Post-orbital constriction

Post-orbital constriction is a cranial feature characterized by a narrowing of the skull behind the orbits (eye sockets). This feature is often used in the study of paleoanthropology and primatology to differentiate between different primate species and to understand their evolutionary history.

Etymology

The term "post-orbital constriction" is derived from the Latin words "post" meaning "after", "orbital" referring to the "eye socket", and "constriction" meaning "narrowing". Thus, it refers to the narrowing of the skull that occurs behind the eye sockets.

Description

Post-orbital constriction is a feature that is often observed in the skulls of primates, particularly those of prosimians and some New World monkeys. It is less common in Old World monkeys and hominoids. The degree of post-orbital constriction can vary greatly among different primate species, and it is often used as a morphological marker to differentiate between them.

The presence of post-orbital constriction is thought to be related to the size and position of the brain and the muscles used for chewing. Species with a large degree of post-orbital constriction tend to have a smaller brain and larger chewing muscles, while those with less constriction have a larger brain and smaller chewing muscles.

Evolutionary significance

The degree of post-orbital constriction is often used in paleoanthropology to understand the evolutionary history of primates. It is thought that the reduction in post-orbital constriction over time is related to the expansion of the brain, particularly the frontal lobes, and the reduction in the size of the chewing muscles. This trend is particularly evident in the evolution of hominoids, where there is a clear trend towards less post-orbital constriction over time.

See also

• Cranial capacity
• Cephalic index
• Primate anatomy

References

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Post-orbital constriction gallery

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