Ohio History Journal

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)

• 1
 

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

• 2
 

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.

• 3
 

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.

• 4
 

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.

• 5