HOMINOID SKULL COMPARISON CHECKLIST
First fill in the name of each skull on your data chart. (word version) Then follow the checklist below to fill in the characteristics of each skull on the data chart. Record all measurements in millimeters.
1. Forehead: Does the skull extend above the eyes? Is the forehead large, small, or medium?
2. Chin: How pronounced is the chin? Does it stick out like yours or slope back?
3. Sagittal crest: This is the bony ridge along the top of the skull to which large chewing muscles attach. Is there a sagittal crest? How pronounced is it? Is it large, small, or medium?
4. Prognathism: Examine the skull for existence of a “muzzle” or snout – a protrusion of parts of the face below the eyes. Gorillas (and dogs) have pronounced prognathisms. Humans do not.
5. Facial slope: Use a ruler and a protractor to measure the angle of the face as shown in the diagram below.
6. Supraoribital brow ridge: Look for a bony ridge protruding above the eyes. Large, small or medium?
7. Dental arcade: The arch, or shape of the jaw will be either box shaped (sides parallel), “U”–shaped (parabolic sides), “V”-shaped, or intermediate.
8. Canines: The canine is the third tooth from the center of the top and bottom jaw. Describe them. Are they long, or short?; sharp, or dull? Is there a diastema present (a gap between the upper incisors and canines)?
9. Foramen magnum: This is the large opening in the base of the skull through which the spinal cord passes. The position of this hole reflects the body posture (and indirectly the loco motor pattern) of a hominoid. Is the foramen magnum located toward the rear or more forward?
10. Number of teeth – Top/Bottom: Count the number of teeth in the upper and lower jaw. Record the number of incisors, canine, premolars, molars in one-half of the upper jaw as the numerator and the same count for one-half of the lower jaw as the denominator.
11. Cranial Module: Calculating the cranial module provides a rough numerical value for the size of the cranium. Measure the maximum length by placing one end of a caliper on the most forward projecting point of the forehead and the other end on the posterior point at the back of the skull. The maximum width is determined with the calipers on the sides (temples) of the skull at the widest point. The maximum height is measured by putting the skull on its side; then hold one end of the calipers on the midpoint of the anterior of the foramen magnum and the other end at the intersection of the coronal and sagittal sutures on top, in the midline. Add these and then divide by three.
12. On the back of your data table answer these questions using the data you have collected. (include the question)
a. Which two skulls show the greatest difference? Support your answer.
b. Why do you think the two skulls in question A show such differences? Be specific
c. Which two skulls do you feel share the most similarities? Support your answer.
d. Why do you think the two skulls in question C share such similarities? Be specific.
e. Are the species that these skulls came from related? Support your answer
f. Construct a graph comparing the cranial module data for all skulls. What trend can you infer from this graph?