KNM ER 406 is one of the most complete specimens of Paranthropus boisei.
In frontal view, note the characteristic "flaring" zygomatics
- the cheek bones project far out to the sides creating a large space
for the massive chewing muscles to pass through. The space can be seen
by slowly rotating the skull to the left. These muscles attach to bony
ridges on the top of the skull. Rotate back to frontal view and look at
the two ridges behind the orbits. These are the temporal lines.
They converge to form the sagittal crest. Keeping an eye on the
temporal lines, rotate the skull to the right, and observe the form of
the sagittal crest. It is a bony ridge positioned on top of the skull.
This is very different from the similar species Paranthropus
aethiopicus.
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