Hubbry Logo
Greater wing of sphenoid boneGreater wing of sphenoid boneMain
Open search
Greater wing of sphenoid bone
Community hub
Greater wing of sphenoid bone
logo
8 pages, 0 posts
0 subscribers
Be the first to start a discussion here.
Be the first to start a discussion here.
Greater wing of sphenoid bone
Greater wing of sphenoid bone
Greater wing of sphenoid bone
View on Wikipedia
from Wikipedia
Greater wing of sphenoid bone
Figure 1: Sphenoid bone, upper surface.
Figure 2: Sphenoid bone, anterior and inferior surfaces.
Details
Identifiers
Latinala major ossis sphenoidalis
TA98A02.1.05.024
TA2610
FMA52868
Anatomical terms of bone

The greater wing of the sphenoid bone, or alisphenoid, is a bony process of the sphenoid bone, positioned in the skull behind each eye. There is one on each side, extending from the side of the body of the sphenoid and curving upward, laterally, and backward.

Structure

[edit]

The greater wings of the sphenoid are two strong processes of bone, which arise from the sides of the body, and are curved upward, laterally, and backward; the posterior part of each projects as a triangular process that fits into the angle between the squamous and the petrous part of the temporal bone and presents at its apex a downward-directed process, the spine of sphenoid bone.

Cerebral surface

[edit]

The superior or cerebral surface of each greater wing [Fig. 1] forms part of the middle cranial fossa; it is deeply concave, and presents depressions for the convolutions of the temporal lobe of the brain. It has a number of foramina (holes) in it:

Lateral surface

[edit]

The lateral surface [Fig. 2] is convex, and divided by a transverse ridge, the infratemporal crest, into two portions.

  • The superior temporal surface, convex from above downward, concave from before backward, forms a part of the temporal fossa, and gives attachment to the temporalis;
  • the inferior infratemporal surface, smaller in size and concave, enters into the formation of the infratemporal fossa, and, together with the infratemporal crest, serves as an attachment to the lateral pterygoid muscle.

It is pierced by the foramen ovale and foramen spinosum, and at its posterior part is the sphenoidal spine, which is frequently grooved on its medial surface for the chorda tympani nerve.

To the sphenoidal spine are attached the sphenomandibular ligament and the tensor veli palatini muscle.

Medial to the anterior extremity of the infratemporal crest is a triangular process that serves to increase the attachment of the lateral pterygoid muscle; extending downward and medialward from this process on to the front part of the lateral pterygoid plate is a ridge that forms the anterior limit of the infratemporal surface, and, in the articulated skull, the posterior boundary of the pterygomaxillary fissure.

Orbital surface

[edit]

The orbital surface of the great wing [Fig. 2], smooth, and quadrilateral in shape, is directed forward and medially and forms the posterior part of the lateral wall of the orbit.

  • Its upper serrated edge articulates with the orbital plate of the frontal bone.
  • Its inferior rounded border forms the postero-lateral boundary of the inferior orbital fissure.
  • Its medial sharp margin forms the lower boundary of the superior orbital fissure and has projecting from about its center a little tubercle that gives attachment to the inferior head of the lateral rectus muscle; at the upper part of this margin is a notch for the transmission of a recurrent branch of the lacrimal artery.
  • Its lateral margin is serrated and articulates with the zygomatic bone.
  • Below the medial end of the superior orbital fissure is a grooved surface, which forms the posterior wall of the pterygopalatine fossa, and is pierced by the foramen rotundum.

Margin

[edit]

Commencing from behind [Fig. 2], that portion of the circumference of the great wing that extends from the body to the spine is irregular.

  • Its medial half forms the anterior boundary of the foramen lacerum, and presents the posterior aperture of the pterygoid canal for the passage of the corresponding nerve and artery.
  • Its lateral half articulates, by means of a synchondrosis, with the petrous portion of the temporal, and between the two bones on the under surface of the skull, is a furrow, the sulcus of the auditory tube, for the lodgement of the cartilaginous part of the auditory tube.

In front of the spine the circumference presents a concave, serrated edge, bevelled at the expense of the inner table below, and of the outer table above, for articulation with the squamous part of the temporal bone.

At the tip of the great wing is a triangular portion, bevelled at the expense of the internal surface, for articulation with the sphenoidal angle of the parietal bone; this region is named the pterion.

Medial to this is a triangular, serrated surface, for articulation with the frontal bone; this surface is continuous medially with the sharp edge that forms the lower boundary of the superior orbital fissure, and laterally with the serrated margin for articulation with the zygomatic bone.

Development

[edit]

The greater wing of the sphenoid bone starts as a separate bone, and is still separate at birth in humans.

Function

[edit]

The sphenoid bone assists with the formation of the base and the sides of the skull, and the floors and walls of the orbits. It is the site of attachment for most of the muscles of mastication. Many foramina and fissures are located in the sphenoid that carry nerves and blood vessels of the head and neck, such as the superior orbital fissure (with ophthalmic nerve), foramen rotundum (with maxillary nerve) and foramen ovale (with mandibular nerve).[1]

Clinical significance

[edit]

In patients with neurofibromatosis type 1, malformation of the sphenoid bone wings may occur, due to aberrant cell development. This can ultimately lead to blindness if left untreated.

In other animals

[edit]

In many mammals, e.g. the dog, the greater wing of the sphenoid bone stays through life a separate bone called the alisphenoid.

Additional images

[edit]
  • The seven bones that articulate to form the orbit.
    The seven bones that articulate to form the orbit.
  • Base of skull. Inferior surface.
    Base of skull. Inferior surface.
  • Left infratemporal fossa.
    Left infratemporal fossa.
  • The skull from the front.
    The skull from the front.
  • Articulation of the mandible. Medial aspect.
    Articulation of the mandible. Medial aspect.
  • Muscles of the right orbit.
    Muscles of the right orbit.
  • Greater wing of sphenoid bone
    Greater wing of sphenoid bone
  • Greater wing of sphenoid bone
    Greater wing of sphenoid bone
  • Greater wing of sphenoid bone
    Greater wing of sphenoid bone
  • Greater wing of sphenoid bone
    Greater wing of sphenoid bone
  • Greater wing of sphenoid bone
    Greater wing of sphenoid bone
[edit]

References

[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Greater wing of sphenoid bone

View on Grokipedia
from Grokipedia
The greater wing of the is a paired, triangular bony projection that extends laterally from the body of the , forming key components of the skull's architecture, including the floor of the middle cranial fossa, the posterior wall of the , and the lateral aspect of the . It articulates with multiple surrounding bones, such as the frontal, parietal, temporal, and zygomatic bones, contributing to the structural integrity at junctions like the . This wing is essential for supporting neurovascular structures and muscular attachments, making it a critical element in the complex , often described as the "keystone" of the cranium due to its central position and extensive connections. Anatomically, the greater wing features distinct cerebral, orbital, and temporal surfaces, with the cerebral surface contributing to the anterior floor of the middle cranial fossa and the orbital surface forming most of the posterior orbital wall. Its borders include a sharp anterior margin that forms the posterior aspect of the , a broad posterior margin articulating with the , and an inferior margin blending into the infratemporal crest. The wing's three-dimensional curved shape enhances its role in enclosing vital spaces, such as parts of the and , while providing attachment sites for muscles like the temporalis on its temporal surface and the upper fibers of the lateral pterygoid on its infratemporal surface. Several important foramina perforate the greater wing, facilitating the passage of and vessels. The , located at the junction with the lesser wing, transmits the (CN III), (CN IV), (CN VI), ophthalmic division of the (CN V1), and . Inferiorly, the allows passage of the maxillary division of the (CN V2), while the foramen ovale conveys the mandibular division (CN V3), the accessory meningeal artery, and the ; the foramen spinosum, posterior to ovale, transmits the and vein. These openings underscore the greater wing's role in channeling neurovascular elements from the to the face and orbit. In terms of relations, the greater wing lies adjacent to the superiorly, the anteriorly, and the inferiorly, with its lateral extent visible externally on the anterior to the squamous . It forms a bridge between the cranial base and , influencing developmental processes where membranous from adjacent areas contributes to its formation. Clinically, fractures of the greater wing can lead to complications such as cranial nerve palsies, vision impairment, or leaks due to its proximity to the and middle fossa. Additionally, it is implicated in conditions like sphenoid wing dysplasia in type 1 and various benign or malignant lesions that may affect its foramina and surfaces, often requiring imaging for diagnosis.

Anatomy

Location and relations

The greater of the is a triangular, plate-like projection that arises posterolaterally from the body of the and extends laterally, superiorly, and posteriorly in a curved manner, resembling a bat . It forms key components of the skull's architecture, including the floor of the middle cranial fossa, the posterolateral wall of the , and the lateral wall of the (also contributing to the ). In terms of spatial relations, the greater wing articulates anteriorly with the and laterally with the as part of the orbital wall, posteriorly with the , and superiorly with the . These relations position the greater wing centrally within the skull base, bridging the and viscerocranium while contributing to the lateral side walls of the cranium. The orientation of the greater wing projects upward, outward, and posteriorly from the sphenoid body, integrating into the skull base and side walls to provide structural continuity. Its cerebral surface indirectly aids in delineating the middle cranial fossa from the anterior cranial fossa by forming the inferior boundary of the middle fossa, in conjunction with the lesser wings superiorly.

Borders and articulations

The greater wing of the possesses four primary borders that enable its articulations with neighboring cranial and facial bones, primarily through fibrous sutures that confer rigidity to the while permitting growth during development. These borders form immovable syndesmotic joints, characterized by that interdigitates the bone edges for enhanced stability. The anterior border articulates with the orbital plate of the via the sphenofrontal suture, delineating the posterior limit of the and contributing to the lateral orbital rim. The posterior border connects with the squamous portion of the through the sphenosquamosal suture, a vertically oriented seam located lateral to the foramen spinosum, which helps bound the posterior aspect of the middle cranial fossa and the . The superior border joins the anteroinferior angle of the at the sphenoparietal suture, forming part of the —a key junction where four bones meet—and supporting the lateral wall of the . The lateral or inferior border articulates with the frontal process of the via the sphenozygomatic suture, reinforcing the and the inferior boundary of the , with occasional minor involvement in the sphenopalatine suture adjacent to the . These sutures typically feature serrated, interlocking margins that increase tensile strength and resist shear forces across the . They play a role in accommodating growth through gradual remodeling, with synostosis (bony fusion) generally commencing in late childhood and completing by , often around 8–15 years of age depending on the specific suture, after which further expansion is limited. Anatomical variations in these borders and articulations include the occasional presence of accessory sutures or sutural (, particularly along the sphenozygomatic or sphenoparietal margins, which may arise from irregular ossification patterns. Incomplete fusions or anomalous suture configurations can also occur in congenital conditions, such as isolated craniosynostoses, potentially altering skull morphology and requiring clinical evaluation.

Surfaces

The greater wing of the features four primary surfaces—cerebral, temporal, orbital, and infratemporal—each exhibiting unique contours, markings, and structural adaptations that interface with adjacent cranial and facial cavities. These surfaces vary in thickness, generally becoming thinner toward the orbital margin and thicker in the temporal region, with distinctive vascular grooves and muscular ridges tailored to their respective functions. The cerebral surface, oriented superiorly, is deeply concave and constitutes a significant portion of the floor of the middle cranial fossa. This surface bears digitate impressions (impressiones digitatae) and cerebral ridges (juga cerebralia) that correspond to the gyri and sulci of the temporal and meningeal lobes of the brain, providing a molded interface for cerebral support. Additionally, it includes shallow sulci that accommodate branches of the middle meningeal vessels, enhancing the vascular accommodation within the . The temporal surface, also referred to as the , presents a convex contour and contributes to the lateral walls of both the temporal and infratemporal fossae. Divided by the infratemporal crest—a prominent ridge running anteroposteriorly—it provides attachment sites for the deep fibers of the on its superior portion, facilitating masticatory mechanics. The temporal crest itself serves as a key landmark, separating the above from the infratemporal region below, with subtle ridges reinforcing muscle origins. The orbital surface is a smooth, quadrilateral thin plate that forms the posterior and lateral wall of the orbit, articulating anteriorly with the and superiorly with the orbital plate of the . Its gently curved contour includes an arcuate line along the superomedial margin, which indirectly borders the by separating it from the lesser wing. This surface's minimal markings ensure a streamlined contribution to the orbital cavity, maintaining structural integrity without prominent protrusions. The infratemporal surface, directed inferiorly and oriented largely horizontally, forms the roof of the in conjunction with the squamous . It features the infratemporal crest posteriorly and provides attachment for the superior head of the , with shallow grooves and ridges accommodating these fibers and facilitating their insertion toward the mandibular condyle. These markings, including subtle vascular impressions, underscore its role in supporting pterygoid muscle dynamics within the deep facial space.

Foramina and fissures

The greater wing of the sphenoid bone features several key foramina and fissures that serve as passages for neurovascular structures between the and extracranial regions. These openings are primarily located on the infratemporal surface and the margins of the wing, facilitating the transmission of and associated vessels while contributing to the compartmentalization of the skull base. The is situated at the medial aspect of the greater wing, at its junction with the body of the , connecting the middle cranial fossa to the . It transmits the (CN V2), the artery of the foramen rotundum (a branch of the ), and occasional emissary veins. This foramen's position underscores its role in directing sensory innervation from the to the midface. Positioned posterior to the on the greater wing, the foramen ovale lies within the floor of the middle cranial fossa and opens into the . It conveys the (CN V3), the accessory meningeal artery, the , and sometimes an emissary vein. This opening is essential for the passage of motor and sensory fibers supplying the lower face, jaw, and . The foramen spinosum, located posterolateral to the foramen ovale in the greater wing, also communicates between the middle cranial fossa and the . It transmits the and vein, along with the meningeal branch of the (nervus spinosus). This foramen's vascular contents are clinically notable for their potential involvement in epidural hematomas following trauma. The foramen Vesalius, a variable and often inconstant opening, is typically found medial to the foramen ovale within the greater wing of the sphenoid, near the base of the medial pterygoid plate. When present, it transmits connecting the to the pterygoid venous , aiding in venous drainage from the . Its presence occurs in approximately 80% of cases, though it may be absent or asymmetrical without pathological implication. The forms a cleft between the greater and lesser wings of the sphenoid, at the apex of the orbit, linking the middle cranial fossa to the orbital cavity. It transmits the (CN III), (CN IV), (CN VI), ophthalmic nerve (CN V1), and the , with additional sympathetic fibers and branches of the inferior ophthalmic vein. This fissure's contents are critical for orbital innervation and venous outflow. Inferiorly, the pterygomaxillary fissure arises between the posterior aspect of the maxilla and the greater wing of the sphenoid (specifically the lateral pterygoid plate), connecting the infratemporal fossa to the pterygopalatine fossa. It provides passage for branches of the maxillary artery and associated neurovascular elements, supporting blood supply and innervation to the deep face.

Development

Ossification process

The greater wing of the sphenoid bone undergoes a dual ossification process, primarily intramembranous from mesenchymal tissue derived from the lateral plate mesenchyme, with endochondral components contributing at the junction with the sphenoid body. Intramembranous ossification begins in the ala temporalis and alar process regions, where mesenchymal cells differentiate directly into osteoblasts to form bone matrix without a cartilaginous intermediate. The endochondral aspect involves prior cartilage formation that calcifies at the medial root near the body. Ossification centers for the greater wing appear during the 8th to 10th gestational week, with the initial center emerging at the root below the future . Two primary centers develop in the greater wing anlage—one in the ala temporalis laterally and another in the alar process medially—fusing by approximately 12 weeks to form a cohesive structure. Rapid proceeds through the second trimester, with the wing largely formed by membranous bone by late . Postnatally, integrate with the sphenoid body, fusing soon after birth with complete consolidation by the end of the first year. Sutures with adjacent bones, such as the temporal and frontal, remain patent for growth and close progressively by . The wing expands laterally through appositional growth at its borders, driven by periosteal deposition influenced by expanding volume and masticatory muscle forces.

Embryological origins

The greater wing of the sphenoid bone, also known as the alisphenoid or ala temporalis, derives primarily from cells, with contributions from paraxial in the overall sphenoid complex. The anlage of the greater wing forms from mesenchymal condensations associated with the presphenoid and mesencephalic , where cells migrate to populate the lateral aspects of the developing cranial base. During the fourth to sixth weeks of embryonic development ( 17–23), the greater wing emerges as lateral outgrowths from the sphenoid body , driven by proliferation of mesenchymal cells surrounding emerging neural structures. This process is influenced by induction from the , particularly through interactions with the trigeminal and optic nerves, which guide the formation of foramina and shape the mesenchymal condensations. Initial connections to the sphenoid complex form , but fusion of the greater wing to the sphenoid body occurs postnatally, typically soon after birth, with full consolidation by the end of the first year. The patterning of these elements, including anterior-posterior identity along the cranial base, is regulated by , which orchestrate the differentiation and positional specification of neural crest-derived . Disruptions in the embryological origins, such as incomplete migration of cells, can result in anomalies like due to aberrant suture formation or aplasia/ of the greater wing, altering cranial base architecture.

Function

Structural support

The greater wing of the sphenoid bone forms a significant portion of the floor of the middle , providing essential support for the weight of the of the brain and helping to resist the mechanical stresses imposed by . This concave cerebral surface, positioned laterally to the sphenoid body, creates a stable platform that accommodates the while maintaining the integrity of the against internal forces generated by and brain tissue. In addition to its role in the cranial base, the greater wing reinforces the lateral walls of the skull by articulating with the frontal, parietal, and temporal bones through sutures, thereby distributing masticatory forces originating from the across the skull base. Its triangular, winged morphology acts as a structural , linking the to the cranium and preventing collapse under lateral impacts or compressive loads, enhancing its capacity for load-bearing. The greater wing integrates seamlessly with the sphenoid body, contributing to the overall rigidity of the cranium by forming part of its central keystone structure that interconnects multiple cranial elements for enhanced mechanical stability.

Attachments and passages

The greater wing of the sphenoid bone serves as a key site for muscular attachments that facilitate mandibular movements essential for mastication. The attaches to its temporal surface, contributing to the elevation of the during jaw closure. The superior head of the originates from the infratemporal surface and infratemporal crest of the greater wing, enabling protrusion, depression, and lateral deviation of the to support chewing and grinding motions. Ligamentous attachments on the greater wing provide stability to the . The arises from the angular spine (spina angularis) at the posterior angle of the greater wing and extends to the lingula of the , limiting excessive forward protrusion of the and aiding in joint stabilization during mastication. Several in the greater wing transmit neurovascular structures critical for sensory and motor innervation of the face and oral cavity, as well as vascular supply to intracranial structures. The transmits the (CN V2), providing sensory innervation to the midface, , , and upper teeth. The foramen ovale conveys the (CN V3), which supplies sensory innervation to the lower face, , and lower teeth while providing motor innervation to the ; it also transmits the accessory meningeal artery and the for parasympathetic supply to the . The , posterior to ovale, transmits the and vein, which supply arterial blood to the and drain venous blood from the , along with a meningeal branch of the . Additionally, pass through the variably present foramen of Vesalius (sphenoidal emissary ) in the greater wing, facilitating venous drainage from the to the pterygoid venous plexus and potentially aiding in pressure equalization between intracranial and extracranial venous systems. These passages collectively support trigeminal nerve-mediated sensation and motor control for facial and oral functions, while ensuring vascular nourishment to the dura and .

Clinical significance

Trauma and fractures

Fractures of the greater wing of the sphenoid bone typically result from high-impact trauma to the temporal or orbital regions, such as accidents, falls from height, or assaults, which account for the majority of cases. These injuries often occur as part of complex skull base fractures, including Le Fort III patterns that involve separation of the midface from the cranium and extend through the sphenoid. High-energy mechanisms are particularly associated with such fractures, with accidents being a leading cause in up to 50% of instances. Common fracture patterns include linear fractures along the junction of the greater wing and sphenoid body, often propagating transversely or obliquely through the orbital surface, and comminuted fractures in severe trauma. Due to the proximity of the , these fractures carry a risk of vascular , with disruptions to the canal observed in a significant subset of cases. The thin orbital surface of the greater wing contributes to its vulnerability in lateral impacts. Immediate consequences encompass cerebrospinal fluid (CSF) leaks through foramina such as the foramen rotundum or ovale, cranial nerve palsies (notably involving the maxillary division of the trigeminal nerve, CN V2), and formation of epidural hematomas from venous injury to the sphenoparietal sinus. These effects arise from dural tears and direct compression at the superior orbital fissure or orbital apex. Diagnosis relies on computed tomography (CT) imaging, which demonstrates bony discontinuity and associated soft tissue injuries; such fractures occur in approximately 7-16% of nonpenetrating head injuries, with higher incidence in motor vehicle accidents comprising 10-20% of skull base fractures.

Pathologies and malformations

The greater wing of the sphenoid bone is susceptible to congenital malformations, particularly in neurofibromatosis type 1 (NF1), an autosomal dominant disorder caused by mutations in the NF1 gene on chromosome 17. In 4%–11% of NF1 cases, or of the greater wing occurs, resulting in herniation into the and subsequent orbital , often manifesting as pulsatile proptosis and restricted extraocular movements such as and hypotropia. This malformation arises from dysplastic bone development and can lead to compressive effects on orbital structures without associated optic pathway gliomas in many instances. Additionally, syndromes like , driven by FGFR2 mutations, involve premature fusion of the inter-sphenoid around 3 weeks postnatally, restricting anteroventral facial growth and altering the position of the greater wing, contributing to and midface . Fibrous dysplasia is another common benign condition affecting the greater wing, occurring in 10-25% of cases involving the and s. It involves replacement of normal with fibro-osseous tissue, leading to bony expansion, proptosis, and potential compression of orbital structures or . Tumors affecting the greater wing include sphenoid wing meningiomas, which are typically slow-growing, dural-based lesions classified as WHO grade I in approximately 85% of cases. These benign tumors often invade the , causing of the sphenoid wing with irregular edges and extension into the , leading to proptosis in about 74% of patients and restriction of extraocular movements. The results in volumetric overgrowth, with surgical resection often removing a median of 86% of affected to alleviate symptoms. Other non-traumatic pathologies include erosive lesions from , a cystic squamous epithelium-lined filled with keratin debris that can develop in the sphenoid wing, causing bony remodeling and orbital with proptosis and . Metastatic lesions from primaries such as , , or may also erode the greater wing, presenting as osteolytic defects on imaging. Infections like , often secondary to invasive such as in immunocompromised patients, can involve the greater wing through osteolysis and abnormal enhancement, with spread facilitated via skull base foramina like the . Surgical management of these pathologies frequently employs the pterional craniotomy approach for tumor resection or malformation reconstruction, allowing access to the sphenoid wing while minimizing brain retraction. Key risks include optic nerve damage from compression or manipulation during decompression, potentially leading to persistent visual deficits in up to 5% of cases, and (CSF) , with complication rates ranging from 5% to 10% across supratentorial craniotomies. Postoperative visual stabilization is more likely with proactive decompression, though recurrence rates for meningiomas remain around 22% despite gross-total resection in 20%–43% of attempts.

Comparative anatomy

In mammals

In therian mammals, the greater wing of the sphenoid bone, known as the alisphenoid, manifests as broad lateral expansions arising from the sphenoid body, which collectively form the floor of the middle cranial fossa and contribute to the lateral walls of the . These wing-like structures are a conserved feature across all therian mammals, providing essential structural integrity to the while enclosing critical neurovascular elements. Variations in the alisphenoid's form reflect adaptations to diverse cranial architectures and lifestyles among mammals. In carnivores, such as dogs, the alisphenoid is notably robust and expansive, extending to form a significant portion of the and offering enhanced attachment sites for powerful masticatory muscles like the temporalis and masseter, which support the biomechanical demands of predation and bone-crushing. Conversely, in , the alisphenoid remains prominent within their compact skulls, facilitating attachments for pterygoid muscles essential for gnawing, though its relative proportions are scaled to accommodate the streamlined cranial design typical of these species. In , the alisphenoid is comparatively enlarged, accommodating the expanded braincase by broadening the and enhancing orbital support. Functionally, the alisphenoid exhibits strong conservation across mammals, consistently featuring foramina such as the rotundum and ovale that transmit branches of the (cranial nerve V) and associated meningeal vessels, ensuring reliable sensory innervation and vascular supply to the face and . This arrangement underscores its role in protecting and facilitating neural pathways amid varying cranial sizes. Evolutionarily, patterns of the alisphenoid are similarly conserved, predominantly intramembranous within the membrane surrounding the , though incorporating cartilaginous elements in some regions, which fuse with adjacent bones during development.

In other vertebrates

In reptiles, the epipterygoid serves as the primary homologue to the mammalian alisphenoid (greater wing of the sphenoid), contributing to the formation of the lateral wall of the braincase. It ossifies separately from the prootic and is less expanded compared to the mammalian condition, reflecting a more primitive configuration adapted for supporting the temporal region and jaw musculature. In squamates, for instance, the epipterygoid ossifies to enclose the braincase laterally, with membrane bone development occurring deep to the masticatory muscles. In birds, equivalents to the greater wing are incorporated into the fused cranium through the orbital cartilages and basal plate elements of the chondrocranium, which undergo extensive reduction to facilitate a lightweight optimized for flight. The posterior orbital , derived from the pila antotica, fuses with surrounding structures but contributes minimally to the orbital wall, often resorbing or persisting only as a narrow strip in species like ostriches or . This reduction eliminates many discrete bony elements, resulting in a kinetically flexible yet compact cranium with fenestrated interorbital septa. In amphibians and fish, structures homologous to the greater wing are rudimentary or absent, with sphenoid-like elements primarily existing as cartilaginous components of the chondrocranium rather than fully ossified bones. The parasphenoid, a dermal bone along the ventral skull base, acts as an evolutionary precursor in these groups, providing midline support but lacking the lateral expansions seen in higher vertebrates; in fish, it ossifies intramembranously without cartilaginous intermediaries, while in amphibians like urodeles, prootic extensions form partial alisphenoid laminae from cartilage. This cartilaginous foundation underscores the primitive state of the neurocranium in aquatic forms. Key differences between these vertebrate groups and mammals include fewer foramina perforating the lateral braincase walls in lower vertebrates, such as the absence of distinct separations for V2 and V3 in amphibians, which simplifies neural passages compared to the multiple openings in the mammalian greater wing. Adaptations also diverge based on locomotion: aquatic species like rely on a flexible, cartilaginous chondrocranium for and minimal structural demands, whereas terrestrial reptiles show enhanced for robust jaw support, contrasting with the mammalian emphasis on encephalization and orbital protection.

References

  1. https://www.ncbi.nlm.nih.gov/books/NBK544308/
  2. https://pressbooks-dev.oer.hawaii.edu/anatomyandphysiology/chapter/the-skull/
  3. https://teachmeanatomy.info/head/osteology/sphenoid-bone/
  4. https://www.kenhub.com/en/library/anatomy/the-sphenoid-bone
  5. https://radiopaedia.org/articles/greater-wing-of-sphenoid?lang=us
  6. https://teachmeanatomy.info/head/areas/cranial-fossa/middle/
  7. https://www.kenhub.com/en/library/anatomy/the-temporal-bone
  8. https://www.imaios.com/en/e-anatomy/anatomical-structures/greater-wing-129732
  9. https://www.kenhub.com/en/library/anatomy/the-skull-joints
  10. https://www.kenhub.com/en/library/anatomy/the-zygomatic-bone
  11. https://radiopaedia.org/articles/sphenofrontal-suture?lang=us
  12. https://thejns.org/pediatrics/view/journals/j-neurosurg-pediatr/26/2/article-p200.xml
  13. https://www.kenhub.com/en/library/anatomy/accessory-bones-of-the-skull
  14. https://www.ncbi.nlm.nih.gov/books/NBK526011/
  15. https://www.anatomystandard.com/ossa-et-juncturae/cranium/os-sphenoidale.html
  16. https://www.kenhub.com/en/library/anatomy/the-temporal-fossa
  17. https://www.elsevier.com/resources/anatomy/skeletal-system/axial-skeleton/temporal-surface-of-greater-wing-right/23334
  18. https://www.imaios.com/en/e-anatomy/anatomical-structures/orbital-surface-of-greater-wing-1536896772
  19. https://www.imaios.com/en/e-anatomy/anatomical-structures/infratemporal-surface-of-greater-wing-1536896652
  20. https://www.ncbi.nlm.nih.gov/books/NBK546621/
  21. https://radiopaedia.org/articles/foramen-rotundum
  22. https://pmc.ncbi.nlm.nih.gov/articles/PMC3616549/
  23. https://www.ncbi.nlm.nih.gov/books/NBK535432/
  24. https://pmc.ncbi.nlm.nih.gov/articles/PMC4378719/
  25. https://www.ncbi.nlm.nih.gov/books/NBK531490/
  26. https://www.ncbi.nlm.nih.gov/books/NBK513269/
  27. https://pmc.ncbi.nlm.nih.gov/articles/PMC8602018/
  28. https://www.sciencedirect.com/topics/medicine-and-dentistry/sphenoid
  29. https://vertebrate-zoology.arphahub.com/article/65934/
  30. https://pmc.ncbi.nlm.nih.gov/articles/PMC2847450/
  31. https://www.nature.com/articles/s41598-022-08972-w
  32. https://www.nature.com/articles/s41467-019-09197-8
  33. https://pmc.ncbi.nlm.nih.gov/articles/PMC3686507/
  34. https://pmc.ncbi.nlm.nih.gov/articles/PMC7987388/
  35. https://pubs.rsna.org/doi/full/10.1148/rg.210094
  36. https://www.ncbi.nlm.nih.gov/books/NBK549799/
  37. https://radiopaedia.org/articles/sphenomandibular-ligament?lang=us
  38. https://radiopaedia.org/articles/foramen-vesalii-1
  39. https://pmc.ncbi.nlm.nih.gov/articles/PMC3773063/
  40. https://ajronline.org/doi/10.2214/ajr.184.5.01841700
  41. https://radiologykey.com/skull-base-fractures-and-their-complications/
  42. https://www.researchgate.net/publication/14870974_Transsphenoid_basilar_skull_fracture_CT_patterns
  43. https://pmc.ncbi.nlm.nih.gov/articles/PMC5702760/
  44. https://geiselmed.dartmouth.edu/radiology/wp-content/uploads/sites/47/2019/04/Skull-base-fractures-and-their-complications-2014-Baugnon.pdf
  45. https://pmc.ncbi.nlm.nih.gov/articles/PMC7747570/
  46. https://onlinelibrary.wiley.com/doi/10.1111/joa.13790
  47. https://ajronline.org/doi/10.2214/ajr.178.3.1780717
  48. https://pubmed.ncbi.nlm.nih.gov/32114535/
  49. https://pmc.ncbi.nlm.nih.gov/articles/PMC12352960/
  50. https://europepmc.org/article/pmc/5524278
  51. https://pmc.ncbi.nlm.nih.gov/articles/PMC7959418/
  52. https://pubmed.ncbi.nlm.nih.gov/29317363/
  53. https://pmc.ncbi.nlm.nih.gov/articles/PMC12491361/
  54. https://www.miketaylor.org.uk/dino/out-of-copyright/Flower1885-osteology-of-the-mammalia.pdf
  55. https://pmc.ncbi.nlm.nih.gov/articles/PMC1231738/
  56. https://onlinelibrary.wiley.com/doi/10.1111/j.1469-185X.2007.00031.x
  57. https://elischolar.library.yale.edu/cgi/viewcontent.cgi?article=1086&context=peabody_museum_natural_history_postilla
  58. https://www.ajol.info/index.php/az/article/download/152990/142582/0
  59. https://en.wikisource.org/wiki/The_Osteology_of_the_Reptiles/Chapter_1
  60. https://frontiersinzoology.biomedcentral.com/articles/10.1186/s12983-021-00406-z
  61. https://www.pnas.org/doi/10.1073/pnas.2411138122
  62. https://journals.australian.museum/media/Uploads/Journals/17313/511_complete.pdf
  63. https://www.researchgate.net/publication/280972175_The_evolutionary_and_morphological_history_of_the_parasphenoid_bone_in_vertebrates
  64. https://pmc.ncbi.nlm.nih.gov/articles/PMC8299565/
Add your contribution
Related Hubs
User Avatar
No comments yet.