufficient, and has proposed to make
three orders of them, which he names after the Iguanodon, Cetiosaurus,
and Megalosaurus.
The importance of discovering, if possible, a portion of the jaw of an
Iguanodon was fully recognised by Dr. Mantell, and, urged on by the
encouragement he had received from the illustrious Cuvier, he eagerly
sought for the required evidence. But nearly a quarter of a century
elapsed before it was forthcoming. In 1841 and 1848, however, portions
of the lower jaw, with some teeth attached, were found; and his memoir
_On the Structure of the Jaws and Teeth of the Iguanodon_ was
published by the Royal Society in 1848. For this important
communication the gold medal of the society was awarded to the author.
The second of these finds (by Captain Brickenden) confirmed in every
essential particular the inferences suggested by the detached teeth.
The first important connected series of bones of this monster was
discovered in 1834, by Mr. Bensted, in the "Kentish Rag" quarries of
the Lower Greensand formation at Maidstone. Mr. Bensted, who was the
proprietor of the quarry, one day had his attention drawn by the
workmen to what they supposed to be petrified wood in some pieces of
stone which they had been blasting. He perceived that what they
supposed to be wood was fossil bone, and, with a zeal and care which
have always characterised this estimable man (says Professor Owen) in
his endeavour to secure for science any evidence of fossil remains in
his quarry, he immediately resorted to the spot. He found that the
bore, or blast, by which these remains were brought to light had been
inserted into the centre of the specimen, so that the mass of stone
containing it had been shattered into many pieces, some of which were
blown into the adjoining fields! All these pieces he had carefully
collected, and, proceeding with equal ardour and success to the
removal of the matrix from the fossils, he succeeded, after a month's
labour, in exposing them to view, and in fitting the fragments in
their proper place. This valuable specimen was presented to Dr.
Mantell (and afterwards purchased with the rest of his collection by
the British Museum), and its present condition is the result of his
skill, as well as that of its discoverer. Certain gentlemen in
Brighton, anxious that the specimen should be placed in the hands of
the original discoverer of Iguanodon, purchased and presented it to
Dr. Mantell--a tribute of respect which was highly gratifying to him.
(Wall-case 6.)
It belonged to a young Iguanodon. This fortunate discovery was one of
those Cuvier foresaw, and has served to verify his sagacious
conjecture that some of the great bones collected by the doctor from
the Wealden strata of Sussex belonged to the same animal, and to
confirm other conclusions formed by the discoverer of the Iguanodon.
Great was Dr. Mantell's delight on finding that every bone he had
ascribed to Iguanodon solely from analogy was present in the Maidstone
specimen. One of the chief advantages of this discovery was that it
afforded demonstration of the characters of the vertebræ, which, as
previously stated, are very important to the anatomist. Of these
Professor Owen has given full descriptions, and has shown that they
differ from those of any animal previously known, whether living or
extinct.
It is very interesting, in the light of recent discoveries, to read
the conclusions arrived at by Mantell and Owen, with regard to the
organisation of this great Wealden reptile, and to see how, with the
exception of certain details, they have been confirmed. Considering
the imperfect nature of the materials at their command, it is
wonderful that their forecasts should have turned out so successful.
Thus Professor Owen predicted for the Iguanodon a total length of
twenty-eight feet, and specimens discovered of late years show a
length of twenty-four feet. In some, the thigh-bone exceeded a yard in
length; this indicated an animal of great size, since in the largest
crocodiles this bone is scarcely a foot long. Again, Dr. Mantell, from
a study of the imperfect jaw-bones in his collection, concluded that
the lower jaw was invested with a well-developed fleshy flexible lip,
and that the mouth was provided with a tongue of great mobility and
power. "There are strong reasons," he says, "for supposing that the
lip was flexible, and, in conjunction with the long fleshy prehensile
tongue, constituted the instrument for seizing and cropping the leaves
and branches, which, from the construction of the molars, we may
infer, constituted the chief food of the Iguanodon. The mechanism of
the maxillary organs (jaws), as elucidated by recent discoveries, is
thus in perfect harmony with the remarkable characters which rendered
the first known teeth so enigmatical; and in the Wealden herbivorous
reptile we have a solution of the problem, how the integrity of the
type of organisation peculiar to the class of cold-blooded vertebrata
was maintained, and yet adapted, by simple modifications, to fulfil
the conditions required by the economy of a gigantic terrestrial
reptile, destined to obtain support exclusively from vegetable
substances; in like manner, as the extinct colossal herbivorous
Edentata (sloths, see Chapter XII.), which flourished in South America
ages after the country of the Iguanodon and its inhabitants had been
swept away from the face of the earth."
Dr. Mantell also was the first to prove, from the nature of the
Wealden strata, that they were deposited in or near the estuary of a
mighty river. With regard to the aspect of the country in which the
Iguanodon flourished, he showed that coniferous trees probably clothed
its Alpine regions; palms and arborescent ferns, and cycadaceous
plants (_i.e._ plants resembling the modern zamia, or "false palm"),
constituted the groves and forests of its plains and valleys; and in
its fens and marshes the equisetaceæ (mare's-tails) and plants of a
like nature prevailed.
[Illustration: Plate VII.
A GIGANTIC DINOSAUR, IGUANODON BERNISSARTENSIS.
Length about 30 feet.]
The Iguanodons of the Wealden epoch did not live and die where their
bones are now found--the condition in which their fossil relics occur
proves that they floated down the streams and rivers, with rafts of
trees and other spoils of the land, till, arrested in their course,
they sank down and became buried in the fluviatile and sometimes
marine sediments then being slowly laid down. In this way only can we
account for the generally broken and rolled condition of the bones,
their separation from each other, the numerous specimens of teeth
which must have been detached from their sockets, and the broken stems
and branches of trees without leaves that have been found in the
Wealden strata of England.
Since the days of Dr. Mantell, the remains of Iguanodon, or closely
allied genera, have been found on the continent, in other parts of
England, and in North America, in strata of various ages, from the
Trias or New Red Sandstone to the Chalk (see Table of Strata, Appendix
I.). The American Hadrosaurus must have decidedly resembled the
Iguanodon.
The beautiful restoration by our artist (plate VII.) is based upon the
Belgian specimens described in the following chapter.