现代人头骨断面轮廓的性别鉴定——基于几何形态测量的研究

人类头骨在大小、粗壮度和形状上具有性别差异。长期以来,性别鉴定的方法主要是根据头骨的大小和粗壮度,用肉眼进行粗略观察。受研究方法的限制,忽略了头骨细微的解剖结构及形状差别。为获取头骨性别差异的更多信息,探究头骨断面轮廓的性别差异,本文选用距今300年左右墓葬出土的云南现代人成年男性和女性头骨各30例作为研究材料,利用3D激光扫描技术及逆向工程软件提取头骨断面的外轮廓信息,在此基础上,采用几何形态测量方法对头骨冠状面、矢状面的外轮廓形状的性别差异进行了比较。研究结果显示:男女头骨在冠状面、正中矢状面顶骨部、正中矢状面枕骨部的形状上性别差异不显著,而在正中矢状面额骨部的形状上差异显著。本文对于古人类学和体质人类学鉴定人类头骨的性别差异,以及探讨不同地区、不同时代人群头面部形状的变异具有一定的参考价值。     

Divergence in size,but not in shape: variation in skull size and shape within Ommatotriton newts

Using a geometric morphometric approach, we explored the variation in skull size and skull shape in banded newts (genus Ommatotriton). The genus Ommatotriton is represented by two allopatric, genetically well‐defined species: Ommatotriton ophryticus and O. vittatus. Within each species, two subspecies have been recognised. The samples used in this study cover the geographical and genetic variation within each species. We found statistically significant variation in skull size between species and among populations within species. When corrected for size, there was no significant variation in shape between species. Our results indicate that the variation in skull shape within the genus Ommatotriton is almost entirely due to size‐dependent, allometric shape changes. The exception is the shape of the ventral skull in males. Males of O. ophryticus and O. vittatus significantly diverge in the shape of the ventral cranium. The ventral skull, more precisely the upper jaw and palate, is directly functionally related to feeding. In general, our results indicate that allometry is a significant factor in the morphological variation of banded newts. However, the divergence in the ventral skull shape of males indicates that sexual selection and niche partitioning may have influenced the evolution of skull shape in these newts.     

Geographic Variation in the Skull Morphometry of Four Populations of Batrachuperus karlschmidti(Urodela: Hynobiidae)

Geographic variation of morphology is an important topic of evolutionary biology, and research on geographic variation can provide insights on the formation, evolution, and adaptation of species and subspecies. The vertebrate skull is a developmentally and functionally complex morphological structure with multiple functions, that is susceptible to vary according to selection pressure. In this study, geographic variations in skull morphology of Batrachuperus karlschmidti from four different geographic populations(Shade, Gexi,Shangluokema, and Xinduqiao) were examined via geometric morphometrics. No significant differences were found among these populations with regard to skull size; however, significant variation was found in skull shape. The most notable shape changes are the relative sizes and positions of the frontal, maxilla,pterygoid, and vomer. Skull shape changes were not related to allometry. However, due to limitation of sample populations and size, the results of this study need to be further verified by more sample populations and individuals in the future. The results of this study contribute to our knowledge about these aspects of morphological variability in this species as well as in hynobiid salamanders.     

Repeated loss of frontal sinuses in arctoid carnivorans

Many mammal skulls contain air spaces inside the bones surrounding the nasal chamber including the frontal, maxilla, ethmoid, and sphenoid, all of which are called paranasal sinuses. Within the Carnivora, frontal sinuses are usually present, but vary widely in size and shape. The causes of this variation are unclear, although there are some functional associations, such as a correlation between expanded frontal sinuses and a durophagous diet in some species (e.g., hyenas) or between absent sinuses and semiaquatic lifestyle (e.g., pinnipeds). To better understand disparity in frontal sinus morphology within Carnivora, we quantified frontal sinus size in relationship to skull size and shape in 23 species within Arctoidea, a clade that is ecologically diverse including three independent invasions of aquatic habitats, by bears, otters, and pinnipeds, respectively. Our sampled species range in behavior from terrestrial (rarely or never forage in water), to semiterrestrial (forage in water and on land), to semiaquatic (forage only in water). Results show that sinuses are either lost or reduced in both semiterrestrial and semiaquatic species, and that sinus size is related to skull size and shape. Among terrestrial species, frontal sinus size was positively allometric overall, but several terrestrial species completely lacked sinuses, including two fossorial badgers, the kinkajou (a nocturnal, arboreal frugivore), and several species with small body size, indicating that factors other than aquatic habits, such as space limitations due to constraints on skull size and shape, can limit sinus size and presence. J. Morphol. 276:22–32, 2015. © 2014 Wiley Periodicals, Inc.     

Geometric morphometrics of the skull of various murid rodents (Mammalia, Rodentia): relation of the skull shape to the trophic specialization

Presented is a brief overview of basic principles and notions of geometric morphometrics, a new approach to quantitative analysis of shape variations. This approach is applied to analysis of variation of the skull shape in the sample of 18 muroid genera belonging to the families Cricetidae, Arvicolidae and Gerbillidae. The skull shape is described by landmarks, and skulls are compared by resistant fit and superimposition methods. Under consideration is relation of skull shape to the trophic specialization, to family belonging, and to body size. Axial skull reveals more conspicuous relation to each of the factor analyzed as compared to mandible. Zygomatic region and tooth raw are most differentiable, while change of auditory bulla is of secondary effect. Transition from omnivorous through granivorous to grass-eating specialization involves the same trend in each of the family studied in the case of axial skull but not of mandible. Most dependent of trophic specialization appeared to be shape of axial skull rather then of mandible. Arvicolines are most specific in respect to the skull shape. Shape to size relation, although rather slight, also involves the same zygomatic-dental region. The results obtained indicate probably that geometric morphometrics does reveal variations in the skull shape that are free of the size effect.     

Frontal Bone Insufficiency in Gsk3β Mutant Mice

The development of the mammalian skull is a complex process that requires multiple tissue interactions and a balance of growth and differentiation. Disrupting this balance can lead to changes in the shape and size of skull bones, which can have serious clinical implications. For example, insufficient ossification of the bony elements leads to enlarged anterior fontanelles and reduced mechanical protection of the brain. In this report, we find that loss of Gsk3β leads to a fully penetrant reduction of frontal bone size and subsequent enlarged frontal fontanelle. In the absence of Gsk3β the frontal bone primordium undergoes increased cell death and reduced proliferation with a concomitant increase in Fgfr2-IIIc and Twist1 expression. This leads to a smaller condensation and premature differentiation. This phenotype appears to be Wnt-independent and is not rescued by decreasing the genetic dose of β-catenin/Ctnnb1. Taken together, our work defines a novel role for Gsk3β in skull development.     

Craniometry of cranial vault bones in newborn infants

10 craniometric measurements of the skull bones' fornix have been performed on 89 dried infant skulls. The authors have shown that the craniometric variability of the skull bone's fornix is connected with the skull length rather than with its height. The skull length is determined mostly by the squama of the temporal bone and occipital squama. The shape of the skull vault is determined mainly by parietal bone and squama of the frontal bone. Parietal bones shut unpaired fontanelle, but the remaining bones, under investigation, contribute to the closure of anterolateral and postero-lateral fontanelle.     

Changes in the skull morphology of the Arctic wolf, Canis lupus arctos, during the twentieth century

Measurements of a large series of skulls of the Arctic wolf, Canis lupus arctos . have shown that since 1930 there has been an overall reduction in the size of the skulls, together with widening of the cranium, shortening of the facial region, and reduction in size of the teeth. This suggests that hybridization and subsequent introgression occurred with huskies ( Canis familiaris ) during the 1930s, which is consistent with historical accounts. Since 1950 there has been a reversion in skull morphology to a more 'wolf-like' form, suggesting that hybridization is no longer occurring.
The skull of a wolf/dog hybrid is intermediate in size between the skulls of wolves and huskies but its shape is allometrically dissimilar. Skulls of wolves from the period 1930–50 are moi-e similar to the skull of this hybrid than in the other time periods.
The skull of a male canid from a carcass collected on Ellesmere Island and presented to the Natural History Museum. London, in 1986 was at first thought to be from a wolf/dog hybrid but analyses of the measurements show that it is more likely to be from an Arctic wolf with severe abnormalities to the jaws.     

Roles for modularity and constraint in the evolution of cranial diversity among Anolis lizards

Complex organismal structures are organized into modules, suites of traits that develop, function, and vary in a coordinated fashion. By limiting or directing covariation among component traits, modules are expected to represent evolutionary building blocks and to play an important role in morphological diversification. But how stable are patterns of modularity over macroevolutionary timescales? Comparative analyses are needed to address the macroevolutionary effect of modularity, but to date few have been conducted. We describe patterns of skull diversity and modularity in Caribbean Anolis lizards. We first diagnose the primary axes of variation in skull shape and then examine whether diversification of skull shape is concentrated to changes within modules or whether changes arose across the structure as a whole. We find no support for the hypothesis that cranial modules are conserved as species diversify in overall skull shape. Instead we find that anole skull shape and modularity patterns independently converge. In anoles, skull modularity is evolutionarily labile and may reflect the functional demands of unique skull shapes. Our results suggest that constraints have played little role in limiting or directing the diversification of head shape in Anolis lizards.     

Advancement of the orbits and the midface in one piece, combined with frontal repositioning, for the correction of Crouzon's deformities

We describe the use of radical craniofacial osteotomies, to improve the correction of exorbitism and to obtain better esthetic results in children with Crouzon's syndrome. We suggest some minor modifications to improve the fixation and the mechanical stability of the mobilized segments of the skull. Our procedure consists, essentially, of advancement of both orbits and the midface in one piece, plus advancement and reshaping of the frontal area. The results obtained by this technique, in children with a Crouzon's deformity without open bite, have been most satisfactory. We believe the satisfactory resultant appearance will be maintained during and after growth of the face, although these children have not been followed long enough yet to ascertain this with certainty.     

A tale of two cities: The genetic mechanisms governing calvarial bone development

The skull bones must grow in a coordinated, three‐dimensional manner to coalesce and form the head and face. Mammalian skull bones have a dual embryonic origin from cranial neural crest cells (CNCC) and paraxial mesoderm (PM) and ossify through intramembranous ossification. The calvarial bones, the bones of the cranium which cover the brain, are derived from the supraorbital arch (SOA) region mesenchyme. The SOA is the site of frontal and parietal bone morphogenesis and primary center of ossification. The objective of this review is to frame our current in vivo understanding of the morphogenesis of the calvarial bones and the gene networks regulating calvarial bone initiation in the SOA mesenchyme.     

Semi-automatic classification of skeletal morphology in genetically altered mice using flat-panel volume computed tomography

Rapid progress in exploring the human and mouse genome has resulted in the generation of a multitude of mouse models to study gene functions in their biological context. However, effective screening methods that allow rapid noninvasive phenotyping of transgenic and knockout mice are still lacking. To identify murine models with bone alterations in vivo, we used flat-panel volume computed tomography (fpVCT) for high-resolution 3-D imaging and developed an algorithm with a computational intelligence system. First, we tested the accuracy and reliability of this approach by imaging discoidin domain receptor 2- (DDR2-) deficient mice, which display distinct skull abnormalities as shown by comparative landmark-based analysis. High-contrast fpVCT data of the skull with 200 microm isotropic resolution and 8-s scan time allowed segmentation and computation of significant shape features as well as visualization of morphological differences. The application of a trained artificial neuronal network to these datasets permitted a semi-automatic and highly accurate phenotype classification of DDR2-deficient compared to C57BL/6 wild-type mice. Even heterozygous DDR2 mice with only subtle phenotypic alterations were correctly determined by fpVCT imaging and identified as a new class. In addition, we successfully applied the algorithm to classify knockout mice lacking the DDR1 gene with no apparent skull deformities. Thus, this new method seems to be a potential tool to identify novel mouse phenotypes with skull changes from transgenic and knockout mice on the basis of random mutagenesis as well as from genetic models. However for this purpose, new neuronal networks have to be created and trained. In summary, the combination of fpVCT images with artificial neuronal networks provides a reliable, novel method for rapid, cost-effective, and noninvasive primary screening tool to detect skeletal phenotypes in mice.     

Evolution of cranial telescoping in echolocating whales (Cetacea: Odontoceti)

Odontocete (echolocating whale) skulls exhibit extreme posterior displacement and overlapping of facial bones, here referred to as retrograde cranial telescoping. To examine retrograde cranial telescoping across 40 million years of whale evolution, we collected 3D scans of whale skulls spanning odontocete evolution. We used a sliding semilandmark morphometric approach with Procrustes superimposition and PCA to capture and describe the morphological variation present in the facial region, followed by Ancestral Character State Reconstruction (ACSR) and evolutionary model fitting on significant components to determine how retrograde cranial telescoping evolved. The first PC score explains the majority of variation associated with telescoping and reflects the posterior migration of the external nares and premaxilla alongside expansion of the maxilla and frontal. The earliest diverging fossil odontocetes were found to exhibit a lesser degree of cranial telescoping than later diverging but contemporary whale taxa. Major shifts in PC scores and centroid size are identified at the base of Odontoceti, and early burst and punctuated equilibrium models best fit the evolution of retrograde telescoping. This indicates that the Oligocene was a period of unusually high diversity and evolution in whale skull morphology, with little subsequent evolution in telescoping.     

Burrowing constrains patterns of skull shape evolution in wrasses

The evolution of behavioral and ecological specialization can have marked effects on the tempo and mode of phenotypic evolution. Head-first burrowing has been shown to exert powerful selective pressures on the head and body shapes of many vertebrate and invertebrate taxa. In wrasses, burrowing behaviors have evolved multiple times independently, and are commonly used in foraging and predator avoidance behaviors. While recent studies have examined the kinematics and body shape morphology associated with this behavior, no study to-date has examined the macroevolutionary implications of burrowing on patterns of phenotypic diversification in this clade. Here, we use three-dimensional geometric morphometrics and phylogenetic comparative methods to study the evolution of skull shape in fossorial wrasses and their relatives. We test for skull shape differences between burrowing and non burrowing wrasses and evaluate hypotheses of shape convergence among the burrowing wrasses. We also quantify rates of skull shape evolution between burrowing and non burrowing wrasses to test for whether burrowing constrains or accelerates rates of skull shape evolution in this clade. We find that while burrowing and non burrowing wrasses exhibit similar degrees of morphological disparity, for burrowing wrasses, it took nearly twice as long to amass this disparity. Furthermore, while the disparities between groups are evenly matched, we find that most burrowing species are confined to a particular region of shape space with most species exhibiting narrower heads than many non-burrowing species. These results suggest head-first burrowing constrains patterns of skull shape diversification in wrasses by potentially restricting the range of phenotypes that can perform this behavior.     

Stability and robustness of an organelle number control system: modeling and measuring homeostatic regulation of centriole abundance

Control of organelle abundance is a fundamental unsolved problem in cell biology. Mechanisms for number control have been proposed in which organelle assembly is actively increased or decreased to compensate for deviations from a set-point, but such phenomena have not been experimentally verified. In this report we examine the control of centriole copy number. We develop a simple scheme to represent organelle inheritance as a first-order Markov process and describe two figures of merit based on entropy and convergence times that can be used to evaluate performance of organelle number control systems. Using this approach we show that segregation of centrioles by the mitotic spindle can shape the specificity of the steady-state centriole number distribution but is neither necessary nor sufficient for stable restoration of centriole number following perturbations. We then present experimental evidence that living cells can restore correct centriole copy number following transient perturbation, revealing a homeostatic control system. We present evidence that correction occurs at the level of single cell divisions, does not require association of centrioles with the mitotic spindle, and involves modulation of centriole assembly as a function of centriole number during S-phase. Combining our experimental and modeling results, we identify two processes required for error correction, de novo assembly and number-limiting, and show that both processes contribute to robust and stable homeostatic control of centriole number, yielding a system capable of suppressing biological noise at the level of organelle abundance.     

Pervasive genetic integration directs the evolution of human skull shape

It has long been unclear whether the different derived cranial traits of modern humans evolved independently in response to separate selection pressures or whether they resulted from the inherent morphological integration throughout the skull. In a novel approach to this issue, we combine evolutionary quantitative genetics and geometric morphometrics to analyze genetic and phenotypic integration in human skull shape. We measured human skulls in the ossuary of Hallstatt (Austria), which offer a unique opportunity because they are associated with genealogical data. Our results indicate pronounced covariation of traits throughout the skull. Separate simulations of selection for localized shape changes corresponding to some of the principal derived characters of modern human skulls produced outcomes that were similar to each other and involved a joint response in all of these traits. The data for both genetic and phenotypic shape variation were not consistent with the hypothesis that the face, cranial base, and cranial vault are completely independent modules but relatively strongly integrated structures. These results indicate pervasive integration in the human skull and suggest a reinterpretation of the selective scenario for human evolution where the origin of any one of the derived characters may have facilitated the evolution of the others.     

Canine TCOF1; cloning, chromosome assignment and genetic analysis in dogs with different head types

We describe the construction of a dog embryonic head/neck cDNA library and the isolation of the dog homolog of the Treacher Collins Syndrome gene, TCOF1. The protein shows a similar three-domain structure to that described for human TCOF1, but the dog gene lacks exon 10 and contains two exons not present in the human sequence. In addition, exon 19 is differentially spliced in the dog. How these structural differences relate to TCOF1 phosphorylation is discussed. Isolation of a genomic clone allowed the exon/intron boundaries to be characterized and the dog TCOF1 gene to be mapped to CF Chr 4q31, a region syntenic to human Chr 5. Genetic analysis of DNA of dogs from 13 different breeds identified nine DNA sequence variants, three of which gave rise to amino acid substitutions. Grouping dogs according to head type showed that a C396T variant, leading to a Pro117Ser substitution, is associated with skull/face shape in our dog panel. The numbers are small, but the association between the T allele and brachycephaly, broad skull/short face, was highly significant (p= 0.000024). The short period of time during which the domestic dog breeds have been established suggests that this mutation has arisen only once in the history of dog domestication. Received: 12 January 2001 / Accepted: 1 April 2001     

Allometry and performance: the evolution of skull form and function in felids

Allometric patterns of skull‐shape variation can have significant impacts on cranial mechanics and feeding performance, but have received little attention in previous studies. Here, we examine the impacts of allometric skull‐shape variation on feeding capabilities in the cat family (Felidae) with linear morphometrics and finite element analysis. Our results reveal that relative bite force diminishes slightly with increasing skull size, and that the skulls of the smallest species undergo the least strain during biting. However, larger felids are able to produce greater gapes for a given angle of jaw opening, and they have overall stronger skulls. The two large felids in this study achieved increased cranial strength by increasing skull bone volume relative to surface area. Allometry of skull geometry in large felids reflects a trade‐off between the need to increase gape to access larger prey while maintaining the ability to resist unpredictable loading when taking large, struggling prey.     

In vivo impact of Dlx3 conditional inactivation in neural crest‐derived craniofacial bones

Mutations in DLX3 in humans lead to defects in craniofacial and appendicular bones, yet the in vivo activities related to Dlx3 function during normal skeletal development have not been fully elucidated. Here we used a conditional knockout approach to analyze the effects of neural crest deletion of Dlx3 on craniofacial bones development. At birth, mutant mice exhibit a normal overall positioning of the skull bones, but a change in the shape of the calvaria was observed. Molecular analysis of the genes affected in the frontal bones and mandibles from these mice identified several bone markers known to affect bone development, with a strong prediction for increased bone formation and mineralization in vivo. Interestingly, while a subset of these genes were similarly affected in frontal bones and mandibles (Sost, Mepe, Bglap, Alp, Ibsp, Agt), several genes, including Lect1 and Calca, were specifically affected in frontal bones. Consistent with these molecular alterations, cells isolated from the frontal bone of mutant mice exhibited increased differentiation and mineralization capacities ex vivo, supporting cell autonomous defects in neural crest cells. However, adult mutant animals exhibited decreased bone mineral density in both mandibles and calvaria, as well as a significant increase in bone porosity. Together, these observations suggest that mature osteoblasts in the adult respond to signals that regulate adult bone mass and remodeling. This study provides new downstream targets for Dlx3 in craniofacial bone, and gives additional evidence of the complex regulation of bone formation and homeostasis in the adult skeleton. J. Cell. Physiol. 228: 654–664, 2013. © 2012 Wiley Periodicals, Inc.