D. Measure the diameter in centimeters of the circle in each skull. The diameter is the distance across the exact center of each circle.
E. Multiply the cranial diameters by 200 cm2. This gives the cranial capacity (brain volume) in cubic centimeters.
F. Record the cranial capacity for each skull in line 6 of Table 1.
NOTE: This method of measuring cranial capacity differs from the method used when an intact skull is available.
Part II: Jaw and Teeth Characteristics
Jaw Angle (Prognathism)
In front of each skull are two heavy lines, one running parallel to the slope of the upper jaw and one
running through the nose. These two lines are to be used for measuring how far the jaw protrudes
G. With a protractor, measure the outside angle formed by the two lines in each skull (the angle toward the right).
H. Place the protractor onto each skull as shown in Figure 2. Read the angle to using the outside scale on the protractor. The angle is read where the lower skull line crosses the protractor.
I. Record the angles in line 7 of Table 1. An angle of less than 90o means that the lower jaw sticks out in front of the nose. An angle of 90o means that the lower jaw does not stick out in front of the nose. Complete line 8 of Table 1.
A bony ridge running across the top of a skull for muscle attachment is called a sagittal crest. This bony ridge is associated with heavy temporal muscles used to move the lower jaw.
J. Indicate in line 10 of Table 1 whether or not a brow ridge is present.
Number and Types of Teeth
Use the diagrams in Figure 3 for this part of the investigation.
K. Count and record the number of teeth for each lower jaw inline 11 of Table 1.
L. Count the number of each tooth type for each lower jaw. “M” on Figure 3 is for molar, “P” is for
premolar, “C” is for canine, and “I” is for incisor.
M. Record in lines 12 to 15 of Table 1 the tooth type totals.
N. Record in line 16 of Table 1 the size of canine teeth in each lower jaw.
O. A diastema is a space between teeth. One can see a space in the lower jaw of the gorilla between