Cranial ontogenetic variability,sex ratio and age structure of the Red fox

Describing the sex ratio, age structure of the population and ontogenetic variability of Red fox, Vulpes vulpes (Canidae, Carnivora) skull parameters, this study is based on 416 male and 289 female skulls collected in the Czech Republic. The skulls analysed came from feral individuals, that were shot by hunters. The male to female ratio was 1:0.69 regarding the whole population. Individuals younger than one year prevailed in the population (54% males, 48% females were in their first year of life). Four growth patterns of skull dimensions were described. The first group included mainly skull length dimensions (e.g. condylobasal length). They grew rapidly until the sixth month of life, becoming stabilised afterwards. The second group comprised parameters that were stable throughout the life (e.g. cheek tooth rows). Measurements representing the third growth pattern showed continual growth (mainly width dimensions, e.g. zygomatic breadth). Conversely, smaller dimensions of postorbital breadth were observed after the sixth month of life. Postorbital breadth represented the fourth growth pattern. It was concluded, that male and female Red foxes had similar ontogenetic skull development, even though there were some differences, e.g. in jugular breadth, which increased after the age of six months in males unlike in females.     

Growth-related shape changes in the fetal craniofacial complex of humans (Homo sapiens) and pigtailed macaques (Macaca nemestrina): a 3D-CT comparative analysis

This study investigates whether macaques and humans possess a common pattern of relative growth during the fetal period. The fetal samples consist of 16 male pigtailed macaques (mean age, 20.5 gestational weeks) and 17 humans (9 males and 8 females; mean age, 29.5 gestational weeks). For each individual, three-dimensional coordinates of 18 landmarks on the skull were collected from three-dimensional computed tomographic (CT) reconstructed images and two-dimensional CT axial slices. Early and late groups were created from the human (early mean age, 24 weeks, N = 8; late mean age, 34 weeks, N = 9) and macaque samples (early mean age, 17.7 weeks, N = 7; late mean age, 23 weeks, N = 9). Inter- and intraspecific comparisons were made between the early and late groups. To determine if macaques and humans share a common fetal pattern of relative growth, human change in shape estimated from a comparison of early and late groups was compared to the pattern estimated between early and late macaque groups. Euclidean distance matrix analysis was used in all comparisons. Intraspecific comparisons indicate that the growing fetal skull displays the greatest amount of change along mediolateral dimensions. Changes during human growth are primarily localized to the basicranium and palate, while macaques experience localized change in the midface. Interspecific comparisons indicate that the two primate species do not share a common pattern of relative growth, and the macaque pattern is characterized by increased midfacial growth relative to humans. Our results suggest that morphological differences in the craniofacial skeleton of these species are in part established by differences in fetal growth patterns.     

Morphometric variation in the Hooded seal (Cystophora cristata)

Intra- and intersexual variation in 16 skull dimensions and total body length of 233 aged Hooded seals caught in the north-west Atlantic were investigated. Absolute growth was described by asymptotic growth curves applied to single dimensions, as well as to scores on the first principal component of logarithmically transformed cranial data, which are believed to reflect the multivariate nature of growth. All dimensions were found to be fully developed later in males than in females. The growth of the male skulls was found to continue for more than 20 years, while the females approach final size about–7 years earlier than males, according to the scores on the first principal component. Female seals were found to reach 86 % of final total body length at the time of maturation, which is a generalized pinniped pattern. In both sexes, a yearling skull was characterized by a large brain-case, which decreased relatively with growth. The male skulls were further characterized by an increase in zygomatic width and orbital width in relation to basal length, a pattern which was not found in females.
All the asymptotic values were significantly larger in males than in females. The dimorphism develops mainly as a result of prolonged growth of males after the attainment of sexual maturity.     

Age and growth of sailfish Istiophorus platypterus (Shaw in Shaw and Nodder, 1792) from Mazatlan, Sinaloa, Mexico

Age and growth of the sailfish Istiophorus platypterus were determined for the area off Mazatlan coast, Sinaloa, in the Gulf of California, between September 2002 and August 2003. The lower jaw-fork length and total weight of 572 specimens were measured, and the fourth dorsal spine was collected to determine age. The monthly variation of the sample size displayed a well-defined seasonal pattern, which peaked during the warm period (May?CNovember) and declined during the rest of the year (temperate period). Significant differences were detected in the size structure by sex during the temperate period, with females displaying larger sizes and greater abundance (Female:Male = 3.35:1). In the warm period the size structure was similar, with the sex ratio reaching F:M = 0.73:1. This suggests a different sex-related recruitment in the fishing zone, with males moving more actively than females. While female size remained relatively unchanged over the year, male size increased during the warm period. Age was estimated using the number of growth rings on the cross-sectioned fourth dorsal spine, after the number of absorbed growth rings in the vascularized zone had been estimated. Nine age groups were identified; group-5 was the most abundant, representing 31% of the catch. The trend of the monthly change in the percentage of opaque-edge spines and the average of the marginal increase rate indicated that the formation of growth rings displayed an annual pattern. The von Bertalanffy growth model was adequately fitted to age and back-calculated length data. Significant differences were detected when growth was compared between sexes; females grew faster than males.     

Measurements of tooth wear among Australian Aborigines: I. Serial loss of the enamel crown

The dental casts made from Aboriginal children during the course of a longitudinal growth study in Central Australia provided material for analyzing tooth wear under known environmental conditions. The wear facets produced on the occlusal surfaces were clearly preserved on the dental stone casts and recorded the progress of enamel attrition from ages 6 to 18. These casts were photographed and traced by electronic planimetric methods that automatically recorded the location and size of wear facets on the first and second permanent molars. These areas of worn tooth surface were compared to the total tooth surface. The worn surface was regressed on age to calculate wear rates of each tooth. Discriminant analyses were also performed to determine the significance of dental attrition differences between the sexes at each age group. The total wear on each tooth was highly correlated with age as expected but females wore their teeth at a significantly higher rate than males. The mandibular molars wore more rapidly than maxillary teeth in both sexes. The discriminant analysis successfully grouped 91% of the cases according to age and sex. Pattern of wear, the location, and size of wear facets also differed between age groups and sex. The questions of why there is a difference between male and female wear or why there is greater wear on one arch or arch region have no ready answers. The differing rates and pattern of dental wear do suggest that arch shape and growth rates may be the answer though it has yet to be tested. However, the occlusal surface wear is useful for age estimation in a population and provides a record of shifting masticatory forces during growth.     

Sexual dimorphism in the postcranial skeleton of New World primates

This study examines sexual dimorphism in 24 dimensions of the postcranial skeleton of four platyrrhine species: Callithrix jacchus, Saguinus nigricollis, Saimiri sciureus, and Cebus albifrons. The two callitrichid species show a relatively small amount of variation in the degree of sexual dimorphism among the different dimensions. Variation is considerably higher in the two cebid species as reflected by a mosaic pattern of sexual dimorphisms with males being significantly larger than females in some dimensions, and females significantly larger than males in others. In dimensions of the pectoral girdle and limb bones, males and females in each of the two cebid species are essentially scaled versions of each other, with males being peramorphic compared to females. This pattern is primarily the result of time hypermorphosis, i.e. an extension of the growth period in time in males. Rate hypermorphosis, i.e. an increase in the rate of growth in time in males, appears to play an additional role, however, in S. sciureus. By contrast, in dimensions of the true pelvis, sex differences in shape are dissociated from those in size. They are interpreted as the result of acceleration, i.e. increase in rate of shape change in females, as an adaptation to obstetrical functions. Interspecific analyses indicate positive allometry of mean degree of postcranial dimorphism with respect to body size. This coincides with previous findings by Leutenegger and Cheverud [1982, 1985] on the scaling of sexual dimorphism in body weight and canine size, and thus supports their model which posits selection on body size as the prime mover for the evolution of sexual dimorphism.     

Dental arch form in the cercopithecidae

The dental arches of the major genera of Old World monkeys (superfamily Cercopithecoidea) were studied by morphometric techniques. Bicanine and bimolar breadths and arch lengths were ascertained for maxillary and mandibular arches. This data was then subjected to a variety of statistical tests. Corresponding arch dimensions of the upper and lower dentition showed the highest correlations, while the lowest correlations were generally observed between comparisons of arch dimensions and body size. A new expression was developed, relative male palate size (RMPS), which quantified the degree of sexual dimorphism while correcting for body size. The four hierarchies examined using RMPS values were sexual dimorphism, modes of sexual selection and predator defense and diet. Maxillary bicanine breadth was the only parameter that exhibited sexual dimorphism consistently in each of the four hierarchies, although differences in arch size were identified for diet and predator defense. Species grouped by predator defense showed the most sexual dimorphism in arch parameters.     

The ontogeny of sexual dimorphism in the cranium of Bornean orang-utans (Pongo pygmaeus pygmaeus): II. Allometry and heterochrony

Based on a homogeneous sample of 212 individuals spanning all postnatal periods, we examine the ontogeny of cranial sexual dimorphism in Bornean orang-utans (Pongo pygmaeus pygmaeus) by means of allometric analysis and in terms of heterochrony. The bivariate growth allometries of 20 cranial dimensions against basicranial length yield two major patterns. Confirming the null hypothesis, strong ontogenetic scaling, where growth regressions of both sexes fall along a single ontogenetic continuum, and where shape differences between adult males and females result from the extension of relative growth in the smaller females to larger size in males, is found in 10 cases. Ontogenetic scaling is particularly strong in proportions of (1) the neurocranium directly associated with brain size, (2) the orbital region, and (3) the dental arcade. In terms of heterochrony such a pattern most likely is the result of a process termed "time hypermorphosis", i.e. an extension of the growth period in time in males. The second major pattern seen in the remaining 10 cases shows a departure from ontogenetic scaling, with males exhibiting a significantly steeper slope than females. Departures from ontogenetic scaling, where size and shape are dissociated with adult males being disproportionately larger than adult females, are found in proportions of cranial regions directly associated with secondary sexual character development: prognathism, canine size, and cheek pad area. In terms of heterochrony such a pattern most likely is the result of a process termed "acceleration", i.e. the rate of shape change is increased in males.     

Aging in the lumbar spine. II. L1 and L2

The bodies of the first and second lumbar vertebrae, like those of L3 and L4, show a significant trend toward lowering and broadening with age. Superior, inferior, and midbody transverse breadths increase, but there is little or no increase in endplate "flaring" with age. There is essentially no change in the relationship between anterior and posterior heights, but as reported for L3 and L4, there is a sexual difference in the amount and type of wedging of the bodies of L1 and L2. Posterior wedging (posterior height less than anterior height) of these vertebrae is about twice as common in females as in males. Whites of both sexes show a statistically significant relationship between age and increased biconcavity of the endplates. Black females, but not the males, show a similar trend, especially in L1.     

Some aspects of aging in the lumbar spine

I measured the bodies of vertebrae L3 and L4 of 338 skeletons from the Terry collection in the Smithsonian Institution, including Blacks and Whites, males and females, aged from 20 to 90 years. Transverse breadths of the upper and lower endplates (excluding osteophytes) and minimum transverse breadths all increase with age. In general, the greater broadening occurs in the endplates, but the middle of the body also broadens to such a degree that there is no demonstrable increase in vertebral “flaring” with age. In males, posterior body height decreases relative to anterior height, so that the lumbar bodies become more wedge-shaped with age, but females show essentially no change. Anterior height decreases in proportion to minimum breadth, so that the lumbar bodies become relatively lower and broader, and this change is significantly correlated with age in all groups. Midbody height decreases relative to anterior height, so that Nordin's biconcavity index is reduced with age. The increase in biconcavity remains evident even when average anterior-posterior height is used to calculate the index. At all age levels a high percentage of individuals have biconcavity indices of 80% or less, indicating that Nordin's standard of normality for this index, established from measurement on radiographs of the living, should be revised downward for use in evaluating osteoporosis in skeletal populations.     

Craniofacial dimensions in children in rural Oaxaca, southern Mexico: secular change, 1968-2000

The objective of this investigation was to analyze the underlying cause(s) of secular changes in craniofacial dimensions among indigenous children in an isolated community in Oaxaca, southern Mexico, between 1968-2000. Subjects were schoolchildren resident in a rural, agrarian, Zapotec-speaking community in the Valley of Oaxaca, previously characterized as mildly-to-moderately undernourished with growth-stunting in 1968 and 1978. In 2000, children had experienced a secular increase in height compared with two prior growth surveys. Four craniofacial dimensions (head length, head breadth, and bizygomatic and bigonial breadths) were measured during anthropometric surveys of schoolchildren aged 6-13 years in 1968, 1978, and 2000. Cephalic and zygomandibular indices were calculated. Samples by survey were: 1968, 151 males and 157 females; 1978, 179 males and 184 females; and 2000, 180 males and 186 females. The analysis was based on a total of 1,037 children. Multivariate analysis of covariance was used to assess secular trend effects, with height, age, and age2 as covariates by sex. Over the interval of 32 years, significant secular changes occurred in craniofacial dimensions and one index: 1) head length was shorter in boys and girls; 2) bizygomatic breadth was narrower in boys and girls; 3) head breadth increased over time only among girls; 4) brachycephalization increased significantly in a linear manner among both sexes; and 5) the zygomandibular index decreased significantly only in boys. Thus, the cranial complex remodeled to a shorter head length, both relatively (brachycephalization) and absolutely. Remodeling over time also resulted in a narrower face, with the midface changing at about the same rate as the lower face (i.e., mandible). Secular changes are generally recognized as multifactorial. Changes in the cephalic index and cranium over time in schoolchildren in an isolated rural agrarian Zapotec-speaking community in the Valley of Oaxaca suggest that the underlying forces for the secular change are associated: 1) decreased food (maize) coarseness or grit content (masticatory stress), and 2) relaxed natural selection, resulting in 3) a greater role for developmental plasticity.     

Ontogeny of craniofacial sexual dimorphism in the orangutan (Pongo pygmaeus). I: face and palate

The orangutan is widely recognized as a highly dimorphic species. An ontogenetic approach to the study of sexual dimorphism can assist researchers in understanding both where and when these differences develop. In this study, 357 orangutans from Borneo were divided into five developmental stages representing infancy to mature adulthood. Three-dimensional (3D) coordinate data from 16 landmarks representing the face and palate were analyzed by means of a Euclidean distance matrix analysis (EDMA), a quantitative method for the comparison of forms. Three separate analyses (an age-specific static comparison of forms, a sex-specific analysis of growth trajectories, and an intersex comparison of patterns of relative growth) were carried out with the intent to describe the rate, timing, magnitude, and pattern of growth in the orangutan face and palate. The results indicate that generally males and females share a similar, but not identical, pattern of growth or local form change, but differ in growth rate, timing, and magnitude of difference. Dimorphism in the face and palate can be localized in infancy and traced throughout all age intervals. Orangutan females grow slightly faster than males from infancy to adolescence, at which time male growth exceeds female growth. Female growth ceases with the advent of adulthood, while male growth continues (i.e., both the number and magnitude of the dimorphic dimensions increase). Males and females are similar in facial dimensions and growth related to the orbits, upper face, and palate width. They maintain these similarities throughout development. However, they differ in facial and nasal height, palate length, snout projection, depth of the nasopharynx, and hafting of the face onto the skull. The face broadens and the zygomatic bone flares dramatically in adult males, corresponding to the development of cheek pads. While growth patterns are similar between the two sexes, they differ in the lateral orbit, snout projection, and hafting of the face onto the cranium. Adult dimorphism is the result of growth patterns experienced throughout life, and it is not equally expressed across the cranium. An understanding of patterns of dimorphism, along with the magnitude of difference, may be helpful for interpreting dimorphism in the fossil record.     

Palatal dimensions in 45,X-females

Seventy-two females with 45,X-chromosome complement were examined for palatal dimensions, and the results of the measurements were compared to those of first-degree normal female relatives of the study subjects and population control females. Hard stone casts were prepared for measuring widths and lengths of the maxillary alveolar arch and palatal height between or at the level of the permanent canines, first and second premolars, and first molars with a palatometer and sharp-pointed vernier calipers (0.5 mm). According to the analyses of covariance (history of orthodontic treatment and loss of permanent teeth as cofactors and age as covariate), the differences in palatal dimensions between the groups were statistically significant or highly significant for all dimensions except for palatal height in the posterior segments. The group of the 45,X-females had the highest mean value for palatal height at the level of the canines and systematically the lowest mean values for palatal width in all segments, while no clear difference could be found in the length of the alveolar arch between the 45,X-females and the relatives, the population control group showing the lowest value in the posterior segments. The findings of this study indicate that the narrowed palate rather than the high palate is a frequent but not definite feature in 45,X-females. This may reflect the effect of sex-chromosomes on width but not other dimensions of the palate, resulting in deficiency of transversal growth of the palate possibly through decreased growth of the palatal shelves or through disturbances in the growth of the nasal septum, sutural growth, or--to which the exostosis on the palatal alveolar plates would refer--disturbances in apposition-resorption growth changes of the maxilla.     

青少年的足纹研究

木文报道了安徽省芜湖地区372例青少年11项足纹参数正常值。在左右足问、男女性间以及民族和人种间进行了比较。为记录足心部的花纹,作者在蹠部分区中补增一足弓区。     

The ontogeny of sexual dimorphism in the cranium of Bornean orang-utans (Pongo pygmaeus pygmaeus): I. Univariate analyses

Based on a homogeneous sample of 212 individuals spanning all postnatal age periods, we examine the ontogeny of cranial sexual dimorphism in Bornean orang-utans (Pongo pygmaeus pygmaeus) by means of univariate statistics. A distinct pattern emerges at the early juvenile stage and continues at all subsequent stages with males tending to exceed females in all cranial dimensions. In conjunction, starting at mid-juvenile stage, there is a strong tendency for an increase in number and strength of significant cranial sex differences, all of them in favor of males. Significant sex differences in the viscerocranium, reflecting stronger prognathism in males, emerge prior to those in the neurocranium. The total ontogenetic pattern of cranial sexual dimorphism in orang-utans is remarkably similar to that of gorillas, except that there is no evidence of a sex difference in timing of the adolescent growth spurt in the orang-utan. As for other catarrhine species (Wood 1976), male variance of cranial dimensions tends to be greater than that of females, thus lending support to Leutenegger & Cheverud's (1982, 1985) model on the evolution of character dimorphism by means of variance dimorphism.     

中国14个特殊旁系族群的头面部特征比较

头面部特征是人类学各人种进行分类的重要依据,在人类学的研究中被用作亲缘关系的证据.2006-2016年在四川、云南、西藏、贵州、海南、新疆、内蒙古共调查14个族群成人2989人(男性1434人,女性1555人)的16项头面部指标,比较这些族群头面部特征差异.研究结果如下:1)在男性族群中木雅人、尔苏人、临高人、白马人的...     

Proximate causes of Rensch's rule: does sexual size dimorphism in arthropods result from sex differences in development time?

A prominent interspecific pattern of sexual size dimorphism (SSD) is Rensch's rule, according to which male body size is more variable or evolutionarily divergent than female body size. Assuming equal growth rates of males and females, SSD would be entirely mediated, and Rensch's rule proximately caused, by sexual differences in development times, or sexual bimaturism (SBM), with the larger sex developing for a proportionately longer time. Only a subset of the seven arthropod groups investigated in this study exhibits Rensch's rule. Furthermore, we found only a weak positive relationship between SSD and SBM overall, suggesting that growth rate differences between the sexes are more important than development time differences in proximately mediating SSD in a wide but by no means comprehensive range of arthropod taxa. Except when protandry is of selective advantage (as in many butterflies, Hymenoptera, and spiders), male development time was equal to (in water striders and beetles) or even longer than (in drosophilid and sepsid flies) that of females. Because all taxa show female-biased SSD, this implies faster growth of females in general, a pattern markedly different from that of primates and birds (analyzed here for comparison). We discuss three potential explanations for this pattern based on life-history trade-offs and sexual selection.     

Female biological resiliency: Differential stress response by sex in human remains from ancient Nubia

This research presents male-female differences in stress response evidenced in human remains from the Medieval site of Kulubnarti in Sudanese Nubia. This analysis is unique in that a direct comparison of subadult males and females is rarely possible using archaeological remains. Rather, such analyses invariably rely on evidence of subadult differences retained in adult (sexable) skeletons. In the case of Kulubnarti, natural mummification has made it possible to measure sex-specific differences among subadults as well as adults following five avenues of investigation: 1) mortality, 2) growth and development, 3) enamel hypoplasia, 4) cribra orbitalia, and 5) cortical bone maintenance. A comparison of mean life expectancy (eox) values for males and females aged 10–55+ years revealed a consistent pattern of greater female survivorship, particularly in childhood (age 10 category) where female life expectancy exceeds that of males by 19%. Measures of growth and development, enamel hypoplasia, cribra orbitalia, and cortical bone loss were subsequently used to test a hypothesis of greater female resiliency based on the mortality data. Male-female differences in skeletal maturation are pronounced with male skeletal ages averaging a significant 2.9 years below their dental age. Females show no significant differences with an average skeletal age 0.75 years ahead of dental age. Males begin hypoplasia formation one year earlier than females and, prior to age four, average 18% more hypoplasias (p<0.05). Also, by age 8, males have on average more than twice the frequency of cribra orbitalia (p<0.05). In contrast to their consistent pattern of reduced childhood stress, adult females lose significantly more cortical bone than their male counterparts and have less cortical bone across the adult age range. Nevertheless, females outnumber males of all ages with a sex-ratio below but parallel to that observed in modern populations. The rapid age-related reduction in males relative to females, even in old age, suggests a continuing female resiliency in spite of their greater rate of osteopenia and may reflect a reproductive advantage to the population through heightened female survival and adaptability.     

Age differences in craniofacial dimensions among adults from Indian Knoll,Kentucky

Adult craniofacial expansion with aging has recently been documented in a living US white population sample (Israel, '73a, '77). The present study extends these findings to a prehistoric Amerindian skeletal sample from the Indian Knoll, Kentucky site. Sixteen craniofacial dimensions available for 136 adult males were compared in younger (20–34 years) and older (35–50 years) age groups. Of these, six dimensions showed a significant difference between age groups; all significantly different dimensions were larger in the older adult age group. The multivariate (T²) difference between age groups was highly significant. Comparison of results before and after a size standardization indicated that the majority of differences between age groups were associated with an overall size increase, or expansion with aging, and did not represent merely remodeling, or “shape” changes. The pattern of craniofacial change with age appeared generally similar to that observed in the modern US white sample; however, some differences were noted. It is shown that the age trends observed at Indian Knoll are most likely to reflect true craniofacial growth in size among the adult male inhabitants of the site, rather than secular trends or other artifacts of the sampling procedure. The causes for continuing adult craniofacial expansion are unknown, and probably involve a complex interaction of many factors. However, this pattern of change with age among adults does appear to be characteristic of population samples of widely differing genetic and environmental backgrounds.