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  Analyzing Animal Bones

Zooarchaeological analysis, at its simplest, consists of a tabulation of the taxons present in an assemblage. The presence/absence of mammal, fish, bird, reptile, or amphibian remains in a faunal assemblage is determined by the study of the morphology of each bone. Before species identification can be undertaken, the skeletal element that a bone represents must be determined. Element identification also allows estimation of age at death and, in some cases, determination of sex to proceed.

Taxonomic Identification

Zoological classification follows the basic hierarchy: Kingdom, Phylum, Class, Order, Family, Genus, and Species. Zooarchaeology deals exclusively with the Kingdom of Animalia. Some zooarchaeology, including the study of crustaceans, deals with Phylum other than Chordata but for the purposes of this project, only the Chordata Phylum, animals with a spinal cord or vertebral column, will be analyzed.

Class identification includes the sorting of a faunal assemblage into mammal, fish, bird, reptile and amphibian remains and usually is undertaken as the initial sort of an assemblage. The simplest method for determining the Order of faunal remains is through analysis of teeth, which preserve well in archaeological contexts. Common Orders encountered in zooarchaeology include carnivores and primates. If teeth are unavailable for this determination the functional morphology of each skeletal element is used for the identification of Order, Family, Genus, and Species.

Element Identification

Within each taxonomic class, such as mammal, fish, or bird, the basic shape and number of the elements of the skeleton are fairly constant. Determining the Class of a bone therefore narrows the range of possibilities of the element that it represents. Complete elements are, of course, the easiest to identify but in many cases even small fragments of a bone contain enough diagnostic morphology to allow for identification. It is therefore important to document the completeness of an element to assess the certainty of identification and to establish the number of each element that is actually represented in an assemblage. For example, four femur fragments do not necessarily equate to four femurs.

Age & Sex Determination

Many mammalian bones are made up of a central shaft, or diaphysis, which is capped on each end by an epiphysis. The region between the diaphysis and the epiphysis, the metaphysis, represents the region where bone growth occurs. In juvenile mammals, the epiphysis is not fused to the shaft to allow for this growth. The timing of the fusion of the epiphysis and shaft occurs at different ages for each element. For example, the last element to completely fuse in a human is the collar bone or clavicle which usually occurs around the age of 40 years, well after the complete fusion of the humerus which occurs at approximately 21 years of age. The patterns of wear of teeth can also be used to estimate an animal's age. Malnutrition can cause both of these methods to produce a high degree of error.

The ability to determine an animal's sex from skeletal elements varies greatly with species and element. Some animal species demonstrate sexual dimorphism, or size variation between the sexes, which assists in this analysis. Antlers, dental variations, and pelvic apertures are other useful means for identifying the sex of a skeleton or isolated skeletal element.

   Common Zooarchaeology Taxa
Bear (grizzly) ……Ursus horribilis
Beaver………......Castor canandensis
Bear (American, black).Ursus americanus
Chipmunk (eastern).Tamias stiatus
Coyote…………..Canis latrans
Deer (mule) ……..Odocoileus hemionus
Deer (white-tailed).Odocoileus virginianus
Fox (gray) …Urocyon cinereoargenteus
Fox (red) ………..Vulpes vulpes
Hare (snowshoe)....Lepus americanus
Moose/Elk……….Alces alces
Opossum...............Didelphis marsupialis
Prairie Dog……....Cynomys leucurus
Rabbit (cottontail)..Sylvilagus floridanus
Raccoon…………Procyon lotor
Skunk …………...Mephitis mephitis
Squirrel (gray) …...Sciurus carolinensus
Squirrel (red) ….Tamiasciurus hudsonicus
Wolf ………….....Canis lupus
Woodchuck……...Marmota monax

Cat (domestic) …...Felis catus
Cattle (domestic) …Bos taurus
Chicken (domestic)..Gallus gallus
Dog (domestic) …...Canis familiaris
Duck (mallard) ……Anas platyrhynchos
Goat (domestic) …..Capra hircus
Goose (Canada) ..…Branta canadensis
Goose (domestic) …Anser anser
Horse (domestic) ….Equus caballus
Pig (domestic) …….Sus scrofa
Pigeon (domestic).....Columba livia
Sheep (domestic) …Ovis aires
Turkey ………... ....Meleagris gallopavo
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   Common Calculations

Number of Identifiable Specimens. Also termed Total Number of Fragments (TNF). TNF or NISP calculations have been used to estimate relative abundance of species. Recent research has shown that NISP calculations are taphonomically erroneous and generally misleading. However, given NISP's past popularity, this calculation is necessary for comparison with previously analyzed assemblages.

Minimum Number of Individuals. The most common method of illustrating the constituents of an assemblage is through a calculation of the minimum number of individuals that would have to have existed to create a given sample. There are numerous means of calculating this number and the method selected is usually based on the type of assemblage. MNI is generally determined by counting and siding the most frequent element in an assemblage. For example, an assemblage with 13 tibias suggests that minimally 7 individuals are represented by the assemblage. Using element siding, 13 left tibias would suggest that minimally 13 individuals are represented.

Other Calculations
MNE=Minimum Number of an Element
MAU=Minimum Number of Animal Units
MGUI=Modified General Utility Index
FUI=Food Utility Index
MUI=Meat Utility Index

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