Occipital Crest Research Articles

Prevalence and Morphometry of Occipital Foramen in Dry Skulls and its Clinical Implications.

The occipital emissary foramen (OEF) located on the occipital bone transmits the occipital emissary vein, which connects the occipital vein to the confluence of cranial venous sinuses. The OEF varies in incidence, number, size, and location. Knowledge of this foramen is essential for carrying out suboccipital and transcondylar surgeries without clinical implications. Hence, the study was planned. The aim of the present study is to elaborate on incidence, location, and morphometry consisting of the number and size of this foramen in light of clinical bearing in the context of the Indian population. The study was carried out in the Department of Anatomy using 80 skulls of unknown age and sex. The occipital bone of the skull was observed for the incidence, number, size, and location of the occipital emissary vein and associated clinical implications were elaborated. The incidence of occipital foramen was 36.25% and detected in 29 skulls. All these occipital foramina were patent. The mean diameter of this foramen was 0.6mm. The most common location of these foramina was the left side of the foramen magnum, followed by the left side of the external occipital crest. The information about the incidence, number, size, and location of OEF is important to prevent catastrophic bleeding during surgery in the region of the occipital bone. The awareness of differential morphometry and morphology of occipital foramina is of great importance for neurosurgeons during suboccipital craniotomy and skull base surgeries, including far lateral and transcondylar approaches to access posterior cranial fossa for management of pathologies in the cranial cavity.

Comparative skull osteology of Amphisbaena arda and Amphisbaena vermicularis (Squamata: Amphisbaenidae).

The skull anatomy of amphisbaenians directly influences their capacity to burrow and is crucial for the study of their systematics, which ultimately contributes to our comprehension of their evolution and ecology. In this study, we employed three-dimensional X-ray computed tomography to provide a detailed description and comprehensive comparison of the skull anatomy of two amphisbaenian species with similar external morphology, Amphisbaena arda and Amphisbaena vermicularis. Our findings revealed some differences between the species, especially in the sagittal crest of the parietal bone, the ascendant process, and the transverse occipital crest of the occipital complex. We also found intraspecific variation within A. vermicularis, with some specimens displaying morphology that differed from their conspecifics but not from A. arda. The observed intraspecific variation within A. vermicularis cannot be attributed to soil features because all specimens came from the same locality. Specimen size and soil type may play a role in the observed differences between A. arda and A. vermicularis, as the single A. arda specimen is the largest of our sample and soil type and texture differ between the collection sites of the two species.

A Morphologic and Morphometric Study of the Vermian Fossa and Internal Occipital Crest in Adult Indian Human Skulls

Introduction: The inner surface of the squamous part of occipital bone shows a prominent internal occipital crest that descends and bifurcates close to foramen magnum to enclose a small depression called vermian fossa. It has been reported that the internal occipital crest and vermian fossa affect the dural venous sinuses close to it and influence the cerebrospinal fluid flow. Few studies have reported morphology the morphology and morphometric features of vermian fossa. There is a paucity of literature regarding the morphology and morphometry of the internal occipital crest. Hence, the present study evaluated the morphological and morphometric details of the vermian fossa and internal occipital crest. Objectives: To provide morphologic & morphometric data of the vermian fossa and internal occipital crest in the Indian population. Materials and Methods: This was a cross-sectional study, with a sample size of 64, carried out for a period of three months in the Department of Anatomy. The fossa's morphometric dimensions and the vermian fossa's different shapes observed were documented. The internal occipital crest was observed for shape & length. All data was tabulated, analyzed, and summarized using mean and standard deviation. Results: The vermian fossa was present in 56(82.35%) bones. The type 1 variety was observed in 48(70.6%), type 2 variety in 1 (1.1%) bone and type 3 - atypical variety in 10.3%. The mean length and width of the vermian fossa was 8.9 ±4.41 mm and 8.02±3.50 mm, respectively. The internal occipital crest was sharp in 37(54.4%) bones, rounded in 24(35.3%) bones and wide in 6(8.8%) bones and ill-defined in one bone. The mean length of the internal occipital crest from the internal occipital protuberance to the posterior margin of the foramen magnum was 4.16±0.56 cm. Conclusion: An accurate knowledge of morphology and morphometry of vermian fossa and internal occipital crest and their variations is of significance in diagnostic and therapeutic performance of clinicians and radiologists. Variations in normal anatomical features need to be explored. Hence, this is of importance to anatomists and morphologists. KEY WORDS: occipital crest, vermian fossa, morphology, morphometry, cerebellum.

External occipital protuberance classification with special reference to spine type and its clinical implications

This investigation aimed to study the types of external occipital protuberance (EOP) with special reference to Type 3 (spine type). Detailed information will be useful for clinicians to manage occipital headaches or issues related to the biomechanics of the neck and for accurate radiological interpretations. Thirty-one dry intact cadaveric skulls were studied for EOP classification. In Type III EOP cases, the size of EOP was noticed using different modalities and compared. The superior nuchal lines and external occipital crest were observed for their prominence and any variation. 42% of the skulls belong to Type 1, 51.5% to Type 2, and 6.5% to Type 3 EOP. Superior nuchal lines and external occipital crest were more prominent in Types 2 and 3 EOP. In Type 3 EOP cases, the mean length, width, and thickness of the spine as measured directly on the skull were 16.63mm; 20.1mm, and 7.82mm respectively, the same as radiograph findings. CT examination revealed the average volume as 0.95 cm3. Out of two Type 3 EOP cases, the spine with larger values for its size was having a lesser volume value in CT. Plain lateral radiography is a reliable method to measure the length and thickness of spinous EOP. However, more values of these parameters for morphometry of the EOP spine do not mean more volume of EOP and vice versa. Detailed information regarding the occurrence of occipital spur and its morphology will be of great importance to neurosurgeons, sports, physicians, emergency departments, and radiologists.

Congenital atlanto-occipital dislocation in a patient with Down syndrome: a case report

Down syndrome, also known as trisomy 21, is associated with congenital cervical spine abnormalities, including atlantoaxial instability with or without os odontoideum, atlanto-occipital instability, and hypoplasia of the atlas. Herein, we report a case of Down syndrome complicated by congenital atlanto-occipital dislocation. The patient presented with severe cervical myelopathy at 13 years of age after a 10-year follow-up. Radiography and computed tomography revealed os odontoideum protruding into the foramen magnum and congenital anterior atlanto-occipital dislocation. Additionally, a bifurcated internal occipital crest with a thinned central portion of the occipital bone was noted. Magnetic resonance imaging revealed kyphotic alignment of the spinal cord with severe compression at the foramen magnum level. As the neurological impairment was partially improved by halo vest immobilization, we performed in situ O-C2 fusion with an iliac autograft and decompression of the foramen magnum and posterior arch of C1. An improvement was observed immediately after surgery. Two years after surgery, radiography and computed tomography showed solid O-C2 segment fusion. The accumulation of similar cases is essential for determining the prognosis or optimal treatment for this rare congenital condition.

Comparative study of sex estimates in adult skulls using direct measurement and tomographic image reconstruction.

Sex estimation is an important procedure in forensic anthropology for human identification. The development of new technologies, such as three-dimensional computed tomography (CT), has provided excellent alternatives for this purpose. This study examined and compared a morphological method for sex estimation using two different approaches - direct measurement of physical structures and tomographic analysis using 3D images. A total of 111 skulls from the Museum of Human Anatomy at the University of São Paulo (MAH-USP) were used, (60 males and 51 females). All specimens were scanned by Philips Brilliance 64 CT scanner equipment and their corresponding images were reconstructed in three-dimensional (3D) models. The morphological characteristics of the skulls were analyzed by an observer who was blinded to the sex of the specimens. Five cranial structures were analyzed: external occipital crest, mastoid process, supraorbital margin, glabella, and mental eminence. The structures were scored 1 to 5 according to Buikstra and Ubelaker and validated by Walker. The success rates of the sex estimates obtained through direct measurement of the dry skulls ranged from 67.4% to 70.4% as compared to 60.2% to 68.1% for CT reconstruction. When analyzed separately, the maximum accuracy of the method was 68.33% in males and 88.24% in females in the physical analysis of structures. The glabella and mastoid process were the most effective structures to estimate sex through both techniques, respectively. Our results show that 3D CT images can be accurately used in the morphological analysis for sex estimation, representing a viable alternative in forensic anthropology.

Comparison of rostral spread of lumbosacral epidural volume calculated by body weight or length of the vertebral column in dogs

Introduction: Lumbosacral (LS) epidural volume can be based on body weight (BW) or length from the occipital crest to the sacrococcygeal space (LE), but calculated volumes can differ in dogs < 15 kg. We compared the rostral spread using CT imaging and responses to nociceptive stimulation.

Hyperostotic bones observed in the first record specimen of spotted sicklefish, Drepane punctata (Linnaeus, 1788), from the Gulf of Oman.

This is the first confirmed record of a 430 mm TL spotted sicklefish, Drepane punctata (Linnaeus, 1758), in the Gulf of Oman collected in August 2021. Here, we describe a hyperostotic deformity in the head, maxilla and premaxilla, dorsal fin, caudal fin rays, and neural and haemal spines of some vertebrae. In the head, the occipital and supraoccipital crests were swollen. Also, we compare morphometric and meristic data with other specimens from other geographic regions. Novel hyperostosis characteristics found for D. punctata are compared to previously documented instances.

Establishment of the gender of rabbits by craniometric and morphological features of the skull

Introduction. Sexual dimorphism in rabbits is poorly expressed, which creates a number of difficulties in determining the sex of the animal. The need to determine sex arises during forensic veterinary examination, archaeological and special morphological studies, as well as in the study of age and breed variability of animals using craniological material. This issue is especially relevant for veterinary and sanitary examination, since the sex of the animal can affect the quality of wool or the taste of meat, which affects the quality of the products obtained.Objects and methods. The objects of the study were skulls (n = 4) of Californian breed ofrabbits and skulls (n = 4) of Soviet chinchilla breed. The stages of the study were: the creation of 8 bone preparations by boiling them in water with the addition of bicarbonate of soda, bleaching in a 3% hydrogen peroxide solution, comparison and morphometry.Results. Based on the study, it is possible to identify craniological features characteristic of male and female rabbits: the angle of the lower jaw in males is thicker and more massive, has a more pronounced masticatory fossa; supraorbital processes of male rabbits are more branched and wide; the zygomatic process of the zygomatic bone has a thin elongated shape in females, and a wide oval in males; on the horizontal plate of the palatine bone of femalerabbits there is large number of holes; in males, the lattice opening resembles a cello in shape, and the pituitary gland resembles an oval; the occipito-sphenoid fusion in male rabbits is convex, and the occipital crest has a thickening. Thanks to the use of several breeds of rabbits in the experiment, it can be proved that these patterns relate to sex, and not to breed. The results of the study can be used to determine the sex of an animal by the skull or its fragments, which is important for forensic veterinary examination when using a craniological method for determining the sex of various animal species.

New Approach for Virtual Surgical Planning and Mandibular Reconstruction Utilizing the Occipital Crest as a Native Midline Landmark

Virtual surgical planning (VSP) using computer-aided design and manufacturing (CAD-CAM) has been reported to aid in craniofacial reconstruction. The reported improvements have been related mainly to operative performance, with limited evaluations of the position and function of the temporomandibular joint (TMJ). This study analyzed the radiographic details of postoperative outcomes of mandibular reconstruction related to the TMJ as well as the mandibular Gonion angles utilizing the external occipital crest of the cranial base as an alternative to the sagittal plane for mirror image purposes. The patient initially presented to us with massive disfigurement with a counter-clockwise rotation of the condyle bearing segment of the affected side apparently under the effect of the temporalis muscle with a limited mouth opening and deviation while opening. Post-operative (virtual planning) were analyzed to compare the condyle segment with the previous position as well as the angles of the mandible The virtual surgical planning utilizing the cranial base triangle gives a better position for both the condyle and the angle with a more symmetrical position and the condyle in more favorable position within the glenoid fossa. The external occipital crest is a native midline landmark that could be utilized as an alternative to the sagittal plane for a mirror image in mandibular reconstruction with all the hereditary errors that are sensitive to the position of the sagittal plane virtually. This case report shows a better condyle position with virtual surgical planning versus the traditional method of reconstruction.

Unexpected cranial sexual dimorphism in the tragulid Dorcatherium naui based on material from the middle to late Miocene localities of Eppelsheim and Hammerschmiede (Germany).

Tragulids, chevrotains or mouse deer, were common faunal elements during the Miocene. During that time, Dorcatherium was the most abundant genus, with D. naui being the first described species. Besides their abundance, until recently only very limited cranial material was available for investigation. Here we present a redescription of the first complete skull of D. naui from the middle to late Miocene locality of Eppelsheim, Germany, based on micro-computed tomography. Furthermore, we present a description and comparison of two additional, new skulls of D. naui from the late Miocene hominid locality Hammerschmiede, Germany. Within Dorcatherium, so far, only three other complete skulls are known, all belonging to D. crassum. A comparison between the three skulls of D. naui and the already known skulls of D. crassum shows that these two species differ in morphological features of the skull, such as laterally facing orbitae, separation of supraorbital foramen from supraorbital groove by a bony bridge, well-developed parietal plateau, prominent nuchal tubercle, less-developed nuchal crests, and the presence of an occipital crest. Moreover, two different osteological morphotypes are present in the skulls of D. naui that can be interpreted as a previously unknown sexual dimorphism. Very similar features are observed in D. crassum, which can be likewise related to the same dimorphism. However, males of D. naui differ from males of D. crassum by the presence of frontoparietal bulges, which were probably used for sexual display and during male-male combats in males of D. naui. For the first time, sexual dimorphism in Dorcatherium is described based on skull characteristics, which are, so far, unknown from any other fossil or extant tragulid.

Chiari malformation type I with internal occipital crest duplication: two surgical case reports

Chiari malformation type I with internal occipital crest duplication: two surgical case reports

Anatomy of the vertebral column, ribs and sternum in orange rumped agouti (Dasyprocta leporina Linnaeus, 1758): Structural and Functional perspectives.

The axial skeleton of orange rumped agouti, Dasyprocta leporina, was studied for better understanding of its locomotor behaviour. The bones from eight adult agoutis of both sexes were observed for their anatomical features and functional significance. The vertebral formula was found to be C7 T12 L7 S5 Cy5-6 . The well-developed occipital crest, caudally oriented prominent axis spine and well-developed transverse processes from C3 -C7 indicated a highly flexible neck with greater sagittal mobility. Articular facets were horizontal in anterior series while oblique in the posterior series, which enabled them to perform both lateral and sagittal movements during locomotion. The caudally directed thoracic spines, T12 as anticlinal vertebra and prominent mamillary process in the posterior series were suggestive of strong dorso-ventral flexion/extension and rotation. The robust lumbar vertebrae, well-developed transverse processes with cranio-ventral extension, were the feature for powerful sagittal/dorsoventral movement. The presence of spinous processes and well-developed transverse processes in all caudal vertebrae was an indication of a highly movable tail. The ribs were 13 pairs with first seven as sternal and six as asternal. They were laterally compressed in the anterior series as a cursorial adaptation. A strong muscular attachment to vertebrae provides this rodent speed, agility, dexterity and strength suitable for survival in food chain.

Investigation of a Novel Cranial Ligament Between the Occiput and Cervical Spinal Dura

Introduction The brain and spinal cord are covered by dura mater which attaches to bones and muscles in the cervical region. Dural connective structures have been described as the Ligamentum Craniale Durae Matrice Spinalis (LCDMS) (Von Lanz, 1929). The myodural bridge complex (MBC) is a component of the LCDMS linking suboccipital musculature to the cervical spinal dura. While performing en bloc dissections of the central nervous system, we found a novel connection between the occiput and the cervical spinal dura that has not been previously described that we have termed, the ligamentum kryptos craniale (LKC). In this study, we provide evidence that the LKC is a previously unrecognized component of the LCDMS. Methods A total of 13 cadavers were dissected. Total spinal laminectomy and en bloc dissection was performed on two cadavers, and the occiput was removed via a coronal cut with inferior borders meeting the lateral most aspect of the foramen magnum. Eleven different cadaver skulls were cut at the euryon in transverse section. Five of the 11 cadavers were hemisected to the level of C5. LKC Length from origin to opisthion, thicknesses at opisthion, length from opisthion to cervical dura, and width at opisthion were measured. All measurements were taken with Mitutoyo Absolute IP-67 digital calipers except for LKC width, in which a flexible ruler was used. Photograph evidence was also obtained, and statistical analysis was conducted using Microsoft Excel. Results The LKC was found in all bodies (13 specimens). Its shape was triangular as it exited the foramen magnum and inserted onto the cervical spinal dura (Fig. 1). Its origin spanned across the internal occipital crest, the inferior ridge of the cerebellar fossa, and the opisthion (Fig. 2). Various measurements of the LKCs were made (expressed as means + SD) including the length from origin to opisthion (1.94 ± 0.3 cm, N = 10), thickness at opisthion (0.58 ± 0.05 mm, N = 6), length from opisthion to cervical dura (10.51 ± 2.59 mm, N = 5) and width at opisthion (5.05 ± 0.44 cm, N = 10). Conclusion Based on the findings of this study, we believe the LKC is a novel component of the LCDMS. Data suggests the MBC attaches to the LKC rather than directly to the cervical spinal dura mater. In the clinical setting, the LKC may be relevant to unknown causes of head and neck pain. Future histological studies and microscopic analysis will be necessary to further categorize this structure. References von Lanz, T. (Jun 1929). Über die Rückenmarkshäute : I. Die Konstruktive Form der harten Haut des menschlichen Rückenmarkes und ihrer Bänder. 118, 252-307.

Specialized Position of the Horns, and Frontal and Parietal Bones in Bos taurus (Bovini, Artiodactyla), and Notes on the Evolution of Bos

We explored the unusual position, anatomy and evolutionary significance of the position of the horns in Bos taurus. In the genus Bos, the frontal bone, frontal sinus and parietal bones are shifted and repositioned. A new occipital (pseudo-occipital) crest forms at the edge of the calvaria. The true occipital crest has shifted to the back along with the parietal. The frontal sinus has overridden a parietal sinus. We compared this bone reorganization with the anatomy of deer (Dama and Odocoileus), a gazelle (Gazella dorcas) and a bovid (Eotragus clavatus) in which the bones are in the primitive positions. The fetal Bos has a fontanelle which is not seen in Gazella or Odocoileus. An evolutionary succession can be developed based on the backward shift of the frontal and horns in Bos taurus and other Bovini.

Cyto- and myeloarchitectural brain atlas of the pale spear-nosed bat (Phyllostomus discolor) in CT Aided Stereotaxic Coordinates

The pale spear-nosed bat Phyllostomus discolor, a microchiropteran bat, is well established as an animal model for research on the auditory system, echolocation and social communication of species-specific vocalizations. We have created a brain atlas of Phyllostomus discolor that provides high-quality histological material for identification of brain structures in reliable stereotaxic coordinates to strengthen neurobiological studies of this key species. The new atlas combines high-resolution images of frontal sections alternately stained for cell bodies (Nissl) and myelinated fibers (Gallyas) at 49 rostrocaudal levels, at intervals of 350 µm. To facilitate comparisons with other species, brain structures were named according to the widely accepted Paxinos nomenclature and previous neuroanatomical studies of other bat species. Outlines of auditory cortical fields, as defined in earlier studies, were mapped onto atlas sections and onto the brain surface, together with the architectonic subdivisions of the neocortex. X-ray computerized tomography (CT) of the bat’s head was used to establish the relationship between coordinates of brain structures and the skull. We used profile lines and the occipital crest as skull landmarks to line up skull and brain in standard atlas coordinates. An easily reproducible protocol allows sectioning of experimental brains in the standard frontal plane of the atlas. An electronic version of the atlas plates and supplementary material is available from https://doi.org/10.12751/g-node.8bbcxy

О морфологии лесной куницы (Martes martes) Верхнего Приобья

Over a period of about 30 years, a new population has appeared in the area of the pine marten. This grouping of species is formed by a natural expansion of animals from the adjacent territories of Novosibirsk region or Kazakhstan. The animal inhabited areas unusual for it: pine forests and adjacent birch-aspen woods in the plain forest-steppe of the south-eastern part of Altai Krai (See Fig. 1). The first marten traces were recorded in the mid-1980s near Shadrukha village in Uglovskiy district. The first animal was caught in 1988 in the vicinity of Novo-Uglovskoe village. In 2013, the first population counts were carried out revealing 383 martens. 2249 martens lived in the region in the spring 2019. The newly formed group is poorly studied in zoological terms, and we make an attempt to eliminate this omission. We studied the first representative pine marten hunting sample obtained in 2016- 2019 from the Altai ribbon pine forest population (Barnaul band, 52°42ꞌN and 82°10ꞌE). We applied the classical zoological techniques used during collecting the biological materials (incomplete anatomical autopsy, measuring animal body and its parts, preparation of craniological collection samples). The average popultion parameters of the marten grouping were obtained and studied: body length, tail length, baculum length, 17 craniometric traits for males and females (See Tables 1 and 2). The age of animals was determined by the method of Timofeev-Nadeev (1955) on the development of sagittal and occipital crests on the frontal and parietal bones of the skull. For all mean values, basic statistics was calculated (Х ± m х and CV). Differences were taken as statistically significant at the level of 5% (p < 0.05). Difference testing and cluster analysis of craniometric data (UPGMA, unweighted method of pairwise average) were carried out in Stat Soft STATISTICA 8.0 package. To assess sexual dimorphism, we used the I SD indicator proposed by Rossolimo and Pavlinov (1974): I SD = 100(X♂–X♀)/ X♀, where: ISD is the value (ISD index) of sexual dimorphism, expressed as a percentage; X♂ and X♀ are the mean values of traits for males and females, respectively. As a result of our research we established that the mean values of the studied morphological traits of adult martens from the Altai ribbon pine forest population are as follows: body length 43.95 mm, tail length 22.35 mm in males and 40.2 and 20.12 in females, respectively; the length of the baculum (8 males) 43.04 mm; condylobasal skull length 84.5 mm in males and 77.7 mm in females. The obtained data were compared with the characteristics of some of East and West European populations of the species, information about which was found in literary sources (See Tables 3 and 4). A cluster analysis of 17 populations by skull size showed (See Fig. 2) that Altai pine martens are classified into same cluster with large martens from the Caucasus and Lithuania, exceeding in size many of East European populations with a condylobasal skull length of less than 83.5 mm in males and 76.5 mm in females. At the same time, Altai pine martens are smaller in body and skull sizes than West European martens which have a condylobasal skull length of more than 85 mm in males and 78 mm in females, making up cluster A in the dendrogram of Fig. 2. We consider the question of the intraspecific taxonomic status of the new population without analyzing data on the color and other properties of the fur coat to be premature. The study of the indices of sexual dimorphism of the exterior (7.25-8.31%) and craniometric characteristics (8.11% on average for 17 traits and 8.77% for the condylobasal length of the skull) allows us to conclude that the animals of the new population do not show noticeable differences in this parameter from other groupings of the species range. A thirty-year old history and a continuous increasing in the number of the newly formed pine marten population in the east of the range allows to expect a further strengthening of this grouping. This will create the preconditions for the formation of new foci of sympatry in Altai Krai and in adjacent territories where the sable and pine marten will inhabit. The paper contains 2 Figures, 4 Tables and 29 References. The Authors declare no conflict of interest. No animal was caught for the purposes of this study. Animals were hunted by legal hunters using humane methods of catching

Vermian fossa or median occipital fossa revisited: Prevalence and clinical anatomy

IntroductionThe vermian fossa (VF11Vermian fossa) is a small midline depression at the inferior end of the internal occipital crest (IOC22Internal occipital crest) near the foramen magnum. This study aims to accurately define the usual arrangement (“the norm”) of the inferior end of the internal occipital crest, to determine the prevalence and dimensions of the VF in Central European population, and to state a possible correlation of the VF with anatomical variations and developmental abnormalities. Materials and methodsWe analyzed the prevalence of the VF in 1042 dry skulls. The variable anatomy was classified into either the VF (four categories) or norm. Some rare variations of this region were also encountered. ResultsThe norm was defined as a flat triangular prominence at the inferior end of the IOC, without any depression. As the most frequent arrangement, the norm appeared in 710 (68.14%) skulls. We observed the fossa in 309 (29.65%), type I in 264 (25.34%), type II in 45 (4.32%) and other rarer variations in 23 (2.21%), skulls, by our new classification system. ConclusionDespite many different variations can be encountered in the posterior cranial fossa, the proper definition of the usual arrangement at the inferior end of the IOC is still missing. The knowledge of such anatomical variations is essential to decrease the risk of the hemorrhage from dural venous sinuses during surgical approach. Based on prevalence, the underdeveloped posterior cerebellomedullary cistern may occur along with the VF, and their common occurrence seems probable to have a relationship to Chiari malformation type I. As for the terminology, the term median occipital fossa seems to be more appropriate.

An anatomical description of the vermian fossa: The reappraisal of an overlooked entity

Introduction: The vermian fossa (VF) is a shallow depression at the inferior end of the internal occipital crest, which lodges the inferior part of the cerebellar vermis. Published literature describes the VF as having a highly variable incidence and morphology. The present study is aimed to investigate the incidence, morphology, and morphometry of the VF within a select South African population and to conduct a review of the literature regarding this structure. Material and Methods: A total of 100 dry, adult skulls of South African origin were analyzed to determine the morphological and morphometric parameters of the VF. Results: The VF was found to be present in 62% of cases. The shape of the VF was classified as triangular (27%), quadrangular (8%), and atypical (27%). The average length of the VF was 13.78 mm, and the average width was 11.62 mm. The morphometric findings of this study correlate with that of previous studies; however, the incidence of atypical shaped VF (27%) is higher in comparison to previous studies (9.7%). Discussion and Conclusion: The detailed anatomical description of the VF may aid in the study of diseases which cause alterations in the size and morphology of the vermis of the cerebellum as well as in transvermian approaches to tumors within the fourth ventricle. Furthermore, due to the paucity of anatomical descriptions of the VF, a reappraisal of this structure is warranted as it is of prime importance to clinicians operating in or interpreting radiological images of the posterior cranial fossa.

A reassessment of the cranial morphology of Neoepiblema acreensis (Rodentia: Chinchilloidea), a Miocene rodent from South America.

The rodent Neoepiblema acreensis (Chinchilloidea: Neoepiblemidae) is member of a lineage that reached gigantic dimensions during the Late Miocene of South America-the Neoepiblemidae. In this paper, the cranial anatomy of this rodent is reviewed. Noninvasive imaging is used to reveal internal structures. Our review is based mainly on an almost complete cranium from the Upper Miocene deposits of the western Amazonia of Brazil. The cranium has an elongated rostrum, large frontal sinuses, a deep temporal fossa, well-developed sagittal, nuchal, medial occipital, and secondary crests, and a tympanic fenestra connected to the external acoustic meatus by a thin ventral cleft. Remarkably, the cranium shows the presence of fossae on the posterior region of the frontal and parietal bones, and a "W-shaped" fronto-parietal suture, which are not present in other analyzed chinchilloids. This study contributes to the knowledge of the morphology of this extinct rodent as well as to the phylogenetic relationships and paleobiology of neoepiblemids.