A STRANGE EXTINCT BEAST
The terraces of gravel deposited by existing rivers and the deposits
in caverns in the limestone regions of Western Europe--the so-called
"Pleistocene" strata--contain, besides the flint weapons of man and
rare specimens of his bones, the remains of animals which are either
identical with those living at the present day (though many of them
are not living now in Europe) or of animals very closely similar to
living species. Thus we find the bones of horses like the wild horse
of Mongolia, of the great bull (the Urus of Caesar), of the bison, of
deer and goats, of the Siberian big-nosed antelope, of the musk-ox
(now living within the Arctic circle), of the wild boar, of the
hippopotamus (like that of the Nile), and of lions, hyenas, bears, and
wolves. The most noteworthy of the animals like to, but not identical
with, any living species are the mammoth, which is very close to the
Indian elephant, but has a hairy coat; the hairy rhinoceros, like, but
not quite the same as, the African square-mouthed rhinoceros; and the
great Irish deer, which is like a giant fallow-deer. These three
animals are really extinct kinds or species, but are not very far from
living kinds. In fact, the most recent geological deposits do not
contain any animals so peculiar, when compared with living animals, as
to necessitate a wide separation of the fossil animal from living
"congeners" by the naturalist who classifies animals and tries to
exhibit their degrees of likeness and relationship to one another by
the names he adopts for them. The mammoth is a distinct "species" of
elephant. It requires, it is true, a "specific" or "second" name of
its own; but it belongs to the genus elephant. Hence we call it
_Elephas primigenius_, whilst the living Indian elephant is _Elephas
Indicus_. The reader is referred to the preceding chapter for further
notes about elephants.
The strata next below the Pleistocene gravels and cave deposits are
ascribed to the "Pliocene age"--older than these are the "Miocene" and
the "Eocene," and then you come to the Chalk, a good white landmark
separating newer from older strata.
We know now in great detail the skeletons and jaws of some hundreds of
kinds of extinct animals of very different groups found in the Eocene,
the Miocene, the Pliocene, and the Pleistocene layers of clays, sands,
and gravels of this part of the world. Nothing very strange or unlike
what is now living is found in the Pleistocene--the latest
deposits--but when we go further back strange creatures are
discovered, becoming stranger and less like living things as we pass
through Pliocene to Miocene, and on--downwards in layers, backwards in
time--to the Eocene.
Though the past history of the Mediterranean sea shows that it was
formerly not so extensive as it is now, and that there were junctions
between Europe and Africa across its waters, yet the deeper parts of
that sea are very ancient, and some of the islands have long been
isolated. In Malta the remains of extraordinary species of minute
elephants have been found, one no larger than a small donkey, and in
the island of Cyprus an English lady, Miss Dorothea Bate, has
discovered the bones of a pigmy hippopotamus (like that still living
in Liberia) no larger than a sheep. Miss Bate some three years ago
heard of the existence of a bone-containing deposit of Pleistocene age
in limestone caverns and fissures in the island of Majorca, and with
the true enthusiasm of an explorer determined to carry on some
"digging" there and see what might turn up. In the following spring
she was there, and obtained a number of bones, jaws, and portions of
skulls, which appeared at first sight to be those of a small goat. Its
size may be gathered from the fact that its skull is six inches long.
These and the bones of a few small finches were all that rewarded her
pains. The bones of fossil goats (of living species) are found in
caves at Gibraltar and in Spain; so at first the result seemed
disappointing. But on carefully clearing out the specimens and
examining them in London, Miss Bate found that the supposed goat bones
obtained by her in Majorca were really those of a new and most
extraordinary animal, to which (in a paper published in the
"Geological Magazine" in September, 1910) she has given the name
"_Myotragus balearicus_."
[Illustration: Fig. 16.--Side-view of the skull and lower jaw of a
goat. _inc. i._ The three lower incisor teeth of the left side. _can.
i._ The little canine teeth grouped with them. _p._ The toothless
front part of the upper jaw. _m. s._ Upper molars or "grinders." _m.
i._ Lower molars or grinders. Compare this and the following figures
with Fig. 10, showing the more complete "dentition" of the pig.]
[Illustration: Fig. 17.--Horizontal view of the teeth in the lower and
upper jaw of the goat. In front of the lower jaw the group of three
incisors (_inc. i._) and one canine is seen, whilst the toothless bony
plate (_p._) of the upper jaw, against which they work, is seen in the
right-hand half of the figure. The molars, "grinders," or cheek-teeth
are numbered 1 to 6 in each jaw.]
[Illustration: Fig. 18.--Side view of the skull of a typical "rodent"
mammal, the Coypu rat (_Myocastor coypus_) from South America. _inc.
s._ Upper incisor. _inc. i._ Lower incisor. _m. s._, _m. i._ Upper and
lower molars, grinders or cheek-teeth.]
I must ask the reader now to look at the figures here given (Figs. 16
and 17) of the skull and the lower jaw of a goat. The lower jaw might
(except for size) pass for that of a sheep, ox, antelope or deer. They
are all alike. There are on each side six grinding cheek-teeth
(molars), and then as we pass to the front we find a long toothless
gap until we come to the middle line where the two halves of the jaw
unite. There we see a little semicircular group of eight chisel-like
teeth, which work against the toothless pad of the upper jaw opposed
to them, and are the instruments by which these animals, with an
upward jerk of the head, "crop" the grass and other herbage on which
they feed, to be afterwards triturated by the grinding cheek teeth. A
vast series of living and of fossil animals, called the
Ruminants--including the giraffes, the antler-bearing forms called
deer, the cavicorn or sheath-horned bovines, ovines and caprines, and
the large series of antelopes of Africa and India--all have precisely
this form of jaw, this number and shape and grouping of the teeth. Now
let me call to mind the lower jaw of a hare or rabbit or rat (Figs. 18
and 19). There we find on each side the group of grinding cheek-teeth,
with transverse ridges on their crowns, and a long, toothless gap
before we arrive at the front teeth. But the front teeth are only two
in number, one on each side, close to each other, very large, and each
with a tremendously long, deeply set root. They meet a similar pair of
teeth in the upper jaw, and give the hare, rabbit, rats, mice,
beavers, and porcupines the power of "gnawing" tough substances.
These animals are hence called Rodents, or gnawers, and the two great
front teeth are called "rodent-teeth." No two arrangements of teeth
could be much more unlike than are the group of eight little
chisel-like teeth of the lower jaw of the Ruminants and the two
enormous gnawing teeth of the Rodents. Apparently the two rodent
incisors, or front teeth, of the lower jaw of the rat correspond to
the two middle incisors of the Ruminant's lower jaw; the other front
teeth of the Ruminant have atrophied, disappeared altogether. The
rodent condition has been developed from that of an ancestor which
had several front teeth and not two large ones only; but we have not
at present found the intermediate steps.
[Illustration: Fig. 19.--View in the horizontal plane of the teeth of
the left half of the lower and the left half of the upper jaw of the
Coypu rat to show the single great gnawing incisor on each side, the
four flat grinding molars and the wide gap between molars and
incisors. Compare with Figs. 17 and 22.]
The reader should compare the teeth of the goat and the large rat here
pictured with the more typical and complete series of the pig, given
in Fig. 10, p. 84. The pig's teeth are the same in number as those of
the ancestral primitive typidentate mammal, and their form is near to
that of the ancestor's teeth.
Now I come to the extraordinary interest of Miss Bate's goat-like or
antelope-like animal from Majorca. Although it is shown by its skull
(Fig. 20) and other bones to be distinctly one of the sheath-horned
Ruminants, very like a small goat or antelope, the lower jaw, of which
there are several specimens, does not present in front the little
group of eight small chisel-like "cropping" teeth, but, instead, two
enormous rodent teeth placed side by side, very deeply fixed in the
jaw, and quite like those of some rat-like animals in shape. Hence the
name given to this little marvel by Miss Bate--"Myotragus," "the
rat-goat." This strange little animal also differs from goats and
antelopes in having proportionately much thicker and shorter "feet"
(cannon-bones) than they have.
If the remains of this strange little creature had turned up in more
ancient strata--in Pliocene or Miocene--it would have not been quite
so astonishing. But it would be still very remarkable, since it has
all the characters of a goat-like creature in the shape of its skull,
its bony horn-cores, its limb-bones, and its cheek-teeth; and yet, as
it were monstrously and in a most disconcerting way, protrudes from
its lower jaw two great rats' teeth. Nothing like it or approaching it
or suggesting it, is known among recent or fossil Ruminants. They all
without exception have a lower jaw with the teeth of the exact number
and grouping which you may see in a sheep's lower jaw. We know
hundreds of them, both living and fossil, many from the Pleistocene,
others from Pliocene deposits, and even from the still older Miocene,
but all keep to the one pattern of lower jaw and lower jaw teeth. It
is only in this little island of Majorca, surrounded by very deep
water and not known to have nurtured any other animal so large in size
either in recent or geologic times, that we come upon a Ruminant with
horns like a goat's, but with great rat-like front teeth in place of
the semicircle of eight little cropping toothlets. The wonderful thing
is that the bones found by Miss Bate are light and well preserved,
evidently not very ancient--probably late Pleistocene in age.
[Illustration: Fig. 20.--Drawing of the skull of the rat-toothed goat,
Myotragus--the new extinct beast discovered in limestone fissures in
the island of Majorca by Miss Bate. 1. Side view of the skull and
lower jaw. 2. Appearance of the two rat-like teeth as seen when the
end of the lower jaw is viewed from above.]
The questions that arise are: Where did the rat-goat come from? How
did this utterly peculiar change in a Ruminant's teeth come about?
With regard to the second question, it is a matter of importance that
although we have hitherto not discovered any Ruminants with this
modification of the teeth, still less any cavicorn or sheath-horned
Ruminant so altered, yet it is by no means rare amongst herbivorous
mammals to find such rat-like teeth making their appearance, whilst
the smaller side-teeth of the incisor group or front teeth disappear.
The Australian kangaroos and wombats are a case in point--so is the
lemur-like aye-aye of Madagascar (an insect eater). So is the Hyrax or
"damian" of the Cape, and also the very ancient Plagiaulax from the
prae-chalk Purbeck clay. But perhaps the best case for comparison with
the ruminants is that of the rhinoceroses. There are a great many
species and even genera of fossil and recent rhinoceroses. An old
Miocene kind (called Hyracodon) has eight little teeth in the front of
the lower jaw. In a Pliocene kind of rhinoceros (called _R.
incisivus_) these are reduced to two, the middle two, which are of
great size and project far forward--like those of the rat-goat of
Majorca. Among living rhinoceroses the Indian species have these two
front teeth, but smaller, whilst the square-mouthed African rhinoceros
has none at all! This helps us, as a parallel, to understand "the
strange case" of Myotragus. But, of course, the rhinoceroses are a
distinct line of animal descent--remote from Ruminants. They are (like
horses and tapirs) odd-toed hoofed beasts--not even-toed ones, as are
pigs, camels, and ruminants.
* * * * *
On first considering the question of the origin of the rat-goat of
Majorca, some naturalists will, no doubt, be tempted to suggest that
it is a case of a sudden "sport," a "mutation" as they now call it,
and not a result of gradual slowly developed reduction of the now lost
teeth and correspondingly gradual enlargement of the two middle ones,
taking many thousand generations to bring about. The fact that the
rat-goat is found on an island cut off from competition with other
animals will favour this view. On the other hand, there is the
important and really remarkable fact that familiar as man has been for
ages with Ruminants of many kinds--such as sheep, goats, cattle,
deer--there is absolutely no case on record of an "oddity" or
"monstrosity" resembling the rat-goat's condition occurring in the
teeth of any of the hundreds of thousands of these animals killed and
eaten by man, and therefore closely examined. Professor Bateson, who
a few years ago ransacked the museums of Europe for instances of
"discontinuous variation," or "sports," and wrote a valuable book on
the subject, did not discover any example of the kind. Apart from the
view, which is very generally held, that such sudden "mutations" as
"rat-teeth in a ruminant" are--even should they occur--not
perpetuated, we are not really in any way driven to suppose that the
rat-goat of Majorca originated in that island. It is true that we know
nothing like it in the Pliocene and Miocene of the Mediterranean
region which could have been its immediate ancestor. But probably the
ancestors of the rat-goat were slowly developed from a Miocene
sheath-horned ruminant, a primitive sort of antelope in some part of
North-west Africa, or in an extension of it now submerged in the
Atlantic, and stragglers of this curious and now lost Ruminant stock
were left in Majorca when in Miocene or early Pliocene times that
island became detached from its Hispano-African connection.