Cranial Proportions Research Articles

A Craniometric Analysis of the Subfamily Cervinae (Cervidae, Mammalia)

This study employs Principal Component Analysis to examine cranial measurements from both extant and fossil specimens spanning 38 species and comprising over 300 individuals within the subfamily Cervinae. Our findings elucidate craniometric distinctions among cervids characterized by varying body sizes and certain evolutionary adaptations. While our results generally corroborate previous assertions regarding the limited craniometric variability among plesiometacarpal deer, they also unveil specific cranial adaptations within certain genera and species. The Principal Component Analysis of craniometric data revealed that giant and large-sized deer display significantly broader ecomorphological diversity in cranial shape compared to small-sized deer. Secondly, small-sized deer exhibit greater uniformity in their cranial shape, appearing densely clustered on the factorial map. Thus, we conclude that body size imposes ecological constraints, limiting the available niches due to eco-physiological factors. This study demonstrates that endemic insular deer do not evolve consistent craniometric features attributable to insular isolation, while the cranial proportions of medium-to-small-sized deer delineate a ubiquitous morphological archetype characteristic of numerous cervid taxa spanning diverse phylogenetic lineages and sharing comparable body sizes. This group of “Dama-like” deer, characterized by similar body size, metabolic rates, ecological needs, and cranial morphometry, is referred to here as the fundamental eco-physiological type, typical of warm regions within the Palearctic and Oriental biogeographic realms.

Diploic vein morphology in normal and craniosynostotic adult human skulls.

Diploic veins (DV) run within the cranial diploe, where they leave channels that can be studied in osteological samples. This study investigates overall DV variability in human adults and the effects of sex, age, cranial dimensions, and dysmorphogenesis associated with craniosynostosis (CS). The morphology of macroscopic diploic channels was analyzed in a set of the qualitative and quantitative variables in computed tomography-images of crania of anatomically normal and craniosynostotic adult individuals. Macroscopic diploic channels occur most frequently in the frontal and parietal bones, often with a bilaterally symmetrical pattern. DV-features (especially DV-pattern) are characterized by high individual diversity. On average, there are 5.4 ± 3.5 large macroscopic channels (with diameters >1 mm) per individual, with a mean diameter of 1.7 ± 0.4 mm. Age and sex have minor effects on DV, and cranial proportions significantly influence DV only in CS skulls. CS is associated with changes in the DV numbers, distributions, and diameters. Craniosynostotic skulls, especially brachycephalic skulls, generally present smaller DV diameters, and dolichocephalic skulls display increased number of frontal DV. CS, associated with altered cranial dimensions, suture imbalance, increased intracranial pressure, and with changes of the endocranial craniovascular system, significantly also affects the macroscopic morphology of DV in adults, in terms of both structural (topological redistribution) and functional factors. The research on craniovascular morphology and CS may be of interest in biological anthropology, paleopathology, medicine (e.g., surgical planning), but also in zoology and paleontology.

Demographics of Positional Plagiocephaly and Brachycephaly; Risk Factors and Treatment.

In the last 3 decades, the incidence of positional cranial deformations in infants, such as positional plagiocephaly and positional brachycephaly, has increased. The deviating shape often causes parental concern for the later psychosocial wellbeing of the child. Treatment options are nonoperative, varying from positional change to helmet therapy, of which the effect has often been debated. Multiple risk factors have been associated with an increased risk on the development of these deformations. The goal of this study was to assess the impact of known risk factors on the type and severity of resulting positional cranial deformation.Parents were asked to fill out a questionnaire regarding the presence of risk factors, such as gender, age, pregnancy duration, method of delivery and reasons for atypical deliveries, breech position, birth weight, developmental status, positional preference, family history, number of siblings, and torticollis presence. Treatment methods were documented and plagiocephalometry was used to measure the cranial proportions. All children were invited to participate in short-term follow-up. The significance of the risk factors and the effect of different kinds of therapy are discussed. Although no significant correlation was found between severity and risk factors, some risk factors could be correlated with the kind of positional cranial deformation. Of the different therapies, helmet therapy had a significant impact on the reduction of positional plagiocephaly.

First record of a tomistomine crocodylian from Australia

Based on the known fossil record, the majority of crocodylians from the Cenozoic Era of Australia are referred to the extinct clade Mekosuchinae. The only extant crocodylians in Australia are two species of Crocodylus. Hence, the viewpoint that Crocodylus and mekosuchines have been the only crocodylians inhabiting Australia during the Cenozoic has remained largely undisputed. Herein we describe Australia’s first tomistomine crocodylian, Gunggamarandu maunala gen. et sp. nov., thus challenging the notion of mekosuchine dominance during most of the Cenozoic. The holotype specimen of Gunggamarandu maunala derives from the Pliocene or Pleistocene of south-eastern Queensland, marking the southern-most global record for Tomistominae. Gunggamarandu maunala is known from a large, incomplete cranium that possesses a unique combination of features that distinguishes it from other crocodylians. Phylogenetic analyses place Gunggamarandu in a basal position within Tomistominae, specifically as a sister taxon to Dollosuchoides from the Eocene of Europe. These results hint at a potential ghost lineage between European and Australian tomistomines going back more than 50 million years. The cranial proportions of the Gunggamarandu maunala holotype specimen indicate it is the largest crocodyliform yet discovered from Australia.

Novel Sub-Clustering of Class III Skeletal Malocclusion Phenotypes in a Southern European Population Based on Proportional Measurements.

Current phenotypic characterizations of Class III malocclusion are influenced more by gender or ethnic origin than by raw linear skeletal measurements. The aim of the present research is to develop a Class III skeletal malocclusion sub-phenotype characterization based on proportional cranial measurements using principal component analysis and cluster analysis. Radiometric data from 212 adult subjects (115 women and 96 men) of southern European origin affected by Class III skeletal malocclusion were analyzed. A total of 120 measurements were made, 26 were proportional skeletal measurements, which were used to perform principal component analysis and subsequent cluster analysis. The remaining 94 supplementary measurements were used for a greater description of the identified clusters. Principal component analysis established eight principal components that explained 85.1% of the total variance. The first three principal components explained 51.4% of the variance and described mandibular proportions, anterior facial height proportions, and posterior–anterior cranial proportions. Cluster analysis established four phenotypic subgroups, representing 18.4% (C1), 20.75% (C2), 38.68% (C3), and 22.17% (C4) of the sample. A new sub-clustering of skeletal Class III malocclusions that avoids gender influence is provided. Our results improve clinicians’ resources for Class III malocclusion and could improve the diagnostic and treatment approaches for this malocclusion.

The Effect of Cranial Shape on Esthetic Self-Worth in Bald Men.

During the last 3 decades, the incidence of positional plagiocephaly and brachycephaly has increased. Treatment options are conservative and can include physiotherapy and molding helmet therapy. The decision to start therapy is based on patient history and subjective assessment of cranial shape by the physician and the parents. To determine the impact of these deformations on esthetic self-worth, as well as cranial shape, this study was conducted on a population of adult bald men.Participants were asked to fill in a questionnaire about the amount of comments received on cranial shape, as well as grade their general esthetic and grade craniofacial features using a visual analogue scale. The cranial proportions and symmetry were measured using plagiocephalometry.50 adult bald men were included in this study. The prevalence of nonsynostotic plagiocephaly was 12%; the prevalence of nonsynostotic brachycephaly was 0%. No significant correlation was found between plagiocephaly or brachycephaly, cranial circumference, width or length and amount of comments on cranial shape, cosmetic assessment of appearance or cosmetic assessment of cranial shape. On average, teeth and eyes were given the highest cosmetic value, eyebrows and chin were given the lowest scores.Cranial shape does not have a significant impact on the amount of comments received on cranial shape, nor the cosmetic assessment of either overall appearance or cranial shape in bald men. For bald men, eyes and teeth are more important craniofacial features in cosmetic assessment. There is no clear esthetic need to treat deviating cranial shape with helmet therapy in male patients.

Giant Flying Jaws: Aerodynamic Effects and Constraints on Cranial Hypertrophy in Pterosaurs

Pterosaurs are most well‐known for their expanded and altered forelimbs, which supported muscular membrane wings. Indeed, pterosaurs possessed one of the most derived hand morphologies of any vertebrate animal. However, several pterosaur lineages also possessed enormously expanded cranial and cervical proportions. The most extreme cases occur within ornithocheiroid and azhdarchoid pterosaurs, for which the cranial length, even excluding display crests, regularly exceeded 3.5 times the shoulder to hip distance.The enlarged heads and necks of many pterosaurs had implications for their flight and ecology. Understanding the costs and mechanisms of cranial hypertrophy in pterosaurs also has implications for understanding the evolution of the vertebrate skull, more generally. Investigating this problem is made particularly challenging by the fact that pterosaurs have no living descendants. A numerical modeling approach, using first principles, is likely the most effective way to investigate the evolution of cranial hypertrophy in pterosaurs.I addressed the performance impacts of cranial expansion in pterosaurs through a modeling approach combining aeromechanics and beam mechanics. I focused particularly on azhdarchids. These include some of the most extreme cases of cranial hypertrophy and possessed cervical anatomy amenable to beam theory applications (azhdarchids possessed highly derived cervical vertebrae with an elongate, tubular morphology). I used CT imaging to resolve cortical bone thickness in key elements. I created updated soft tissue reconstruction estimates, and I then applied both volumetric and scaling methods to estimate body masses and mass distribution.The results of this analysis provide new insights regarding the soft tissue morphology, flight dynamics, and wing positions of large pterosaurs. While the skulls were relatively light, the neck of azhdarchoid pterosaurs may have been much more robust than previously suggested. The Relative Cantilever Failure Force (RCFF) values of the cervical vertebrae range from roughly equal to nearly double that of the humeri. The expanded skull and neck of azhdarchid pterosaurs did have a substantial impact on center of mass (COM). To align the center of lift with the forward center of mass, a forward sweep of the wings was required. Rather than being a costly wing position, this would have improved low speed performance by delaying stall of the wingtip. Stability could be achieved dynamically through leading edge adjustments of the propatagium and passively with a wing dihedral and inboard reflex camber. Pterosaurs therefore may have obtained flight advantages from their expanded cranial and cervical proportions, in addition to any advantages to signaling or feeding.I suggest that cranial hypertrophy in pterosaurs is best explained as a case of constraint release, rather than an unusual selective regime. Other flying animals would probably obtain similar advantages from a forward center of mass, but developmental, anatomical, and ecological constraints most likely prevent extreme increases in head size in other flying taxa.Support or Funding InformationI wish to thank Gretchen Augustyn and Family for their financial support of research activities in the Dinosaur Institute of the NHMLAInstallation of two life sized Quetzalcoatlus sculptures by Blue Rhino Studio, demonstrating the giant size and extreme cranial proportions of these pterosaurs.Figure 1

Neonatal Ectotympanic Bone Variation among Lorisiforms and Tarsiers

Ectotympanic bone morphology is a classic characteristic used to differentiate primates and identify fossil affinities, often depicted as either a ring or tube falling along strict phylogenetic lines. Though ectotympanic bone morphology has been frequently cited in academic literature, the way in which this bone lengthens within and across taxa is still not well understood. The lorisiform ectotympanic bone is often characterized as ring‐like and fused to a slightly expanded petrosal bulla, however some authors have suggested that the degree to which the ectotympanic bone contributes to the external auditory meatus may vary within lorisiforms. The ectotympanic of tarsiers is often depicted as slightly elongate, though not as long as catarrhine primates. It is possible, and likely, that the lorisiform ear canal is longer than the lemuriforms though not as long as tarsiers. However, the degree to which the ectotympanic bone contributes to the ear canal has been a subject of some debate. Thus, can ontogeny resolve the questions surrounding the lorisiform and tarsier ectotympanic bones? Across lorisiforms, is the external auditory meatus derived from the petrosal bone, ectotympanic bone, or some combination of the two at birth?To address these questions, three genera of neonatal lorisiforms (Galago senegalensis, Nycticebus pygmaeus, and Loris tardigradus) and one species of tarsier (Tarsius syrichta) were qualitatively analyzed. It was found that in all three lorisiform species, the ectotympanic ring is formed by birth. The elongation of the ectotympanic bone in lorisiforms occurs almost immediately postnatally. The lorisiform and tarsier ectotympanic bones extend laterally as simple tubes, without forming the tubercles that are observed at intermediate stages in catarrhine species. The precise bony makeup of the lorisiform external auditory meatus varies among the genera studied. At birth among Loris and Nycticebus, the ear canal is already elongated but likely incorporates contributions from structures derived from the squamosal and petrous namely the post‐glenoid tubercle and the auditory bulla. The tarsier ectotympanic bone closely resembles the Galago at birth, and we suggest that the tarsier cranial proportions may be an underlying factor in the ultimate lengthening of the bone in this taxon.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Exceptional Disparity in Australian Agamid Lizards is a Possible Result of Arrival into Vacant Niche.

Australia provides abundant examples of continental-scale evolutionary radiations. The collision of two continental shelves around 30 Ma facilitated an influx of squamates and the subsequent squamate radiations resulted in high taxonomic diversity. The morphological disparity seen in these major squamate groups, however, remains underexplored. Here, we examine the major cranial proportions of over 1,000 specimens using 2D linear measurements to explicitly quantify the morphological disparity of Australian agamid lizards (Amphibolurinae) and compare it to that of agamid, acrodont, and iguanian clades from other parts of the world. Our results indicate the Australian Amphibolurinae have exceptionally high cranial disparity, and we suggest that this is linked to the relaxed selective environment that greeted the founders of Amphibolurinae when they first arrived in Australia. Anat Rec, 302:1536-1543, 2019. © 2019 American Association for Anatomy.

Hyper-longirostry and kinematic disparity in extinct toothed whales

AbstractToothed cetacean (Odontoceti) lineages in the Miocene and Pliocene evolved rostra that are proportionally more elongate than any other aquatic mammal or reptile, living or extinct. Their similarities in cranial proportions to billfish may suggest a convergent feeding style, where the rostrum is swept through the water to hit and stun prey. Here we calculated second moment of area from rostral cross sections of these fossil odontocete taxa, as well as from extant ecological analogues, to infer variation in feeding behavior. Our results show that the extremely long rostra of extinct toothed whales vary considerably in functionally relevant measures of shape and likely exhibited a diversity of feeding behaviors, ranging from those similar to modern odontocetes to those convergent with billfish. Eustatic sea-level and temperature maxima of the Miocene likely led to changes in prey characteristics or abundance that enabled the repeated evolution of this extreme morphotype, which later went extinct during late Pliocene climatic deterioration.

Convergencia en las proporciones craneanas entre primates del nuevo y el viejo mundo: un análisis craneofuncional

Convergencia en las proporciones craneanas entre primates del nuevo y el viejo mundo: un análisis craneofuncional

A new Cretaceous Pliosaurid (Reptilia, Plesiosauria) from the Carlile Shale (middle Turonian) of Russell County, Kansas

ABSTRACT The Eulert pliosaurid remains (FHSM VP-321) housed at the Sternberg Museum of Natural History (Kansas, U.S.A.) include one of the world's best examples of a Cretaceous pliosaurid plesiosaur skull. The specimen's original assignment to Brachauchenius lucasi was based solely upon the skull (dorsal surface) and left lower jaw (lateral view) because the specimen was embedded in a plaster mount. The history of B. lucasi is similarly problematic, because the type and a referred skull were formerly visible only in ventral and dorsal views, respectively. Further preparation and comparison of these specimens reveal new data about the arrangement of cranial elements. The Eulert pliosaurid bears several distinct autapomorphies as compared with B. lucasi, including cranial proportions (pretemporal length of palate longer, shorter temporal fenestrae), configuration of skull roof elements (frontals participate in premaxilla-parietal suture, suture occurs further forward), and configuration of the palate (posterior vomers not masked by medial alar extensions of the palatines, caudal vomerian fenestrae positioned further posterior, long slit-like anterior pteryoid vacuity present). Furthermore, FHSM VP-321 possesses double-headed cervical ribs, a feature previously unknown in Cretaceous pliosaurids. This combination of characters merits separation of the Eulert pliosaurid and a referred specimen to a new taxon, Megacephalosaurus eulerti. The type and paratype skulls of M. eulerti are 1.5 m and 1.75 m in length, respectively, and thus 50% and 75% larger than the known 1-m-long skulls of B. lucasi, suggesting that M. eulerti may attain larger size than B. lucasi.

Frank-ter Haar syndrome associated with sagittal craniosynostosis and raised intracranial pressure

BackgroundFrank-ter Haar syndrome is a rare disorder associated with skeletal, cardiac, ocular and craniofacial features including hypertelorism and brachycephaly. The most common underlying genetic defect in Frank-ter Haar syndrome appears to be a mutation in the SH3PXD2B gene on chromosome 5q35.1. Craniosynostosis, or premature fusion of the calvarial sutures, has not previously been described in Frank-ter Haar syndrome.Case presentationWe present a family of three affected siblings born to consanguineous parents with clinical features in keeping with a diagnosis of Frank-ter Haar syndrome. All three siblings have a novel mutation caused by the deletion of exon 13 of the SH3PXD2B gene. Two of the three siblings also have non-scaphocephalic sagittal synostosis associated with raised intracranial pressure.ConclusionThe clinical features of craniosynostosis and raised intracranial pressure in this family with a confirmed diagnosis of Frank-ter Haar syndrome expand the clinical spectrum of the disease. The abnormal cranial proportions in a mouse model of the disease suggests that the association is not coincidental. The possibility of craniosynostosis should be considered in individuals with a suspected diagnosis of Frank-ter Haar syndrome.

Heterochronies in skull development of Lake Tana large African barbs (Labeobarbus; Cyprinidae; Teleostei)

Summary Large African barbs (genus Labeobarbus) of Lake Tana (Ethiopia) form a species flock, which includes 15 species differing in biology, ecology, and shape features, including skull proportions. Early craniogenesis was studied in three species of Lake Tana barbs: L. intermedius, a proposed ancestor of Tana species flock, L. brevicephalus, a small-sized and early-maturating barb, and L. megastoma, a large-sized, piscivorous species. The general sequence of cranial cartilage and bone appearance is the same for the barb species studied. However, they differ greatly in temporal pattern of craniogenesis. As compared to L. intermedius, bony skull development is accelerated relative to chondrocranial development in L. brevicephalus and retarded in L. megastoma. These differences in temporal pattern of craniogenesis are proposed to account for the different cranial proportions displayed by these barbs.

A New Mouse-Eared Bat (Mammalia: Chiroptera, Vespertilionidae) from South China

A small Myotis species belonging to the Myotis siligorensis group was found in four caves in Yunnan province, South China. Twenty specimens of this bat were compared with other East Asian Myotis species. Statistical and physical analysis of this sample demonstrates that, despite their similarity to M. siligorensis, the Yunnan specimens have characteristics of baculum morphology and cranial proportions suggesting that they represent a distinct species.

The cranial anatomy, ontogeny, and relationships of Karpinskiosaurus secundus (Amalitzky) (Seymouriamorpha, Karpinskiosauridae) from the Upper Permian of European Russia

The Upper Permian seymouriamorph tetrapod Karpinskiosaurus from European Russia includes two species: Karpinskiosaurus secundus and Karpinskiosaurus ultimus. Karpinskiosaurus secundus is represented by two specimens with skull lengths of about 75 mm. All specimens of K. ultimus are smaller than those of K. secundus. Revision of the cranial anatomy of all previously known and several new specimens of Karpinskiosaurus shows that the specimens of K. secundus and most of the specimens of K. ultimus represent the ontogenetic series of one species: K. secundus. The holotype specimen of K. ultimus requires revision, with the aim to find out whether it represents a second species of Karpinskiosaurus or not. The available material permits new reconstructions of the largest, holotype skull, and one smaller skull with a length of about 36 mm. Karpinskiosaurus secundus is included in a cladistic analysis for the first time here. The analysis shows it to form a sister taxon to Discosauriscidae. The clade comprising Karpinskiosaurus secundus plus Discosauriscidae forms a sister group to Seymouriidae. Karpinskiosaurus secundus has a large postorbital and a short preorbital region, and the orbits are placed in the posterior portion of the anterior half of the skull length. Among all seymouriamorphs, such cranial proportions are exhibited only by the largest known specimens of Discosauriscus austriacus. None of the specimens of K. secundus described here exhibits the presence of sensory grooves; thus, all specimens composing the ontogenetic sequence of K. secundus are considered to be terrestrial. © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010.

Developmental perspectives on neurocranial proportions in Japan

This study employs juvenile cranial data derived from collections dating to between about 5000 years ago and the present in order to investigate how differences in cranial growth trajectories contributed to inter-group variation in cranial shape among temporally defined Japanese populations. As gene influx from the Asian mainland was insignificant after the Yayoi period (c. CE 300), differences in adult cranial shape among later assemblages from Japan are probably related to developmental adaptations to environmental change. Comparing cranial growth trajectories among groups from different time periods allows indirect testing of several hypotheses about secular changes in cranial growth, including thermoregulatory adaptation, change in levels of masticatory stress, and change in levels of physiological stress. Differences in neurocranial proportions among groups with contrasting adult cranial shapes were found to be already pronounced for the infant cohort (0–3 years of age) and actually tended to decline slightly within later age ranges; differences in mandibular shape were unremarkable early in life, but became more pronounced after infancy. Consequently, changes in chewing stress are unlikely to have been the principal factor driving inter-group differences in cranial proportions. The cranial growth pattern reconstructed from a Medieval Japanese skeletal series showed the greatest magnitude of difference from those reconstructed for other time periods. Unlike in the other groups, there was no marked decline of cephalic index with age for the Medieval series. The unusual trajectory of cranial growth evident in the Medieval sample may result from a high degree of physiological stress due to overall poor nutrition.

A new species of Crocidura (Soricomorpha: Soricidae) from southern Vietnam and north-eastern Cambodia

Knowledge of the Soricidae occurring in Vietnam has recently expanded with the discovery of several species previously unknown to science. Here we describe a new species of white-toothed shrew belonging to the genus Crocidura from lowland areas in southern Vietnam and from a river valley in north-eastern Cambodia. This small to medium sized species is diagnosed on the basis of external features, cranial proportions and morphology of the last upper and lower molars. Comparisons are made with other species of Crocidura known to occur in Vietnam and the biogeography of the regions where the new species has been found, is briefly discussed.

Systematic revision of the endemic deerHaploidoceros n. gen.mediterraneus (Bonifay, 1967) (Mammalia, Cervidae) from the Middle Pleistocene of Southern France

New osteological material of the endemic deer from Lunel-Viel and l’Igue des Rameaux (France) reveals its evolutionary specialization, and gives reason for establishing a new genus,Haploidoceros, with a single speciesH. mediterraneus (Bonifay, 1967). The cranial proportions and morphology suggest thatH. mediterraneus is close to the Late Villafranchian speciesMetacervocerus rhenanus, which may be a possible forerunner of the deer under study. The evolutionary origin ofH. mediterraneus took place in the Iberian glacial refugia during the “Mindel glaciation” of the early Middle Pleistocene. The North-East distribution ofH. mediterraneus was limited by unfavorable climate influence of the Arctic and Alpine Ice Shields.

Estimating body mass in New World “monkeys” (Platyrrhini, Primates), with a consideration of the Miocene platyrrhine, Chilecebus carrascoensis

Well-constrained estimates of adult body mass for species of fossil platyrrhines (New World “monkeys”) are essential for resolving numerous paleobiological questions. However, no consensus exists as to which craniodental measures best correlate with body mass among extant taxa in this clade. In this analysis, we analyze 80 craniodental variables and generate predictive equations applicable to fossil taxa, including the early platyrrhine Chilecebus carrascoensis.We find mandibular length to be the best craniodental predictor of body mass. There is no significant difference in predictive value between osteological and dental measures. Variables associated with the mandible and lower dentition do significantly outperform the cranium and upper dentition. Additionally, we demonstrate that modern platyrrhines differ, morphometrically, from early fossil forms. Chilecebus possesses unusual cranial proportions in several key features, as well as proportionally narrow upper incisors and wide upper cheek teeth. These variables yield widely divergent body mass estimates for Chilecebus, implying that the correlations observed in a crown group cannot be assumed a priori for early diverging fossils. Variables allometrically consistent with those in extant forms yield a body mass estimate of slightly less than 600 grams for Chilecebus, nearly a factor of two smaller than prior preliminary estimates.Scaled to body mass, the brain of Chilecebus is markedly smaller than those of modern anthropoids, despite its lowered body mass estimate advocated here. This finding, in conjunction with a similar pattern exhibited by fossil catarrhines, suggests that increased encephalization arose independently in the two extant subgroups of anthropoids (platyrrhines and catarrhines).