AN ILLUSTRATED FIELD KEY FOR THE
IDENTIFICATION
OF MAMMAL BONES
By GEORGE W. BRAINERD
The key given here is designed for the
identification of mammal
bones in the field by persons who have
not had specialized train-
ing in the subject. Identifications made
under such conditions are,
of course, not always accurate, and of
necessity often cannot be
specific. When accurate identifications
to species or subspecies
are required, the material should be
checked by a specialist who
has a large series of skeletons at his
disposal. It is hoped that if
field workers in archaeology and the
natural sciences have at their
disposal a means for the ready
identification of animal bones, they
will be prompted to collect such
material carefully. Documented
collections of skeletal material can add
considerably to our knowl-
edge of the diet habits of man and of
the carnivores, and to the
understanding of animal distribution and
ecology.
A word may here be added, specifically
to archaeological field
workers, who in the process of their
work usually unearth consider-
able quantities of mammal remains. The
excavator is faced with
two questions: What kinds of bone
fragments can be identified
and what bone fragments should he save?
Almost all bone frag-
ments can be identified if the worker is
sufficiently skilled and has
enough comparative material. The ideal
arrangement is to save
all bone fragments. If such a procedure
is impossible, a random
sample of from 100 to 200 lbs. of
fragments will give a good list
of the species present. In Ohio
archaeological sites the major bulk
of a random collection is composed of
deer bones. If there is in
the field a man able to sort out the
more easily identifiable deer-
bone fragments, he may be able to
discard or, better still, cache
a measured quantity of them, thus
decreasing the bulk of the sample
to be used in museum classification. It
must be emphasized, how-
ever, that every fragment, even after
identification as to species, is of
potential interest to the zoologist for
study of intra-species varia-
(324)
BRAINERD: IDENTIFICATION OF MAMMAL
BONES 325
tion and pathology, and that all
fragments should be saved if
possible.
The illustrations of mammal bones which
form the basis of
this key are limited to the skulls and
limb bones of animals native
to Ohio. The specimens have been
selected, however, with a view
to representing families of animals,
members of which are common-
ly found over a much larger area. A
classification list giving the
common names of the animals making up
these families is in-
cluded.
The identifications made with this key will be more
definitive if it is used with reference
to a list of animals known to
occur in the area from which the
specimens come.
The first plate shows the skull and long
bones of a raccoon,
which is a rather unspecialized animal.
This drawing is included
in order that the beginner may locate
his specimen in relation to
the whole skeleton. By this method it
should be possible for him
to identify a bone, as for example, a
humerus; after which it can
be compared with the series of humeri
shown in the following
plates, and thus be determined as to
family.
The novice in most cases can identify
limb bones to family by
comparison with the illustration. If a
skull matches an illustra-
tion completely in detail and in size as
given by scale, it may
tentatively be assigned to the species
shown. In the general use
of the key it may be of help to the
beginner to remember that the
conformation of the bone, the nature of
muscle attachment ridges,
etc., is of greater significance than
the proportions or size of the
bone when identifying to family. The
size and proportions of the
bone are useful in determining
differences within the family.
The identification may often be carried
beyond family by
checking the members of that family
known to occur in the area
from which the specimen comes. This
check should include a
comparison of the average total lengths
of the representatives of
the family that are native to the area
with the length of the repre-
sentative of that family shown in the
plates. Such comparison
will show whether the bone at hand is of
a size characteristic of
the suspected species. The above method,
using limitations of
area and size of animal, will often
allow a tentative species iden-
tification, although such an
identification, influenced as it is by
326
OHIO ARCHAEOLOGICAL AND HISTORICAL QUARTERLY
intra-species size differences in
animals, the judgment of the in-
vestigator, and the faults of the key,
should be sent to a specialist
for checking before it can be considered
authoritative.
In general it is better for the beginner
to use only mature
bones for his identifications. The bones
of immature animals can
be easily distinguished from those of
adults. The ends (epiphyses)
of the long bones of young animals are
not firmly fused to the
shafts. Until these epiphyses are firmly
fused, the length measure-
ments are unreliable. In such bones the
distinctive "landmarks"
are much less pronounced than in the
bones of older animals. The
surfaces of immature bones weather
rapidly and will show a rough
surface if they have been much exposed.
In immature skulls, the
seams (sutures) of the brain case show
very clearly; angular pro-
jections of adjacent bones interlock
with each other. Older skulls
have the sutures nearly obliterated.
Immature skulls often show
a milk dentition which is confusing to
an investigator unfamiliar
with such material.
This key is designed for the
identification of mammalian
material only. Bones of other
vertebrates can usually be distin-
guished from the bones of mammals by
their surface appearance
as well as by the fact that they show
marked differences in form
from any of the bones illustrated.
Fish bones are distinguished by their
thin, folded structure,
often exhibiting radiating ridges or
reticulations on the surfaces,
and seldom having the smooth rounded
appearance characteristic
of the bones in higher vertebrates.
Amphibian limb bones are hollow, very
light in weight, and
smooth surfaced. These bones quickly
lose their epiphyses upon
exposure, the weathered ends of the
shafts showing a characteristic
thinning of the bone wall.
Turtle remains consist largely of the
shells (carapaces and
plastrons) which are unmistakable. The
bones are ridged some-
what as are fish bones, but are heavily
built, with rounded rough
epiphyses. The long bones are
considerably bowed.
Bird bones are extremely light, and have
a hard, highly polished
surface. Many of the bones are
thin-walled; the interior of the
bone is either hollow or is filled with
a delicately reticulated mesh
of bony material.
BRAINERD: IDENTIFICATION OF MAMMAL BONES 327
Mammal bones are more solidly built than
the bones of the
other classes, and the surface has a
medium high polish unless it
has been destroyed by weathering.
A classification of the animals
illustrated in the key is given
here:
ORDER MARSUPIALIA
DIDELPHIIDAE1
Didelphys virginiana, Virginia opossum
Length 600-825mm.2
ORDER CARNIVORA
MUSTELIDAE (otters, weasels, badgers, skunks)
LUTRINAE
Lutra canadensis canadensis, otter
Length (male) ca. 1025mm.
MUSTELINAE
Mustela vison mink, big brown mink
Length (male) 610-640mm.
Martes pennanti, fisher
Length (male) ca. 900mm.
MELINAE
Mephitis nigra, common skunk
Length 575-600mm.
PROCYONIDAE
Procyon lotor lotor, raccoon
Length ca. 750mm.
URSIDAE
Euarctos americanus americanus, black bear, cinnamon
bear
CANIDAE
Urocyon cinereoargenteus
cinereoargenteus, gray fox
Length 1000-1050mm.
Canis familiaris, common dog
FELIDAE
Lynx rufus rufus, bobcat
Length 850-1000mm.
1 Endings on words used in
classification have the following meanings: -ata, suborder;
-idae, family; -inae, subfamily.
2 Lengths of animals given here have
been taken from M. W. Lyon, Jr., "Mammals of
Indiana," American Midland
Naturalist (Notre Dame, Ind.), XVII (1926), no. 1.
328
OHIO ARCHAEOLOGICAL AND HISTORICAL QUARTERLY
ORDER RODENTIA
MURIDAE
MICROTINAE (voles)
Ondatra zibethica zibethica, muskrat
Length ca. 560mm.
CASTORIDAE
Castor canadensis canadensis, beaver
SCIURIDAE (groundhogs, gophers,
squirrels, chipmunks)
Marmota monax monax, groundhog
Length 550-625mm.
ORDER LAGOMORPHA (hares and rabbits)
LEPORIDAE
Sylvilagus floridanus mearnsi, cotton-tail rabbit
Length ca. 425mm.
ORDER ARTIODACTYLA
CERVIDAE (deer)
Odocoileus americanus, Virginia deer, white-tailed deer.
Length ca. 1825mm.
BOVIDAE (cattle)
Bison bison, American buffalo, bison
Length male ca. 3350mm., female ca.
2135mm.
The drawings included in the plates were
made from projected
photographic negatives of specimens,
with constant comparison with
the original bones. An effort was made
to use specimens of average
size and conformation. The author is
indebted for most of the
specimens shown to the collections of
the National Museum and the
Museum of the Ohio State Archaeological
and Historical Society.