squama

The base is fused with the internal surfaces of the squama and mastoid portion.

Projecting from the lower part of the squama is a long, arched process, the zygomatic process.

Union of the upper and lower portions of the squama takes place in the third month of fetal life.

The part of the squama which forms the fossa lies at first below the level of the zygomatic process.

The curved, expanded plate behind the foramen magnum is named the squama occipitalis.

The squama is ossified in membrane from a single nucleus, which appears near the root of the zygomatic process about the second month.

On the squama occipitis.

There are two surfaces of the squama of the frontal bone: the external surface, and the internal surface.

The posterior end is connected to the squama by two roots, the anterior and posterior roots.

The boundary between the squama and the mastoid portion of the bone, as indicated by traces of the original suture, lies about 1 cm.

The squamosal bone, which is homologous with the squama, and forms the side of the cranium in many bony fish and tetrapods.

From each of these centers, ossification extends upward to form the corresponding half of the squama, and backward to form the orbital plate.

The anterior part, formed by the squama, is smooth, covered in the fresh state with cartilage, and articulates with the condyle of the mandible.

The petrosquamous suture is a cranial suture between the petrous portion and the squama of the temporal bone.

Posteriorly, it blends with the squama and mastoid part, and forms the anterior boundary of the tympanomastoid fissure.

That part of the squama which lies above the highest nuchal lines is named the planum occipitale and is covered by the Occipitalis muscle.

About the fourth year the squama and the two lateral portions unite, and about the sixth year the bone consists of a single piece.

Cercophonius squama (Forest Scorpion)

These canals run from the tympanic cavity forward and downward to the retiring angle between the squama and the petrous portion of the temporal bone.

Cercophonius squama, commonly known as the forest scorpion or wood scorpion, is a scorpion native to southeastern Australia.

The squama of the temporal bone forms the anterior and upper part of the bone, and is scale-like, thin, and translucent.

The squama of the occipital bone, situated above and behind the foramen magnum, is curved from above downward and from side to side.

The planum nuchale of the squama is ossified from two centers, which appear about the seventh week of fetal life and soon unite to form a single piece.

In many mammals, including humans, it fuses with the periotic bone and the auditory bulla to form the temporal bone, then referred to as the squama temporalis.

The structure of the squama is like that of the other cranial bones: the mastoid portion is spongy, and the petrous portion dense and hard.