Theendocranium incomparative anatomy is a part of theskull base invertebrates and it represents the basal, inner part of thecranium. The term is also applied to the outer layer of thedura mater inhuman anatomy.^[1]

Endocranium
Human endocranium (pink fields), inner surface.
Details
Identifiers
Latin	endocranium
Anatomical terms of bone [edit on Wikidata]

Structurally, the endocranium consists of a boxlike shape, open at the top. The posterior margin exhibits theforamen magnum, an opening for thespinal cord. The floor of the endocranium has several paired openings for thecranial nerves, and the anterior margin holds a spongy construction, allowing for theexternal nasal nerves to pass through.^[2] All bones of the structure derive from thecranial neural crest duringfetal development.

In humans and othermammals, the endocranium forms duringfetal development as a cartilaginousneurocranium, that ossifies from several centers.^[3] Several of these bones merge, and in the adultprimates (including humans), the endocranium is composed of only five bony elements (from front to back):^[4]

• Theethmoid bone, lying behind the nose.
• Thesphenoid bone, underlying the forward portion of the brain
• Pairedpetrous part of the temporal bones, containing theinner ear structures
• Most of theoccipital bone, surrounding theforamen magnum

The endocranium inmammals is much reduced in relative size and number of bones compared to the condition in the ancestralland vertebrates, though theoccipital bone occur as one or more stout bony elements in several mammal groups. The occipital bone is also found as several bony elements inbirds andreptiles, while the skull of modernamphibians is generally reduced with a simplified endocranium. The skull of earlylabyrinthodonts were rather complex, and contained in addition to the bones mentioned above several small cartilaginous components that are fused to temporal and occipital bones in mammals:^[2]

• Pairedprootic andopisthotic bones above eachfenestra ovalis, fused to the petrous part of the temporal bones in mammals.
• Pairedexoccipital bones medially and a singlebasioccipital bone below theforamen magnum, part of the occipital bone in mammals.

While the endocranium is an integral part of the skull in mammals,birds andreptiles, its connection to theroofing parts of the skull is more loose in thelower vertebrates. InAgnathans andChondrichthyes, the skull lacks theskull roof dermal elements, their whole cranium being composed of the endocranium, properly called achondrocranium. In mostOsteichthyes, the skull is only loosely joined, and the endocranial elements do not form a unit with the skull roof.

An endocast or endocranial cast is a cast made of the mold formed by the impression thebrain makes on the inside of theneurocranium (braincase), providing a replica of the brain with most of the details of its outer surface. Endocasts can also form naturally, when sediments fill the emptyskull, after which the skull is destroyed and the castfossilized. Scientists are increasingly utilizingcomputerized tomography scanning technology to create digital endocasts without damaging valuable specimens. This gives a 3D representation of the brain. Brain size and complexity can then be determined.

Endocasts were used for looking at the brains ofHomo sapiens to find hemispheric specialization.

• Dermatocranium
• Splanchnocranium