sub-species _(B. bison athabascae)_, distinguished from the
southern and better known form by superior size, a wider forehead,
longer, more slender and incurved horns, and by a thicker and softer
coat, which is also darker in color. Now, it is an interesting fact that
a fossil bison skull from the lower Pliocene of India resembles the
present European species, and in later geological times very similar
bisons closely allied to each other, if not identical, inhabited all
northern regions, including America. These were large animals with wide
skulls, and there is little doubt that from this circumpolar form came
both of the bisons now inhabiting Europe and America. Out of some half
dozen fossil bison which have been described from America, none earlier
than the latest Tertiary, _Bison latifrons_ from the Pleistocene
seems likely to have been the immediate ancestor of recent American
species, and as the one skull of the woodland bison which has been
examined resembles both _latifrons_ and the European species more
than the plains species does, it seems probable that these two more
nearly represent the primitive bison, of which the former inhabitant of
the prairies is a more modified descendant.
The process of elimination has at last led to this outline definition of
a bison, but among the ungulates we have passed over, there are certain
others which concern us because they are American.
Sheep and goats agree together and differ from oxen in being usually of
smaller size; the tail is shorter, the horns of females are much smaller
than those of males, they lack the accessory column on the inner side of
the upper molars, and the cannon bone is longer and more slender; but
when it comes to a comparison of the one with the other, it is by no
means always easy to tell the difference. It is true that the early
Greeks seem to have had a rough and ready rule under which mistakes were
not easy, for Aristotle tells us "Alcmaeon is mistaken when he says that
goats breathe through their ears," but the severely practical methods of
our own day leave us little but some very minute points of
difference. One of the best of these lies in the shape of the
basi-occipital bone, but naturally this can be observed only in the
prepared skull. The terms often employed to denote difference in the
horns can have only a general application, for they break down in
certain species in which the two groups approach each other. The
following table expresses some fairly definite points of separation:
SHEEP (_Ovis_). GOAT (_Capra_).
1. Muzzle hairy except between 1. Muzzle entirely hairy.
and just above the
nostrils.
2. Interdigital glands on all 2. Interdigital glands, when
the feet. present, only on fore feet.
3. Suborbital gland and pit 3. Suborbital gland and pit
usually present. never present.
4. No beard nor caprine 4. Male with a beard and
smell in male. caprine smell.
5. Horns with coarse transverse 5. Horns with fine transverse
wrinkles; yellowish striations, or bold knobs
or brown; sub-triangular in front; blackish; in male
in male, spreading outward more compressed or angular,
and forward with a sweeping backward
circular sweep, points with a scythe-like curve or
turned outward and forward spirally, points turned upward
and backward.
These features are distinctive as between most sheep and most goats, but
the Barbary wild sheep (_Ovis tragelaphus_) has no suborbital gland
or pit, a goat-like peculiarity which it shares with the Himalayan
bharal (_Ovis nahura_), in which the horns resemble closely
those of a goat from the eastern Caucasus called tur (_Capra
cylindricornis_), which for its part has the horns somewhat
sheep-like and a very small beard. This same bharal has the goat-like
habit of raising itself upon its hind legs before butting.
Both groups are a comparatively late development of the bovine stock, as
they do not certainly appear before the upper Pliocene of Europe and
Asia, and even at a later date their remains are not plentiful. Goats
appear to have been rather the earlier, but are entirely absent from
America.
The number of distinct species of sheep in our fauna is a matter of too
much uncertainty to be treated with any sort of authority at this time.
Most of us grew up in the belief that there was but one, the well-known
mountain sheep (_Ovis canadensis_), but seven new species and
sub-species have been produced from the systematic mill within recent
years, six of them since 1897. It is no part of the purpose of the
present paper to dwell upon much vexed questions of specific
distinctness, and it will only be pointed out here that the ultimate
validity of most of these supposed forms will depend chiefly upon the
exactness of the conception of species which will replace among
zoologists the vague ideas of the present time. Whatever the conclusion
may be, it seems probable that some degree of distinction will be
accorded to, at least, one or two Alaskan forms.
As sheep probably came into America from Asia during the Pleistocene, at
a time when Bering's Strait was closed by land, it might be expected
that those now found here would show relationship to the Kamtschatkan
species (_Ovis nivicola_); and such is indeed the case, while
furthermore, in the small size of the suborbital gland and pit, and in
comparative smoothness of the horns, both species approach the bharal of
Thibet and India, which in these respects is goat-like.
When one considers the poverty of the new world in bovine ruminants, it
seems strange that three such anomalous forms should have fallen to its
share as the prong-horn, the white goat and the musk-ox, of none of
which have we the complete history; two of the number being entirely
isolated species, sometimes regarded as the types of separate families.
The prong-horn is a curious compound. It resembles sheep in the minute
structure of its hair, in its hairy muzzle, and in having interdigital
glands on all its feet. Like goats, it has no sub-orbital gland nor
distinct pit. Like the chamois, it has a gland below and behind the ear,
the secretion of which has a caprine odor. It has also glands on the
rump. It is like the giraffe in total absence of the accessory hoofs,
even to the metapodials which support them. It differs from all hollow
horned ungulates in having deciduous horns with a fork or anterior
branch. There is not the least similarity, however, between these horns
and the bony deciduous antlers of deer, for, like those of all bovines,
they are composed of agglutinated hairs, set on a bony core projecting
from the frontal region of the skull.
It is well known that these horn sheaths are at times shed and
reproduced, but the exact regularity with which the process takes place
is by no means certain, although such direct evidence as there is goes
to prove that it occurs annually in the autumn. Prong-bucks have shed
on eight occasions in the Zoological Gardens at Philadelphia, five times
by the same animal, which reached the gardens in October, 1899, and has
shed each year early in November, the last time on October 22, 1903,[1]
and the writer has seen one fine head killed about November 5 in a wild
state, on which the horn-sheaths were loose and ready to drop off.
[Footnote 1: It is interesting to note that the first pair shed measured
7-1/4 inches, on the anterior curve; the second pair 9-1/2, and the last
three 11 inches each. The largest horns ever measured by the writer were
those of a buck killed late in November, 1892, near Marathon, Texas, and
were 15-3/4 inches in vertical height and 21 along the curve.]
But few of these delicate animals have lived long enough in captivity to
permit study of the same individual through a course of years, and the
scarcity of observations made upon them in a wild state is
remarkable. That irregularity in the process would not be without
analogy, is shown by the case of the Indian sambur deer, of which there
is evidence from such authority as that king of sportsmen, Sir Samuel
Baker, and others, that the shedding does not always occur at the same
season, nor is it always annual in the same buck; and by Pore David's
deer, which has been known to shed twice in one year.
When resemblances such as those of the prong-horn are so promiscuously
distributed, the task of fixing their values in estimating affinities is
not a light one, and in fact the most rational conclusion which we may
draw from them is that they point back to a distant and generalized
ancestor, who possessed them all, but that in the distribution of his
physical estate, so to speak, these heirlooms have not come down alike
to all descendants. There is again a complicating possibility that some
may be no more than adaptive or analogous characters, similarly produced
under like conditions of life, but quite independent of a common origin,
and it is seldom that we know enough of the history of development of
any species to conclude with certainty whether or not this has been the
case. At all events, the prong-buck is quite alone in the world at
present, and we know no fossils which unmistakably point to it, although
it has been supposed that some of the later Miocene species of
_Cosoryx_--small deer-like animals with non-deciduous horns,
probably covered with hair, and molars of somewhat bovine type--may have
been ancestral to it, but this is little more than a speculation. What
is certain is that _Antilocapra_ is now a completely isolated form,
fully entitled to rank as a family all by itself.
In the musk-ox (_Ovibos moschatus_), or "sheep-ox," as the generic
name given by Blainville has it, we meet with another strange and lonely
form which has contributed its full share to the problems of systematic
zoology. Its remote and inaccessible range has greatly retarded
knowledge of its structure, and it is only within the last three years
that acquaintance has been made with its soft anatomy, and at the same
time with a maze of resemblances and differences toward other ruminants,
that perhaps more than equals the irregularities of the prong-buck. But
unlike that species, there is in the musk-ox no extreme modification,
such as a deciduous horn, to separate it distinctly from the rest of the
family. A recapitulation of these differences would be too minutely
technical for insertion here, and it must be enough to say that while it
cannot be assigned to either group, yet in the distribution of hair on
the muzzle, in the presence of a small suborbital gland, in shortness of
tail and the light color of its horns, it is sheep-like; in the absence
of interdigital glands, the shortness and stoutness of its cannon bones,
and in the presence of a small accessory inner column on the upper
molars, it is bovine. But in the coarse longitudinal striation of the
bases of its horns it differs from both. The shape of the horns is also
peculiar. Curving outward, downward and then sharply upward, with
broad, flattened bases meeting in the middle line, their outlines are
not unlike those of old bulls of the African buffalo.
At the present time the musk-ox inhabits only arctic America, from
Greenland westward nearly to the Mackenzie River, but its range was
formerly circumpolar, and in Pleistocene times it inhabited Europe as
far south as Germany and France. The musk-ox of Greenland has lately
been set aside as a distinct species. The most we can say is that
_Ovibos_ is a unique form, standing perhaps somewhere between oxen
and sheep, and descended from an ancient ruminant type through an
ancestry of which we know nothing, for the only fossil remains which are
at all distinguishable from the existing genus, are yet closely similar
to it, and are no older than the Pleistocene of the central United
States; in earlier periods its history is a blank about which it is
useless to speculate.
The last of our three anomalies, the white, or mountain goat
(_Oreamnos montanus_), is not as completely orphaned as the other
two, for it seems quite surely to be connected with a small and peculiar
series consisting of the European chamois and several species of
_Nemorhaedus_ inhabiting eastern Asia and Sumatra. These are often
called mountain antelopes, or goat antelopes. So little is yet known of
the soft anatomy of the white goat that we are much in the dark as to
its minute resemblances, but its glandular system is certainly
suggestive of the chamois, and many of its attitudes are strikingly
similar. In all the points in which it approaches goats it is like some,
at least, among antelopes, while in the elongated spines of the anterior
dorsal vertebrae, which support the hump, and in extreme shortness of
the cannon bone, it is far from goat-like. The goat idea, indeed, has
little more foundation than the suggestive resemblance of the profile
with its caprine beard. It is truly no goat at all, and should more
properly be regarded as an aberrant antelope, if anything could be
justly termed "aberrant" in an aggregation of animals, hardly any two of
which agree in all respects of structure. No American fossils seem to
point to _Oreamnos_, and as _Nemorhaedus_ extends to Japan and
eastern Siberia, it is probable that it was an Asiatic immigrant, not
earlier than the Pleistocene.
From this intricate genealogical tangle one turns with relief to the
deer family, where the course of development lies reasonably plain. If
the rank of animals in the aristocracy of nature were to be fixed by the
remoteness of the period to which we know their ancestors, the deer
would out-rank their bovine cousins by a full half of the Miocene
period, and the study of fossils onward from this early beginning
presents few clearer lines of evidence supporting modern theories
respecting the development of species, than is shown in the increasing
size and complexity of the antlers in succeeding geological ages, from
the simple fork of the middle Miocene to those with three prongs of the
late Miocene, the four-pronged of the Pliocene, and finally to the
many-branched shapes of the Pleistocene and the present age. Now it is
further true that each one of these types is represented today in the
mature antlers of existing deer, from the small South American species
with a simple spike, up to the wapiti and red deer carrying six or eight
points, and still more significant is it that the whole story is
recapitulated in the growth of each individual of the higher races. The
earliest cervine animals known seem to have had no antlers at all, a
stage to which the fawn of the year corresponds; the subsequent normal
addition in the life-history, of a tine for each year of growth until
the mature antler is reached, answering with exactness to the stages of
advance shown in the development-history of the race. A year of
individual life is the symbol of a geological period of
progression. This is a marvelous record, of which we may
say--paraphrasing with Huxley the well-known saying of Voltaire--"if it
had not already existed, evolution must have been invented to explain."
The least technical, and for the present purpose the most useful of the
characters distinguishing existing deer from all of the bovine stock,
lies in the antlers, which are solid, of bony substance, and are
annually shed. They are present in the males of all species except the
Chinese water deer, and the very divergent musk-deer, which probably
should not be regarded as a deer at all. They are normally absent from
all females except those of the genus _Rangifer_. Most deer have
canine teeth in the upper jaw, though they are absent in the moose, in
the distinctively American type and a few others. The cleaned skull
always shows a large vacuity in the outer wall in front of the orbit,
which prevents the lachrymal bone from reaching the nasals. No deer has
a gall bladder. There are many other distinctions, but as all have
exceptions they are of value only in combinations.
The earliest known deer, belonging to the genus _Dremotherium_, or
_Amphitragulus_, from the middle Tertiary of France, were of small
size and had four toes, canine teeth and no antlers. Their successors
seem to have borne simple forked antlers or horns, probably covered with
hair, and permanently fixed on the skull. Very similar animals existed
in contemporaneous and later deposits in North America. From this point
the course of progress is tolerably clear as to deer in general,
although we are not sure of all the intermediate details--for it must
not be forgotten that a series of types exhibiting progressive
modifications in each succeeding geological period is quite as
conclusive in pointing out the genealogy of an existing group as if we
knew each individual term in the ancestral series of each of its
members. Thus we do not yet know whether the peculiar antler of the
distinctively American deer, of the genus _Mazama_, is derived from
an American source or took its origin in the old world, for the fossil
antlers known as _Anoglochis_, from the Pliocene of Europe, are
quite suggestive of the _Mazama_ style, but as nothing is known of
the other skeletal details of _Anoglochis_, any such connection
must at present be purely speculative, but the element of doubt in this
special case in no way disturbs the certainty of the general conclusion
that all our present _Cérvidae_ have come through distinct stages
in the successive periods, from the simple types of the middle Tertiary.
The family is undoubtedly of old world origin, and for the most part
belongs to the northern hemisphere, South America being the only
continental area in which they are found south of the equator.
The analytical habit of mind which finds vent in the subdivision of
species, is also exhibited in a tendency to break up large genera into a
number of small ones, but in the present group this practice has the
disadvantage of obscuring a broad distinction between the dominant types
inhabiting respectively the old world and the new. The former,
represented by the genus _Cervus_, has a brow-tine to the antlers;
has the posterior portion of the nasal chamber undivided by the vertical
plate of the vomer; and the upper ends only of the lateral metacarpals
remain, whereas in all these particulars the typical American deer are
exactly opposite. As there are objections to considering these
characters as of family value, arising from the intermediate position of
the circumpolar genera _Alces_ and _Rangifer_, as well as the
water deer and the roe, a broader meaning is given to classification by
retaining the comprehensive genera _Cervus_ and _Mazama_, and
recognizing the subordinate divisions only as sub-genera.
The one representative of _Cervus_ inhabiting America is the
wapiti, or "elk" (_C. canadensis_), which is without doubt an
immigrant from Asia by way of Alaska, and it may be of interest to state
the grounds upon which this conclusion rests, as they afford an
excellent example of the way in which such results are reached. It is an
accepted truth in geographical distribution, that the portion of the
earth in which the greatest number of forms differentiated from one type
are to be found, is almost always the region in which that type had its
origin. Now, out of about a dozen species and sub-species of wapiti and
red deer to which names have been given, not less than eight are
Asiatic, so that Asia, and probably its central portion, is indicated as
the region in which the elaphine deer arose; in confirmation of which is
the further fact that the antler characteristic of these deer seems to
have originated from the same ancestral form as that which produced the
sikine and rusine types, which are also Asiatic. From this centre the
elaphines spread westward and eastward, resulting in Europe in the red
deer, which penetrated southward into north Africa at a time when there
was a land connection across the Mediterranean. In the opposite
direction, the nearer we get to Bering's Straits the closer is the
resemblance to the American wapiti, until the splendid species from the
Altai Mountains (_C. canadensis asiaticus_), and Luehdorf's deer
(_C. c. luehdorfi_) from Manchuria, are regarded only as sub-species
of the eastern American form, which they approach through _C. c.
occidentalis_ of Oregon and the northwestern Pacific Coast.
This evidence is conclusive in itself, and is further confirmed by the
geological record, from which we know that the land connection between
Alaska and Kamtschatka was of Pliocene age, while we have no knowledge
of the wapiti in America until the succeeding period.
While there is not the least doubt that the smaller American deer had an
origin identical with those of the old world, the exact point of their
separation is not so clear. Two possibilities are open to choice:
_Mazama_ may be supposed to have descended from the group to which
_Blastomeryx_ belonged, this being a late Miocene genus from
Nebraska, with cervine molars, but otherwise much like _Cosoryx,_
which we have seen to be a possible ancestor of the prong-horn; or we
may prefer to believe that the differentiation took place earlier in
Europe or Asia, from ancestors common to both. But there is a serious
dilemma. If we choose the former view, we must conclude that the
deciduous antler was independently developed in each of the two
continents, and while it is quite probable that approximately similar
structures have at times arisen independently, it is not easy to believe
that an arrangement so minutely identical in form and function can have
been twice evolved. On the second supposition, we have to face the fact
that there is very little evidence from palaeontology of the former
presence of the American type in Eurasia. But, on the whole, the latter
hypothesis presents fewer difficulties and is probably the correct one;
in which case two migrations must have taken place, an earlier one of
the generalized type to which _Blastomeryx_ and _Cosoryx_ belonged,
and a later one of the direct ancestor of _Mazama_. There is
little difficulty in the assumption of these repeated migrations,
for evidence exists that during a great part of the last half
of the Tertiary this continent was connected by land to the
northwest with Asia, and to the northeast, through Greenland and
Iceland, with western Europe.
The distinction between the two groups is well marked. All the
_Mazama_ type are without a true brow-tine to the antlers; the
lower ends of the lateral metacarpals only remain; the vertical plate of
the vomer extends downward and completely separates the hind part of the
nasal chamber into two compartments; and with hardly an exception they
have a large gland on the inside of the tarsus, or heel. The complete
development of these characters is exhibited in northern species, and it
has been beautifully shown that as we go southward there is a strong
tendency to diminished size; toward smaller antlers and reduction in the
number of tines; to smaller size, and finally complete loss of the
metatarsal gland on the outside of the hind leg; and to the assumption
of a uniform color throughout the year, instead of a seasonal change.
The two styles of antler which we recognize in the North American deer
are too well known to require description. That characterizing the mule
deer (_Mazama hemionus_) and the Columbia black-tailed deer
(_M. columbiana_), seems never to have occurred in the east, nor
south much beyond the Mexican border, and these deer have varied little
except in size, although three subspecies have lately been set off from
the mule deer in the extreme southwest.