The Skull - The Skull Learning Goals At the end of this...

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The Skull Learning Goals At the end of this lecture you should be able to: Describe the main features of the human skull. Discuss how the primate skull is used in taxonomy and behavioural reconstruction. Introduction The skull is certainly the most important part of the body for identifying and classifying primates. It is extremely complex and as such has a wealth of features that can be used for taxonomy and as developmental indicators. In addition it has a number of important functions (diet, special senses, protection, communication) so it can also be used for behavioural reconstruction. This lecture will describe the main features of the primate skull and show some examples of how these features can be used. Modern Human Skull Figures 1 and 2 show the major bones that make up the human skull. You certainly need to know the names, appearance and locations of the bones (in bold on the diagrams) but the other labels should probably be treated as reference material.
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Figure 1. Frontal view of the bones of the skull [Netter 1997]
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Figure 2. Lateral view of the bones of the skull [Netter 1997] You should also be aware of the names of the major sutures (immobile, fibrous joints) between the skull bones. These are named by their location ( sagittal , coronal ), their shape ( lambdoid ), or the bones ( squamous ). Figure 3 also shows some important landmarks. Figure 3. Diagram showing sutures and landmarks of the skull [Aiello & Dean 1990]
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Much of the variation among skulls (especially within species, or between closely related species) does not depend on the presence or absence of specific features (non-metric traits) but on the difference in size and shape of the elements. To quantify this difference a lot of effort has gone into measuring skulls. To allow comparisons that are not swamped by the overall size of the skull these are often expressed as indices (ratios of linear measurements) as illustrated in figure 4. Figure 4. Diagram showing some common cranial indices [Aiello & Dean 1990] In addition there are a large number of named anthropometric landmarks that can be measured. These are often measured as 3D coordinates (X, Y and Z) values with respect to the Frankfurt Plane which is defined as the planes that intersects the porion (most lateral and superior point on the roof of the bony external auditory meatus) and the orbitale (the lowest point on the infraorbital margin). Figure 5 shows some of the more commonly used anthropometric landmarks. These points are all defined descriptively so they can be located on skulls with very different configurations.
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Figure 5. Diagram showing anthropometric landmarks [Aiello & Dean 1990] Taxonomic Indicators Probably the most important use of the skull in terms of human evolution is in taxonomy. The skull is complex and highly variable. It has major features that vary between different primate groups and so it is often the key part of the body for taxonomic distinctions. Often when considering fossils it is the only bone that can be used to differentiate at the species level and
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