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Computational models serve as useful complements to physical experiments, but they require validation to build confidence in their applicability. This study outlines the validation of biomechanical models for mysticete sound reception, specifically using experiments involving an instrumented gray whale skull exposed to underwater sound. Detailed descriptions of the models are provided. The models were evaluated using a set of similarity metrics applied to both measured and computed frequency response functions. While high-quality agreement was not achieved, the models corresponded reasonably well with observed experimental data. A sensitivity analysis examined the models’ responses to variations in input material properties. Although these changes in material properties influenced model response, they accounted for only modest changes in similarity. A more significant challenge to achieving higher accuracy was the mismatch between the acoustic waves generated in experiments and the models’ assumption of plane wave loading. Despite this, the models successfully captured important biomechanical behavior, such as the enhancement of motion of the tympanic bullae relative to the basicranium. Model validation remains an ongoing endeavor, and this study represents an initial step.

The pars basilaris forms a central component of the immature basicranium and owing to its resilience to post-mortem and taphonomic changes, holds significance across evolutionary, clinical, and forensic contexts. While size and shape parameters of the pars basilaris have been investigated, little is known about the influence of the underlying bone mineral density on the morphometry of this bone during growth. This study aimed to investigate the development and growth of the pars basilaris with specific reference to changes in bone density patterning and development of osteological features, during the prenatal and early postnatal periods of life. A total of 109 pars basilari were sourced from the Johannesburg Forensic Paediatric Collection, University of the Witwatersrand, South Africa. The study sample was subdivided into early prenatal (<30 gestational weeks), prenatal (30–40 gestational weeks) and postnatal (birth to 7.5 months) groups and micro-CT scanned to assess bone mineral density patterns across seven regions of interest. Size and shape changes were analysed using 11 digitized landmarks and geometric morphometrics. When comparing across age groups, the assessed dimensions increased with growth manifesting as a deepening at the anterior border of the foramen magnum, development of the lateral angles and widening of the bone at the lateral projections and spheno-occipital synchondrosis. However, no significant changes in the distribution of bone mineral density were observed. An appreciation of morphological changes and bone quality at specific growth sites in the pars basilaris is essential when analyzing remains of unknown provenance for the purposes of identification in disaster victim settings. •Novel bone mineral density analysis of human pars basilari suggests uniform ossification during gestation and infancy.•Three-dimensional landmark data contributes to the understanding of global shape changes during gestation and infancy.•Statistically significant differences in the size of the pars basilaris supports previous findings from dry bone metrics.•Growth regions on the surface of the pars basilaris contributes to the forensic identification of unidentified individuals.

Caiuajara dobruskii is a tapejarid pterosaur from the Cretaceous of the ‘Cemitério dos Pterossauros’ (pterosaur graveyard) site, a unique pterosaur bonebed which is located at the municipality of Cruzeiro do Oeste (Paraná, Brazil). Preliminary inferences on Caiuajara morphology were founded on a few partial skeletons, with no detail on the skull anatomy. Here we describe a new specimen from the pterosaur graveyard site, which corresponds to the most complete skull of Caiuajara dobruskii known so far. Furthermore, we describe and compare other specimens including the holotype, a paratype, and several other undescribed specimens. The new specimen preserves the posterior portion of the skull, allowing a better comprehension of its morphology and provides an appreciation of the anatomic structures of the basicranium, enabling better interpretation of this region. We also described the lower jaw of Caiuajara , reporting a unique feature of its symphyseal which adds to the diagnosis for the species. A variability in the premaxillary crest is also noted in different specimens of Caiuajara , which might be interpreted as sexual dimorphism or ontogenetic variability. Therefore, those new findings allow a better comprehension of its skull and enables a more precise comparison between the skulls of those extinct flying reptiles.

Triassic cynodonts from South America are key taxa in the investigation of the emergence of mammalian characters. One of the most iconic species from the Carnian is Prozostrodon brasiliensis , found in Late Triassic strata from southern Brazil. This non-mammaliaform cynodont represents the earliest-diverging member of Prozostrodontia, a clade that encompasses Mammalia and their closest relatives. Previous descriptions of the skull of Pr. brasiliensis were based on specimens that did not preserve the posterior region, obscuring essential details of the basicranium. Here, we describe a new, complete, and exceptionally well-preserved skull of Pr . brasiliensis found in the same block as the holotype skeleton of the early predatory dinosaur Gnathovorax cabreirai and rhynchosaur specimens. Anatomical data from this specimen provide novel insights into the initial radiation of prozostrodontian cynodonts and reveal a new endemic clade of South American cynodonts – Prozostrodontidae – on the stem lineage of mammals. Graphical Abstract

Background The cranial base develops from multipotent mesenchymal cells through endochondral ossification. Genetic ablation of Sonic hedgehog ( Shh ) or Smoothened ( Smo ) leads to early apoptosis of cranial base cells, thus limiting the study of their role in the early development of cranial base. Our previous studies have shown that administration of 150 mg/kg Vismodegib (a Smo -specific small molecule antagonist) in E9.5- or E10.5-mice leads to premature mineralization of the skull base synchondroses. In the current study, we further investigated the molecular mechanisms underlying this model. Results Mice exposed to Vismodegib exhibit premature hypertrophic differentiation and osteogenesis of the cranial base synchondroses after E14.5. However, the expression of Patched1 ( Ptch1 ), Gli1 , parathyroid hormone-related protein ( PTHrP ), and Phh3 was not downregulated in exposure mice. We demonstrate that Shh and Wnt signaling pathways were activated in the cranial base region at E10.5. Administration of Vismodegib at E10.5 transiently inhibited Shh signaling in the cranial base area and caused upregulation of β-catenin expression along with ectopic expression of lymphoid enhancer-binding factor 1 ( Lef1 ) and Runx2 in the ventral mesenchymal cells of the cranial base primordium at E12.5. Diverse degrees of cranial base craniosynostosis induced by various doses of Vismodegib suggest a dose-dependent effect of Shh in early basicranium development. Conclusions The present experiment suggests that early activation of Shh standardizes normal embryonic development of cranial base after initial morphogenesis, which may be mediated through the “antagonistic” effect of Shh signaling on Wnt signaling. Our study provides new insights into the role of signal-crosstalk in early morphogenesis of the cranial base.

•990 interlandmark distances were mathematically derived using Pythagorean geometry.•Distances include non-traditional measures used to derive discriminant functions.•The functions represent five regions and are applicable to fragmentary remains.•Functions for fragmentary remains have accuracies ranging from 74.0% to 83.2%.•The function for global cranium achieved 88.2%, outperforming previous methods. The skull is the element most frequently presented to forensic anthropologists for analysis yet weathering, corpse maiming, and scavenger activity often result in damage and fragmentation. This fragmentation results in a reduction in the number of traditional calliper derived measurements that can be obtained and subjected to discriminant based analyses for sex estimation. In this investigation, we employed three-dimensional geometric morphometric methods to derive novel interlandmark distance measures across six regions of the cranium including the basicranium, basipalate, zygoma, orbits and the cranium globally to create functions to discriminate sex with high efficacy, even in the event of fragmentation. Forty-five homologous landmarks were digitised across each of 227 (114 males and 113 females) South African crania of European descent (white) sampled from the Raymond A Dart Collection of Human Skeletons, housed in the School of Anatomical Sciences, University of the Witwatersrand, South Africa. A total of 990 interlandmark distances (ILDs) were mathematically derived using Pythagorean geometry. These ILDs were then filtered by region and subjected to both direct and stepwise discriminant function analyses. Discriminant equations where derived for each region and achieved the following average cross-validated sex estimation accuracies: basicranium—74%; basipalate—80.2%; zygomatic—82.4; orbits—71.8%; nasomaxilla—83.7%; global cranium—88.2%. A large number of the ILDs used to derive the discriminant functions are novel, demonstrating the efficacy of geometric morphometric methods and illustrating the need to reassess old methods of data collection using modern methods to determine whether they best capture biological differences. The results of this study provide an invaluable contribution to forensic anthropology in South Africa as it provides an accurate, practical means of assessing sex using fragmentary material that may otherwise have been disregarded. These will undeniable aid in accurate sex estimation and ultimately, victim identification.

The quintessential state-of-the-art atlas on endoscopic approaches to the lateral skull base The endoscope has become a highly effective tool in the arsenal of ear and skull base surgeons. Endoscopic Lateral Skull Base Surgery: Principles, Anatomy, Approaches by endoscopic surgery masters Daniele Marchioni and Livio Presutti, reflects their development of innovative transcanalar approaches to the lateral cranial base using the external auditory canal as a surgical corridor. This unique atlas is designed to teach and clarify current and emerging endoscopic-assisted surgery approaches to the lateral skull base. The common goal of these cutting-edge procedures is to access and treat tumors located in the lateral cranial base via the most minimally-invasive endoscopic approach possible, thereby bypassing delicate cranial nerves, dural, cerebral, and vascular structures. Throughout 14 chapters, an impressive group of skull base surgeons share firsthand insights and expertise in areas vital to endoscopic skull base surgery.

Despite its importance for making biologically meaningful conclusions in geometric morphometric analyses, landmark error is inconsistently assessed. We evaluate a set of 30 landmarks designed to capture shape variation among six major brain regions on endocasts of Euarchontoglires (Primates, Scandentia, Dermoptera, Lagomorpha, Rodentia). Seven trials were performed by three observers on virtual endocasts of three species: Alouatta palliata (Primates), Ochotona pallasi (Lagomorpha), and Octodon degus (Rodentia). Standard deviation for all landmarks was evaluated relative to mean inter-landmark distance, centroid size, and centroid radius. A Procrustes analysis of variance (ANOVA) was performed to assess inter- and intraobserver error. Results show that standard deviations in landmark placement across trials, species, and observers are low (≤ 1.5%). The Procrustes ANOVA found significant differences between observers, accounting for only a small portion of the variation (R 2  = 0.002, p ≤ 0.0001); most of the variation is attributed to species (R 2  = 0.993, p ≤ 0.0001). In a separate analysis, a landmark sampling evaluation curve (LaSEC) which included two additional curve semilandmark sets along the sagittal aspect of the neocortex and cerebellum was applied to 40 landmarked species spanning all five orders of Euarchontoglires. The LaSEC indicated that 99% of the variation is captured at by 30 landmarks. Morphological patterns previously thought to characterize these groups are replicated in a principal component analysis of landmark data for 40 species. Specifically, most variation relates to the relative scale of the neocortex and olfactory bulbs and the flexion of the basicranium. Overall, these landmarks are highly replicable and able to represent morphological patterns within a diverse group such as Euarchontoglires.

Assessments of whether closely related species should be classified into more than one genus have been a longstanding source of controversy in primatology. For example, researchers hold differing opinions about whether cebine species should be classified into one or two genera. In this study, we investigated whether craniofacial shape is a reliable taxonomic indicator among cebines and statistically evaluated whether the magnitude of craniofacial shape differences observed among gracile and robust capuchin species is consistent with a two-genus taxonomic framework. We quantify craniofacial shape using 3D landmark data taken from 72 surface models, representing five cebine species (Cebus albifrons, C. capucinus, C. olivaceus, C. (Sapajus) libidinosus, and C. (S.) macrocephalus). We find that although statistically significant shape differences exist between gracile and robust capuchins in all four craniofacial regions investigated (face and palate, basicranium, calvarium, and frontal region of the calvarium), the magnitude of shape differences between species pairs does not support gracile and robust species being classified into separate genera. The shape of the frontal region of the calvarium and the face and palate show the highest magnitude of shape differences between the gracile and robust capuchin groups, and both regions are good taxonomic predictors, showing correct classification rates of 97% and 96%, respectively. At the species-level, face and palate shape is the only craniofacial measure that consistently shows high classification rates among species (84-97% for combined-sex analyses). Our findings suggest that robust capuchin species that are often assigned to Sapajus may be more appropriately considered as Cebus under a single-genus framework for cebines based on craniofacial shape evidence.

Several groups of stem cryptodires became adapted to coastal marine environments as early as the Late Jurassic, 40 million years before the Pan-Chelonioidea. The Plesiochelyidae are a major component of this first radiation of crown-group turtles into marine habitats. They are abundant in many European localities, but their systematics is still greatly confused. Only three species are represented by cranial material: Plesiochelys etalloni, Plesiochelys planiceps, and Portlandemys mcdowelli. In the present study, we describe a cranium and a mandible from the Kimmeridgian of Porrentruy (Switzerland), which we refer to a new species, Portlandemys gracilis n. sp. This new taxon differs from Portlandemys mcdowelli in several aspects of the cranium and mandible, notably in being generally more gracile, but the two species share a narrow skull, a more acute angle between the labial ridges on the mandible, and a unique configuration of the anterodorsal part of the basicranium. The cranial anatomy of plesiochelyid turtles is discussed in details based primarily on these new specimens and new cranial material of Plesiochelys etalloni from Solothurn, Switzerland. Several characters (e.g., the contribution of the parietal to the foramen nervi trigemini, the configuration of the dorsum sellae and sella turcica, the presence of an infolding ridge on the posterior surface of the quadrate) appear as potential candidates to help elucidate plesiochelyid relationships. Some of these characters are included in a previously published phylogenetic dataset and help to stabilize the relationships of plesiochelyid turtles and closely related taxa. For the first time, our results suggest that plesiochelyids, 'Thalassemys' moseri, and Solnhofia parsonsi (representing the Eurysternidae) form a clade at the base of Eucryptodira.