Osteometry

Osteometry is the measurement of bones and can be used for many purposes in anthropology. These include such assessments as obtaining the shape and size of bones, determining an index or to estimate the living stature of an individual. Some tools used in taking measurements include spreading calipers, sliding calipers, tape measures and osteometric boards.

Watch this short clip to see how the osteometric board and sliding calipers are used.

Measurements obtained from the cranium are taken from landmarks. While there are many special features on the skull, accurately locating points is important for the purpose of obtaining accurate cranial measurements. The measurements taken can then be used to determine an index. An index is a ratio of one measurement to another, which is used as a simple way to make a comparison. Taking measurements from long bones is also used to determine indices. Each index has a specific purpose, and there are many indices that can be used to establish the shape and proportions of specific parts of the skeleton.

Exercise 1

Bone Landmarks

Evaluate the pictures as shown below. Match the each location with the best description in the lab.

Exercise 2

Cranial Measurements

On your own skull, use a flexible measuring tape (or if you don't have one, you can use a string, mark off the distance, and then use a ruler to measure the string) to take the measurements of your skull as described in the lab. You may need to recruit a partner to help you. Note that we will actually be overestimating each measurement, in a lab setting, a spreading caliper would be used to measure the distance between the two points so you didn’t have to go up and over the cranium.

Enter the measurements into the formula in the lab to calculate your Cranial Index.

Exercise 3

Long Bone Measurements

Visit the Eforensics laboratory website and measure the long bones there in 3D. Follow the directions below and enter your numbers in the lab assignment on Canvas.

Part A

Visit the Eforensics laboratory and begin with the femur. Click the “measure” button just above the femur image and then use your mouse and click to measure the length of the bone. Record the length in the lab. When you have finished the femur, use the tabs on the left to do the humerus and tibia.

Remember to use centimeters and NOT inches when measuring the bones.

*Note: The tibia is a bone that has a long history of measurement complications. In this case, go ahead and do a true maximum, from the distal end of the medial malleolus to the most anterior part of the tibia.

Eforensics Laboratory

Part B

The intermembral index is a ratio of the length of the arms relative to the length of the legs. The closer the ratio is to 100, the more equal in length the limbs are to each other.

Arm and leg length are related to the type of locomotion an animal employs, so we can use this ratio to identify living primates and learn about how extinct animals would have moved based on their fossilized bones. We will use this index frequently in the second half of this class.

Using the measurements you took from in Part A and the formula below, calculate the intermembral index of the eforensics skeleton.

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