THE ANCIENT
LIFE-HISTORY
OF THE EARTH
Chapter 19:
THE MIOCENE PERIOD.
The Miocene rocks comprise those Tertiary deposits which contain
less than about 35 per cent of existing species of shells
(Mollusca), and more than 5 per cent—or those deposits
in which the proportion of living shells is less than of extinct
species. They are divisible into a Lower Miocene
(Oligocene) and an Upper Miocene series.
In Britain, the Miocene rocks are very poorly developed, one
of their leading developments being at Bovey Tracy in Devonshire,
where there occur sands, clays, and beds of lignite
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or imperfect coal. These strata contain numerous plants,
amongst which are Vines, Figs, the Cinnamon-tree, Palms, and many
Conifers, especially those belonging to the genus Sequoia (the
"Red-Foods"). These Bovey Tracy lignites are of Lower Miocene age,
and they are lacustrine in origin. Also of Lower Miocene age are
the so-called "Hempstead Beds" of Yarmouth in the Isle of Wight.
These attain a thickness of less than 200 feet, and are shown by
their numerous fossils to be principally a true marine formation.
Lastly, the Duke of Argyll, in 1851, showed that there existed at
Ardtun, in the island of Mull, certain Tertiary strata containing
numerous remains of plants; and these also are now regarded as
belonging to the Lower Miocene.
In France, the Lower Miocene is represented in Auvergne,
Cantal, and Velay, by a great thickness of nearly horizontal
strata of sands, sandstone, clays, marls, and limestones, the
whole of fresh-water origin. The principal fossils of these
lacustrine deposits are Mammalia, of which the remains
occur in great abundance. In the valley of the Loire occur the
typical European deposits of Upper Miocene age. These are known
as the "Faluns," from a provincial term applied to shelly sands,
employed to spread upon soils which are deficient in lime; and
the Upper Miocene is hence sometimes spoken of as the "Falunian"
formation. The Faluns occur in scattered patches, which are rarely
more than 50 feet in thickness, and consist of sands and marls.
The fossils are chiefly marine; but there occur also land and
fresh-water shells, together with the remains of numerous Mammals.
About 25 per cent of the shells of the Faluns are identical with
existing species. The sands, limestones, and marls of the Department
of Gers, near the base of the Pyrenees, rendered famous by the
number or Mammalian remains exhumed from them by M. Lartet, also
belong to the age of the Faluns.
In Switzerland, between the Alps and the Jura, there occurs
a great series of Miocene deposits, known collectively as the
"Molasse," from the soft nature of a greenish sandstone, which
constitutes one of its chief members. It attains a thickness of
many thousands of feet, and rises into lofty mountains, some of
which—as the Rigi—are more than 6000 feet in height.
The middle portion of the Molasse is of marine origin, and is
shown by its fossils to be of the age of the Faluns; but the
lower and upper portions of the formation are mainly or entirely
of fresh-water origin. The Lower Molasse (of Lower Miocene age)
has yielded about 500 species of plants, mostly of tropical or
sub-tropical forms. The Upper
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Molasse has yielded about the same number of plants, with about
900 species of Insects, such as wood-eating Beetles Water-beetles,
White Ants, Dragon-flies, &c.
In Belgium, strata of both Lower and Upper Miocene age are
known,—the former (Rupelian Clays) containing numerous
marine fossils; whilst the latter (Bolderberg Sands) have
yielded numerous shells corresponding with those of the Faluns.
In Austria, Miocene strata are largely developed, marine
beds belonging to both the Lower and Upper division of the formation
occurring extensively in the Vienna basin. The well-known Brown
Coals of Radaboj, in Croatia, with numerous plants and insects,
are also of Lower Miocene age.
In Germany, deposits belonging to both the Lower and Upper
division of the Miocene formation are extensively developed. To
the former belong the marine strata of the Mayence basin, and
the marine Rupelian Clay near Berlin; whilst a celebrated
group of strata belonging to the Upper Miocene occurs near
Epplesheim, in Hesse-Darmstadt, and is well known for the number
of its Mammalian remains.
In Greece, at Pikermé, near Athens, there occurs a
celebrated deposit of Upper Miocene age, well known to
palæontologists through the researches of M. M. Wagner, Roth,
and Gaudry upon the numerous Mammalia which it contains. In
Italy, also, strata of both Lower and Upper Miocene age are
well developed in the neighbourhood of Turin.
In the Siwâlik Hills, in India, at the southern foot
of the Himalayas, occurs a series of Upper Miocene strata, which
have become widely celebrated through the researches of Dr Falconer
and Sir Proby Cautley upon the numerous remains of Mammals and
Reptiles which they contain. Beds of corresponding age, with
similar fossils, are known to occur in the island of Perim in
the Gulf of Cambay.
Lastly, Miocene deposits are found in North America, in
New Jersey, Maryland, Virginia, Missouri, California, Oregon,
&c., attaining a thickness of 1500 feet or more. They consist
principally of clays, sands, and sandstones, sometimes of marine
and sometimes of fresh-water origin. Near Richmond, in Virginia,
there occurs a remarkable stratum, wrongly called "Infusorial
Earth," which is occasionally 30 feet in thickness, and consists
almost wholly of the siliceous envelopes of certain low forms of
plants (Diatoms), along with the spicules of Sponges and other
siliceous organisms (see fig. 16). The White River Group of
Hayden occurs in the Upper Missouri region, and is largely exposed
over the barren and desolate
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district known as the "Mauvaises Terres." They have a thickness of
1000 feet or more, and contain numerous remains of Mammals. They
are of lacustrine origin, and are believed to be of the age of the
Lower Miocene. Upon the whole, about from 15 to 30 per cent of the
Mollusca of the American Miocene are identical with
existing species.
In addition to the regions previously enumerated, Miocene strata
are known to be developed in Greenland, Iceland, Spitzbergen,
and in other areas of less importance.
The life of the Miocene period is extremely abundant,
and, from the nature of the deposits of this age, also extremely
varied in its character. The marine beds of the formation have
yielded numerous remains of both Vertebrate and Invertebrate
sea-animals; whilst the fresh-water deposits contain the skeletons
of such shells, fishes, &c., as now inhabit rivers or lakes.
Both the marine and the lacustrine beds have been shown to contain
an enormous number of plants, the latter more particularly; whilst
the Brown Coals of the formation are made up of vegetable matter
little altered from its original condition. The remains of
air-breathing animals, such as Insects, Reptiles, Birds, and
Mammals, are also abundantly found, more especially in the
fresh-water beds.
The plants of the Miocene period are extraordinarily numerous,
and only some of the general features of the vegetation of this
epoch can be indicated here. Our chief sources of information as
to the Miocene plants are the Brown Coals of Germany and Austria,
the Lower and Upper Molasse of Switzerland, and the Miocene strata
of the Arctic regions. The lignites of Austria have yielded very
numerous plants, chiefly of a tropical character—one of the
most noticeable forms being a Palm of the genus Sabal
(fig. 234, B), now found in America. The plants of the Lower
Miocene of Switzerland are also mostly of a tropical character,
but include several forms now found in North America, such as a
Tulip-tree (Liriodendron) and a Cypress (Taxodium).
Amongst the more remarkable forms from these beds may be mentioned
Fan-Palms (Chamœrops, fig. 234, A), numerous tropical
ferns, and two species of Cinnamon. The plant-remains of the
Upper Molasse of Switzerland indicate an extraordinarily rank and
luxuriant vegetation, composed mainly of plants which now live
in warm countries. Among the commoner plants of this formation may
be enumerated many species of Maple (Acer), Plane-trees
(Platanus fig. 235), Cinnamon-trees (fig. 236), and other
members of the Lauraceœ, many species of
Proteaccœ (Banksia, Grevillea, &c.),
several species of Sarsaparilla (Smilax), Palms, Cypresses,
&c.
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In Britain, the Lower Miocene strata of Bovey Tracy have yielded
remains of Ferns, Vines, Fig, Cinnamon, Proteaccœ, &c.,
along with numerous Conifers. The most abundant of these last is a
gigantic pine—the Sequoia Couttsiœ—which is
very nearly allied to the huge Sequoia (Wellingtonia)
gigantea of California. A nearly-allied form (Sequoia
Langsdorffi) has been detected in the leaf-bed of Ardtun,
in the Hebrides.
Fig. 234.—Miocene Palms A, Chamœrops Helvetica; B,
Sabal major. Lower Miocene of Switzerland and France.
Fig. 235.—Platanus aceroides, an Upper Miocene
Plane-tree. a, Leaf; b, The core of a bundle
of fruits; c, A single fruit.
Fig. 236.—Cinnamomum polymorphum. a, Leaf;
b, Flower. Upper Miocene.
In Greenland, as well as in other parts of the Arctic regions,
Miocene strata have been discovered which have yielded a great
number of plants, many of which are identical with species found
in the European Miocene. Amongst these
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plants are found many trees, such as Conifers, Beeches, Oaks,
Maples, Plane-trees, Walnuts, Magnolias, &c., with numerous
shrubs, ferns, and other smaller plants. With regard to the Miocene
flora of the Arctic regions, Sir Charles Lyell remarks that "more
than thirty species of Coniferæ have been found, including
several Sequoias (allied to the gigantic Wellingtonia of California),
with species of Thujopsis and Salisburia, now peculiar
to Japan. There are also beeches, oaks, planes, poplars, maples,
walnuts, limes, and even a magnolia, two cones of which have
recently been obtained, proving that this splendid evergreen not
only lived but ripened its fruit within the Arctic circle. Many
of the limes, planes, and oaks were large-leaved species; and both
flowers and fruits, besides immense quantities of leaves, are in
many cases preserved. Among the shrubs are many evergreens, as
Andromeda, and two extinct genera, Daphnogene and
M'Clintockia, with fine leathery leaves, together with
hazel, blackthorn, holly, logwood, and hawthorn. A species of
Zamia (Zimites) grew in the swamps, with Potamogeton,
Sparganium, and Menyanthes; while ivy and villes twined
around the forest-trees, and broad-leaved ferns grew beneath their
shade. Even in Spitzbergen, as far north as lat. 78° 56', no
less than ninety-five species of fossil plants have been obtained,
including Taxodium of two species, hazel, poplar, alder,
beech, plane-tree, and lime. Such a vigorous growth of trees within
12° of the pole, where now a dwarf willow and a few herbaceous
plants form the only vegetation, and where the ground is covered
with almost perpetual snow and ice, is truly remarkable."
Taking the Miocene flora as a whole, Dr Heer concludes from his
study of about 3000 plants contained in the European Miocene
alone, that the Miocene plants indicate tropical or sub-tropical
conditions, but that there is a striking inter-mixture of forms
which are at present found in countries widely removed from one
another. It is impossible to state with certainty how many of the
Miocene plants belong to existing species, but it appears that
the larger number are extinct. According to Heer, the American
types of plants are most largely represented in the Miocene flora,
next those of Europe and Asia, next those of Africa, and lastly
those of Australia. Upon the whole, however, the Miocene flora
of Europe is mostly nearly allied to the plants which we now
find inhabiting the warmer parts of the United States; and this
has led to the suggestion that in Miocene times the Atlantic
Ocean was dry land, and that a migration of
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American plants to Europe was thus permitted. This view is
borne out by the fact that the Miocene plants of Europe are most
nearly allied to the living plants of the eastern or Atlantic
seaboard of the United States, and also by the occurrence of a
rich Miocene flora in Greenland. As regards Greenland, Dr Heer
has determined that the Miocene plants indicate a temperate
climate in that country, with a mean annual temperature at least
30° warmer than it is at present.
The present limit of trees is the isothermal which gives the
mean temperature of 500 Fahr. in July, or about the parallel of
67° N. latitude. In Miocene times, however, the Limes, Cypresses,
and Plane-trees reach the 79th degree of latitude, and the Pines
and Poplars must have ranged even further north than this.
The Invertebrate Animals of the Miocene period are very
numerous, but they belong for the most part to existing types,
and they can only receive scanty consideration here. The little
shells of Foraminifera are extremely abundant in some beds,
the genera being in many cases such as now flourish abundantly in
our seas. The principal forms belong to the genera Textularia
(fig. 237), Robulina, Glandulina, Polystomella, Amplistegina,
Fig. 237.—Textularia Meyeriana, greatly
enlarged. Miocene Tertiary.
&c. Corals are very abundant, in many instances forming regular
"reefs;" but all the more important groups are in existence at
the present day. The Red Coral (Corallium), so largely
sought after as an ornamental material, appears for the first
time in deposits of this age. Amongst the Echinoderms,
we meet with Heart-Urchins (Spatangus), Cake-Urchins
(Scutella; fig. 238), and various other forms, the majority
of which are closely allied to forms now in existence.
Numerous Crabs and Lobsters represent the Crustacea; but
the most important of the Miocene Articulate Animals are the
Insects. Of these, more than thirteen hundred species
have been determined by Dr Heer from the Miocene strata of
Switzerland alone. They include almost all the existing orders
of insects, such as numerous and varied forms of Beetles
(Coleoptera), Forest-bugs (Hemiptera), Ants
(Hymenoptera), Flies (Diptera), Termites and
Dragon-flies (Neuroptera), Grasshoppers (Orthoptera),
and Butterflies (Lepidoptera).
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One of the latter,
the well-known Vanessa Pluto of the Brown Coals of Croatia,
even exhibits the pattern of the wing, and to some extent its
original coloration; whilst the more durably-constructed insects
are often in a state of exquisite preservation.
Fig. 238.—Different views of Scutella subrotunda,
a Miocene "Cake-Urchin" from the south of France.
The Mollusca of the Miocene period are very numerous,
but call for little special comment. Upon the whole, they are
generically very similar to the Shell-fish of the present day;
whilst, as before stated, from fifteen to thirty per cent of
the species are identical with those now in existence.
So far as the European area is concerned, the Molluscs indicate
a decidedly hotter climate than the present one, though they
have not such a distinctly tropical character as is the case
with the Eocene shells. Thus we meet with many Cones, Volutes,
Cowries, Olive-shells, Fig-shells, and the like, which are
decidedly indicative of a high temperature of the sea.
Polyzoans are abundant, and often attain considerable
dimensions; whilst Brachiopods, on the other hand, are
few in number. Bivalves and Univalves are extremely
plentiful; and we meet here with the shells of Winged-Snails
(Pteropods), belonging to such existing genera as
Hyalea (fig. 239) and Cleodora. Lastly, the
Cephalopods are represented both by the chambered shells
of Nautili and by the internal skeletons of Cuttle-fishes
(Spirulirostra.)
Fig. 239.—Different views of the shell of Hyalea
Orbignyana, a Miocene Pteropod.
The Fishes of the Miocene Period are very abundant but of
little special importance. Besides the remains of Bony Fishes, we
meet in the marine deposits of this age with numerous pointed
teeth belonging to different kinds of Sharks. Some of the genera of
these—such as Carcharodon (fig. 241), Oxyrhina
(fig. 240), Lamna, and Galeocerdo—are very
widely distributed, ranging through
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both the Old and New Worlds; and some of the species attain gigantic
dimensions.
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Fig. 240.—Tooth of Oxyrhina xiphodon. Miocene.
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Fig. 241.—Tooth of Carcharodon productus. Miocene.
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Amongst the Amphibians we meet with distinctly modern
types, such as Frogs (Rana) and Newts or Salamanders.
The most celebrated of the latter is the famous Andrias
Scheuchzeri (fig. 242), discovered in the year 1725 in the
fresh-water Miocene deposits of Œningen, in Switzerland.
The skeleton indicates an animal nearly five feet in length; and
it was originally described by Scheuchzer, a Swiss physician, in
a dissertation published in 1731, as the remains of one of the
human beings who were in existence at the time of the Noachian
Deluge. Hence he applied to it the name of Homo diluvii
testis. In reality, however, as shown by Cuvier, we have here
the skeleton of a huge Newt, very closely allied to the Giant
Salamander (Menopoma maxima) of Java.
The remains of Reptiles are far from uncommon in the Miocene
rocks, consisting principally of Chelonians and Crocodilians. The
Land-tortoises (Testudinidœ) make their first appearance
during this period. The most remarkable form of this group is the
huge Colossochelys Atlas of the Upper Miocene deposits of
the Siwâlik Hills in India, described by Dr Falconer and Sir
Proby Cautley. Far exceeding any living Tortoise in its dimensions,
this enormous animal is estimated as having had a length of about
twenty feet, measured from the tip of the snout to the extremity
of the tail, and to have stood upwards of seven feet high. All the
details of its organisation, however, prove that it must have been
"strictly a land animal, with herbivorous habits, and probably of
the most inoffensive nature." The accomplished palæontologist
just quoted, shows further that some of the traditions of the
Hindoos would render it not improbable that this colossal Tortoise
had survived into the earlier portion of the human period.
Of the Birds of the Miocene period it is sufficient to
remark that though specifically distinct, they belong, so far
as known, wholly to existing groups, and therefore present no
points of special palæontological interest.
Fig. 242.—Front portion of the skeleton of Andrias
Scheuchzeri, a Giant Salamander from the Miocene Tertiary of
Œningen, in Switzerland. Reduced in size.
The Mammals of the Miocene are very numerous, and only
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the more important forms can be here alluded to. Amongst the
Marsupials, the Old World still continued to possess species
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of Opossum (Didephys), allied to the existing American
forms. The Edentates (Sloths, Armadillos, and Ant-eaters),
at the present day mainly South American, are represented by two
large European forms. One of these is the large Macrotherium
giganteum of the Upper Miocene of Gers in Southern France,
which appears to hare been in many respects allied to the existing
Scaly Ant-eaters or Pangolins, at the same time that the
disproportionately long fore-limbs would indicate that it possessed
the climbing habits of the Sloths. The other is the still more
gigantic Ancylotherium Pentelici of the Upper Miocene of
Pikermé, which seems to have been as large as, or larger than,
the Rhinoceros, and which must have been terrestrial in its habits.
This conclusion is further borne out by the comparative equality
of length which subsists between the fore and hind limbs, and is
not affected by the curvature and crookedness of the claws, this
latter feature being well marked in such existing terrestrial
Edentates as the Great Ant-eater.
The aquatic Sirenians and Cetaceans are represented
in Miocene times by various forms of no special importance. Amongst
the former, the previously existing genus Halitherium
continued to survive, and amongst the latter we meet with remains
of Dolphins and of Whales of the "Zeuglodont" family. We may
also note here the first appearance of true "Whalebone Whales,"
two species of which, resembling the living "Right Whale" of
Arctic seas, and belonging to the same genus (Balœna),
have been detected in the Miocene beds of North America.
The great order of the Ungulates or Hoofed Quadrupeds
is very largely developed in strata of Miocene age, various new
types of this group making their appearance here for the first
time, whilst some of the characteristic genera of the preceding
period are still represented under new shapes. Amongst the Odd-toed
or "Perissodactyle" Ungulates, we meet for the first time with
representatives of the family Rhinoceridœ comprising
only the existing Rhinoceroses. In India in the Upper Miocene beds
of the Siwâlik Hills, and in North America, several species
of Rhinoceros have been detected, agreeing with the existing forms
in possessing three toes to each foot, and in having one or two
solid fibrous "horns" carried upon the front of the head. On the
other hand, the forms of this group which distinguish the Miocene
deposits of Europe appear to have been for the most part hornless,
and to have resembled the Tapirs in having three-toed hind-feet,
but four-toed fore-feet.
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The family of the Tapirs is represented, both in the Old and New
Worlds, by species of the genus Lophiodon, some of which
were quite diminutive in point of size, whilst others attained
the dimensions of a horse. Nearly allied to this family, also,
is the singular group of quadrupeds which Marsh has described
from the Miocene strata of the United States under the name of
Brontotheridœ. These extraordinary animals, typified
by Brontotherium (fig. 243) itself, agree with the existing
Tapirs of South America and the Indian Archipelago in having the
fore-feet four-toed, whilst the hind-feet are three-toed; and
a further point of resemblance is found in the fact (as shown by
the form of the nasal bones) that the nose was long and flexible,
forming a short movable proboscis or trunk, by means of which the
animal was enabled to browse on shrubs or trees. They differ,
however, from the Tapirs, not only in the apparent presence of
a long tail, but also in the possession of a pair of very large
"horn-cores," carried upon the nasal bones, indicating that the
animal possessed horns of a similar structure to those of the
"Hollow-horned" Ruminants (e.g., Sheep and Oxen).
Brontotherium gigas is said to be nearly as large as an
Elephant, whilst B. Ingens appears to have attained dimensions
still more gigantic. The well-known genus Titanotherium of
the American Miocene would also appear to belong to this group.
Fig. 243.—Skull of Brontotherium ingens. Miocene
Tertiary, United States. (After Marsh.)
The family of the Horses (Equidœ) appears under
various forms in the Miocene, but the most important and best
known of these is Hipparion. In this genus the general
conformation of the skeleton is extremely similar to that of the
existing Horses, and the external appearance of the animal must
have been very much the same. The foot of Hipparion,
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however, as has been previously mentioned,
differed from that of the Horse in the fact that whilst both
possess the middle toe greatly developed and enclosed in a
broad hoof, the former, in addition, possessed two lateral
toes, which were sufficiently developed to carry hoofs, but
were so far rudimentary that they hung idly by the side of the
central toe without touching the ground (see fig. 230). In the
Horse, on the other hand, these lateral toes, though present,
are not only functionally useless, but are concealed beneath
the skin. Remains of the Hipparion have been found in
various regions in Europe and in India; and from the immense
quantities of their bones found in certain localities, it may
be safely inferred that these Middle Tertiary ancestors of the
Horses lived, like their modern representatives, in great
herds, and in open grassy plains or prairies.
Amongst the Even-toed or Artiodactyle Ungulates, we for
the first time meet with examples of the Hippopotamus, with
its four-toed feet, its massive body, and huge tusk-like lower
canine teeth. The Miocene deposits of Europe have not hitherto
yielded any remains of Hippopotamus; but several species
have been detected in the Upper Miocene of the Siwâlik Hills
by Dr Falconer and Sir Proby Cautley. These ancient Indian forms,
however, differ from the existing Hippopotamus amphibius
of Africa in the fact that they possessed six incisor teeth in
each jaw (fig. 244), whereas the latter has only four.
Amongst the other Even-toed Ungulates, the family of the Pigs
(Suida) is represented by true Swine (Sus Erymanthius),
Peccaries (Dicotyles antiquus), and by forms which, like
the great Elotherium of the American Miocene, have no
representative at the present day. The Upper Miocene of India has
yielded examples of the Camels. Small Musk-deer (Amphitragulus
and Dremotherium) are known to have existed in France and
Greece; and the true Deer (Cervidœ), with their solid
bony antlers, appear for the first time here in the person of
species allied to the living Stags (Cervus), accompanied
by the extinct genus Dorcatherium. The Giraffes
(Camelopardalidœ), now confined to Africa, are known to
have lived in India and Greece; and the allied Helladotherium,
in some respects intermediate between the Giraffes and the Antelopes,
ranged over Southern Europe from Attica to France. The great group
of the "Hollow-horned" Ruminants (Cavicornia), lastly,
came into existence in the Miocene period; and though the typical
families of the Sheep and Oxen are apparently wanting, there are
true Antelopes, together with forms which, if systematically
referable to the Antilopidœ, nevertheless are more or
less clearly transitional between this and the family of the Sheep
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and Goats. Thus the Palœoreas of
the Upper Miocene of Greece may be regarded as a genuine Antelope;
but the Tragoceras of the same deposit is intermediate in
its characters between the typical Antelopes and the Goats.
Fig. 244.—a, Skull of Hippopotamus Sivalensis,
viewed from below, one-eighth of the natural size; b, Molar
tooth of the same, showing the surface of the crown, one-half of
the natural size: c, Front of the lower jaw of the same,
showing the six incisors and the tusk-like canines, one-eighth of
the natural size. Upper Miocene, Siwâlik Hills; (After
Falconer and Cautley.)
Perhaps
the most remarkable, however, of these Miocene Ruminants is the
Sivatherium giganteum (fig. 245) of the Siwâlik Hills,
in India. In this extraordinary animal there were two pairs of horns,
supported by bony "horn-cores," so that there can be no hesitation
in referring Sivatherium to the Cavicorn Ruminants. If all
these horns had been simple, there would have been no difficulty
in considering Sivatherium as simply a gigantic four-horned
Antelope, essentially similar to the living Antilope
(Tetraceros) quadricornis of India. The hinder pair
of horns, however, is not only much larger than the front pair,
but each possesses two branches or snags—a peculiarity
not to be paralleled amongst any existing Antelope, save the
abnormal Prongbuck (Antilocapra) of North America. Dr
Murie, however, in an admirable memoir on the structure and
relationships
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of Sivatherium, has drawn attention
to the fact that the Prongbuck sheds the sheath of its
horns annually, and has suggested that this may also have been the
case with the extinct form. This conjecture is rendered probable,
amongst other reasons, by the fact that no traces of a horny
sheath surrounding the horn-cores of the Indian fossil have been
as yet detected. Upon the whole, therefore, we may regard the
elephantine Sivatherium as being most nearly allied to
the Prongbuck of Western America, and thus as belonging to the
family of the Antelopes.
Fig. 245.—Skull of Sivatherium giganteum, reduced
in size. Miocene, India. (After Murie.)
It is to the Miocene period, again, to which we must refer the
first appearance of the important order of the Elephants and their
allies (Proboscideans), all of which are characterised by
their elongated trunk-like noses, the possession of five toes to
the foot, the absence of canine teeth, the development of two or
more of the incisor teeth into long tusks, and the adaptation of
the molar teeth to a vegetable diet. Only three generic groups of
this order are known-namely, the extinct Deinotherium, the
equally extinct Mastodons, and the Elephants; and all
these three types are known to have been in existence as
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early as the Miocene period, the first of them being exclusively
confined to deposits of this age. Of the three, the genus
Deinotherium is much the most abnormal in its characters; so
much so, that good authorities regard it as really being one of the
Sea-cows (Sirenia)—though this view has been rendered
untenable by the discovery of limb-bones which can hardly belong
to any other animal, and which are distinctly Proboscidean in
type. The most celebrated skull of the Deinothere (fig. 246) is one
Fig. 246.—Skull of Deinotherium giganteum, greatly
reduced. From the Upper Micene of Germany.
which was exhumed from the Upper Miocene deposits of Epplesheim,
in Hesse-Darmstadt, in the year 1836. This skull was four and a
half feet in length, and indicated an animal larger than any
existing species of Elephant. The upper jaw is destitute of incisor
or canine teeth, but is furnished on each side with five molars,
which are opposed to a corresponding series of grinding teeth in
the lower jaw. No canines are present in the lower jaw; but the
front portion of the jaw is abruptly bent downwards, and carries
two huge tusk-like incisor teeth, which are curved downwards and
backwards, and the use of which is rather problematical. Not
only does the Deinothere occur in Europe, but remains belonging
to this genus have also been detected in the Siwâlik Hills, in
India.
The true Elephants (Elephas) do not appear to have existed
during the Miocene period in Europe, but several species have been
detected in the Upper Miocene deposits of the Siwâlik Hills,
in India. The fossil forms, though in all cases specifically, and
in some cases even sub-generically, distinct, agree with those
now in existence in the general conformation of their skeleton,
and in the principal characters of their dentition. In all, the
canine teeth are wanting in both jaws; and there are no incisor
teeth in the lower jaw, whilst there are two incisors in the
front of the upper jaw, which are developed into two huge "tusks."
There are six molar teeth on each side of both the upper and lower
jaw, but only one, or at most a part of two, is in actual use
at any given time; and as this becomes worn away, it is pushed
forward and replaced by its successor behind it. The molars are of
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very large size, and are each composed of a number of transverse
plates of enamel united together by ivory; and by the process
of mastication, the teeth become worn down to a flat surface,
crossed by the enamel-ridges in varying patterns; These patterns
are different in the different species of Elephants, though constant
for each; and they constitute one of the most readily available
means of separating the fossil forms from one another. Of the
seven Miocene Elephants of India, as judged by the characters of
the molar, teeth, two are allied to the existing Indian Elephant,
one is related to the living African Elephant, and the remaining
four are in some respects intermediate between the true Elephants
and the Mastodons.
Fig. 247.—A, Molar tooth of Elephas planifrons,
one-third of the natural size, showing the grinding
surface—from the Upper Miocene of India; B, Profile view
of the last upper molar of Mastodon Sivalensis, one-third
of the natural size—from the Upper Miocene of India. (After
Falconer.)
The Mastodons, lastly, though quite elephantine in their
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general characters, possess molar teeth
which have their crowns furnished with conical eminences or
tubercles placed in pairs (fig. 247, B), instead of having the
approximately flat surface characteristic of the grinders of the
Elephants. As in the latter, there are two upper incisor teeth,
which grow permanently during the life of the animal, and which
constitute great tusks; but the Mastodons, in addition, often
possess two lower incisors, which in some cases likewise grow
into small tusks. Three species of Mastodon are known to
occur in the Upper Miocene of the Siwâlik Hills of India;
and the Miocene deposits of the European area have yielded the
remains of four species, of which the best known are the M.
Longirostris and the M. Angustidens.
Whilst herbivorous Quadrupeds, as we have seen, were extremely
abundant during Miocene times, and often attained gigantic
dimensions, Beasts of Prey (Carnivora) were by no means
wanting, most of the principal existing families of the order
being represented in deposits of this age. Thus, we find aquatic
Carnivores belonging to both the living groups of the Seals and
Walruses; true Bears are wanting, but their place is filled by the
closely-allied genus Amphicyon, of which various species
are known; Weasels and Otters were not unknown, and the
Hyœnictis and Iditherium of the Upper Miocene
of Greece are apparently intermediate between the Civet-cats and
the Hyænas; whilst the great Cats of subsequent periods are
more than adequately represented by the huge "Sabre-toothed Tiger"
(Machairodus), with its immense trenchant and serrated
canine teeth.
Amongst the Rodent Mammals, the Miocene rocks have yielded
remains of Rabbits, Porcupines (such as the Hystrix
primigenius of Greece), Beavers, Mice, Jerboas, Squirrels,
and Marmots. All the principal living groups of this order were
therefore differentiated in Middle Tertiary times.
The Cheiroptera are represented by small insect-eating
Bats; and the order of the Insectivorous Mammals is represented
by Moles, Shrew-mice, and Hedgehogs.
Fig. 248.—Lower jaw of Pliopithcus antiquus. Upper
Miocene, France.
Lastly, the Monkeys (Quadrumana) appear to have existed
during the Miocene period under a variety of forms, remains of
these animals having been found both in Europe and in India; but
no member of this order has as yet been detected in the Miocene
Tertiary of the North American continent. Amongst the Old World
Monkeys of the Miocene, the two most interesting are the
Pliopithecus and Dryopithecus of France. The former
of these (fig. 248) is supposed to have been most nearly related
to the living Semnopitheci of Southern Asia, in
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which case it must have possessed a long tail. The Mesopithecus
of the Upper Miocene of Greece is also one of the lower Monkeys
as it is most closely allied to the existing Macaques. On the
other hand, the Dryopithecus of the French Upper Miocene
is referable to the group of the "Anthropoid Apes," and is most
nearly related to the Gibbons of the present day, in which the tail
is rudimentary and there are no cheek-pouches. Dryopithecus
was, also, of large size, equalling Man in stature, and apparently
living amongst the trees and feeding upon fruits.
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