Cranium in lateral view

Cranium in lateral view

Farmingdale State College (SUNY), Department of Biology

BIO451: Human Evolutionary Anatomy

Lab 3: Hominoid Cranial Anatomy

Objectives: – Compare and contrast cranial shape in chimpanzees, gorillas, orangutans, fossil

hominids, and modern humans

– More specifically, trace trends in changing cranial base angle, endocranial

volume, prognathism, the position of the foramen magnum, and postorbital

constriction across those taxa

– Identify diagnostic features such as the nuchal crest, sagittal crest, sagittal keel,

supraorbital torus, and occipital bun

Use the figures and descriptions in the text of Chapter 5 of Aiello and Dean (2002),

the labeled hominoid skull and fossil skull picture handouts on Blackboard, as well

as the array of extant and fossil cranial casts in front of you to help you answer the

following questions. Feel free to use extra sheets of paper and/or make your own

drawings/diagrams to help.

Cranium in lateral view

1. Rank the specimens in terms of endocranial volume – which taxon has the largest brain and which taxon has the smallest brain? Does this match the result if you

were to rank them in terms of body size instead? What other aspects of cranial

morphology might changes in brain size be related to?

2. Compare the position of the superior nuchal lines in the human and great ape crania. What differences do you see?

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3. Note the degree of cranial base flexion in the different specimens. Describe any differences you see.

4. Describe any differences in the prognathism you see in the great ape, fossil hominin, and modern human crania. Which specimen is the most prognathic?

Which specimen is the most orthognathic?

Cranium in inferior view

5. Note the position of the foramen magnum in the various crania. Which specimen has the most anteriorly positioned foramen magnum? Which specimen has the

most posteriorly positioned foramen magnum? How would you describe the

position of the foramen magnum in the fossil hominins?

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6. Note that the length of the basioccipital is also correlated with the position of the foramen magnum. Note any differences in relative basicranial length in the

various specimens.

7. Note the orientation of the petrous portions of the temporal bone in great apes compared to modern humans. In particular note the orientation of the petrous

apex relative to the external auditory meatus and relative to the mid-sagittal plane.

Which specimen has more vertically oriented petrous apices in line with the mid-

sagittal plane? What morphology is seen in the fossil hominin specimens?

8. Describe any differences you see in bizygomatic breadth among the crania. Which taxa have the overall widest crania?

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9. Look for depressions just anterior to the foramen magnum. These are markings for the longus capitis muscle, a skull flexor. Are the markings larger in great apes

or humans? What condition is seen in the fossil hominins?

Skull in occipital view

10. Note again the relative position of the nuchal lines among the great ape, modern human, and fossil hominin specimens. Which specimens have a nuchal crest?

Which specimens have a nuchal torus? Which specimens have a sagittal crest?

Which specimens have a sagittal keel? Which specimens have an occipital bun?

Do modern humans have any sagittal or nuchal cresting?

11. Draw the outline of each cranium in occipital view. At what point is the cranium the widest for each taxon? Put a star at that position on each outline.

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Skull in superior/dorsal view

12. Note the position of the temporal lines in the various specimens. Where they meet, they are said to form a sagittal crest. Which specimens exhibit a sagittal

crest? Note the position of the sagittal crest in the various specimens, if it exists.

Does the crest form more anteriorly or more posteriorly?

13. Describe any differences you see in the degree of postorbital constriction (the width across the neurocranium just posterior to the browridges) across the various

taxa. How is this related to the differences in bi-zygomatic width and brain size

that you described above?

 
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