Sagittal crest

File:CanineSkull.jpg

A bony ridge on the top of the skull to which jaw muscles are attached

The sagittal crest is a prominent bony ridge that runs along the midline of the top of the skull in certain mammals, including some primates and carnivores. It serves as an attachment site for the temporalis muscle, which is one of the main muscles involved in chewing.

Anatomy and Function

The sagittal crest is formed by the fusion of the parietal bones along the midline of the skull. It is most commonly found in species that require strong jaw muscles for processing tough or fibrous food. The presence and size of the sagittal crest can vary significantly among different species and even among individuals within a species.

In species with a pronounced sagittal crest, such as the gorilla or the wolf, the crest provides a larger surface area for the attachment of the temporalis muscle. This muscle extends from the sagittal crest down to the coronoid process of the mandible, allowing for powerful biting and chewing actions.

Evolutionary Significance

The development of a sagittal crest is often associated with dietary adaptations. In hominins, for example, the presence of a sagittal crest is typically seen in species that consumed a diet consisting of hard or fibrous plant materials. The robust Australopithecus species, such as Australopithecus boisei, are known for having a well-developed sagittal crest, which suggests a diet that required significant chewing force.

In contrast, modern humans (Homo sapiens) do not have a sagittal crest, reflecting a dietary shift towards softer foods and the use of tools to process food, which reduced the need for large jaw muscles.

Comparative Anatomy

The presence of a sagittal crest is not limited to primates. Many carnivorous mammals, such as canids and felids, also exhibit this feature. In these animals, the sagittal crest supports the powerful jaw muscles needed for capturing and subduing prey.

In some cases, the sagittal crest can be sexually dimorphic, meaning it is more pronounced in one sex than the other. This is often seen in species where males engage in physical contests or displays that involve biting or other uses of the jaw.

Clinical Relevance

While the sagittal crest itself is not typically a focus in human medicine, understanding its function and evolutionary history can provide insights into the musculoskeletal adaptations of the skull. In veterinary medicine, the sagittal crest may be of interest when examining the skulls of domestic animals, particularly in breeds that have been selectively bred for specific traits.

Also see

• Temporalis muscle
• Mastication
• Parietal bone
• Australopithecus
• Coronoid process