Problems of body-weight estimation in fossil primates

Body-weight estimates of fossil primates are commonly used to infer many important aspects of primate paleobiology, including diet, ecology, and relative encephalization. It is important to examine carefully the methodologies and problems associated with such estimates and the degree to which one can have confidence in them. New regression equations for predicting body weight in fossil primates are given which provide body-weight estimates for most nonhominid primate species in the fossil record. The consequences of using different subgroups (evolutionary “grades”) of primate species to estimate fossil-primate body weights are explored and the implications of these results for interpreting the primate fossil record are discussed. All species (fossil and extant) were separated into the following “grades”: prosimian grade, monkey grade, ape grade, anthropoid grade, and all-primates grade. Regression equations relating lower molar size to body weight for each of these grades were then calculated. In addition, a female-anthropoid grade regression was also calculated for predicting body weight infernales of extinct, sexually dimorphic anthropoid species. These equations were then used to generate the fossil-primate body weights. In many instances, the predicted fossil-primate body weights differ substantially from previous estimates.     

中国中生代鸟类的体重估计及其演化趋势

体重是一项重要的生物学指标,生物的体重受到发育、繁殖和进化等诸多因素的影响。对于灭绝生物体重的估计有助于进一步恢复它们的各种生物学信息。本研究采用统计学的方法,对422件现生鸟类(分属于21目229种)的体重和18项骨骼量度指标分别进行一元回归分析,结果显示判定系数的分布范围在0.5～0.91之间,多数指标的判定系数均集中在0.8～0.9之间。采用另外64件测量有体重数据和骨骼量度的鸟样本对回归方程的估算准确率进行检验,发现前肢中肱骨长度和尺骨宽度以及后肢中胫跗骨宽度3项指标的估算准确率高于其他指标。分析结果还表明前肢两项指标对于估算鸣禽、猛禽和攀禽类等树栖鸟类的体重准确率较后肢显著;后肢指标对于估算陆禽类等地栖鸟类体重的准确率高于前肢指标。这一结果反映出与体重相关程度较高的骨骼量度指标在不同习性的鸟类当中存在着一定的差异。对于化石鸟类的体重估计,采用估算准确率较高并且便于测量的肱骨长度和胫跗骨宽度两项回归方程加以计算。通过对中国中生代鸟类的体重进行估算,结果显示中生代鸟类在系统发育过程中,反鸟类经历了体重逐渐减轻的过程,而今鸟类的体重开始不断增大并且出现显著的分异。     

The astragalus of Paleogene artiodactyls: comparative morphology, variability and prediction of body mass

Martinez, J.-N. & Sudre, 1. 1995 11 30 The astragalus of Paleogene artiodactyls: comparative morphology, variability and prediction of body mass. Lethaia , Vol. 28, pp. 197–209. Oslo. ISSN 0024–1164.
The morphology of the astragalus is analysed in nineteen Paleogene artiodactyls (suborders Palaeodonta, Suina, Ancodonta and Ruminantia). This morphology is related to the functional adaptations of the appendicular skeleton, but some diagnostic characters can be seen at the family level. For the populations examined, the proportions of this bone show a low intraspecific variability, which does not allow detection of any dimorphism. An allometric relationship between the dimensions of the astragalus and the body mass has been established for extant species, allowing estimates for the fossil species. In most cases, the interval between the two extreme estimations using the astragalus includes the estimated body mass using M/1 area. The limits of this method are discussed, and it is suggested that the dimensions of the astragalus give a better estimation of the body mass than the dental area. □ Artiodactyls, astragalus, comparative morphology, body mass, allometry, Paleogene .     

Quantitative trait loci for body size components in mice

Do body size components, such as weights of internal organs and long bone lengths, with different functions and different developmental histories also have different genetic architectures and pleiotropic patterns? We examine murine quantitative trait loci (QTL) for necropsy weight, four long bone lengths, and four organ weights in the LG/J × SM/J intercross. Differences between trait categories were found in number of QTL, dominance, and pleiotropic patterns. Ninety-seven QTLs for individual traits were identified: 52 for long bone lengths, 30 for organ weights, and 15 for necropsy weight. Results for long bones are typically more highly significant than for organs. Organ weights were more frequently over- or underdominant than long bone lengths or necropsy weight. The single-trait QTLs map to 35 pleiotropic loci. Long bones are much more frequently affected in groups while organs tend to be affected singly or in pairs. Organs and long bones are found at the same locus in only 11 cases, 8 of which also include necropsy weight. Our results suggest mainly separate genetic modules for organ weights and long bone lengths, with a few loci that affect overall body size. Antagonistic pleiotropy, in which a locus has opposite effects on different characteristics, is uncommon.     

The relationship between organ weights and body weights, facial dimensions, and dental dimensions in a population of olive baboons (Papio cynocephalus anubis)

Questions concerned with the relationship between organ weights and body weight on an intraspecific level are best answered by using a sample of animals collected in the wild from a single locale during a single season. The organ weights and body weights for this study were obtained from the necropsy reports prepared in the field (Athi Plain, Kenya) by H. C. McGill, Jr. on 36 adult animals (18 males and 18 females). Dental and facial measurements were taken by M.I. Siegel. In order to avoid erroneous results produced by statistical treatment of combined sex samples of sexually dimorphic species, data on the sexes were analyzed separately. Means and standard deviations are reported for selected organ weights and body dimensions (heart, lung, liver, spleen, kidney, adrenal, brain, and pancreas weights, crown–rump length, crown–heel length, head circumference, chest circumference, and body weight). All of the above measures were significantly (p<0.05) different between the sexes. Logarithms of these measures were significantly correlated with the logarithm of body weight in males for heart, lung, liver, spleen, kidney, and adrenal weights, crown–heel length, and head and chest circumference, and in females for crown–heel length, heart, liver, and kidney weights. Partial correlational analysis, removing the effects of body size (weight), showed mostly negative correlational relationships between dental and visceral dimensions. Most of the correlations between facial and visceral dimensions were negative. Allometric equations were calculated for the dental, facial, and visceral dimensions versus body weight, and are compared with prior published results.     

Geometry and evolutionary parallelism in the long bones of cavioid rodents and small artiodactyls

Morphological parallelism between South American cavioid rodents and small artiodactyls from the Old World has been postulated for a long time. Our study deals with this question from the point of view of biomechanical characteristics of the long bones. For this, cross-sectional area, second moment of the area, polar moment, athletic ability indicators and strength were calculated for the long bones (i.e. humerus, radius, femur and tibia) of five species of cavioids and two species of artiodactyls. Regressions of all these variables to body mass were established. Regarding the cross-sectional area, the confidence intervals show that the exponents calculated are not significantly different from the geometrical predicted value. The exponents obtained for the second moment of area and the polar moment are not significantly different from the geometrical prediction, except for the humerus. The two indicators of athletic ability scaled as expected, but the bending indicator of athletic ability of the femur was not correlated to body mass. The exponent calculated for femur strength is not different from zero, while the strength of the humerus decreases slightly with the body mass. Additional statistical tests (ANCOVAs) showed no difference between the values of these variables calculated for the samples studied of artiodactyls and rodents. The present results are consistent with the hypothesis that there is significant evolutionary parallelism between cavioid rodents and small artiodactyls.     

Determination of sex from arm bone measurements

Discriminant function analysis has been applied to numerous dimensions of the cranial and postcranial skeleton for sex determination of U.S. blacks and whites and is extended here to five measurements of the arm and wrist. These include maximum lengths of the long arm bones in addition to two measurements that reflect wrist breadth. Our results indicate that whites are more accurately classified than blacks, but seven of the 31 possible measurement combinations common to both groups yield functions with sex prediction accuracies comparable to most, but not all, functions based on other parts of the skeleton.     

Body weight prediction in early fossil hominids: Towards a taxon-“independent” approach

The choice of a model taxon is crucial when investigating fossil hominids that clearly do not resemble any extant species (such as Australopithecus) or show significant differences from modern human proportions (such as Homo habilis OH 62). An “interhominoid” combination is not adequate either, as scaling with body weight is strongly divergent in African apes and humans for most skeletal predictors investigated here. Therefore, in relation to a study of seven long bone dimensions, a new taxon-“independent” approach is suggested. For a given predictor, its taxonomic “independence” is restricted to the size range over which the body weight-predictor relationship for African apes and humans converges. Different predictors produce converging body weight estimates (BWEs) for different size ranges: taxon-“independent” estimates can be calculated for small- and medium-sized hominids (e. g., for weights below 50 kg) using femoral and tibial dimensions, whereas upper limb bones provide converging results for large hominids (above 50 kg). If the remains of Australopithecus afarensis really belong to one species, the relationship of male (above 60 kg) to female body weight (approximately 30 kg) does not fall within the observed range of modern hominoids. Considering Sts 14 (22 kg) to represent a small-sized Australopithecus africanus, the level of encephalization lies well above that of extant apes. If OH 62 (approximately 25 kg), with limb proportions less human-like than those of australopithecines, indeed represents Homo habilis (which has been questioned previously), an increase in relative brain size would have occurred well before full bipedality, an assumption running counter to current assumptions concerning early human evolution. © 1993 Wiley-Liss, Inc.     

Allometry and adaptation in the long bones of a digging group of rodents (Ctenomyinae)

Previous studies of rodent appendicular morphology suggest that digging activity induces changes in long bones, producing shorter and thicker structures. Subsequent hypotheses have been tested in Ctenomyinae, a group of octodontid rodents globally adapted to subterranean life. Slopes of the equations calculated for extant animals and their corresponding confidence intervals agree with expectations in almost all cases. Results on fossil taxa are less clear, but suggest a morphocline from a plesiomorphic condition of the appendicular skeleton, present in the fossil genera, departing little from that of the current epigeous rodents, to a more derived long bone design in the species of the living genus Ctenomys , in accordance with their digging activity.     

Mechanics of posture and gait of some large dinosaurs

Dimensions of dinosaur bones and of models of dinosaurs have been used as the basis for calculations designed to throw light on the posture and gaits of dinosaurs.
Estimates of the masses of some dinosaurs, obtained from the volumes of models, are compared with previous estimates. The positions of dinosaurs' centres of mass, derived from models, show that some large quadrupedal dinosaurs supported most of their weight on their hind legs and were probably capable of rearing up on their hind legs.
Distributions of bending moments along the backs of large dinosaurs are derived from measurements on models. The tensions required in epaxial muscles to enable Diplodocus to stand are calculated. It is likely that the long neck of this dinosaur was supported by some structure running through the notches in the neural spines of its cervical and dorsal vertebrae. The nature of this hypothetical structure is discussed.
An attempt is made to reconstruct the walking gait of sauropod dinosaurs, from the pattern of footprints in fossil tracks.
The dimensions of dinosaur leg bones are compared to predictions for mammals of equal body mass, obtained by extrapolation of allometric equations. Their dimensions are also used to calculate a quantity which is used as an indicator of strength in bending. Comparisons with values for modern animals lead to speculations about the athletic performance of dinosaurs.
Estimates of pressures exerted on the ground by the feet of dinosaurs are used in a discussion of the ability of dinosaurs to walk over soft ground.     

Body mass and stature estimation based on the first metatarsal in humans

Archaeological assemblages often lack the complete long bones needed to estimate stature and body mass. The most accurate estimates of body mass and stature are produced using femoral head diameter and femur length. Foot bones including the first metatarsal preserve relatively well in a range of archaeological contexts. In this article we present regression equations using the first metatarsal to estimate femoral head diameter, femoral length, and body mass in a diverse human sample. The skeletal sample comprised 87 individuals (Andamanese, Australasians, Africans, Native Americans, and British). Results show that all first metatarsal measurements correlate moderately to highly (r = 0.62-0.91) with femoral head diameter and length. The proximal articular dorsoplantar diameter is the best single measurement to predict both femoral dimensions. Percent standard errors of the estimate are below 5%. Equations using two metatarsal measurements show a small increase in accuracy. Direct estimations of body mass (calculated from measured femoral head diameter using previously published equations) have an error of just over 7%. No direct stature estimation equations were derived due to the varied linear body proportions represented in the sample. The equations were tested on a sample of 35 individuals from Christ Church Spitalfields. Percentage differences in estimated and measured femoral head diameter and length were less than 1%. This study demonstrates that it is feasible to use the first metatarsal in the estimation of body mass and stature. The equations presented here are particularly useful for assemblages where the long bones are either missing or fragmented, and enable estimation of these fundamental population parameters in poorly preserved assemblages.     

Biometric study of ruminant carpal bones and implications for phylogenetic relationships

The mammalian Carpus is a complex of several small bones with multiple interactions during walking. Therefore, it is highly probable that different mammalian families developed distinctive constellations in their Carpi, which could be useful for biometric identification of phylogenetic groupings. The carpal bones of nineteen extant ruminant species (nine bovid, nine cervid, and one moschid) have been investigated to search for biometric traits which are diagnostic for the three families. Additionally, we searched for diverging functional adaptations in the carpal constellations. Therefore, measurements have been taken from the five main carpals, which are carrying the body weight. As a sesamoid bone, Os carpi accessorium was excluded. After transformation of the data into their natural logarithms, multivariate methods of factor analyses and discriminant analyses were performed for each bone. Bivariate plots of the factor scores allowed a clear separation of bovids and cervids. The only one species of the Moschidae (Moschus moschiferus) lies closer to the cervids than to the bovids. The grouping is due to phylogenetic relationships and not due to functional differences in the groups or differing habitat preferences. Generally, the carpals of cervids are more slender and higher in contrast to the bulky and flat carpals in bovids. This approach could be used to assign isolated carpal bones found in fossil sites to their ruminant family.     

Estimating the body size of eocene primates: A comparison of results from dental and postcranial variables

Estimating body weights for fossil primates is an important step in reconstructing aspects of their behavior and ecology. To date, the body size of Eocene euprimates—the Adapidae and Omomyidae—has been estimated only from molar area. Studies on other primates and mammals demonstrate that body weights estimated from teeth are not always concordant with those estimated from postcranial variables. We derive estimates for Eocene primates based on tarsal bone variables to compare with previously published values derived from dental measures. Stepsirhine-wide, family-level, and subfamily-level models are developed and compared. We also compare the accuracy and precision of dental- and tarsal-based regression models for predicting weight in extant species. Tarsal bone and dental area measures prove to be equally robust in predicting body weight; however, highly disparate estimates are often obtained from different variables. Equations based on lower-level taxonomic groups perform better than more widely based models. However, all equations considered yield fairly large errors, which can affect interpretations of paleoecology. The choice of the more robust prediction is not straightforward.     

The estimation of age at death and ages of formation of transverse lines from measurements of human long bones

A radiographic method is presented which estimates the age at death from the diaphyseal length of a child's long bone or bones. Mean lengths are calculated from adult males and females separately in the skeletal population under study, and the child's age derived from the proportion of adult length attained at his or her death. The calculations come from double logistic curves originally derived from a sample of Colorado children (McCammon, 1970). In radiographs of immature or adult long bones, similar equations are based on the location of the center of ossification, from which distances to transverse lines yield estimated ages when these lines were formed. In a population, ages at death, ages of attainment of transverse lines, and ages when anomalous enamel is laid down in teeth are all contributions to paleopathology and paleodemography. These equations can predict when spaced transverse lines were annually formed. If such spaced lines can be seen in radiographs of early fossil hominids, their spacing can distinguish between short childhood, as in apes, and the longer immature developmental span found in modern children.     

Weight of the skeleton during postnatal development

The weight of all bones and the length of humeri, radii, femora and tibiae have been determined in a series of 150 dry, fat-free skeletons from American Whites and Negroes of both sexes, ranging in age from 23 days to 22 years. Six skeletons were eliminated from the series because of evidence of previous illness. A comparison of the lengths of femur plus tibia of this series with the mean statures of a large series of living children at given ages indicates similarity in the growth patterns. Statistical analyses of the data show that the skeletal weight cannot be estimated reliably from age by cither an exponential growth equation or by a logistic function. The weight of the skeleton, however, is related to the lengths of the measured limb bones by allometric equations, and such equations involving each of the four bones are presented for estimation of skeletal weight in the living. Although the standard errors of estimate of the equations based on lengths of each of these four bones differ very little, the radius is recommended over the other three because it is more readily accessible in the living for a roentgenogram and its shadow on the film shows least distortion.     

Scaling relationships between craniofacial sexual dimorphism and body mass dimorphism in primates: implications for the fossil record

Craniofacial remains (the most abundant identifiable remains in the fossil record) potentially offer important information about body size dimorphism in extinct species. This study evaluates the scaling relationships between body mass dimorphism and different measures of craniofacial dimorphism, evaluating taxonomic differences in the magnitude and scaling of craniofacial dimorphism across higher taxonomic groups. Data on 40 dimensions from 129 primate species and subspecies demonstrate that few dimensions change proportionally with body mass dimorphism. Primates show general patterns of greater facial vs. neurocranial and orbital dimorphism, and greater dimorphism in lengths as opposed to breadths. Within any species, though, different craniofacial dimensions can yield very different reconstructions of size dimorphism. There are significant taxonomic differences in the relationships between size and craniofacial dimorphism among primate groups that can have a significant impact on reconstructions of body mass dimorphism. Hominoids tend to show lower degrees of facial dimorphism proportional to size dimorphism than other primates. This in turn implies that strong craniofacial dimorphism in Australopithecus africanus could imply very strong body size dimorphism, conflicting with the relatively modest size dimorphism inferred from postcrania. Different methods of estimating the magnitude of size dimorphism from craniofacial measurements yield similar results, and yield comparatively low percent prediction errors for a number of dimensions. However, confidence intervals for most estimates are so large as to render most estimates highly tentative.     

Sex differences in the vertebral column of gombe chimpanzees

Male and female chimpanzees from Gombe National Park, Tanzania (Pan troglodytes schweinfurthii) differ in live body weights but not in cranial capacity or fore-and hindlimb long bone lengths. Skeletal dimensions of the limbs and vertebral column indicate a mosaic of sex differences. Vertebral column measurements generally are greater in males. While linear measurements identify differences in the breadth and depth of the lower cervical and upper thoracic vertebrae, areal assessments show significant differences in weight-bearing surfaces throughout the thoracic and lumbar segments. These can be interpreted in terms of distribution of weight and body composition (i.e. amount of musculature).     

On mammalian sperm dimensions

Data on linear sperm dimensions in mammals are presented. There is information on a total of 284 species, representing 6.2% of all species; 17.2% of all genera and 49.2% of all families have some representation, with quantitative information missing only from the orders Dermoptera, Pholidota, Sirenia and Tubulidentata. In general, sperm size is inverse to body mass (except for the Chiroptera), so that the smallest known spermatozoa are amongst those of artiodactyls and the largest are amongst those of marsupials. Most variations are due to differences in the lengths of midpiece and principal piece, with head lengths relatively uniform throughout the mammals.     

Long-bone circumference and weight in mammals, birds and dinosaurs

The mid-shaft circumferences of the humerus and femur are closely related to body weight in living terrestrial vertebrates. Because these elements are frequently preserved in subfossil and fossil vertebrate skeletal materials, the relationship can be used to estimate body weight in extinct vertebrates. When the allometric equations are applied to the mid-shaft circumferences of these elements in dinosaurs, the weights calculated for some giant sauropods ( Brachiosaurus ) are found to be lighter than previous estimates.