A sagittal crest is a ridge of bone running lengthwise along the midline of the top of the skull

Skull

The skull is a bony structure in the head of many animals that supports the structures of the face and forms a cavity for the brain.The skull is composed of two parts: the cranium and the mandible. A skull without a mandible is only a cranium. Animals that have skulls are called craniates...

 (at the sagittal suture

Sagittal suture

The sagittal suture is a dense, fibrous connective tissue joint between the two parietal bones of the skull. The term is derived from the Latin word Sagitta, meaning "arrow". The derivation of this term may be demonstrated by observing how the sagittal suture is notched posteriorly, like an arrow,...

) of many mammal

Mammal

Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...

ian and reptilian skulls, among others.

The presence of this ridge of bone indicates that there are exceptionally strong jaw

Jaw

The jaw is any opposable articulated structure at the entrance of the mouth, typically used for grasping and manipulating food. The term jaws is also broadly applied to the whole of the structures constituting the vault of the mouth and serving to open and close it and is part of the body plan of...

 muscles. The sagittal crest serves primarily for attachment of the temporalis muscle

Temporalis muscle

The temporal muscle is one of the muscles of mastication.-Structure:It arises from the temporal fossa and the deep part of temporal fascia...

, which is one of the main chewing muscles. Development of the sagittal crest is thought to be connected to the development of this muscle. A sagittal crest usually develops during the childhood of an animal in conjunction with the growth of the temporalis muscle, as a result of convergence and gradual heightening of the temporal lines.

A sagittal crest tends to be present on the skulls of adult animals that rely on powerful biting and clenching of their teeth, usually as a part of their hunting strategy. Skulls of some dinosaur species, including tyrannosaurs, possessed well developed sagittal crests. Among mammals, dogs, cats, lions, and many other carnivores have sagittal crests, as do some leaf eaters, including tapirs and some apes.

Sagittal crests are found in robust great apes, and some early hominins (Paranthropus

Paranthropus

The robust australopithecines, members of the extinct hominin genus Paranthropus , were bipedal hominids that probably descended from the gracile australopithecine hominids...

). Prominent sagittal crests are found among male gorillas and orangutans, and do occur but only rarely in male chimpanzee

Chimpanzee

Chimpanzee, sometimes colloquially chimp, is the common name for the two extant species of ape in the genus Pan. The Congo River forms the boundary between the native habitat of the two species:...

s such as Bili Ape

Bili Ape

Bili Ape, also Bondo Mystery Ape, is the name given to a large chimpanzee that inhabits Bili Forest in the Democratic Republic of the Congo....

s.

The largest sagittal crest ever discovered in the human lineage belongs to the "Black Skull", Paranthropus aethiopicus

Paranthropus aethiopicus

Paranthropus aethiopicus is an extinct species of hominid. The finding discovered in 1985 by Alan Walker in West Turkana, Kenya, KNM WT 17000 , is one of the earliest examples of robust pliocene hominids...

 field number KNM WT 17000, the earliest known robust hominid ancestor and the oldest robust australopithecine discovered to date. The prominence of the crest appears to have been an adaptation for the aethiopicus's heavy chewing, and the Black Skull's cheek teeth are correspondingly large. Smaller sagittal crests are also present on the skulls of other Paranthropines, including Paranthropus boisei and Paranthropus robustus.

See also

• Mountain Gorilla
  Mountain Gorilla
  The Mountain Gorilla is one of the two subspecies of the Eastern Gorilla. There are two populations. One is found in the Virunga volcanic mountains of Central Africa, within three National Parks: Mgahinga, in south-west Uganda; Volcanoes, in north-west Rwanda; and Virunga in the eastern Democratic...
  
  
• Paranthropus aethiopicus
  Paranthropus aethiopicus
  Paranthropus aethiopicus is an extinct species of hominid. The finding discovered in 1985 by Alan Walker in West Turkana, Kenya, KNM WT 17000 , is one of the earliest examples of robust pliocene hominids...
  
  (The Black Skull)
• Phrenology
  Phrenology
  Phrenology is a pseudoscience primarily focused on measurements of the human skull, based on the concept that the brain is the organ of the mind, and that certain brain areas have localized, specific functions or modules...
  
  
• Sagittal Keel
  Sagittal Keel
  The Sagittal keel is a thickening of bone on part or all of the midline of the frontal, or parietals where they meet along the sagittal suture, or on both bones. Sagittal keels occur in Homo erectus and occasionally Homo heidelbergensis, where they probably served as an armour against shock to the...
  
  

External links

• "Black Skull" (Australopithecus aethiopicus, specimen KNM-WT 17000)—ArcheologyInfo.com