Skull Material Research Articles

Exploration of the dynamics of otic capsule and intracochlear pressure: Numerical insights with experimental validation.

The otic capsule and surrounding temporal bone exhibit complex 3D motion influenced by frequency and location of the bone conduction stimulus. The resultant correlation with the intracochlear pressure is not sufficiently understood, thus is the focus of this study, both experimentally and numerically. Experiments were conducted on six temporal bones from three cadaver heads, with BC hearing aid stimulation applied at the mastoid and classical BAHA locations across 0.1-20 kHz. Three-dimensional motions were measured on various skull regions, including the promontory and stapes. Intracochlear pressure was measured using a custom acoustic receiver. The experiment was digitally recreated by a custom finite element model (FEM), based on the LiUHead, with the addition of an auditory periphery. The Young's modulus of the cortical bone domain within the FEM was varied between 4, 8, and 20 GPa. The predicted differential intracochlear pressures aligned with experimental data for most frequencies, and showed that skull deformation, particularly in the otic capsule, depends on skull material properties. Both experimental and FEM results indicated that the otic capsule behaves as a rigid accelerometer, imposing inertial loads on cochlear fluids, even above 7 kHz. Future work should explore the solid-fluid interactions between the otic capsule and cochlear contents.

Digital skull anatomy of the Oligocene North American tortoise Stylemys nebrascensis with taxonomic comments on the species and comparisons with extant testudinids of the Gopherus–Manouria clade

The anatomy of North American tortoises is poorly understood, despite a rich fossil record from the Eocene and younger strata. Stylemys nebrascensis is a particularly noteworthy turtle in this regard, as hundreds of specimens are known from Oligocene deposits, and as this species is one of the earliest fossil turtles to have been described in the scientific literature. Since its initial description based on a shell, many specimens with more complete material have been referred to Stylemys nebrascensis. Here, we review and confirm the referral of an important historic specimen to Stylemys nebrascensis, which includes shell, non-shell postcranial, and skull material. This allows us to document unique skull features of Stylemys nebrascensis (e.g., an unusual ‘poststapedial canal’ that connects the posterior skull surface with the cavum acustico-jugulare) and to refer another well-preserved skull to the species. Based on computed-tomography scanning of these two skulls, we provide a detailed description of the cranial and mandibular osteology of Stylemys nebrascensis. Stylemys nebrascensis has a combination of plesiomorphic skull characteristics (e.g., retention of a medial jugal process) and derived traits shared with extant gopher tortoises (e.g., median premaxillary ridge) that suggest it may be a stem-representative of the gopher tortoise lineage. This supports the hypothesis that extant and fossil tortoises from North America form a geographically restricted clade that split from Asian relatives during the Paleogene.

Fast and accurate transcranial ultrasound simulation using the asymptotic model of the Civa Healthcare platform

To ensure its efficacy and safety, transcranial ultrasound therapy treatment planning requires accurate pressure field simulations and phase law corrections. Despite their long computation time and high memory usage, full numerical methods are often used since they are considered more accurate than semi-analytical methods. This work will present the so-called “pencil method“, a fast asymptotic model embedded in the CIVA HealthCare simulation platform. It allows computation in harmonic and impulse mode and the consideration of complex configurations, including solid obstacles, considering, at each interface, refractions and reflections with or without mode conversion of the acoustic field. This model was successfully compared to a recent collaborative work by Aubry et al. that presented a set of numerical benchmarks for transcranial propagation, to allow comparisons between various modeling tools. It was used to investigate the influence of parametric variation of skull material properties on the quality of acoustic focusing through the human skull. Its ability to predict the thermal rise at the intracranial target was validated against experimental data obtained ex-vivo through human skulls. Finally, works in progress will be shared about its connection to the open-source Kranion software developed at the FUS Foundation to facilitate comparison between clinical and simulated data.

Reappraisal of the first historical record of Aristonectes Cabrera, 1941 (Elasmosauridae, Aristonectinae) from the Upper Cretaceous of central Chile

This contribution reassesses the first historical specimen from the Upper Cretaceous of Chile, referred to the genus Aristonectes in the late sixties. A detailed description allows an improved understanding of those elements comprising the mandibular ramus. These are found to be coincident with those of the holotype of Aristonectes quiriquinensis, with only minor differences in size, which are explainable due to different ontogenetic stages of the specimens. Therefore, the re-studied material is now referred to as A. quiriquinensis, being the second available skull material of the species. The new description recognizes that the available elements belong to the right side of the skull. Moreover, the material also preserves part of the right orbit, a portion previously unknown in the available skulls of Aristonectes spp. The assessed orbit outline reveals the presence of the prefrontal, forming the anteroventral margin of the orbit. A similar topology is observed in other aristonectines such as Morturneria seymourensis and Kaiwhekea katiki, but also in the non-aristonectine austral elasmosaurid Tuarangisaurus keyesi. The orbit outline of Aristonectes quiriquinensis is here disclosed for the first time, showing this to be remarkably similar to that of Kaiwhekea, but probably differs from that of Aristonectes parvidens, at least based in their available skull elements. This suggests that A. quiriquinensis could be a more basal taxon with respect to A. parvidens.

A new fossil Squamata from the Quiricó Formation (Lower Cretaceous), Sanfranciscana Basin, Minas Gerais, Brazil

The Borioteiioidea (Polyglyphanodontia) is a group of lizards commonly found in Cretaceous Laurasian deposits and is considered as the sister group of Teiidae. While the Asian record comprises several well-preserved skulls and skeletons, other Laurasian occurrences are generally known from disarticulated skull material and isolated teeth. Additionally, the Gondwanan record is rare, with only one species described so far, Bicuspidon hogreli, from the Ifezouane Formation, Kem Kem Beds of Morocco. Given their wide geographic distribution, several biogeographic hypotheses were suggested to explain the temporal and spatial distribution of borioteiioids. In this study, we report the first record of a borioteiioid from the Lower Cretaceous of South America. The specimen was unearthed from Aptian deposits of the Quiricó Formation (Sanfranciscana Basin), Brazil, and consists of both anterior portions of dentaries. Among other characteristics, the material has transversally wide mid-posterior teeth with two distinct cusps (labial and lingual), as typically seen in species of the genus Bicuspidon. It also exhibits additional features, such first mental foramen facing anteriorly and the remaining ones forming a line in the lateral portion of the dentary, anterior symphyseal process extending from the anterior margin of the symphysis, and symphysis bearing an oval-shaped and thick process. These characteristics allowed us to erect a new species of Borioteiioidea, Cryptobicuspidon pachysymphysealis gen. et sp. nov. Cryptobicuspidon pachysymphysealis is one of the oldest records of Borioteiioidea known so far and suggests that Polyglyphanodontini borioteiioids originated in Gondwana with a posterior dispersal to North America and Europe during the Late Cretaceous.

Hwiccewyrm trispiculum gen. et sp. nov., a new leptopleuronine procolophonid from the Late Triassic of southwest England.

The fissure fill localities of southwest England and South Wales are well-known for preserving rich assemblages of predominantly small-bodied Late Triassic to Early Jurassic tetrapods, but many aspects of these assemblages remain contentious. The age of the Late Triassic fissures is disputed, with some lines of argument suggesting a latest Triassic (Rhaetian) age, whereas other evidence suggests they may be as old as Carnian. The fissures have been hypothesized by some workers to have formed on an archipelago, with island effects invoked to explain aspects of the assemblages such as the abundance of small-bodied species. Procolophonids were a successful group of Triassic parareptiles, best known from Early to early Late Triassic assemblages, but have only recently been described from one of the fissure fill sites (Ruthin) based upon fragmentary remains. Here, we describe new procolophonid specimens from another fissure (Cromhall) that represent at least six individuals of different sizes, with much of the skeleton represented including well-preserved skull material. The Cromhall procolophonid shows strong similarities to Late Triassic procolophonids from Scotland, Brazil and North America, but both autapomorphies and a unique character combination demonstrate that it represents a new species, which we name as Hwiccewyrm trispiculum gen. et sp. nov. Phylogenetic analysis places Hwiccewyrm in a derived clade within Leptopleuroninae, together with Leptopleuron, Hypsognathus, and Soturnia. The largest specimens of Hwiccewyrm demonstrate a body size that is similar to Leptopleuron and Hypsognathus, supporting other recent work that has questioned the insular dwarfism hypothesis for the fissure fill assemblages.

Jaw anatomy of Vegavis iaai (Clarke et al., 2005) from the Late Cretaceous Antarctica, and its phylogenetic implications

Vegavis iaai is without any doubt the most complete and well-known Mesozoic bird from Antarctica. In spite of being known by several specimens, its highly specialized postcranial anatomy has obscured the recognition of its phylogenetic affinities. Skull material from Vegavis is scarce, and the lower jaw is known by a relatively well-preserved articular region of a partially articulated specimen (MACN-PV 19.748). The aim of the present contribution is to describe this articular region and to analyze its potential phylogenetic information. The articular region of Vegavis shows a unique combination of characters that separates it from most Mesozoic lineages. On the contrary, its anatomy is congruent with that of neornithine birds, and particularly from the neoavian clade Aequorlitornithes. Detailed comparisons led to the recognition of several shared features, including a well-developed transverse crest posterior to the articular cotyles, that bears a well-developed lateral tubercle; a short and ventrally deflected retroarticular process; a dorsally exposed posterior fossa; tree cotyles for jaw articulation, with a well-developed caudal cotyle fused to the medial cotyle; and lateral crest anteriorly projected with respect to the lateral cotyle. The three-cotyle articulation of the jaw of Vegavis invited us to review skull anatomy of its close kin Polarornis. A review of the bones of Polarornis indicates that the element previously identified as a quadrate is an uncertain bone, and thus, skull-jaw articulation of this taxon remains unknown. In contrast with previous contributions, we were not able to find diagnostic features of the Galloanserae clade on Vegavis jaw. The neoavian-like jaw of Vegavis contrasts with the anseriform signature of its postcranium, suggesting that this bird held some kind of morphological mosaicism on its skeleton.

EARLY PLEISTOCENE SEROTINE BAT <i>EPTESICUS PRAEGLACIALIS</i> (VESPERTILIONIDAE, CHIROPTERA) FROM THE TAURIDA CAVE IN CRIMEA

The cranial and mandibular remains of a large serotine bat Eptesicus praeglacialis Kormos, 1930 are described from the Lower Pleistocene deposits of the Taurida cave in the central Crimea. This is the first finding of the skull material of E. praeglacialis and the first record of the species in Crimea. Judging by the tooth wear stages, the remains of both young and adult specimens are present in the taphocenosis. The small mammal tooth marks on the bones (caused by eating the remnants of soft tissues) in the absence of signs of digestion, characterizing materials from the predatory bird pellets, indicate that the taphocenosis includes the remains of E. praeglacialis individuals that used the cave as a shelter and died there. This corresponds to the idea of appearance of hibernation in caves as a climatically determined ecological adaptation in some European forest-dwelling bats (including Eptesicus) at the Pliocene–Pleistocene transition.

Cranial osteology, taxonomic reassessment, and phylogenetic relationships of the Early Cretaceous (Aptian-Albian) turtle Trinitichelys hiatti (Paracryptodira).

We describe the skull of the Early Cretaceous (Aptian-Albian) baenid turtle Trinitichelys hiatti using micro-computed tomography to provide new insights into the cranial anatomy of basal baenids and into the evolution of paracryptodires. We show that the validity of Trinitichelys hiatti vs Arundelemys dardeni still holds true, that the most basal known baenids for which skull material is known share an intriguing combination of features that are typical of either Pleurosternidae or Baenidae, and that the carotid system of Trinitichelys hiatti is intermediate to that of pleurosternids and more advanced baenids. Our expanded phylogenetic analysis confirms the traditional placement of Arundelemys dardeni, Lakotemys australodakotensis, and Trinitichelys hiatti as basal baenids, retrieves Helochelydridae along the stem of Baenoidea, but recovers Dinochelys whitei, Glyptops ornatus, Dorsetochelys typocardium, and Uluops uluops as basal branching Paracryptodira.

Revision of the oldest varanid, Saniwa orsmaelensis Dollo, 1923, from the earliest Eocene of northwest Europe

Saniwa is an extinct genus of varanid squamate from the Eocene of North America and Europe. Up to now, only one poorly known species, Saniwa orsmaelensis Dollo, 1923, has been reported from Europe. Diagnostic material was limited to vertebrae with only preliminary description and no figure provided, except of one dorsal vertebra that was designated as the lectotype. New specimens from the earliest Eocene of Dormaal, Belgium and Le Quesnoy, France, including recently recovered skull material, are described and illustrated here. These fossils representing the oldest varanid squamate allow further comparisons with the type species, Saniwa ensidens Leidy, 1870, from the early and middle Eocene of North America and to propose a new diagnosis for S. orsmaelensis. Its arrival in Europe is probably linked to rapid environmental changes around the Paleocene Eocene Thermal Maximum (PETM). The occurrence of S. orsmaelensis is restricted to the early Eocene of northwest Europe and paleogeographic considerations regarding the distribution of the genus Saniwa Leidy, 1870 suggest an Asian origin, but an African origin cannot be completely excluded.

Application of nanoindentation technology in testing the mechanical properties of skull materials

Three-point bending test, compression test and tensile test can detect the mechanical properties of the whole layer of skull, but cannot detect the mechanical properties of the inner plate, the diploe and the outer plate of the skull. In this study, nanoindentation technology was applied to detect mechanical properties of micro-materials of the skull, and differences in micro-mechanical properties of the inner, diploe and outer plates of the skull and cranial suture of human carcasses at different ages were analyzed. The differences in hardness (HIT) and modulus of elasticity (E) were statistically significant among different age groups (P < 0.01). In terms of structure, the E of diploe was higher than that of other structures, while HIT had no significant statistical difference. In terms of location, both HIT and E showed that left frontal (LF) was significantly higher than coronal suture (CS). The above results were consistent with the multi-factor ANOVAs. In addition, the multi-factor ANOVAs further explained the interaction of HIT and E with age, location and structure. It was believed that the nanoindentation technique could be used to analyze laws of micromechanical properties of different structures of human cadaveric skull and cranial suture.

New Skull Material of Taeniolabis taoensis (Multituberculata, Taeniolabididae) from the Early Paleocene (Danian) of the Denver Basin, Colorado.

Taeniolabis taoensis is an iconic multituberculate mammal of early Paleocene (Puercan 3) age from the Western Interior of North America. Here we report the discovery of significant new skull material (one nearly complete cranium, two partial crania, one nearly complete dentary) of T. taoensis in phosphatic concretions from the Corral Bluffs study area, Denver Formation (Danian portion), Denver Basin, Colorado. The new skull material provides the first record of the species from the Denver Basin, where the lowest in situ specimen occurs in river channel deposits ~730,000 years after the Cretaceous-Paleogene boundary, roughly coincident with the first appearance of legumes in the basin. The new material, in combination with several previously described and undescribed specimens from the Nacimiento Formation of the San Juan Basin, New Mexico, is the subject of detailed anatomical study, aided by micro-computed tomography. Our analyses reveal many previously unknown aspects of skull anatomy. Several regions (e.g., anterior portions of premaxilla, orbit, cranial roof, occiput) preserved in the Corral Bluffs specimens allow considerable revision of previous reconstructions of the external cranial morphology of T. taoensis. Similarly, anatomical details of the ascending process of the dentary are altered in light of the new material. Although details of internal cranial anatomy (e.g., nasal and endocranial cavities) are difficult to discern in the available specimens, we provide, based on UCMP 98083 and DMNH.EPV 95284, the best evidence to date for inner ear structure in a taeniolabidoid multituberculate. The cochlear canal of T. taoensis is elongate and gently curved and the vestibule is enlarged, although to a lesser degree than in Lambdopsalis.

Alvarezsaurid osteology: new data on cranial anatomy

ABSTRACT Alvarezsaurs were a group of theropod dinosaurs found in Asia, North America, South America and Europe during Jurassic and Cretaceous periods. In spite of being known by several specimens, diverse aspects of their anatomy remain poorly known. The aim of the present paper is to describe and analyse some points of the neuroanatomy of a newly collected alvarezsaurid specimen. A partial skeleton of an indeterminate Late Cretaceous alvarezsaurid theropod (HGM L08-59) from the collection of Henan Geological Museum in Zhengzhou, China, preserved a partial skull that allows to study some aspects of braincase anatomy. Anatomical features observed in HGM L08-59 and other alvarezsaurs indicate that members of this clade exhibited a notably enhanced somatosensory control during locomotion. The study of skull material of HGM L08-59 as well as that of other alvarezsaur skulls, sheds some doubts on the phylogenetic position of supposed Jurassic alvarezsaurs from China (i.e., Haplocheirus, Aorun and Shishugounykus). Further, some skull features of Haplocheirus are reminiscent to those of ornithomimosaurs and are dissimilar to alvarezsaurs. A comprehensive phylogenetic analysis will shed light on this complex topic that is highly relevant on discussions about early radiation of coelurosaurian theropods.

New skull material of Pleistocene dwarf deer from Crete (Greece)

In the Pleistocene faunas of the island of Crete, Cervidae was one of the most abundant taxa. Respective species vary in body size, including dwarfs, and skeletal morphology; however, the number of species and the identity of the mainland ancestor(s) are still debated. In this paper, we morphologically and morpho­metrically describe and analyze eight skulls of Cretan deer from a so far little known fossil site near Gerani, Rethymnon, Greece. The recorded character suite allows for affiliation to dwarfed Candiacervus Kuss, 1975, Candiacervus ropalophorus de Vos, 1984 and C. reumeri van der Geer, 2018. It comprises previously unknown unique traits, some of them hinting to sexual dimorphism. Comparisons of the Candiacervus skulls presented here with those of cervids belonging to Megalocerotini Brooke, 1828, s.s. and s.l. stress certain similarities; yet more material is needed to reconstruct Candiacervus’ phylo­genetic position. The newly detected craniodental specifics allow for more insights into island adaptation of Candiacervus; at the same time, they blur the morphological heritage of their mainland ancestors.

WAVE PROPAGATION IN THE CRANIUM AND THE CEREBROSPINAL FLUID

In this paper, wave propagation in head generated by a local axisymmetric impact on its outer surface is studied. The skull material is treated as isotropic and homogeneous, but presence of the cerebrospinal fluid (considered as a compressible but inviscid irrotational fluid) inside the cranium has been accounted for in the analysis. Some numerical results obtained on the basis of the analytical study, are also presented.

Dental health of Vikings from Kopparsvik on Gotland

AbstractThe prevalence, distribution, and location of dental caries were studied in complete and partial human dentitions dating from the Viking Age dating (900–1050 AD) excavated in Kopparsvik on island of Gotland, Sweden. 18 individuals and a total of 370 teeth were examined, using a strong light source and dental probe. Carious lesions were found in a large number of the individuals, 14 out of 18. The percentage of teeth affected by caries (11,9%) corresponds well with studied skull materials from the same period. The surface most susceptible to caries was the occlusal surface, whereas only a few proximal lesions and one single carious root surface was found. The tooth most commonly affected by caries was the mandibular first molar. The tooth most commonly missing ante‐mortem was also the mandibular molar, and the tooth most commonly missing post mortem was the mandibular incisor. Other findings included apical infections, which were detected clinically in 3% of the teeth.

New Primitive Caseid (Synapsida, Caseasauria) from the Early Permian of Germany

A new genus and species of a basal synapsid Caseidae, Martensius bromackerensis, is described based on four partial to nearly complete mostly articulated skeletons that provide a comprehensive knowledge of the skeletal morphology. All four specimens were collected from a single site, the Bromacker quarry, in the Lower Permian Artinskian Tambach Formation, Germany. The Bromacker caseid is the first to be reported from Germany and can be easily distinguished from all other caseids based on substantial lists of autapomorphic and plesiomorphic characters. Of the four caseid specimens only the smallest, a juvenile, and the largest, an adult designated as the holotype, are nearly complete, articulated, and possess skull material: in the juvenile a small partially articulated portion of the skull, and in the adult a nearly complete but dorsoventrally crushed skull. The two specimens are distinguished from one another by features attributed to different ontogenetic stages of development, which include skeletal ossification, proportional dimensions of elements, and most interestingly marginal dentitions. The last category includes a feature unique among caseids of an ontogenetic change in the dentition from insectivorous in the juvenile specimen to what is believed to be an omnivorous dentition in the adult.A phylogenetic analysis posits the Late Pennsylvanian Eocasea martiniReisz and Frobisch, 2014, as the basalmost member of the monophyletic Caseidae and the later occurring middle Early Permian Bromacker caseid as the sister taxon of the remaining late Early and Middle Permian members of the clade. This series of relationships parallels a proposed chronology of evolutionary changes in the dentitions and associated diets of caseids.

New Data on Morphometry and Appendicular Skeleton of South Indian Hedgehog Paraechinus nudiventris Horsfield, 1851 (Mammalia: Eulipotyphla: Erinaceidae) from Urban Landscapes of Tamil Nadu, India

The South Indian hedgehog (Paraechinus nudiventris) is a lesser known, highly exploited small mammal native to Tamil Nadu, Kerala and Andhra Pradesh in India. This species initially has a broader distribution history, due to ongoing threats, their population is decreased. Apart from distribution range the all other details such as ontology and morphology is still lacking. This study aims to investigate the skull and appendicular skeleton of P. nudiventris. Results revealed the head and body length of hedgehogs was measured as 140–200 mm, and their body weight ranges from 160 to 288 g. The male hedgehogs are larger in compared with females. The additional and more detailed data of the skull and skeletal material of Indian endemic mammal P. nudiventris (Madras hedgehog) would be useful towards its preservation and protection and disease’s management.

THE INFLUENCE OF BRAIN TISSUE MATERIAL PARAMETERS ON THE RESPONSE OF DYNAMIC CHARACTERISTICS BASED ON FINITE ELEMENT MODEL

Aiming at the uncertainty of material parameters of human brain tissue, the influence of tissue material performance sensitivity on frequency and mode shape under free vibration is studied. In this paper, the 50th percentile finite element (FE) model of human head and neck with detailed anatomical characteristics has been chosen as the research object, the parameters of skull, cerebrospinal fluid (CSF) and brain tissue materials with high sensitivity are analyzed by orthogonal test design and variance analysis. The results show that the natural frequencies of Group 7, Group 8 and Group 9 are all around 230[Formula: see text]Hz, which are basically consistent with the initial parameter of 229.18[Formula: see text]Hz, and the intracranial displacements of the three groups are also concentrated on the lateral nasal cartilage. The main reason is that the Young’s modulus of the skull used in three groups of experiments is 9780[Formula: see text]Mpa, which is close to the initial parameter of 8000[Formula: see text]Mpa. It indicates that the material parameter of the skull has the greatest influence on the dynamic characteristics of human head and neck, followed by the CSF and brain tissue. This study provides an effective method for vehicle safety and head and neck injury protection, and supplies a reference for FE analysis of head collision damage.

Skull Anatomy and Pneumaticity of the Enigmatic Coelurosaurian Theropod Bicentenaria argentina.

The enigmatic basal coelurosaur Bicentenaria argentina is a small theropod that comes from the Upper Cretaceous of Patagonia. It is constituted by more than 130 elements, including cranial remains. These are represented by an incomplete snout, palate, dermatocranium, and lower jaws still in articulation. The skull material of Bicentenaria was preliminarily studied by previous authors. In this study, we conducted a CT scan of the holotype of Bicentenaria, which allowed us to fully describe all preserved skull bones, including some previously unknown elements. The morphological analysis indicates that Bicentenaria shares many cranial features with other basal coelurosaurs as compsognathids, Ornitholestes, and tyrannosauroids. Otherwise, results of this analysis show that Bicentenaria exhibits a set of traits unique to this taxon. Furthermore, several pneumatic recesses were closely matched with those pneumatic features present in many derived coelurosaurs, particularly tyrannosauroids. This new information, together with future discoveries, will improve our knowledge about the muscular correlates of Bicentenaria and other coelurosaurs, and may shed light about the phylogenetic relationships of this group. Anat Rec, 2019. © 2019 American Association for Anatomy Anat Rec, 303:1884-1900, 2020. © 2019 American Association for Anatomy.