Skulls Research Articles

Is cranial anatomy indicative of fossoriality? A case study of the mammaliaform Hadrocodium wui.

Determining the ecology of fossil species presents considerable challenges due to the often fragmentary preservation of specimens. The mammaliaform Hadrocodium wui from the Jurassic of China is known only from the cranium and mandible but may have had a fossorial lifestyle. It shares morphological similarities with talpid moles and soricid shrews and is closely related to other fossorial mammaliaforms. However, the lack of postcranial elements has so far precluded a definitive assessment regarding its fossorial behavior. Using a combination of geometric morphometric analysis of the lower mandible and finite element analyses of the cranium, comparisons between H. wui and extant groups are made. H. wui resembles talpid moles more closely than shrews in mandible shape. However, there are more similarities between H. wui and semi-fossorial/semi-aquatic moles than fully fossorial moles. The skull of H. wui is particularly weak in every tested biomechanical scenario when compared to the related mammaliaform Morganucodon oehleri and talpid moles. This weakness is potentially a result of the reduction in thickness of the zygomatic arch. In contrast, the shrew crania show similar stress magnitudes and distribution. These results imply that H. wui was not fully fossorial and fed on a diet of softer invertebrates. Skull morphology may therefore not be sufficient to infer fossoriality in forelimb-digging species.

Computational simulation of cranial soft tissue expansion on the cranium during early postnatal growth in humans.

The importance of interactions between neighbouring rapidly growing tissues of the head during development is recognised, yet this competition for space remains incompletely understood. The developing structures likely interact through a variety of mechanisms, including directly genetically programmed growth, and are mediated via physiological signalling that can be triggered by structural interactions. In this study, we aimed to investigate a different but related potential mechanism, that of simple mechanical plastic deformation of neighbouring structures of the head in response to soft tissue expansion during human postnatal ontogeny. We use computational modelling and normative real-world data to evaluate the potential for mechanical deformation to predict early postnatal cranial shape changes in humans. We test some aspects of the spatial packing hypothesis applied to the growing brain and masticatory muscles, and their effects on the cranium, with a particular focus on the basicranium and face. A simple finite element model of an early postnatal human cranium, brain and masticatory muscles was created from CT and MRI. Growth of the brain and muscles was simulated using a tissue expansion material. The effect of the expanding soft tissues on the cranium was assessed using geometric morphometrics, comparing the baseline model to simulation results, and also to normative cranial shape data collected from neonatal MRI (0-4 months of age). Findings revealed that cranial shape changes present in the normative sample were consistent with cranial base flexion and were largely allometric (size-linked). Simulation of brain expansion produced broadly similar shape changes of the basicranium with most growth occurring in the cranial vault, while masticatory muscle expansion produced smaller and more widespread changes throughout the cranium. When simulated together, expansion of the masticatory muscles exerted a constraining effect on the results of brain expansion. Our findings that the simple growth simulations were able to mimic biological growth suggest that the relationship between regions of the developing head may be partly structural within the first few months of postnatal ontogeny in humans.

Measurement and Analysis of Optical Transmission Characteristics of the Human Skull.

The brain, as a vital part of central nervous system, receives approximately 25% of body's blood supply, making accurate monitoring of cerebral blood flow essential. While fNIRS is widely used for measuring brain physiology, complex tissue structure affects light intensity, spot size, and detection accuracy. Many studies rely on simulations with limited experimental validation. In this study, we used real adult skulls and agar to create a mimic model, building a transmission optical system with 13 wavelength filters and varying agar thicknesses. Peak intensity of transmitted light and size of scattered spot were measured at different wavelengths, and transmittance, total attenuation coefficient, and spot diameter enlargement of cranial mimics at different wavelengths were obtained. Results showed wavelengths below 550 nm struggled to penetrate the skull, while those above 700 nm penetrated deeper and diffused more. This suggests that short wavelengths capture epidermal PPG signals, whereas longer wavelengths detect both epidermal and intracranial signals.

A comparative study of experimental and simulated ultrasound beam propagation through cranial bones

Objective.Transcranial ultrasound is used in a variety of treatments, including neuromodulation, opening the blood-brain barrier, and high intensity focused ultrasound therapies. To ensure safety and efficacy of these treatments, numerical simulations of the ultrasound field within the brain are used for treatment planning and evaluation. This study investigates the accuracy of numerical modelling of the propagation of focused ultrasound through cranial bones.Approach.Holograms of acoustic fields after propagation through four human skull specimens were measured for frequencies ranging from 270 kHz to 1 MHz, using both quasi-continuous and pulsed modes. The open-source k-Wave toolbox was employed for simulations, using an equivalent-source hologram and a uniform bowl source with parameters that best matched the measured free-field pressure distribution.Main results.The average absolute error in k-Wave simulations with sound speed and density derived from CT scans compared to measurements was 15% for the spatial-peak acoustic pressure amplitude, 2.7 mm for the position of the focus, and 35% for the focal volume. Optimised uniform bowl sources achieved calculation accuracy comparable to that of the hologram sources.Significance.This method is demonstrated as a suitable tool for prediction of focal position, size and overall distribution of transcranial ultrasound fields. The accuracy of the shape and position of the focal region demonstrate the suitability of the sound speed and density mapping used here. However, large errors in pressure amplitude and transmission loss in some individual cases show that alternative methods for mapping individual skull attenuation are needed and the possibility of considerable errors in pressure amplitude should be taken into account when planning focused ultrasound studies or interventions in the human brain, and appropriate safety margins should be used.

Morphometric Analysis of Accessory Palatine Canals in Human Dry Skulls: Clinical Implications for Maxillofacial Surgery

Morphometric Analysis of Accessory Palatine Canals in Human Dry Skulls: Clinical Implications for Maxillofacial Surgery

Quantitative Neuroanatomical Measurement on Photogrammetric Model: Validation Study.

To examine and compare the accuracy of measurements obtained from photogrammetric models versus direct measurements taken on dry skulls, with the aim to verify the feasibility of photogrammetry for quantitative analysis in microsurgical neuroanatomy. Two dry human skulls were used. Each was scanned using the dual camera system of a smartphone The selected photos were separately processed using 2 different softwares to create three-dimensional models. Subsequently, 41 anatomical measurements (both linear and curvilinear) based on common anatomical landmarks were taken both directly on dry skulls and on photogrammetric models and compared. Analyzed factors included measurement error, intrarater and interrater reliability, and intermodality agreement. Four photogrammetric models were created. Analysis revealed similar errors when comparing photogrammetric and direct measurements. Measurements from digital models exhibited robust reliability among repeated measures and different observers, supported by very high intraclass correlation coefficient values. Mean measurement difference between Agisoft Metashape software-generated models and direct measurement was 0.01 cm with no systematic bias observed. Conversely, the Metascan app-derived models showed a mean measurement difference of-0.35 cm compared with direct measurement, displaying good agreement for smaller measurements and a systematic proportional bias with increasing measurement size. Two photogrammetric models were validated as quantitative analysis techniques for laboratory neuroanatomical studies, showing acceptable measurement error, high intrarater and interrater reliability, and good to very good agreement compared with direct measurement on dry skulls, replacing expensive and time-consuming methods such as computed tomography scans and neuronavigation systems.

Soft Metalens for Broadband Ultrasonic Focusing through Aberration Layers

Aberration layers (AL) often present significant energy transmission barriers in microwave engineering, electromagnetic waves, and medical ultrasound. However, achieving broadband ultrasonic focusing through aberration layers like the human skull using conventional materials such as metals and elastomers has proven challenging. In this study, we introduce an inverse phase encoding method employing tunable soft metalens to penetrate heterogeneous aberration layers. Through the application of effective-medium theory, we determined the refractive index of micro-tungsten particles in silicone elastomer, closely aligning with experimental findings. The soft metalens allows for transmission across broadband frequencies (50 kHz to 0.4 MHz) through 3D-printed human skull models mimicking aberration layers. In ex vivo transcranial ultrasound tests, we observed a 9.3 dB intensity enhancement at the focal point compared to results obtained using an unfocused transducer. By integrating soft materials, metamaterials, and gradient refractive index, the soft metalens presents future opportunities for advancing next-generation soft devices in deep-brain stimulation, non-destructive evaluation, and high-resolution ultrasound imaging.

Cranial osteology and neuroanatomy of the late Permian reptile Milleropsis pricei and implications for early reptile evolution.

Millerettidae are a group of superficially lizard-like Permian stem reptiles originally hypothesized as relevant to the ancestry of the reptile crown group, and particularly to lepidosaurs and archosaurs. Since the advent of cladistics, millerettids have typically been considered to be more distant relatives of crown reptiles as the earliest-diverging parareptiles and therefore outside of 'Eureptilia'. Despite this cladistic consensus, some conspicuous features of millerettid anatomy invite reconsideration of their relationships. We provide a detailed description of the late Permian millerettid Milleropsis pricei using synchrotron X-ray phase-contrast micro-computed tomography focusing on the cranial anatomy of three individuals known from a burrow aggregation. Our data reveal a suite of neuroanatomical features Milleropsis shares with neodiapsids that are absent both in other 'parareptiles' and in early diverging groups of 'eureptiles'. Traits shared between Milleropsis and neodiapsids include: the presence of a tympanic emargination on the quadrate, quadratojugal and squamosal, the loss of epipterygoid contribution to the basicranial articulation suggesting a more kinetic palatoquadrate, the absence of a sphenethmoid and the pathway of the abducens nerve through the braincase. Our findings suggest that the early reptile neurocranium, a region poorly sampled in phylogenetic analyses due to relative visual inaccessibility and poor preservation, has the potential to inform the phylogenetic relationships of early reptiles.

Cross-species characterization of transcranial ultrasound propagation.

Transcranial ultrasound stimulation (TUS) has shown promising prospects as a non-invasive neuromodulation technique for both animals and humans. However, ultrasonic propagation characteristics within the brain differ significantly from those in free space. There is currently a lack of comprehensive studies on the effects of skull thickness on focal point position, full width at half maximum (FWHM), and acoustic intensity. This study investigates the transcranial acoustic field characteristics of 500kHz focused ultrasound, with a focus on the impact of skull thickness. The study combined finite element simulations to evaluate the effects of skull thickness on 500kHz focused ultrasound with experimental investigations across multiple species (mouse, rat, pig, and human). The simulation and experimental results indicate that the skull changes focal length (-4.4-4.7mm) and axial focal region (-7.93-7.59mm), and the skull causes significant attenuation of acoustic intensity, which increases with skull thickness. The attenuation rate of human skulls is greater than 80%. We found that the skull thickness has little effect on focal point position (<0.9mm) and focal region (<1.44mm) in lateral and vertical directions. Skull thickness has great influence on focal length, axial focal region and acoustic intensity, but has little effect on focal point position and focal region in lateral and vertical directions. And improving axial spatial resolution is a potential method to reduce changes of axial focal region.

Cranial anatomy and holotype reconstruction of the Late Cretaceous turtle, Australobaena chilensis from the Quiriquina Formation, Chile

Resolving the phylogeny of fossil turtles is uniquely challenging given the high potential for the unification of convergent lineages due to systematic homoplasy. Equivocal reconstructions of turtle evolution and biogeographic or palaeo-climatic data with phylogenetic hypotheses and new images of the holotype reconstructions of fossil turtles are important for prehistoric turtle fossil remains. Here we describe the cranial anatomy and holotype reconstruction of the Late Cretaceous turtle, Australobaena chilensis from the Quiriquina Formation of the Maastricht Ocean Horizon Chile, which was identified as a new genus and species of Baenidae (an extinct family of para-cryptodiran turtles) in 2002 by Karl and Tichy. The holotype is “SMF R 415”, a partially destroyed skull without a lower jaw, and with a unique cranial plane. This taxon belongs to Baenidae, an extinct freshwater family from the Cretaceous period in North America. This is the first baenid fossil found outside of North America, and we re-describe and reconstruct it with new photographs and illustrations of the cranial anatomy of this material (Holotype).

Morphological assessment of mandible: Way to effective anaesthesia

The biggest bone in the human skull, the mandible shapes the inferior third of the face and forms the lower jawline. The inferior alveolar nerve and vessels enter the mandibular canal through the mandibular foramen, which punctures the internal surface of the ramus. It is located at the level of the occlusal surfaces of the lower teeth, midway between the anterior and posterior borders of the ramus, and ends at the mental foramen. Most people have a single mandibular canal, while there are some variations in shape (oval, round, or pear-shaped) and whether an accessory canal can be distinguished (canal bifurcation). Failure of inferior alveolar nerve block (IANB) anesthesia can be attributed to these anatomical variables as well as operator technique. The anesthetic solution is administered as near to the mandibular foramen as feasible by adhering to the landmarks. Repeated injections of the local anesthetic solution in children due to IANB failure can be a tiresome task since they may cause the kid to behave negatively and there is a chance that the solution will be administered in excess of the safe suggested dosage. Data regarding the shifting position of the mandibular foramen from childhood to puberty is lacking in the literature. In light of this, this research was carried out to evaluate, using radiographic techniques, how the mandibular foramen's locations change as a kid grows and develops from childhood to adolescent.

Intracranial Anatomy of Oxyodontherium Zeballosi (Litopterna, Macraucheniidae) from the Río Quinto Formation, San Luis Province, Argentina

ABSTRACT Utilising segmental data of MHIN-UNSL-GEO-V 465, we extend and re-evaluate previous observations on the morphology of the macraucheniid Oxyodontherium zeballosi comparing with additional micro and medical CT evidence from published data on Litopterna and other South American Native Ungulates (SANU). This new anatomical information includes qualitative and quantitative data on cranial pneumatization, nasal and encephalic cavities, and body mass estimates. The calculated Encephalization Quotients for MHIN-UNSL-GEO-V 465 range between 0.32 and 0.43, which are relatively low compared to other macraucheniids. The neopallial height ratio indicates a less expanded neopallial surface than in Huayqueriana and other Miocene SANU, and a higher ratio than several early ungulates. Our data reveal that O. zeballosi shares characteristics with the protolipternid cf. Miguelsoria parayirunhor, such as a shallow rostral tympanic process and a bulkier pars canalicularis of the inner ear. Although O. zeballosi shows less pneumatic spaces than other macraucheniids, it does show an important degree of pneumatization in the anterior portion of the caudal cranium, especially affecting frontals, parietals, and the alisphenoid. Finally, the estimated body mass of O. zeballosi is around 122–180 kg. This study increases the knowledge of the internal cranial anatomy of litopterns providing potentially valuable characters for future phylogenetic analyses.

Sex Estimation Through Orbital Measurements: A Machine Learning Approach for Forensic Science.

Sex estimation has been extensively investigated due to its importance for forensic science. Several anatomical structures of the human body have been used for this process. The human skull has important landmarks that can serve as reliable sex estimation predictors. In this study, orbital measurements from 92 dried skulls, comprising 35 males and 57 females, were utilized to develop a machine-learning-based classifier for sex estimation with potential applications in forensic science. The parameters evaluated included optic foramen height (OFH), optic foramen width (OFW), optic canal height (OCH), optic canal width (OCW), intraorbital distance (IOD), extraorbital distance (EOD), orbit height (OH), and orbit width (OW). A Random Forest classifier was employed to analyze the data, achieving an overall test accuracy of 0.68. The model demonstrated a precision of 0.65, indicating a moderate level of false positives. The recall was 0.70, reflecting that 70% of the positive cases were correctly identified. The F1 score was calculated at 0.675, suggesting a balanced performance between precision and recall. The area under the curve (ROC AUC) score was also 0.72, indicating that the model can distinguish between classes. The most important features in the best subset were OW (0.2429), IOD (0.2059), EOD (0.1927), OFH (0.1798), and OFW (0.1787), highlighting their significant contributions to the model's predictions. These findings suggest that orbital measurements could potentially serve as reliable predictors for automated sex estimation, contributing to advancements in forensic identification techniques.

Morphometric Analysis of the Greater Palatine Foramina in the Bosnia and Herzegovina Population.

The goal of this research was to examine the morphological characteristics and exact anatomical positioning of the greater palatine foramen (GPF), with reference to nearby anatomical landmarks. The research was performed on dry human skulls belonging to the Bosnian and Herzegovina population, using digital vernier calipers. The study began by noting the GPF's position relative to the maxillary molars, then measuring its distance from the median palatine suture (MPS), the incisive fossa (IF), the posterior border of the hard palate (PBHP), and the posterior nasal spine (PNS). Measurements were conducted bilaterally, and afterwards the data were analyzed using Student's t-test and Chi-squared test. A statistical significance was set at P<0.05. The statistical analysis revealed that: the distance of the greater palatine foramen (GPF) from the midline is approximately 15.80±1.28 mm on the right side and 15.86±1.19 mm on the left side. The distance of the GPF from the incisive fossa measures about 40.12±2.19 mm on the right side and 40.34±2.08 mm on the left side. The GPF is positioned around 4.00±1.07 mm on the right side and 4.35±1.34 mm on the left side from the posterior border of the hard palate. Lastly, the distance from the GPF to the posterior nasal spine means 17.55±1.99 mm on the right side and 17.61±1.81 mm on the left side in the entire study population. The highest percentage of skulls (73.05%) showed the GPF positioned at the level of the third molar. The findings of this study further emphasize the variations in the location of the greater palatine foramen and underline the importance of thorough preoperative assessment in patients undergoing maxillofacial surgeries and regional block anesthesia.

Sex estimation techniques based on skulls in forensic anthropology: A scoping review.

Sex estimation is an essential topic in the field of individual identification in forensic anthropology. Recent studies have investigated a growing range of techniques for estimating sex from human skulls. This study aims to provide a scoping review of the literature on techniques used in skull-based sex estimation, serving as a valuable reference for researchers. The literature search was performed using PubMed, Scopus, and Web of Science from January 2020 to February 2024. Eligible studies have investigated issues of interest to forensic anthropology about sex estimation using skull samples. A total of 73 studies met the inclusion criteria and were categorized and analyzed based on the anatomic sites, modalities, trait types, and models. Their accuracy in estimating sex was subsequently examined, and the results were charted. Our review highlights that the 3D medical imaging technique has enhanced the efficiency and stability of skull-based sex estimation. It is anticipated that advancements in 3D imaging and computer vision techniques will facilitate further breakthroughs in this field of research.

Accuracy of augmented reality navigated surgery for placement of zygomatic implants: a human cadaver study.

Placement of zygomatic implants in the most optimal prosthetic position is considered challenging due to limited bone mass of the zygoma, limited visibility, length of the drilling path and proximity to critical anatomical structures. Augmented reality (AR) navigation can eliminate some of the disadvantages of surgical guides and conventional surgical navigation, while potentially improving accuracy. In this human cadaver study, we evaluated a developed AR navigation approach for placement of zygomatic implants after total maxillectomy. The developed AR navigation interface connects a commercial navigation system with the Microsoft HoloLens. AR navigated surgery was performed to place 20 zygomatic implants using five human cadaver skulls after total maxillectomy. To determine accuracy, postoperative scans were virtually matched with preoperative three-dimensional virtual surgical planning, and distances in mm from entry-exit points and angular deviations were calculated as outcome measures. Results were compared with a previously conducted study in which zygomatic implants were positioned with 3D printed surgical guides. The mean entry point deviation was 2.43 ± 1.33 mm and a 3D angle deviation of 5.80 ± 4.12° (range 1.39-19.16°). The mean exit point deviation was 3.28 mm (±2.17). The abutment height deviation was on average 2.20 ± 1.35 mm. The accuracy of the abutment in the occlusal plane was 4.13 ± 2.53 mm. Surgical guides perform significantly better for the entry-point (P = 0.012) and 3D angle (P = 0.05); however, there is no significant difference in accuracy for the exit-point (P = 0.143) when using 3D printed drill guides or AR navigated surgery. Despite the higher precision of surgical guides, AR navigation demonstrated acceptable accuracy, with potential for improvement and specialized applications. The study highlights the feasibility of AR navigation for zygomatic implant placement, offering an alternative to conventional methods.

Morphometrics of human skulls and mandibles obtained from Southwestern Nigeria: implications in clinical manoeuvres

BackgroundCraniometric data can be useful in the estimation of sex, age, stature, and ethnicity. Despite Nigeria’s diverse and multifaceted demography, there is a dearth of information on detailed morphometry of specific features of the Nigerian cranium. This study sought to provide detailed descriptions of various dimensions on the Nigerian mandibular bone, nose, foramen magnum, and orbit for use in clinico-anatomical studies, dentistry, anthropology, and forensic medicine. Using 33 skulls and 17 mandibles, without gender bias, obtained from the departmental museum, 17 parameters were measured linearly on each mandible and thirty-six parameters on each skull using a digital Vernier calliper. Mean and standard deviation of data sets generated were analysed using t-test at p < 0.05.ResultsThe distance between the cranial and caudal angles of the mandible was 3.48 ± 0.21 mm. The distance from the rostral point of the dental bone to the condylar, coronoid, and angular processes was 4.86 ± 0.25 mm, 2.64 ± 0.52 mm, and 3.72 ± 0.30 mm, respectively. The distance between the most medial points of the most rostral left & right mental foramina in the skulls was 4.51 ± 0.17 mm. The distance between the most medial points of the most rostral left & right mental foramina in the skulls was 4.51 ± 0.17 mm. Most orbit skull types were megaseme in nearly 61%, and orbital asymmetry was also observed. However, the right orbit (26.07 ± 2.106) was significantly higher (p < 0.0001) than left orbit (24.80 ± 1.850). The most common shape of the foramen magnum was the oval-like foramen (78%). The common nose types were platyrrhine in 50% and mesorrhine in 26%.ConclusionInsights from this study might provide practical reference information for mandibular and orbital reconstructive surgeries in clinical settings, skull classification in forensic science, and research purposes.

Development and Assessment of a High-Fidelity Simulator for the Microsurgical Dissection of the Sylvian Fissure

BackgroundThe dissection of the Sylvian fissure (SF) is a crucial technique requiring considerable expertise and skills traditionally acquired through years of experience. The continous decline in surgical case-load necessitates the development of efficient alternative training opportunities. However, building a realistic and effective training simulator for the microsurgical dissection of the SF as an integral part of the neurosurgical curriculum, remains a challenging endeavor. This work aims to develop and evaluate a high-fidelity phantom simulator for effective and transferable training of the SF dissection with a focus on middle cerebral artery aneurysm clipping. MethodsA phantom simulator replicating the anatomy and tactile properties of the human skull, brain and meninges was developed incorporating additive manufacturing, neurosurgical expertise, and tissue engineering. Neurosurgical residents and experienced vascular neurosurgeons (n = 16) tested and rated the simulator’s face and content validities and answered questions on the model’s educational usefulness. ResultsThe resulting Sylvian fissure model is anatomically and haptically faithful, reusable and modifiable. The simulator overwhelmingly received positive ratings in face and content validity, with mean scores of 4.8 and 4.7 out of 5, respectively. Neurosurgeons deemed the simulator as highly accurate in respect to anatomical and tactile accuracy. Neurosurgical residents and neurosurgeons rated the simulator as superior in comparison to traditional teaching and training mehtods. ConclusionsThe presented methodology demonstrates that the development and assessment of a high-fidelity hands-on simulator for the focused training of one of the most delicate neurosurgical procedures is achievable in a timely manner and without extensive investments.

Fracture mechanics properties of human cranial bone

The mechanical properties of the human skull have been examined and established previously in the literature, for example, the transversal isotropy of cranial bone and properties including the Elastic modulus and Poisson's ratio. However, despite the existing data, there are still mechanical properties which remain to be determined for the human skull. The present study aims to characterise the fracture properties of human cranial bone within the Linear Elastic Fracture Mechanics (LEFM) framework. Unembalmed human (2 female and 3 male) cortical cranial bone samples were harvested from the frontal, and left and right parietal bones and were tested in Mode I (N = 124), Mode II (N = 31) and Mixed-Mode I-II (N = 47) loading conditions. For Mode I, samples were tested using Single Edge Notched Beams (SENB) under symmetric 3-point bending, while for Mixed-Mode I-II samples were tested under asymmetric 3-point bending. For Mode II, 4-point bend tests were carried out. All samples fractured in a brittle fashion. From these tests, reference values of stress intensity factor (KI and KII) and the strain energy release rate (JI, GI, GII, GI-II) for the frontal, left and right parietal bones were calculated. It was determined that the fracture toughness of the frontal, and left and right parietal bones are not statistically different from each other and that they exhibit symmetry about the sagittal plane. It was also demonstrated that, as is the case for other human bones and for the age range tested here, the fracture toughness of human cranial bone is lower for females (KIfemale 2.48 (±2.16) MPa∗m0.5, KImale 4.75 (±2.58) MPa∗m0.5, GIfemale 1.07 (±3.01) kJ/m2, GImale 1.85 (±1.93) kJ/m2, JIfemale 1.57 (1.89) kJ/m2 and JImale 4.03 (±3.32) kJ/m2) and varies with age. More experimental work should be carried out to confirm the extrapolation of these conclusions to the other fracture modes tested here.Although these results are influenced by the age range and the age gap within the group of donors, the primary data presented here is valuable to those wishing to predict crack evolution and propagation in the human cranial bone and may prove useful in developing failure criterion or simulations of skull fracture using Finite Element Analysis.

Taphonomic Approach to the Interpretation of Isolated Human Skulls: Distinguishing Natural from Intentional Deposition

The human cranium is probably the most common single anatomical element manipulated after the death of the individual. However, it is not uncommon to find isolated crania for which it is difficult to unequivocally determine the nature of the deposition, either intentional or natural. In order to establish whether naturally deposited and intentionally deposited skulls are characterised by different taphonomic patterns, we evaluated the state of preservation of 75 isolated crania (68 naturally deposited and 7 intentionally deposited) from sites in Africa, Europe, Near East and Asia, from approximately 2 million to 20,000 years BP. As a comparative reference, we evaluated the preservation pattern of further 101 skulls from individuals buried in primary deposition at two cemeteries. Finally, to determine whether the breakage pattern of skull-cups (skulls intentionally modified and manufactured into bowls) mimics a natural skull breakage, we analysed the preservation pattern of 19 skull-cups from archaeological and ethnographic contexts. Preservation and breakage patterns were evaluated using the Zonation method and the Landmark method. Results suggest that the intentionally deposited skulls have a pattern of preservation similar to the skulls found in cemeteries, and for both these categories, skulls were generally better preserved than naturally deposited skulls. The natural breakage pattern of isolated skulls also significantly differs from the breakage pattern of skulls modified into skull-cups, suggesting that it is unlikely that skull-cups were fashioned in a manner that imitates natural breakage patterns.