Skull Shape Research Articles

Using linear measurements to diagnose the ecological habitat of Spinosaurus.

Much of the ecological discourse surrounding the polarising theropod Spinosaurus has centred on qualitative discussions. Using a quantitative multivariate data analytical approach on size-adjusted linear measurements of the skull, we examine patterns in skull shape across a range of sauropsid clades and three ecological realms (terrestrial, semi-aquatic, and aquatic). We utilise cluster analyses to identify emergent properties of the data which associate properties of skull shape with ecological realm occupancy. Results revealed terrestrial ecologies to be significantly distinct from both semi- and fully aquatic ecologies, the latter two were not significantly different. Spinosaurids (including Spinosaurus) plotted away from theropods in morphospace and close to both marine taxa and wading birds. The position of nares and the degree of rostral elongation had the greatest effect on categorisation. Comparisons of supervised (k-means) and unsupervised clustering demonstrated categorising taxa into three groups (ecological realms) was inappropriate and suggested instead that cluster division is based on morphological adaptations to feeding on aquatic versus terrestrial food items. The relative position of the nares in longirostrine taxa is associated with which skull bones are elongated. Rostral elongation is observed by either elongating the maxilla and the premaxilla or by elongating the maxilla only. This results in the nares positioned towards the orbits or towards the anterior end of the rostrum respectively, with implications on available feeding methods. Spinosaurids, especially Spinosaurus, show elongation in the maxilla-premaxilla complex, achieving similar functional outcomes to elongation of the premaxilla seen in birds, particularly large-bodied piscivorous taxa. Such a skull construction would bolster "stand-and-wait" predation of aquatic prey to a greater extent than serving other proposed feeding methods.

Cranial sutures.

Cranial sutures are not of great concern to the modern neurosurgeon, except when abnormalities interfere with the skull's shape and its ability to expand during childhood. It is a commonplace that a craniotomy may cross a variety of sutures without providing any extra difficulty to the operator. The sagittal suture does remain useful as a definition of the midline of the cranium and as an indicator of the underlying sinus. Galen for reasons that are far from clear, "observed" relationships between the sutures, the meninges and the pericranium which led him to advise avoidance of any surgical proximity to the sutures. The result of this proscription was a severe limit of the access surgeons considered was appropriate and thus limited their ability to care for their patients.

Skull Part Relationships and Shape Prediction Toward the Missing Part Completion

Skull Part Relationships and Shape Prediction Toward the Missing Part Completion

A Comprehensive Review of Chromosome 7, Partial Monosomy 7p Syndrome

Partial monosomy syndrome of chromosome 7p is a rare chromosomal disorder characterized by the deletion (monosomy) of part of the short arm (p) of chromosome number 7 (7p). Associated symptoms and findings may be variable and may depend on the size and specific location of the 7p deleted segment. However, in many cases, there is premature closure of the fibrous joints (cranial sutures) between some of the bones of the skull (craniosynostosis), leading to an abnormal head shape. For example, depending on the specific sutures involved, the forehead may appear unusually “triangular” (trigonocephaly) or the head may appear abnormally long and narrow with a pointed or conical point (toriscephaly). Partial monosomy syndrome of chromosome 7p is also usually characterized by premature closure of one or more fibrous joints (cranial sutures) between certain bones in the skull (craniosynostosis), potentially leading to a deformed skull and abnormal head shape. In people with partial monosomy syndrome of chromosome 7p, there is a deletion (monosomy) of part of the short arm (p) of chromosome number 7. Based on reports in the medical literature, there is considerable variability in the size and location of the 7p deleted segment, potentially affecting the range and severity of symptoms and associated findings. Reported cases include variable “distal” deletions that extend to the terminal band (eg, from 7p13-pter to 7p21,p22-pter) and various “interstitial” deletions (eg, from 7p13 or 7p15 to 7p21).

3D printing for Growth Adaptive Medical Devices: an alternative approach for craniosynostosis

An adaptive medical device is a piece of equipment designed to adjust or respond to changes in a patient’s condition or environment. The use of 3D printing technology for the development of adaptive medical devices has opened up new possibilities for customization, efficiency, and accessibility in healthcare. Sagittal craniosynostosis is a birth defect that arises due to a premature fusion of the sagittal suture in infants. This disease causes a misshapen skull and a rise of intracranial pressure that can lead to cognitive impairments. At six months of age, the preferred technique for craniosynostosis is an open vault remodeling surgery, an extremely invasive procedure with severe blood loss for the patient and significant postoperative pain. In this context, growth adaptive cranial plates, that can be tuned depending on the patient to achieve the desired skull shape through the deformation of the structure, can be a valid alternative. Cellular and lattice structures offer tailorable mechanical properties in relation to the designed geometry. Specifically, the geometry of cellular materials can be modified in relation to the final mechanical requirements. In this study, the predictability of the deformation of a PLA structure composed by honeycomb unit cells was studied performing compression simulations. The geometry was then modified, simulations and compression tests were then repeated in order to find an equation that could describe the relation between the internal angle of the honeycomb and the relative Poisson ratio. This relation can be further exploited for the production of customized adaptive devices for the treatment of sagittal craniosynostosis.

Apert Syndrome: A Case Report

Background: Apert syndrome is a type 1 acrocephalosyndactyly, a rare syndrome characterized by the presence of multiple craniosynostoses, dysmorphic facial manifestations, and syndactyly of hand and feet. It affects 1:100.00 of birth and is the second most common of syndromic craniosynostosis. Molecular genetic tests that identify the heterozygous pathogenic variant in FGFR2 genes - identical with Apert syndrome cost too high to be applicable in developing countries. Therefore, the diagnosis of Apert syndrome should be suspected from the clinical findings. Three cases from the Community of Indonesian Apert Warrior Group were collected. These series were based on medical and surgical records. We obtained the patient characteristics from the phenotypic manifestations only. Case report: We present a case of a newborn baby girl, with similar anatomical findings, such as skull shape abnormality, midface hypoplasia, intraoral disfigurement, and hands and feet deformities that resemble Apert Syndrome. Our series presents similar Apert syndrome characteristics, such as typical craniofacial dysmorphic with symmetrical syndactyly of both upper and lower extremities. These clinical findings are essential to establish an initial diagnosis of Apert Syndrome.

Peculiarities of the parietal bones of the vault of the human skull structure and shape, taking into account sex and craniotype

The development of neurosurgery and the increase in requirements for the performance of surgical approaches performed through the bones of the skull vault lead to the formation of new requests for detailing and clarification of the craniometric characteristics of the parietal bones. The purpose of our study is to establish the features of the shape and other spatial indicators of the parietal bones of the skull of a mature person, taking into account sex and certain types of craniotype. The study was conducted on 130 studied preparations of bone structures of the head of adults from the collected collection of the Department of Normal Anatomy of the Kharkiv National Medical University, in the amount of 82 bone preparations, including isolated parietal bones, as well as 48 tomograms obtained during the examination of patients. The basis for establishing a craniotype is the principle of calculating the cranial index. For statistical analysis, we used the programs Statistica 13.5.0.17 (trial version) and Microsoft Excel of the corporate package MS 365. To establish the peculiarities of the structure and shape of the parietal bones, the following craniometric indicators were determined: the length and width of the parietal tubers, the parietal chord and the arch, calculated the curvature index of the parietal bone. The obtained data were analyzed for mature people of different genders and three established craniotypes. It has been established that brachycephals are characterized by an expanded and expanded form of the parietal bones, which is associated with the predominance of the transverse dimensions of the entire cerebral skull. For mesocephals, the most typical intermediate- average form depending on the values of the cranial index. Dolichocephals have an elongated and narrowed form of the parietal bones, which is combined with general changes in the cerebral skull. Additional linear parameters of the parietal bones are directly dependent on the established craniotype. The dolichocephalic type is characterized by maximum length values of parietal tubers: ¯x =18.43 mm (right) and ¯x =18.24 mm (left) with minimum width parameters: up to ¯x =15.71 mm and ¯x =15.02 mm. Representatives of the brachycranic type are characterized by the minimum indicators of the length of the parietal tubers: from ¯x =12.73 mm to ¯x =12.81 mm and the maximum indicators for the width - ¯x =23.52 mm (right) and ¯x =23.04 mm (left). The parietal chord, like the parietal arch, had a similar trend in the distribution of indicators, namely: an increase from dolichocrania to brachycrania. In men with a dolichocephalic type of skull structure, the average values of these parameters were at the level of ¯x =108.2 mm (right) and 107.6 mm (left) for the parietal chord, and ¯x =114.2 mm and ¯x =113.2 mm for the parietal arcs In men with brachycranic type, the parietal chord reached - ¯x =116.6 mm (right) and ¯x =115.8 mm (left), and the parietal arch reached - ¯x =127.8 mm (right) and ¯x =126.9 mm ( left). In women, a similar principle of size distribution has been established, taking into account a small, 2-3 mm, general decrease in indicators compared to men. The curvature index of the parietal bones was determined: the maximum average values ¯x =83.00-83.58 were obtained in dolichocephals, the minimum values were ¯x =80.56-81.64 in brachycephals. This indicates an increase in the curvature of bones in brachycephals, given that the absolute value of the index is inversely proportional to the degree of curvature. Thus, the obtained data indicate a stable relationship between the craniotype of the skull and additional parameters of the parietal bones.

Skull shape and size changes in different subpopulations of the California Sea Lion (Zalophus californianus) in Mexico

Abstract California sea lions (Zalophus californianus) are distributed along the Gulf of California and northeastern Pacific coast. Genetic studies have suggested the existence of 3 to 4 subpopulations in Mexico—1 on the Pacific coast of the Baja California peninsula (PC) and 3 in the Gulf of California—but the extent of this divergence is unclear, and it remains unknown if these subpopulations are morphologically distinct. In this context, we analyzed variation in skull size and shape of adult males between 5 and 13 years of age among 2 (north and central) of the 3 subpopulations of Z. californianus from the Gulf of California and the PC in Mexico. However, since the sample sizes for the 2 subpopulations in the Gulf of California were small, we merged all samples into 1 that we called the Gulf of California (GC) subpopulation. Artificial neural networks and geometric morphometrics were used to analyze skull images to quantify the extent to which these geographically separated subpopulations are undergoing morphological divergence. Our results find no significant differences in size in any view between the 2 subpopulations, but significant differences in the morphology of the dorsal, ventral, and lateral views of the skull between the 2 subpopulations. Overall, Z. californianus from the GC subpopulation have wider and lower skulls, extended back and outward with a more voluminous (bulky) nuchal crest, and narrow rostrum in comparison with skulls of Z. californianus from the PC subpopulation. Results concur with a previous genetic-based study, demonstrating that Z. californianus from both subpopulations in Mexico are diverging in their skull morphology and perhaps suggesting that they are experiencing different evolutionary pressures.

Spring-assisted posterior vault expansion: a parametric study to improve the intracranial volume increase prediction

Spring-assisted posterior vault expansion has been adopted at the London Great Ormond Street Hospital for Children to treat raised intracranial pressure in patients affected by syndromic craniosynostosis, a congenital calvarial anomaly causing the premature fusion of skull sutures. This procedure involves elastic distractors used to dynamically reshape the skull and increase the intracranial volume (ICV). In this study, we developed and validated a patient-specific model able to predict the ICV increase and carried out a parametric study to investigate the effect of surgical parameters on that final volume. Pre- and post-operative computed tomography data relative to 18 patients were processed to extract simplified patient-specific skull shape, replicate surgical cuts, and simulate spring expansion. A parametric study was performed to quantify each parameter’s impact on the surgical outcome: for each patient, the osteotomy location was varied in a pre-defined range; local sensitivity of the predicted ICV to each parameter was analysed and compared. Results showed that the finite element model performed well in terms of post-operative ICV prediction and allowed for parametric optimization of surgical cuts. The study indicates how to optimize the ICV increase according to the type of procedure and provides indication on the most robust surgical strategy.

Evaluation, treatment, complications, and prognosis of craniosynostosis

Craniosynostosis is a congenital craniofacial anomaly that typically presents at birth and affects the skull's shape. It is characterized by the premature fusion of one or more cranial sutures in infants, which can impair brain development and function. While craniosynostosis is considered rare, it has a global prevalence of around three to six cases in 10,000 live births. This review article aims to synthesize the latest developments in diagnostic techniques, treatment strategies, and potential complications for the benefit of healthcare providers, researchers, and affected families. This review commenced on 31 October 2023, following a thorough examination of existing literature. Diverse databases, including PubMed, Web of Science, and Cochrane, were utilized for the literature review. Early diagnosis and evaluation involve a multidisciplinary approach, including clinical assessments, medical history reviews, and advanced imaging techniques like computed tomography (CT) scans and magnetic resonance imaging (MRI). Surgical intervention is the primary treatment option, with the goal of releasing or reshaping the fused sutures to allow for normal skull growth. While open surgical procedures like suturectomy have been prevalent, less invasive methods like minimally invasive endoscopic strip craniectomy are becoming more popular due to reduced complications. Untreated craniosynostosis can lead to complications such as increased intracranial pressure, developmental delays, vision and hearing problems, and psychosocial impacts, emphasizing the importance of timely intervention. However, surgical treatments carry their own risks, necessitating a well-planned and individualized approach. Overall, the prognosis for craniosynostosis is generally positive, and factors such as the specific type of craniosynostosis, the timing of treatment, and the quality of post-operative care all influence outcomes. Prenatal diagnosis and multidisciplinary care have emerged as valuable tools for improving prognosis.

Artificial intelligence-based forensic sex determination of East Asian cadavers from skull morphology

Identification of unknown cadavers is an important task for forensic scientists. Forensic scientists attempt to identify skeletal remains based on factors including age, sex, and dental treatment remains. Forensic scientists commonly consider skull or pelvic shape to evaluate the sex; however, these evaluations require sufficient experience and knowledge and lack objectivity and reproducibility. To ensure objectivity and reproducibility for sex evaluation, we applied a gated attention-based multiple-instance learning model to three-dimensional (3D) skull images reconstructed from postmortem head computed tomography scans. We preprocessed the images, trained with 864 training data, validated the model with 124 validation data, and evaluated the performance of our model in terms of accuracy with 246 test data. Furthermore, three forensic scientists evaluated the 3D skull images, and their performances were compared with those of the model. Our model showed an accuracy of 0.93, which was higher than that of the forensic scientists. Our model primarily focused on the entire skull owing to visualization but focused less on the areas often investigated by forensic scientists. In summary, our model may serve as a supportive tool to identify cadaver sex based on skull shape. Further studies are required to improve the model’s performance.

Carrion converging: Skull shape predicts feeding ecology in vultures

AbstractThe link between skull shape and dietary ecology in birds at macroevolutionary scales has recently been called into question by analyses of 3D shape that reveal that cranial anatomy is mainly influenced by other factors such as allometry. It is still unknown whether this form‐function disconnect also exists at smaller evolutionary scales, for example within specialized ecological guilds. Vultures are a diverse guild of 23 extant species in two families (Accipitridae and Cathartidae) that exhibit evolutionary convergence as a result of highly specialized feeding ecology. Vultures are the only known obligate scavengers among vertebrates and are usually grouped together under this single dietary category, but within this specialized diet there are three distinct, species‐specific feeding strategies termed ripper, gulper, and scrapper. We use three‐dimensional geometric morphometrics to quantify the relative contributions of feeding ecology, allometry, and phylogeny on vulture skull shape, along with several non‐vulture raptors of similar size, range and ecology. Families show clear separation in shape, but phylogenetic signal is comparatively weak (Kmult = 0.33). Taking into account the influence of phylogeny, skull shape is not significantly correlated with either skull size or feeding type, but there are examples of strong, significant convergence and parallel shape evolution across feeding groups. Furthermore, skull shape performs strongly in predicting feeding ecology in a phylogenetic discriminant function analysis. These findings highlight the importance of detailed assessment of feeding behavior in studies of ecomorphology, rather than broader dietary categories alone, and reveal that ecology can be readily inferred from form given appropriate information.

Sparse convolutional neural network for high-resolution skull shape completion and shape super-resolution

Traditional convolutional neural network (CNN) methods rely on dense tensors, which makes them suboptimal for spatially sparse data. In this paper, we propose a CNN model based on sparse tensors for efficient processing of high-resolution shapes represented as binary voxel occupancy grids. In contrast to a dense CNN that takes the entire voxel grid as input, a sparse CNN processes only on the non-empty voxels, thus reducing the memory and computation overhead caused by the sparse input data. We evaluate our method on two clinically relevant skull reconstruction tasks: (1) given a defective skull, reconstruct the complete skull (i.e., skull shape completion), and (2) given a coarse skull, reconstruct a high-resolution skull with fine geometric details (shape super-resolution). Our method outperforms its dense CNN-based counterparts in the skull reconstruction task quantitatively and qualitatively, while requiring substantially less memory for training and inference. We observed that, on the 3D skull data, the overall memory consumption of the sparse CNN grows approximately linearly during inference with respect to the image resolutions. During training, the memory usage remains clearly below increases in image resolution—an times 8 increase in voxel number leads to less than times 4 increase in memory requirements. Our study demonstrates the effectiveness of using a sparse CNN for skull reconstruction tasks, and our findings can be applied to other spatially sparse problems. We prove this by additional experimental results on other sparse medical datasets, like the aorta and the heart. Project page at https://github.com/Jianningli/SparseCNN.

Hybridization and its impact on the ontogenetic allometry of skulls in macaques.

The role of hybridization in morphological diversification is a fundamental topic in evolutionary biology. However, despite the accumulated knowledge on adult hybrid variation, how hybridization affects ontogenetic allometry is less well understood. Here, we investigated the effects of hybridization on postnatal ontogenetic allometry in the skulls of a putative hybrid population of introduced Taiwanese macaques (Macaca cyclopis) and native Japanese macaques (Macaca fuscata). Genomic analyses indicated that the population consisted of individuals with varying degrees of admixture, formed by male migration from Japanese to Taiwanese macaques. For overall skull shape, ontogenetic trajectories were shifted by hybridization in a nearly additive manner, with moderate transgressive variation observed throughout development. In contrast, for the maxillary sinus (hollow space in the face), hybrids grew as fast as Taiwanese macaques, diverging from Japanese macaques, which showed slow growth. Consequently, adult hybrids showed a mosaic pattern, that is, the maxillary sinus is as large as that of Taiwanese macaques, while the overall skull shape is intermediate. Our findings suggest that the transgressive variation can be caused by prenatal shape modification and nonadditive inheritance on regional growth rates, highlighting the complex genetic and ontogenetic bases underlying hybridization-induced morphological diversification.

Variants of the typical variability of alveolar arches in different craniotypes

Background. The implementation of the principles of evidence-based medicine in applied and fundamental research consists in the precision of morphometric measurements in determining the types, dimensions and spatial location of the facial and cerebral parts of the skull. Published scientific data on the variability of morphometric parameters of the alveolar arches are contradictory and heterogeneous due to the lack of definition of interdependencies with gender, age characteristics and individual features of the skull.Goal. Investigation of the regularities between morphometric values and forms of the alveolar arches of the upper jaw in mesocrane, brachycrane and dolichocrane types of the skull.Materials and methods. Morphometry was performed on 93 preparations of skulls with lower jaws of both sexes of the first and second periods of adulthood with physiological types of bite and the shapes of the alveolar arches of the upper jaw were established. Taking into account the value of the transverse-longitudinal index, the skulls of mesocrane (n=54; 58.1%), brachycrane (n=23; 24.7%) and dolichocrane (n=16; 17.2%) types were identified. The length, width, depth and diagonal of the alveolar arches were studied as morphometric parameters.Results. The minimum and maximum limits of fluctuations of values, average statistical indicators, coefficients of variation are determined. The variability of the parameters of the alveolar arches of the upper jaw depending on the shape of the facial skull and gender characteristics was established. It is proved that the smallest values of the depth of the alveolar arch of the upper jaw are noted in brachycranes, the largest – in dolichocrans, while the smallest dimensions of the length, width of the alveolar arch of the upper jaw are determined in dolichocrans, and the largest – in brachycranes, while the smallest diagonal values of the alveolar arch of the upper jaw are revealed in mesocrans.Conclusions. The shape of the alveolar arches in the mesocrane type of skull has a proportional arcuate shape, in brachycrania − an arcuate «wide and short» shape, in dolichocrania − an arcuate «narrow and long» shape. The obtained new data on the variant variability of the alveolar arches should be used when planning treatment tactics for patients with complete adentia.

Skull morphology of bottlenose dolphins worldwide and patterns of adaptation between coastal and offshore environments

AbstractThe morphological differentiation between coastal and offshore ecotypes of bottlenose dolphins (genus Tursiops) has been researched since the 1960s, particularly in T. truncatus (Montagu, 1821), although most morphological studies have focused on localized populations. Therefore, it is unclear how patterns observed in these individual populations integrate within the global morphological variation. Here we carry out a meta‐analysis of global morphological variation between coastal and offshore ecotypes from 532 museum specimens, using both linear measurements (LM; 282 specimens), and shape data using geometric morphometrics (GM; 290 specimens). Together these analyses show consistent differentiation in skull morphology between coastal and offshore ecotypes, and provide a detailed description of variation patterns within each ecotype. These patterns show high individual morphological variation in the coastal ecotype between locations, while the offshore ecotype appears morphologically more uniform across the areas sampled. Overall, most skull shape variation can be described by features noticeable dorsally in the structures of the rostrum, whereas more limited change was found in ventral traits. Our results suggest that individual coastal populations may vary according to local environmental conditions, while those corresponding to the offshore ecotype appear to share similar morphological characteristics that might increase fitness in offshore habitats.

More than one way to eat a mouse: Skull shape variation within a monophyletic group of mammals (Marsupialia; Dasyurinae)

AbstractFunctional requirements for different diets have a strong selective pressure leading to convergent adaptations across different groups of mammals. As body size has an influence on many biomechanical and physiological characteristics, it is logical that dietary adaptations often have a strong link to body size resulting in observed ‘size guilds’ in many diverse phylogenetic lineages. However, non‐allometric variation in skull shape may provide an alternative pathway for species to adapt to diets or prey handling by breaking the mould away from the line of least evolutionary resistance, increased body size. We investigated the relationships between cranial shape and body size in the evolutionary context of the shift from insectivory to hypercarnivory in a monophyletic group of 16 dasyurine marsupial species. Analysis of 35 Procrustes‐corrected 3D skull landmarks revealed that overall, there was a correlation between mean skull shape and size that correlated with diet. However, the dominant shape variation (almost 80% irrespective of phylogeny, and more than 90% when constrained by phylogeny) was not size‐related. This non‐allometric pattern of skull shape reveals adaptation for different feeding strategies that is independent of absolute size. This highlights the potential for specific ‘thresholds’ in size and shape to exist that have the potential to mark shifts from one dietary niche to the next, that might be applied to the evolution of carnivorous taxa from other lineages.

Automated three-dimensional analysis of facial asymmetry in patients with syndromic coronal synostosis: A retrospective study

Craniosynostosis, characterized by premature fusion of one or more cranial sutures, results in a distorted skull shape. Only three studies have assessed facial asymmetry manually in unicoronal synostosis patients. It is therefore important to understand how uni- and bicoronal synostosis affect facial asymmetry with a minimum risk of human bias.An automated algorithm was developed to quantify facial asymmetry from three-dimensional images, generating a mean facial asymmetry (MFA) value in millimeters to reflect the degree of asymmetry. The framework was applied to analyze postoperative 3D images of syndromic patients (N = 35) diagnosed with Muenke syndrome, Saethre-Chotzen syndrome, and TCF12-related craniosynostosis with respect to MFA values from a healthy control group (N = 89).Patients demonstrated substantially higher MFA values than controls: Muenke syndrome (unicoronal 1.74 ± 0.40 mm, bicoronal 0.77 ± 0.21 mm), Saethre-Chotzen syndrome (unicoronal 1.15 ± 0.20 mm, bicoronal 0.69 ± 0.16 mm), and TCF12-related craniosynostosis (unicoronal 1.40 ± 0.51 mm, bicoronal 0.66 ± 0.05 mm), compared with controls (0.49 ± 0.12 mm). Longitudinal analysis identified an increasing MFA trend in unicoronal synostosis patients.Our study revealed higher MFA in syndromic patients with uni- and bicoronal synostosis compared with controls, with the most pronounced MFA in Muenke syndrome patients with unilateral synostosis. Bicoronal synostosis patients demonstrated higher facial asymmetry than expected given the condition’s symmetrical presentation.

Cranial Neural Crest Specific Deletion of Alpl (TNAP) via P0-Cre Causes Abnormal Chondrocyte Maturation and Deficient Cranial Base Growth.

Bone growth plate abnormalities and skull shape defects are seen in hypophosphatasia, a heritable disorder in humans that occurs due to the deficiency of tissue nonspecific alkaline phosphatase (TNAP, Alpl) enzyme activity. The abnormal development of the cranial base growth plates (synchondroses) and abnormal skull shapes have also been demonstrated in global Alpl-/- mice. To distinguish local vs. systemic effects of TNAP on skull development, we utilized P0-Cre to knockout Alpl only in cranial neural crest-derived tissues using Alpl flox mice. Here, we show that Alpl deficiency using P0-Cre in cranial neural crest leads to skull shape defects and the deficient growth of the intersphenoid synchondrosis (ISS). ISS chondrocyte abnormalities included increased proliferation in resting and proliferative zones with decreased apoptosis in hypertrophic zones. ColX expression was increased, which is indicative of premature differentiation in the absence of Alpl. Sox9 expression was increased in both the resting and prehypertrophic zones of mutant mice. The expression of Parathyroid hormone related protein (PTHrP) and Indian hedgehog homolog (IHH) were also increased. Finally, cranial base organ culture revealed that inorganic phosphate (Pi) and pyrophosphate (PPi) have specific effects on cell signaling and phenotype changes in the ISS. Together, these results demonstrate that the TNAP expression downstream of Alpl in growth plate chondrocytes is essential for normal development, and that the mechanism likely involves Sox9, PTHrP, IHH and PPi.

Sexual dimorphism in skull size and shape of Laticauda colubrina (Serpentes: Elapidae).

Sexual dimorphism in size and shape is widespread among squamate reptiles. Sex differences in snake skull size and shape are often accompanied by intersexual feeding niche separation. However, allometric trajectories underlying these differences remain largely unstudied in several lineages. The sea krait Laticauda colubrina (Serpentes: Elapidae) exhibits very clear sexual dimorphism in body size, with previous studies having reported females to be larger and to have a relatively longer and wider head. The two sexes also differ in feeding habits: males tend to prey in shallow water on muraenid eels, whereas females prey in deeper water on congerid eels. I investigated sexual dimorphism in skull shape and size as well as the pattern of skull growth, to determine whether males and females follow the same ontogenetic trajectories. I studied skull characteristics and body length in 61 male and female sea kraits. The sexes differ in skull shape. Males and females follow distinct allometric trajectories. Structures associated with feeding performance are female-biased, whereas rostral and orbital regions are male-biased. The two sexes differ in allometric trajectories of feeding-related structures (female biased) that correspond to dietary divergence between the sexes. Sea kraits exhibit clear sexual dimorphism in the skull form that may be explained by intersexual differences in the feeding habits as well as reproductive roles. The overall skull growth pattern resembles the typical pattern observed in other tetrapods.