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The basilar part of the occipital bone (also basioccipital) extends forward and upward from the foramen magnum, and presents in front an area more or less quadrilateral in outline. In the young skull, this area is rough and uneven, and is joined to the body of the sphenoid by a plate of cartilage.
Due to its many attachments and features, the occipital bone is described in terms of separate parts. From its front to the back is the basilar part, also called the basioccipital, at the sides of the foramen magnum are the lateral parts, also called the exoccipitals, and the back is named as the squamous part.
The singular basioccipital is the rear lower part of the braincase, below the foramen magnum. It is homologous to the basilar part of the occipital bone . In the ancestral tetrapod, the basioccipital makes up most of a large central knob-like surface, the occipital condyle, which articulates with the vertebrae as a ball-and-socket joint .
The nasal bones exhibit a distinct central row of conical caputegulae, symmetrically separated from the osteoderms above and to the sides of them. At the rear of the skull, the part of the foramen magnum formed by the basioccipital is located obliquely above and in front of the occipital condyle. [2]
There are two important foramina, or windows, two important fissures, or grooves, and one canal surrounding the globe in the orbit. There is a supraorbital foramen, an infraorbital foramen, a superior orbital fissure, an inferior orbital fissure and the optic canal, each of which contains structures that are crucial to normal eye functioning.
The hind area of the basilar part of occipital bone (basioccipital area) is convex. The position of the condylar canal and muscle arrangements of the basioccipital area of Diplobune are different from Anoplotherium and Dacrytherium. The postglenoid process is bulky and projects down compared to the two anoplotheriid genera.
The Orbital Fascia forms the periosteum of the orbit.. It is loosely connected to the bones and can be readily separated from them. Behind, it is united with the dura mater by processes which pass through the optic foramen and superior orbital fissure, and with the sheath of the optic nerve.
In Ziapelta, the bones of the upper rear skull sides, the exoccipitalia, do not contribute to this condyle which is fully formed by the basioccipital, the lower rear braincase element. More to below this basioccipital shows three deep parallel grooves, bordered by four rims. The middle groove has the opening of the foramen basioccipitale. To ...