Ontogenetic Shape Change Research Articles

Quantitative analysis of the influences of phylogeny and ecology on phocid and otariid pinniped (Mammalia; Carnivora) cranial morphology

Pinnipeds (seals, sea lions and walruses) are secondarily marine carnivorans that exhibit a wide range of feeding and reproductive specializations. Extant pinnipeds are split into three families: Phocidae (seals), Otariidae (sea lions) and Odobenidae (walruses). Morphometric analyses were used to examine cranial morphology in otariid and phocid pinnipeds. Phocids are more ecologically and taxonomically diverse than otariids, and this study quantitatively assessed the effects of life history, phylogeny and ecology on cranial morphology in these closely related clades of aquatic carnivorans. Fifty-three to 58 three-dimensional landmarks were gathered from 138 specimens, representing 31 of the 33 extant species of otariids and phocids. Principal components analysis was used to identify major axes of variation, and principal component scores were compared with phylogenetic distances and ecological variables to test for significant correlates of skull morphology. Results showed that phocids exhibit a much greater diversity of adult skull morphology than otariids. Shape differences within adult otariids were dominated by males of only one species, Otaria flavescens. In contrast, several species of phocids deviated markedly from the mean phocid morphology. These atypical morphologies were consistently associated with specializations of either feeding or mating strategies. Ontogenetic shape changes are greater, relative to interspecific differences, in otariids than in phocids, and shape dimorphism was observed in only one otariid and two phocid species. Unexpectedly, neither otariids nor phocids showed strong correlations between phylogenetic relationship and cranial morphology. Both clades show strong correlations between cranial shape and some life history and some environmental variables, but phocids show stronger correlations with life-history variables, perhaps reflecting the broad range of reproductive strategies observed in phocids.

Leaf Serration in Seedlings of Heteroblastic Woody Species Enhance Plasticity and Performance in Gaps But Not in the Understory

Leaf heteroblasty refers to dramatic ontogenetic changes in leaf size and shape, in contrast to homoblasty that exhibits little change, between seedling and adult stages. This study examined whether the plasticity in leaf morphology of heteroblastic species would be an advantage for their survival and growth over homoblastic congeners to changes in light. Two congeneric pairs of homoblastic (Hoheria lyallii, Aristotelia serrata) and heteroblastic species (H. sexstylosa, A. fruticosa) were grown for 18 months in canopy gap and forest understory sites in a temperate rainforest in New Zealand. Heteroblastic species that initially had serrated leaves reduced leaf serration in the understory, but increased in the gaps. Heteroblastic species also produced thicker leaves and had higher stomatal pore area (density×aperturelength), maximum photosynthetic rate, survival, and greater biomass allocation to shoots than homoblastic relatives in the gaps. Findings indicate that increased leaf serration in heteroblastic species is an advantage over homoblastic congeners in high light.

The pattern of endocranial ontogenetic shape changes in humans

Humans show a unique pattern of brain growth that differentiates us from all other primates. In this study, we use virtual endocasts to provide a detailed description of shape changes during human postnatal ontogeny with geometric morphometric methods. Using CT scans of 108 dried human crania ranging in age from newborns to adults and several hundred landmarks and semi-landmarks, we find that the endocranial ontogenetic trajectory is curvilinear with two bends, separating three distinct phases of shape change. We test to what extent endocranial shape change is driven by size increase and whether the curved ontogenetic trajectory can be explained by a simple model of modular development of the endocranial base and the endocranial vault. The hypothesis that endocranial shape change is driven exclusively by brain growth is not supported; we find changes in endocranial shape after adult size has been attained and that the transition from high rates to low rates of size increase does not correspond to one of the shape trajectory bends. The ontogenetic trajectory of the endocranial vault analyzed separately is nearly linear; the trajectory of the endocranial base, in contrast, is curved. The endocranial vault therefore acts as one developmental module during human postnatal ontogeny. Our data suggest that the cranial base comprises several submodules that follow their own temporally and/or spatially disjunct growth trajectories.

Sexual dimorphism and ontogenetic variation in the carapace of A. pallipes (Lereboullet, 1858)

In this study we aimed to describe the morphological variability of the carapace of Austropotamobius pallipes (the only native river‐dwelling crayfish in central Italy) by geometric morphometrics. In particular, we investigated aspects of morphological variation related to sexual dimorphism and ontogenesis. In the white‐clawed crayfish, differences in carapace form due to sexual maturity and dimorphism between adults were significant. In particular, our study showed that the carapace form undergoes most changes during ontogeny and that sexual dimorphism occurs only between adult specimens. In fact, most ontogenetic changes in the carapace shape are allometric and almost inevitably it implies divergence in the ontogenetic allometric trajectories. Major changes take place mainly after reaching maturity. Morphological differences between males and females, expressed in both size and shape, can be explained by allometry and interpreted as a direct effect of growth, different ecology between sexes and amongst age classes, and sexual factors, the latter mainly regarding fertility and clutch size. This suggests that, in A. pallipes, allometry is an important aspect in ontogeny and most shape differences among age classes (mainly regarding the relative rostrum shortening and the lateral stretching of the entire carapace region) are likely to be size‐related adjustments.

Ontogeny, systematics, and evolution of the effaced Early Cambrian trilobitesPeachellaWalcott, 1910 andEopeachellanew genus (Olenelloidea)

Although used in biostratigraphy and in studies of early Cambrian trilobite evolution, the olenelloid genusPeachellahas received little research attention. The ontogenetic and evolutionary origins of its derived features—an effaced cephalon and grossly inflated genal spines—have remained mysterious. Based on examination of new and existing collections,P. iddingsiandP. brevispinaare here described in detail, including aspects of their respective ontogenies and the first description of the thorax ofP. iddingsi.A new monotypic genus,Eopeachella, is also described from recently collected material from the Delamar Member of the Pioche Formation, Nevada.Eopeachella angustispinan. gen. n. sp., is less derived and stratigraphically older than bothPeachellaspecies and bridges the morphological gap betweenPeachellaand typical olenelloids. The study reveals that cephalic effacement was progressively attained during both ontogeny and phylogeny in theEopeachella + Peachellaclade. Comparative ontogeny with other olenelloids reveals that progressive effacement was a trend superimposed upon and independent of a conserved pattern of ontogenetic shape change in the glabella and did not represent a peramorphic “extension” of glabellar ontogeny. Genal spine inflation was also achieved progressively (in a proximal-to-distal direction) through both ontogeny and phylogeny in theEopeachella + Peachellaclade. Genal spine inflation that convergently arose in later trilobite groups may have been similarly ontogenetically dynamic. Discovery ofE. angustispinaandP. brevispinain the Delamar Member raises olenelloid diversity in this member to at least 20 species; a higher diversity than in any coeval unit.

Ontogenetic shape changes in Pomacentridae (Teleostei, Perciformes) and their relationships with feeding strategies: a geometric morphometric approach

The present study explores the shape changes of cranial structures directly involved in food capturing during growth after reef settlement in two species of Pomacentridae (Dascyllus aruanus and Pomacentrus pavo). Landmark-based geometric morphometrics were used to study allometric patterns and related shape changes in four skeletal units: neurocranium, suspensorium and opercle, mandible and premaxilla. At settlement, the larvae of both species have a relatively similar morphology, especially with respect to the mandible. Their shapes suggest a feeding mode defined as ram/suction-feeding. Ontogenetic shape changes show a shift to a suction feeding mode of prey capture. The main transformations involved are an increase in height of the suspensorium and the opercle, an elevation of the supraoccipital crest, a relative shortening of the mandible, and a lengthening of the ascending process of the premaxilla. Shape changes of the mandible in the two studied species also reflect an increase of biting capacities. The high disparity between adult shape results from differences in the rate and in the length of ontogenetic trajectories, from divergence of the ontogenetic trajectories (neurocranium, mandible, and premaxilla) and parallel shifts of the trajectories in the size-shape space (suspensorium and opercle). In an evolutionary context, allometric heterochronies during ontogeny of different skeletal unit of the head may be considered as a basis for the explanation of the diversity of damselfishes. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 95, 92–105.

Three‐dimensional ontogenetic shape changes in the human cranium during the fetal period

Knowledge of the pattern of human craniofacial development in the fetal period is important for understanding the mechanisms underlying the emergence of variations in human craniofacial morphology. However, the precise character of the prenatal ontogenetic development of the human cranium has yet to be fully established. This study investigates ontogenetic changes in cranial shape in the fetal period, as exhibited in Japanese fetal specimens housed at Kyoto University. A total of 31 human fetal specimens aged from approximately 8 to 42 weeks of gestation underwent helical computed tomographic scanning, and 68 landmarks were digitized on the internal and external surfaces of the extracted crania. Ontogenetic shape change was then analyzed cross-sectionally and three-dimensionally using a geometric morphometric technique. The results of the present study are generally consistent with previously reported findings. It was found that during the prenatal ontogenetic process, the growth rate of the length of the cranium is greater than that of the width and height, and the growth rate of the length of the posterior cranial base is smaller than that of the anterior cranial base. Furthermore, it was observed that the change in shape of the human viscerocranium is smaller than that of the neurocranium during the fetal period, and that concurrently the basicranium extends by approximately 8 degrees due to the relative elevation of the basilar and lateral parts of occipital bone. These specific growth-related changes are the opposite of those reported for the postnatal period. Our findings therefore indicate that the allometric pattern of the human cranium is not a simple continuous transformation, but changes drastically from before to after birth.

A conceptual framework for mapping quantitative trait Loci regulating ontogenetic allometry.

Although ontogenetic changes in body shape and its associated allometry has been studied for over a century, essentially nothing is known about their underlying genetic and developmental mechanisms. One of the reasons for this ignorance is the unavailability of a conceptual framework to formulate the experimental design for data collection and statistical models for data analyses. We developed a framework model for unraveling the genetic machinery for ontogenetic changes of allometry. The model incorporates the mathematical aspects of ontogenetic growth and allometry into a maximum likelihood framework for quantitative trait locus (QTL) mapping. As a quantitative platform, the model allows for the testing of a number of biologically meaningful hypotheses to explore the pleiotropic basis of the QTL that regulate ontogeny and allometry. Simulation studies and real data analysis of a live example in soybean have been performed to investigate the statistical behavior of the model and validate its practical utilization. The statistical model proposed will help to study the genetic architecture of complex phenotypes and, therefore, gain better insights into the mechanistic regulation for developmental patterns and processes in organisms.

Limb growth in captive Galago senegalensis: getting in shape to be an adult

Since primate infants are not simply miniature adults, adult shape results from differential growth patterns of individual body segments. Initially an infant relies on its mother for transportation, and later begins independent locomotion. Skeletal growth patterns must meet the functional demands of independent locomotion. In this study we sought to determine whether Galago senegalensis braccatus follow the general primate pattern of decreasing intermembral index (IMI) throughout ontogeny. We also asked whether ontogenetic attainment of adult limb proportions coincides with attainment of independent locomotion, i.e., do infants reach adult limb proportions near the time they begin independent locomotion (approximately 7 weeks of age)? Mixed-longitudinal data were taken from a sample of 10 captive-born Galago senegalensis. Linear lengths of the trunk, arm, forearm, thigh, and leg were measured in the animals from birth until they were approximately 500 days old. The IMI and the ratio of each limb segment to both trunk length and the cube root of body mass were calculated. The results of a Mann-Whitney Wilcoxon rank-sum test for unmatched samples indicate that G. senegalensis do exhibit the primate pattern of decreasing IMI throughout ontogeny, and that the IMIs of infants at the time of initial locomotor independence are significantly higher than those of adult IMIs. Some (but not all) measures of relative limb lengths differed between neonates or 7-week-old infants and adults. Therefore, the hypothesis that infants acquire adult limb proportions by the time they begin independent locomotion is not supported by this study. The current results indicate that ontogenetic shape changes in galagos are a complex process and apparently cannot be explained by simple initial locomotor competency.

Ecological consequences of ontogenetic changes in head shape and bite performance in the Jamaican lizardAnolis lineatopus

It has been documented extensively that body size affects the physiology and musculoskeletal function of organisms. However, less well understood is how body size affects the ecology of organisms through its effects on physiology and performance. We explored the effects of body size on morphology and performance in different ontogenetic classes and sexes of a common Anolis lizard (A. lineatopus). Next, we tested whether these morphological and performance differences may affect functional aspects of the diet such as prey size and prey hardness. Our data showed that males, females and juveniles differ significantly in head size, head shape and bite force. Multiple regression models indicated that head shape and bite force are significantly correlated to prey size and hardness. Yet juveniles had relatively large heads and bit disproportionately hard for their size, allowing them to eat prey as large as those of females. However, for a given prey size, males and females ate more robust prey than did juveniles. Additionally, males ate relatively harder prey than did juveniles. These data suggest that: (1) body size affects the dietary ecology of animals through its effect on head size and bite force; (2) changes in head morphology independent of changes in overall size also have important effects on performance and diet. © 2006 The Linnean Society of London, Biological Journal of the Linnean Society, 2006, 89, 443–454.

A Hyperspace Model to Decipher the Genetic Architecture of Developmental Processes: Allometry Meets Ontogeny

To better utilize limited resources for their survival and reproduction, all organisms undergo developmental changes in both body size and shape during ontogeny. The genetic analysis of size change with increasing age, i.e., growth, has received considerable attention in quantitative developmental genetic studies, but the genetic architecture of ontogenetic changes in body shape and its associated allometry have been poorly understood partly due to the lack of analytical tools. In this article, we attempt to construct a multivariate statistical framework for studying the genetic regulation of ontogenetic growth and shape. We have integrated biologically meaningful mathematical functions of growth curves and developmental allometry into the estimation process of genetic mapping aimed at identifying individual quantitative trait loci (QTL) for phenotypic variation. This model defined with high dimensions can characterize the ontogenetic patterns of genetic effects of QTL over the lifetime of an organism and assess the interplay between genetic actions/interactions and phenotypic integration. The closed forms for the residual covariance matrix and its determinant and inverse were derived to overcome the computational complexity typical of our high-dimensional model. We used a worked example to validate the utility of this model. The implications of this model for genetic research of evo-devo are discussed.

Development of the caudal exoskeleton of the pliomerid trilobite Hintzeia plicamarginis new species

The later juvenile ontogeny of the caudal plate of the early Ordovician pliomerid trilobite Hintzeia plicamarginis new species likely comprised an initial phase during which the rate of appearance of new segments subterminally exceeded that of segment release into the thorax, a short phase of constant segment numbers, and a later phase during which release occurred but in which no new segments appeared. A distinct terminal region became manifest in the second phase. During the second and third phases growth coefficients for individual segments were about 1.1--1.2 per instar. Although the shapes of segments varied during growth, the pattern of ontogenetic shape change appears to have been broadly similar among segments. This suggests an homonomous trunk segment morphology regardless of thoracic or caudal identity in maturity. These results imply that control of trunk exoskeletal segment appearance and articulation were decoupled in this trilobite, and that the terminal region had a distinct mature morphology. H. plicamarginis is described as a new species.

Ontogenetic variability in external morphology of native (Canadian) and non-native (Slovak) populations of pumpkinseed Lepomis gibbosus (Linnaeus 1758)

External morphology of native Canadian (River Otonabee, Looncall Lake) and non-native Slovak (River Danube) pumpkinseed was examined using both triple regression analysis (distance-based measurements) and geometrical analysis (coordinate-based measurements) within an ontogenetical aspect. In general, the results from the geometrical analysis comply with those from the triple regression analysis. The smallest pumpkinseed (predominantly juveniles) differed significantly from the largest pumpkinseed (predominantly adults) in all the three populations. The major difference was that adults had a deeper body and larger belly area than juveniles, which is probably associated with more space for gonads in mature fish. Developmental patterns and external morphology in pumpkinseed from the River Otonabee seemed to be closer to pumpkinseed from the Danube than to those from Lake Looncall. This suggests that, in the pumpkinseed examined, ontogenetic changes in external shape depend on environmental conditions (epigenetical information) rather than on geographical and/or genetical isolation. Further examination of early development, fecundity, number of spawning acts per season, parental care, egg size, age at maturation, etc., will follow to test this hypothesis.

A morphometric study on morphological plasticity of shell form in crevice-dwelling Pterioida (Bivalvia)

Relative warp analysis and eigenshape analysis were used to explore the patterns of variation of erratic shell shapes in and among six species of crevice-dwelling pterioid bivalves. The results of morphometric analyses revealed that a great deal of the variance of shell shape within each species can be reduced into principal components which display patterns of variation common to all species examined. In the species with striking variability, a few sets of principal components account for most of the variance of shell shape. On the other hand, in the species lacking considerable variability, several components contribute to form a given variety. Comparison of relative warp and eigenshape scores with centroid sizes indicates that the direction of ontogenetic shape change has been modified through evolution to produce adaptations to habitats such as crevices or the undersides of rocks. © 2003 The Linnean Society of London, Biological Journal of the Linnean Society, 2003, 79, 285–297.

The evolution of development: two portraits of skull ossification in pipoid frogs.

Development creates morphology, and the study of developmental processes has repeatedly shed light on patterns of morphological evolution. However, development itself evolves as well, often concomitantly with changes in life history or in morphology. In this paper, two approaches are used to examine the evolution of skull development in pipoid frogs. Pipoids have highly unusual morphologies and life histories compared to other frogs, and their development also proves to be remarkable. First, a phylogenetic examination of skull bone ossification sequences reveals that jaw ossification occurs significantly earlier in pipoids than in other frogs; this represents a reversal to the primitive vertebrate condition. Early jaw ossification in pipoids is hypothesized to result from the absence of certain larval specializations possessed by other frogs, combined with unusual larval feeding behaviors. Second, thin-plate spline morphometric studies of ontogenetic shape change reveal important differences between pipoid skull development and that of other frogs. In the course of frog evolution, there has been a shift away from salamander-like patterns of ontogenetic shape change. The pipoids represent the culmination of this trend, and their morphologies are highly derived in numerous respects. This study represents the first detailed examination of the evolution of skull development in a diverse vertebrate clade within a phylogenetic framework. It is also the first study to examine ossification sequences across vertebrates, and the first to use thin-plate spline morphometrics to quantitatively describe ontogenetic trajectories.

Chondrocranial development in larval Rana sylvatica (Anura: Ranidae): morphometric analysis of cranial allometry and ontogenetic shape change.

This study provides baseline quantitative data on the morphological development of the chondrocranium in a larval anuran. Both linear and geometric morphometric methods are used to quantitatively analyze size-related shape change in a complete developmental series of larvae of the wood frog, Rana sylvatica. The null hypothesis of isometry was rejected in all geometric morphometric and most linear morphometric analyses. Reduced major axis regressions of 11 linear chondrocranial measurements on size indicate a mixture of allometric and isometric scaling. Measurements in the otic and oral regions tend to scale with negative allometry and those associated with the palatoquadrate and muscular process scale with isometry or positive allometry. Geometric morphometric analyses, based on a set of 11 chondrocranial landmarks, include linear regression of relative warp scores and multivariate regression of partial warp scores and uniform components on log centroid size. Body size explains about one-quarter to one-third of the total shape variation found in the sample. Areas of regional shape transformation (e.g., palatoquadrate, otic region, trabecular horns) are identified by thin-plate spline deformation grids and are concordant with linear morphometric results. Thus, the anuran chondrocranium is not a static structure during premetamorphic stages and allometric patterns generally follow scaling predictions for tetrapod cranial development. Potential implications regarding larval functional morphology, cranial development, and chondrocranial evolution in anurans are discussed.

THE EVOLUTION OF DEVELOPMENT: TWO PORTRAITS OF SKULL OSSIFICATION IN PIPOID FROGS

Development creates morphology, and the study of developmental processes has repeatedly shed light on patterns of morphological evolution. However, development itself evolves as well, often concomitantly with changes in life history or in morphology. In this paper, two approaches are used to examine the evolution of skull development in pipoid frogs. Pipoids have highly unusual morphologies and life histories compared to other frogs, and their development also proves to be remarkable. First, a phylogenetic examination of skull bone ossification sequences reveals that jaw ossification occurs significantly earlier in pipoids than in other frogs; this represents a reversal to the primitive vertebrate condition. Early jaw ossification in pipoids is hypothesized to result from the absence of certain larval specializations possessed by other frogs, combined with unusual larval feeding behaviors. Second, thin-plate spline morphometric studies of ontogenetic shape change reveal important differences between pipoid skull development and that of other frogs. In the course of frog evolution, there has been a shift away from salamander-like patterns of ontogenetic shape change. The pipoids represent the culmination of this trend, and their morphologies are highly derived in numerous respects. This study represents the first detailed examination of the evolution of skull development in a diverse vertebrate clade within a phylogenetic framework. It is also the first study to examine ossification sequences across vertebrates, and the first to use thin-plate spline morphometrics to quantitatively describe ontogenetic trajectories.

Three-dimensional Bolton-Brush Growth Study landmark data: ontogeny and sexual dimorphism of the Bolton standards cohort.

The treatment of craniofacial reconstructive surgery patients may benefit from comparison to average referent three-dimensional landmark data. These data may be useful for diagnosis, treatment planning, prosthetic design, or outcomes assessment. With regard to subadult patients, we hypothesize that the pattern of ontogenetic shape change of same sex, same ethnicity, referent populations will show gross uniformity. We present a preliminary shape analysis of 50 three-dimensional landmarks derived from 317 Bolton-Brush Growth Study biorthogonal image pairs. We determine which landmarks can be collected from scanned radiographs reliably by four operators for the precisely locatable points, ontogenetic trends in landmark configuration shape change, and patterns of sexual dimorphism. Participants were Bolton standards individuals (16 male and 16 female) who contributed biplane cephalograms seven or more times with annual or greater spacing between ages 3 and 18 years. After removing outliers, we searched for ontogenetic heterogeneity, including sexual dimorphism and within sex-specific Procrustes coordinate shape spaces. A cut-off of 4.3-mm interoperator error left 32 landmarks in our analysis. Three different approaches (principal component analysis, age-trend analysis, and principal components of age residuals) all found no patterns of individual variation around sex-specific average trends of shape change. Male shape change peaks at age 15, a correlate of the growth spurt. Simultaneous frontal and lateral anatomic landmark identification improves three-dimensional localization reliability. Three-dimensional craniodental shape change from ages 8 to 18 within the Bolton standards presents little heterogeneity. Considerations of ethnicity aside, these may be initial grounds for use of these data as a normative referent.

Wind-induced stresses in cherry trees: evidence against the hypothesis of constant stress levels

We calculated the wind-induced bending moments and stresses generated in the stems of five Prunus serotina conspecifics differing in height and canopy shape and size (based on detailed measurements of stem projected area and location with respect to ground level) to test the hypothesis that wind-loads generate uniform and constant stress levels along the lengths of tree twigs, branches, and trunks. These calculations were performed using five different wind speed profiles to evaluate the relative importance of the shape of wind speed profiles versus the ’geometry’ of tree shape on stem stress distributions and magnitudes. Additionally, we evaluated the effect of absolute tree size and stem taper on wind- induced stresses by scaling the size of smaller conspecifics to the absolute height of the largest of the five trees yet retaining the original stem proportions (i.e., diameter relative to stem length) for each plant. Finally, we also determined how the factor of safety for wind-loading (i.e., the quotient of stem yield stress and wind-load stress) changed as a function of tree size (and, presumably, age). Our results indicate that wind-load stress levels (1) vary along stem length even for the same wind speed profile and the same maximum wind speed; (2) would increase to dangerous levels with increasing tree height if it were not for ontogenetic changes in stem taper and canopy shape that reduce stress intensities to manageable levels; (3) tend to be more dependent on stem taper and canopy shape and size than on the shape of the wind speed profile; and (4) the factor of safety against wind-induced mechanical failure decreases as trees get larger, but varies along the length of large trees such that preferential stem failure is likely and functionally adaptive. We thus (1) reject the hypothesis of constant wind-induced stress levels; (2) support the view that size-dependent changes in stem taper are required to maintain wind-load mechanical reliability; and (3) suggest that certain portions of mature trees are ’designed’ to fail under high winds speeds, thereby reducing drag and the bending moments and stresses experienced by trunks.

Three-Dimensional Bolton–Brush Growth Study Landmark Data: Ontogeny and Sexual Dimorphism of the Bolton Standards Cohort

Abstract Objective: The treatment of craniofacial reconstructive surgery patients may benefit from comparison to average referent three-dimensional landmark data. These data may be useful for diagnosis, treatment planning, prosthetic design, or outcomes assessment. With regard to subadult patients, we hypothesize that the pattern of ontogenetic shape change of same sex, same ethnicity, referent populations will show gross uniformity. We present a preliminary shape analysis of 50 three-dimensional landmarks derived from 317 Bolton–Brush Growth Study biorthogonal image pairs. We determine which landmarks can be collected from scanned radiographs reliably by four operators for the precisely locatable points, ontogenetic trends in landmark configuration shape change, and patterns of sexual dimorphism. Participants: Participants were Bolton standards individuals (16 male and 16 female) who contributed biplane cephalograms seven or more times with annual or greater spacing between ages 3 and 18 years. Design: A...