A landmark-free morphometrics pipeline for high-resolution phenotyping: application to a mouse model of Down syndrome.

Characterising phenotypes often requires quantification of anatomical shape. Quantitative shape comparison (morphometrics) traditionally uses manually located landmarks and is limited by landmark number and operator accuracy. Here, we apply a landmark-free method to characterise the craniofacial skeletal phenotype of the Dp1Tyb mouse model of Down syndrome and a population of the Diversity Outbred (DO) mouse model, comparing it with a landmark-based approach. We identified cranial dysmorphologies in Dp1Tyb mice, especially smaller size and brachycephaly (front-back shortening), homologous to the human phenotype. Shape variation in the DO mice was partly attributable to allometry (size-dependent shape variation) and sexual dimorphism. The landmark-free method performed as well as, or better than, the landmark-based method but was less labour-intensive, required less user training and, uniquely, enabled fine mapping of local differences as planar expansion or shrinkage. Its higher resolution pinpointed reductions in interior mid-snout structures and occipital bones in both the models that were not otherwise apparent. We propose that this landmark-free pipeline could make morphometrics widely accessible beyond its traditional niches in zoology and palaeontology, especially in characterising developmental mutant phenotypes.

Evaluating the muscle attachment hypothesis for sagittal cresting in Gorilla and Pongo.

Primate mandibular morphology is often associated with jaw functionality of the masticatory complex in the context of variation in diets. Recent research into the disparities between the diet and jaw functionality in male and female hominoids is inconclusive and suggests that sexual dimorphism in the mandible may be influenced by external factors such as temporalis and masseter muscle morphology, which in turn may be influenced by sexual selection. As the muscles associated with mastication (i.e., the type of chewing exhibited by primates and other mammals) encompass the mandible as well as the neurocranium, including the sagittal crest among some individuals, this study investigates sex-specific associations between regions of the mandibular ramus and neurocranium associated with mastication in a dentally mature sample of Gorilla and Pongo. A total of four cranial and mandibular variables were measured in two Gorilla taxa (Gorilla gorilla gorilla and Gorilla beringei graueri) and one Pongo taxon (Pongo pygmaeus pygmaeus) (n = 220). For all three taxa, we investigate (a) whether the degree of sexual dimorphism in cranial regions associated with sagittal cresting (sagittal crest size (SCS) and temporalis muscle attachment area (TMAA)) is proportional to the degree of mandibular ramus area (MRA) and coronoid process height (CPH) sexual dimorphism, (b) whether there are sex differences in scaling relationships between TMAA and MRA, and (c) whether there are sex differences in the strength of association between TMAA and CPH. We show that for G. g. gorilla, variables associated with sagittal cresting show higher sexual dimorphism values than our two mandibular ramus variables, which is not the case for G. b. graueri or for P. p. pygmaeus. All three taxa show similar sex-specific scaling relationships between TMAA and MRA, where for males this relationship does not diverge from isometry, and for females there is a negative allometric relationship. Our findings also show intraspecific sex differences in allometric slopes between MRA and TMAA for all three taxa. Only G. g. gorilla shows a significant association between TMAA and CPH, which is observed in both sexes. Although there are some statistical associations between the cranial and mandibular regions associated with mastication, our results show that among male gorillas and orangutans, patterns of variation in the sagittal crest, TMAA, mandibular ramus and the coronoid process cannot be explained by the muscle attachment hypothesis alone. These findings have implications surrounding the associations between social behaviour and the morphology of the craniofacial complex.

New craniodental fossils of Paranthropus robustus from Kromdraai, South Africa (2014-2017 excavations).

Since the initial discovery of Paranthropus robustus at the site of Kromdraai in 1938, the hypodigm of this species has been expanded by subsequent work at the localities of Swartkrans and Drimolen, with a few fossils also known from Cooper's D, Gondolin and Sterkfontein Member 5. Beginning in 2014, systematic excavations at Kromdraai uncovered a large and previously unknown fossiliferous area, shedding light on Units O and P in the earliest part of the site's stratigraphic sequence. The aim of this paper is to provide detailed descriptions and illustrations of 30 P. robustus craniodental specimens recovered between 2014 and 2017 within the Unit P deposits at Kromdraai. This new sample predates all prior conspecific specimens found at this site (including the holotype of P. robustus from Kromdraai, TM 1517). Its basic dental morphology dimensions and cranial features are compared in a preliminary analysis with other P. robustus samples. The P. robustus sample from Kromdraai Unit P documents previously unknown portions of the P. robustus juvenile cranium. The new dental and cranial remains aid in the exploration of potential morphological distinctions between site-specific P. robustus samples and are compared favorably in size and morphology with the small P. robustus specimens from Drimolen (e.g., DNH 7). These findings do not support the hypothesis that the specimens from Drimolen belong to a different taxonomic group. Instead, they reinforce the presence of a significant degree of sexual dimorphism within P. robustus. The Kromdraai Unit P specimens also contribute to the biodemographic profile of P. robustus. The notable prevalence of infants (i.e., juvenile individuals before the emergence of their first permanent molars) mirrors the natural mortality profiles observed in wild chimpanzees. This suggests a closer resemblance in the processes of accumulation in Kromdraai Unit P and Drimolen than at Swartkrans.

What we see is what we touch? Sex estimation on the skull in virtual anthropology.

BACKGROUND: The increased use of virtual bone images in forensic anthropology requires a comprehensive study on the observational errors between dry bones and CT reconstructions. Here, we focus on the consistency of nonmetric sex estimation traits on the human skull. MATERIALS AND METHODS: We scored nine nonmetric traits on dry crania and mandibles (n = 223) of archaeological origin and their CT reconstructions. Additionally, we 3D surface scanned a subsample (n = 50) and repeated our observations. Due to the intricate anatomy of the mental eminence, we split it into two separate traits: the bilateral mental tubercles and the midsagittal mental protuberance. We provide illustrations and descriptions for both these traits. RESULTS: We obtained supreme consistency values between the CT and 3D surface modalities. The most consistent cranial traits were the glabella and the supraorbital margin, followed by the nuchal crest, zygomatic extension, mental tubercles, mental protuberance, mental eminence, mastoid process and ramus flexure, in descending order. The mental tubercles show higher consistency scores than the mental eminence and the mental protuberance. DISCUSSION: The increased interchangeability of the virtual modalities with each other as compared to the dry bone modality could be due to the lack of tactility on both the CT and surface scans. Moreover, tactility appears less essential with experience than a precise trait description. Future studies could revolve around the most consistent cranial traits, combining them with pelvic traits from a previous study, to test for accuracy.

Desmoplastic fibroma of the pediatric cranium with CTNNB1 mutation: case report and literature review.

PURPOSE: Desmoplastic fibroma (DF) is an uncommon intermediate bone tumor rarely involving the skull with unidentified pathogenesis. We report the first case of pediatric temporoparietal cranial desmoplastic fibroma (DF) with a CTNNB1 gene mutation and review the previous literature. CASE PRESENTATION: A 3-year-old boy had a firm, painless mass on the right temporoparietal region for 22 months. The cranial CT scan showed isolated osteolytic destruction in the outer plate and diploe of the right temporoparietal bone. Gross total resection of the lesion and cranioplasty were performed. After that, a growing epidural hematoma was observed so another operation was performed to remove the artificial titanium plate. Postoperative pathology indicated a DF diagnosis and molecular pathology suggested a missense mutation in exon 3 of the CTNNB1 gene (c.100G > A,p.Gly34Arg). CONCLUSION: Pediatric cranial DF is rare and easy to be misdiagnosed before operation. For cranial DF, lesion resection can be performed and perioperative management should be strengthened. Mutations in the CTNNB1 gene might be one of the molecular pathologic features of DF.

Sella turcica and facial bones: Morphological integration in the human fetal cranium.

OBJECTIVES: The cranial base plays a significant role in facial growth, and closer analyses of the morphological relationship between these two regions are needed to understand the morphogenesis of the face. Here, we aimed to study morphological integration between the sella turcica (ST) and facial bones during the fetal period using geometric morphometrics. MATERIALS AND METHODS: Magnetic resonance images of 47 human fetuses in the Kyoto Collection, with crown-rump lengths of 29.8-225 mm, were included in this study. Anatomical homologous landmarks and semilandmarks were registered on the facial bones and the midsagittal contour of the ST, respectively. The shape variations in the craniofacial skeleton and the ST were statistically investigated by reducing dimensionality using principal component analysis (PCA). Subsequently, the morphological integration between the facial bones and ST was investigated using two-block partial least squares (2B-PLS) analysis. RESULTS: PCA showed that small specimens represented the concave facial profile, including the mandibular protrusion and maxillary retrusion. The 2B-PLS showed a strong integration (RV coefficient = 0.523, r = .79, p < .01) between the facial bones and ST. The curvature of the anterior wall of the ST was highly associated with immature facial morphology characterized by a concave profile. CONCLUSION: The strong integration between the two regions suggested that the anterior ST may be associated with facial morphology. This result quantitatively confirms previous studies reporting ST deformities in facial anomalies and induces further research using postnatal subjects.

Changes in Craniofacial Morphology Induced by Unilateral Nasal Obstruction in Mice of Different Ages.

BACKGROUND: Nasal obstruction in humans leads to mouth breathing and subsequent hypoxia in the entire body. Furthermore, nasal obstruction in growing children affects craniofacial growth and development. OBJECTIVE: To investigate the effects of unilateral nasal obstruction (UNO) on craniofacial growth in mice of different ages, particularly on the morphology of the nasomaxillary complex and mandible. METHODS: Mice aged 3, 6 and 12 weeks were selected as representatives of juvenile, adolescent and adult stages, respectively. A total of 30 male C57BL/6J mice (10 mice each at the ages of 3, 6 and 12 weeks) were used in this study for a 3-week experiment. The mice in each age stage were randomly and evenly assigned to either the control group (C3+3, C6+3 and C12+3) or the experimental group (E3+3, E6+3 and E12+3). The UNO model in experimental group was constructed by plugging the mouse's left nostril, thereby disrupting its normal nasal breathing pattern and inducing hypoxia. The control group underwent the sham procedure. After 3 weeks, the length, width and height of the cranium, nasomaxillary complex and mandible of each group were measured on two-dimensional images constructed by micro-computed tomography. Furthermore, the impact of UNO on mouse growth was evaluated through the measurement of femoral length. RESULTS: In juvenile mice, UNO inhibited the growth of cranial width, cranial height and mandibular length. In adolescent mice, UNO impeded the growth of the femoral length, cranial length, nasomaxillary length and mandibular length. In adult mice, no significant negative effects of UNO on craniofacial growth were found. CONCLUSION: Referring to the experimental results, in addition to actively treating nasal obstruction in patients, it is important to monitor the growth of the mandible in juveniles, as well as the nasomaxillary and mandibular growth in adolescents during orthodontic clinical practice.

Human Malformed Perinatal Anthropological Crania Contribute to New Insight in the Extension of Bone Malformations in Cranial Development.

INTRODUCTION: We describe five abnormal crania which may provide more diagnostic data for assessment of abnormal crania in newborns. METHODS: Five malformed perinatal crania from the Saxtorphian Collection are described using published prenatal abnormal cranial development criteria. These malformations were compared to normal cranial development arising from the migration of neural crest cells. Visual and photographic investigations were performed. RESULTS: The malformed crania were occipital encephalocele, holoprosencephaly, anencephaly, and two without a recognizable diagnosis. The anthropological crania were malformed in the same regions as formerly observed in fetal pathology. These regions were comparable to fields formed during normal cell migration from the neural crest. This has seemingly not previously been demonstrated. One undiagnosed cranium may represent a Treacher Collins syndrome (Case 3). The other undiagnosed cranium (Case 4) could be from a scaphocephalic specimen. DISCUSSION: Sharp borderlines between malformed and non-malformed regions in cranial syndromes may enable improvement in diagnostics.

Vertebrate cranial evolution: Contributions and conflict from the fossil record.

In modern vertebrates, the craniofacial skeleton is complex, comprising cartilage and bone of the neurocranium, dermatocranium and splanchnocranium (and their derivatives), housing a range of sensory structures such as eyes, nasal and vestibulo-acoustic capsules, with the splanchnocranium including branchial arches, used in respiration and feeding. It is well understood that the skeleton derives from neural crest and mesoderm, while the sensory elements derive from ectodermal thickenings known as placodes. Recent research demonstrates that neural crest and placodes have an evolutionary history outside of vertebrates, while the vertebrate fossil record allows the sequence of the evolution of these various features to be understood. Stem-group vertebrates such as Metaspriggina walcotti (Burgess Shale, Middle Cambrian) possess eyes, paired nasal capsules and well-developed branchial arches, the latter derived from cranial neural crest in extant vertebrates, indicating that placodes and neural crest evolved over 500 million years ago. Since that time the vertebrate craniofacial skeleton has evolved, including different types of bone, of potential neural crest or mesodermal origin. One problematic part of the craniofacial skeleton concerns the evolution of the nasal organs, with evidence for both paired and unpaired nasal sacs being the primitive state for vertebrates.

Disentangling Mechanical and Sensory Modules in the Radiation of Noctilionoid Bats.

AbstractWith diverse mechanical and sensory functions, the vertebrate cranium is a complex anatomical structure whose shifts between modularity and integration, especially in mechanical function, have been implicated in adaptive diversification. Yet how mechanical and sensory systems and their functions coevolve, as well as how their interrelationship contributes to phenotypic disparity, remain largely unexplored. To examine the modularity, integration, and evolutionary rates of sensory and mechanical structures within the head, we analyzed hard and soft tissue scans from ecologically diverse bats in the superfamily Noctilionoidea, a clade that ranges from insectivores and carnivores to frugivores and nectarivores. We identified eight regions that evolved in a coordinated fashion, thus recognizable as evolutionary modules: five associated with bite force and three linked to olfactory, visual, and auditory systems. Interrelationships among these modules differ between Neotropical leaf-nosed bats (family Phyllostomidae) and other noctilionoids. Consistent with the hypothesis that dietary transitions begin with changes in the capacity to detect novel food items followed by adaptations to process them, peak rates of sensory module evolution predate those of some mechanical modules. We propose that the coevolution of structures influencing bite force, olfaction, vision, and hearing constituted a structural opportunity that allowed the phyllostomid ancestor to take advantage of existing ecological opportunities and contributed to the clade's remarkable radiation.

Making meaning from fragmentary fossils: Early Homo in the Early to early Middle Pleistocene.

In celebration of the 50th anniversary of the Journal of Human Evolution, we re-evaluate the fossil record for early Homo (principally Homo erectus, Homo habilis, and Homo rudolfensis) from early diversification and dispersal in the Early Pleistocene to the ultimate demise of H. erectus in the early Middle Pleistocene. The mid-1990s marked an important historical turning point in our understanding of early Homo with the redating of key H. erectus localities, the discovery of small H. erectus in Asia, and the recovery of an even earlier presence of early Homo in Africa. As such, we compare our understanding of early Homo before and after this time and discuss how the order of fossil discovery and a focus on anchor specimens has shaped, and in many ways biased, our interpretations of early Homo species and the fossils allocated to them. Fragmentary specimens may counter conventional wisdom but are often overlooked in broad narratives. We recognize at least three different cranial and two or three pelvic morphotypes of early Homo. Just one postcranial morph aligns with any certainty to a cranial species, highlighting the importance of explicitly identifying how we link specimens together and to species; we offer two ways of visualizing these connections. Chronologically and morphologically H. erectus is a member of early Homo, not a temporally more recent species necessarily evolved from either H. habilis or H. rudolfensis. Nonetheless, an ancestral-descendant notion of their evolution influences expectations around the anatomy of missing elements, especially the foot. Weak support for long-held notions of postcranial modernity in H. erectus raises the possibility of alternative drivers of dispersal. New observations suggest that the dearth of faces in later H. erectus may mask taxonomic diversity in Asia and suggest various later mid-Pleistocene populations could derive from either Asia or Africa. Future advances will rest on the development of nuanced ways to affiliate fossils, greater transparency of implicit assumptions, and attention to detailed life history information for comparative collections; all critical pursuits for future research given the great potential they have to enrich our evolutionary reconstructions for the next fifty years and beyond.

Evolution of hyperossification expands skull diversity in frogs.

Frogs (Anura) are one of the most diverse vertebrate orders, comprising more than 7,000 species with a worldwide distribution and extensive ecological diversity. In contrast to other tetrapods, frogs have a highly derived body plan and simplified skull. In many lineages of anurans, increased mineralization has led to hyperossified skulls, but the function of this trait and its relationship with other aspects of head morphology are largely unexplored. Using three-dimensional morphological data from 158 species representing all frog families, we assessed wide-scale patterns of shape variation across all major lineages, reconstructed the evolutionary history of cranial hyperossification across the anuran phylogeny, and tested for relationships between ecology, skull shape, and hyperossification. Although many frogs share a conserved skull shape, several extreme forms have repeatedly evolved that commonly are associated with hyperossification, which has evolved independently more than 25 times. Variation in cranial shape is not explained by phylogenetic relatedness but is correlated with shifts in body size and ecology. The species with highly divergent, hyperossified skulls often have a specialized diet or a unique predator defense mechanism. Thus, the evolution of hyperossification has repeatedly facilitated the expansion of the head into multiple new shapes and functions.

Hyalomatrix coverage in scalp wounds with exposed cranium and dura.

AIM: The armamentarium of options available for soft tissue reconstruction of the scalp spans the reconstructive ladder. The purpose of this paper is to describe a case series of patients with exposed cranium and dura who were successfully reconstructed using esterified hyalomatrix (eHAM, Hyalomatrix, Medline Industries Inc., US). METHODS: After obtaining Institutional Review Board approval, a retrospective review of the senior author's (ALF) patient database was completed. Patients who underwent scalp reconstruction using eHAM were identified. Each patient's chart was reviewed and data collected on demographics, days to skin graft, duration of follow-up, pathology, comorbidities and complications. RESULTS: This case series consisted of five patients aged ≥18 years, with scalp wounds exposing dura or cranium, who were treated with eHAM as a bridge to definitive coverage with a skin graft. Each wound successfully granulated the exposed critical structure with the use of the eHAM. The mean time to skin graft coverage was 41 days, with a range of 13-79 days. Of the series of five patients, four had a follow-up of ≥12 weeks. The mean defect size was 90.2cm2. CONCLUSION: Complex scalp reconstruction can be accomplished using healing by secondary intention, skin grafts, local flaps, tissue expansion and free tissue transfer. As shown in this case series, another option available in select patients is using a dermal substitute such as eHAM. This is one treatment option available to reconstructive surgeons in multiple specialties.

Computed tomographic characteristics of frontal sinus ossifying fibroma in a dog.

A 10-year-old female spayed Kelpie cross was presented to The Austin Vet Specialists for further investigation of a mineralized, lobulated frontal sinus mass that had previously been detected radiographically. Computed tomography (CT) revealed a large, expansile, well-defined, heterogeneously mineral attenuating mass invading both frontal sinuses. The mass was surgically debulked via a frontal sinusotomy approach. Histopathology was consistent with ossifying fibroma. This  is the first published report to describe frontal sinus ossifying fibroma in a dog, and the second to describe CT features of ossifying fibroma involving the cranium in a dog.

Sex Estimation of Han Adults in Western China Based on Three-Dimensional Cranial CT Reconstruction.

OBJECTIVES: To examine the reliability and accuracy of Walker's model for estimating the sex of Han adults in western China by using cranium three-dimensional (3D) CT reconstruction, and to study the suitable cranial sex estimation model for Han people in western China. METHODS: A total of 576 cranial CT 3D reconstructed images from Hanzhong Hospital in Shaanxi Province from 2017 to 2021 were collected. These images were divided into the experimental group with 486 samples and the validation group with 90 samples. Walker's model was used by observer 1 to estimate the sex of experimental group samples. The logistic function applicable to Han people in western China was corrected by observer 1. The 90 samples in the validation group were scored and substituted into the modified logistic function to complete the back substitution test by observer 1, 2 and 3. RESULTS: The accuracy of sex estimation of Han adults in western China was 63.2%-77.2% by applying Walker's model. The accuracy of modified logistic function was 82.9%. The accuracy of sex estimation through back substitution test by 3 observers was 75.6%-91.1%, with a Kappa value of 0.689 (P<0.05) for inter-observer consistency and 0.874 (P<0.05) for intra-observer consistency. CONCLUSIONS: There are great differences in bone characteristics among people from different regions. The modified logistic function can achieve higher accuracy in Han adults in western China.

Anatomical variability, multi-modal coordinate systems, and precision targeting in the marmoset brain.

Localising accurate brain regions needs careful evaluation in each experimental species due to their individual variability. However, the function and connectivity of brain areas is commonly studied using a single-subject cranial landmark-based stereotactic atlas in animal neuroscience. Here, we address this issue in a small primate, the common marmoset, which is increasingly widely used in systems neuroscience. We developed a non-invasive multi-modal neuroimaging-based targeting pipeline, which accounts for intersubject anatomical variability in cranial and cortical landmarks in marmosets. This methodology allowed creation of multi-modal templates (MarmosetRIKEN20) including head CT and brain MR images, embedded in coordinate systems of anterior and posterior commissures (AC-PC) and CIFTI grayordinates. We found that the horizontal plane of the stereotactic coordinate was significantly rotated in pitch relative to the AC-PC coordinate system (10 degrees, frontal downwards), and had a significant bias and uncertainty due to positioning procedures. We also found that many common cranial and brain landmarks (e.g., bregma, intraparietal sulcus) vary in location across subjects and are substantial relative to average marmoset cortical area dimensions. Combining the neuroimaging-based targeting pipeline with robot-guided surgery enabled proof-of-concept targeting of deep brain structures with an accuracy of 0.2 mm. Altogether, our findings demonstrate substantial intersubject variability in marmoset brain and cranial landmarks, implying that subject-specific neuroimaging-based localization is needed for precision targeting in marmosets. The population-based templates and atlases in grayordinates, created for the first time in marmoset monkeys, should help bridging between macroscale and microscale analyses.

Cranial shape variation in domestication: A pilot study on the case of rabbits.

Domestication leads to phenotypic characteristics that have been described to be similar across species. However, this "domestication syndrome" has been subject to debate, related to a lack of evidence for certain characteristics in many species. Here we review diverse literature and provide new data on cranial shape changes due to domestication in the European rabbit (Oryctolagus cuniculus) as a preliminary case study, thus contributing novel evidence to the debate. We quantified cranial shape of 30 wild and domestic rabbits using micro-computed tomography scans and three-dimensional geometric morphometrics. The goal was to test (1) if the domesticates exhibit shorter and broader snouts, smaller teeth, and smaller braincases than their wild counterparts; (2) to what extent allometric scaling is responsible for cranial shape variation; (3) if there is evidence for more variation in the neural crest-derived parts of the cranium compared with those derived of the mesoderm, in accordance with the "neural crest hypothesis." Our own data are consistent with older literature records, suggesting that although there is evidence for some cranial characteristics of the "domestication syndrome" in rabbits, facial length is not reduced. In accordance with the "neural crest hypothesis," we found more shape variation in neural crest versus mesoderm-derived parts of the cranium. Within the domestic group, allometric scaling relationships of the snout, the braincase, and the teeth shed new light on ubiquitous patterns among related taxa. This study-albeit preliminary due to the limited sample size-adds to the growing evidence concerning nonuniform patterns associated with domestication.

Cranial shape variation in mink: Separating two highly similar species.

European and American minks (Mustela lutreola and Neovison vison, respectively) are very similar in their ecology, behavior, and morphology. However, the American mink is a generalist predator and seems to adapt better to anthropized environments, allowing it to outcompete the European mink in areas where it has been introduced, threatening the survival of the native species. To assess whether morphological differences may be contributing to the success of the American mink relative to the European mink, we analyzed shape variation in the cranium of both species using 3D geometric morphometrics. A set of 38 landmarks and 107 semilandmarks was used to study shape variation between and within species, and to assess how differences in size factored into that variation. Sexual dimorphism in both size and shape was also studied. Significant differences between species were found in cranial shape, but not in size. Relative to American mink, European mink have a shorter facial region with a rounder forehead and wider orbits, a longer neurocranium with less developed crests and processes, and an antero-medially placed tympanic bullae with an anteriorly expanded cranial border. Within species, size-related sexual dimorphism is highly significant, but sexual dimorphism in shape is only significant in American mink, not in European mink. Additionally, two trends common to both species were discovered, one related to allometric changes and another to sexual size dimorphism. Shape changes related to increasing size can be subdivided into two, probably related, groups: increased muscle force and growth. The first group somewhat parallels the differences between both mink species, while the second group of traits includes an anterodorsal expansion of the face, and the neurocranium shifting from a globous shape in small individuals to a dorsoventrally flattened ellipse in the largest ones. Finally, the sexual dimorphism trend, while also accounting for differences in muscle force, seems to be related to the observed dietary differences between males and females. Overall, differences between species and sexes, and shape changes with increasing size, seem to mainly relate to differences in masticatory-muscle volume and therefore muscle force and bite force, which, in turn, relate to a wider range of potential prey (bigger prey, tougher shells). Thus, muscle force (and dietary range) would be larger in American mink than in European mink, in males than in females, and in larger individuals than in smaller ones.

Developmental stages of the ballan wrasse from first feeding through metamorphosis: Cranial ossification and the digestive system.

We have described six developmental stages for the ballan wrasse, from the first feeding until the juvenile stage, supported by specific descriptions of cranial ossification, maturation of the digestive tract, and growth-correlated stages. The initial formation and development of bones are closely linked to the functional anatomical structures required for the mechanics of its feeding behavior and ingestion, particularly the jaws and branchial regions involved in opening the mouth and capturing food particles. The overall ontogeny of the cranial structure compares to that of other teleosts. The cranial ossification of the ballan wrasse skull and the development of its dentary apparatus-first pharyngal teeth and later oral teeth-is linked to the development of the digestive system and to their feeding habits, from preying on zooplankton to feeding on crustaceans and invertebrates on rocks and other substrates. As ballan wrasse is a nibbler, eating small meals, the digestive tract is short compared to the length of the fish; there is no stomach or peptic digestion and also no distinctive bulbus and pyloric ceca. The liver and exocrine pancreas and their outlets terminating in the lumen of the most anterior part of the intestine are important in the digestive process and develop with a larger volume than that in gastric teleosts, relative to the digestive system.

Evolution of cranial capacity revisited: A view from the late Middle Pleistocene cranium from Xujiayao, China.

The Late Middle Pleistocene hominin fossils from the Xujiayao site in northern China have been closely studied in light of their morphological variability. However, all previous studies have focused on separated cranial fragments. Here, we report the first reconstruction of a fairly complete posterior cranium, Xujiayao 6 (XJY 6), confidently dated to ∼200-160 ka, which facilitated an assessment of its overall cranial size. XJY 6 was reconstructed from three of the original fragments-the PA1486 (No.7/XJY 6a) occipital bone, PA1490 (No.10/XJY 6b) right parietal bone, and PA1498 (No.17/XJY 15) left temporal bone-which originated from the same young adult individual. The XJY 6 endocranial capacity, estimated by measuring endocranial volume, was estimated using multiple regression formulae derived from ectocranial and endocranial measurements on select samples of Pleistocene hominins and recent modern humans. The results indicate that the larger pooled sample of both Pleistocene and recent modern humans was more robust for the endocranial capacity estimate. Based on the pooled sample using the ectocranial and endocranial measurements, we conservatively estimate the XJY 6 endocranial volume to be ∼1700 cm3 with a 95% confidence interval of 1555-1781 cm3. This is close to Xuchang 1, which dates to 125-105 ka and whose endocranial volume is ∼1800 cm3. Thus, XJY 6 provides the earliest evidence of a brain size that falls in the upper range of Neanderthals and modern Homo sapiens. XJY 6, together with Xuchang 1, Homo floresiensis, Homo luzonensis, and Homo naledi, challenge the general pattern that brain size gradually increases over geological time. This study also finds that hominin brain size expansion occurred at different rates across time and space.