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PubMed2004

Ecological correlates and evolutionary divergence in the skull of turtles: a geometric morphometric assessment.

Resource use and phylogeny are often correlated with morphological variation. Moreover, because biological shapes are often complex and evolve depending on several internal constraints, they must be assessed using integrative methods. We analyzed the morphological variation of the turtle skull in the context of an adaptive radiation. Our focus are turtles of the superfamily Testudinoidea, which are remarkably diverse, both in number of species and in ecology. In this study, we depict morphological variation in the turtle skull in three dimensions with respect to diet, phylogeny, and habitat using modern geometric morphometrics. Our study revealed that morphological specialization was related to both diet and habitat. Morphological variation is decomposed in regard of both resource use (habitat and diet) and phylogeny. Feeding mode depending on environment was suggested as a key factor determining morphological evolution and diversification of turtle skulls. Diet (especially durophagy) leads to parallel morphologies in different clades. Phylogeny seemed to constrain only localized features of the skull and remained of minor influence, because overall morphotypes, closely correlated with ecological factors, occurred in both clades. In conclusion, the adaptive radiation of the Testudinoidea is revealed to demonstrate a clear relationship between the skull shape and life style.

Adaptation, Physiological↗
PubMed2007

Three-dimensional laser surface imaging and geometric morphometrics resolve frontonasal dysmorphology in schizophrenia.

BACKGROUND: Although a role for early developmental disturbance(s) in schizophrenia is postulated, it has proved difficult to identify hard, biological evidence. The brain and face emerge in embryologic intimacy, such that in neurodevelopmental disorders, brain dysmorphogenesis is accompanied by facial dysmorphogenesis. METHODS: Three-dimensional (3D) laser surface imaging was used to capture the facial surface of patients and control subjects in 37 male and 32 female patients who satisfied DSM-IV criteria for schizophrenia in comparison with 58 male and 34 female control subjects. Surface images were analyzed using geometric morphometrics and 3D visualizations to identify domains of facial shape that distinguish patients from control subjects. RESULTS: Both male and, particularly, female patients evidenced significant facial dysmorphology. There was narrowing and reduction of the mid to lower face and frontonasal prominences, including reduced width and posterior displacement of the mouth, lips, and chin; increased width of the upper face, mandible, and skull base, with lateral displacement of the cheeks, eyes, and orbits; and anterior displacement of the superior margins of the orbits. CONCLUSIONS: The frontonasal prominence, which enjoys the most intimate embryologic relationship with the anterior brain and also orchestrates aspects of development in maxillary and mandibular domains, evidences a characteristic topography of dysmorphogenesis in schizophrenia.

Adult↗
PubMed2001

Changes in soft tissue facial profile of craniofacial microsomia patients: geometric morphometrics.

To analyze changes in the soft tissue profile associated with an inverted L osteotomy, preoperative, early postoperative, and late postoperative lateral cephalographs of 13 children with craniofacial microsomia (mean age 9 +/- 2 years) were scanned, and 11 soft tissue landmarks were digitized (digitization errors insignificant; P > 0.05). Cephalometry, Euclidean distance matrix analysis (EDMA), and thin-plate spline (TPS) analysis were carried out on the mean soft tissue landmark configurations. Cephalometry indicated that there were very few statistically significant differences in mean measurements pre- and postoperatively. In contrast, EDMA determined that there were significant differences (P < 0.05) between mean preoperative, early postoperative, and late postoperative soft tissue configurations, particularly in the labiomental region. Transformation grids obtained from TPS analysis indicated clockwise rotation of the soft tissue configurations with anteroinferior elongation in the labiomental region. Geometric morphometrics indicated that the soft tissue lower facial height increased secondary to the associated underlying skeletal change, improving the profile of patients treated with an inverted L osteotomy of the mandible for the correction of craniofacial microsomia.

Cephalometry↗
PubMedDate not supplied

Heterochrony and geometric morphometrics: a comparison of cranial growth in Pan paniscus versus Pan troglodytes.

Heterochrony, the classic framework in which to study ontogeny and phylogeny, in essence relies on a univariate concept of shape. Though principal component (PC) plots of multivariate shape data seem to resemble classical bivariate allometric plots, the language of heterochrony cannot be translated directly into general multivariate methodology. We simulate idealized multivariate ontogenetic trajectories and explore their appearance in PC plots of shape space and size-shape space. Only if the trajectories of two related species lie along exactly the same path in shape space can the classic terminology of heterochrony apply and pure dissociation of size change against shape change be detected. Regional heterochrony--the variation of apparent heterochrony by region--implies a dissociation of local growth fields and cannot be identified in an overall PC analysis. We exemplify a geometric morphometric approach to these issues using adult and subadult crania of 48 Pan paniscus and 47 Pan troglodytes specimens. On each specimen, we digitized 47 landmarks and 144 semilandmarks on facial curves and the external neurocranial surface. We reject the hypothesis of global heterochrony in the cranium of Pan as well as regional heterochrony for the lower face, the upper face, and the neurocranium.

Aging↗
PubMed2004

Geometric morphometric analysis of allometric variation in the mandibular morphology of the hominids of Atapuerca, Sima de los Huesos site.

Allometry is an important factor of morphological integration that contributes to the organization of the phenotype and its variation. Variation in the allometric shape of the mandible is particularly important in hominid evolution because the mandible carries important taxonomic traits. Some of these traits are known to covary with size, particularly the retromolar space, symphyseal curvature, and position of the mental foramen. The mandible is a well studied system in the context of the evolutionary development of complex morphological structures because it is composed of different developmental units that are integrated within a single bone. In the present study, we investigated the allometric variation of two important developmental units that are separated by the inferior nerve (a branch of CN V3). We tested the null hypothesis that there would be no difference in allometric variation between the two components. Procrustes-based geometric morphometrics of 20 two-dimensional (2D) landmarks were analyzed by multivariate regressions of shape on size in samples from 121 humans, 48 chimpanzees, and 50 gorillas (all recent specimens), eight fossil hominids from Atapuerca, Sima de los Huesos (AT-SH), and 17 Neandertals. The findings show that in all of the examined species, there was significantly greater allometric variation in the supra-nerve unit than in the infra-nerve unit. The formation of the retromolar space exhibited an allometric relationship with the supra-nerve unit in all of the species studied. The formation of the chin-like morphology is an "apodynamic" feature of the infra-nerve unit in the AT-SH hominids. The results of this study support the hypothesis that allometry contributes to the organization of variation in complex morphological structures.

Animals↗
PubMed2005

Facial surface analysis by 3D laser scanning and geometric morphometrics in relation to sexual dimorphism in cerebral--craniofacial morphogenesis and cognitive function.

Over early fetal life the anterior brain, neuroepithelium, neural crest and facial ectoderm constitute a unitary, three-dimensional (3D) developmental process. This intimate embryological relationship between the face and brain means that facial dysmorphogenesis can serve as an accessible and informative index of brain dysmorphogenesis in neurological and psychiatric disorders of early developmental origin. There are three principal challenges in seeking to increase understanding of disorders of early brain dysmorphogenesis through craniofacial dysmorphogenesis: (i) the first, technical, challenge has been to digitize the facial surface in its inherent three-dimensionality; (ii) the second, analytical, challenge has been to develop methodologies for extracting biologically meaningful shape covariance from digitized samples, making statistical comparisons between groups and visualizing in 3D the resultant statistical models on a 'whole face' basis; (iii) the third, biological, challenge is to demonstrate a relationship between facial morphogenesis and brain morphogenesis not only in anatomical-embryological terms but also at the level of brain function. Here we consider each of these challenges in turn and then illustrate the issues by way of our own findings. These use human sexual dimorphism as an exemplar for 3D laser surface scanning of facial shape, analysis using geometric morphometrics and exploration of cognitive correlates of variation in shape of the 'whole face', in the context of studies relating to the early developmental origins of schizophrenia.

Adult↗
PubMed2000

Principal components analysis of distal humeral shape in Pliocene to recent African hominids: the contribution of geometric morphometrics.

The shape of the distal humerus in Homo, Pan (P. paniscus and P. troglodytes), Gorilla, and six australopithecines is compared using a geometric approach (Procrustes superimposition of landmarks). Fourteen landmarks are defined on the humerus in a two-dimensional space. Principal components analysis (PCA) is performed on all superimposed coordinates. I have chosen to discuss the precise place of KNM-KP 271 variously assigned to Australopithecus anamensis, Homo sp., or Praeanthropus africanus, in comparison with a sample of australopithecines. AL 288-1, AL 137-48 (Hadar), STW 431 (Sterkfontein), and TM 1517 (Kromdraai) are commonly attributed to Australopithecus afarensis (the two former), Australopithecus africanus, and Paranthropus robustus, respectively, while the taxonomic place of KNM-ER 739 (Homo or Paranthropus?) is not yet clearly defined. The analysis does not emphasize a particular affinity between KNM-KP 271 and modern Homo, nor with A. afarensis, as previously demonstrated (Lague and Jungers [1996]

Animals↗
PubMed2002

Geometric morphometric differences between Panstrongylus geniculatus from field and laboratory.

The finding of Panstrongylus geniculatus nymphs inside a house in northeastern Antioquia, Colombia, and the reports related to their increasing presence in homes suggest the need for surveillance methods for monitoring the invasion processes. We analyzed the morphological differences between a wild population and its laboratory descendants, using the techniques of geometric morphometry, with the idea that such differences might parallel those between sylvatic and synanthropic populations. The analyses over five generations showed differences in size but not in shape. Head size and wing size were both reduced from sylvatic to laboratory populations, but the decrease in head size occurred only up to the second generation while the decrease in wing size proceeded up to the fifth generation. In contrast, although a decrease in sexual size dimorphism has been proposed as a marker of colonization in human dwellings, we did not detect any significant loss of dimorphism between sexes of P. geniculatus over the five generations studied. We conclude that size changes may have a physiological origin in response to a change of ecotopes, but more than five generations may be required for the expression of permanent morphological markers of human dwellings colonization.

Animals↗
PubMed2006

Quantitative analysis of human mandibular shape using three-dimensional geometric morphometrics.

Human mandibular morphology is often thought to reflect mainly function, and to be of lesser value in studies of population history. Previous descriptions of human mandibles showed variation in ramal height and breadth to be the strongest difference among recent human groups. Several mandibular traits that differentiate Neanderthals from modern humans include greater robusticity, a receding symphysis, a large retromolar space, a rounder gonial area, an asymmetric mandibular notch, and a posteriorly positioned mental foramen in Neanderthals. Nevertheless, the degree to which these differences are part of modern human variation and/or are related to size and function remains unclear. The aim of this study was to document geographic and functional patterning in the mandibular shape of recent humans, to assess the effects of allometry on mandibular form, and to quantitatively evaluate proposed "Neanderthal" mandibular traits through comparison with samples of geographically diverse recent humans. Data were collected in the form of three-dimensional coordinates of 28 landmarks. Unlike previous studies, this analysis found that modern human mandibular shape exhibits considerable geographic patterning, with some aspects of mandibular morphology reflecting a climatic gradient, and others, a functional specialization. Population history is also reflected in mandibular form, albeit relatively weakly. Proposed "Neanderthal" traits were found to separate Neanderthal from modern human mandibles successfully in the statistical analysis. Of these, the retromolar gap was found to be related to increased mandibular size in modern humans. The status of this trait as a Neanderthal autapomorphy should therefore be treated with caution.

Anatomy, Comparative↗
PubMed2005

Morphological evolution of the lizard skull: a geometric morphometrics survey.

Patterns of diversity among lizard skulls were studied from a morphological, phylogenetic, and functional perspective. A sample of 1,030 lizard skulls from 441 species in 17 families was used to create a lizard skull morphospace. This morphospace was combined with a phylogeny of lizard families to summarize general trends in the evolution of the lizard skull. A basal morphological split between the Iguania and Scleroglossa was observed. Iguanians are characterized by a short, high skull, with large areas of attachment for the external adductor musculature, relative to their sister group. The families of the Iguania appear to possess more intrafamilial morphological diversity than families of the Scleroglossa, but rarefaction of the data reveals this to be an artifact caused by the greater number of species represented in Iguanian families. Iguanian families also appear more dissimilar to one another than families of the Scleroglossa. Permutation tests indicate that this pattern is real and not due to the smaller number of families in the Iguanidae. Parallel and convergent evolution is observed among lizards with similar diets: ant and termite specialists, carnivores, and herbivores. However, these patterns are superimposed over the more general phylogenetic pattern of lizard skull diversity. This study has three central conclusions. Different clades of lizards show different patterns of disparity and divergence in patterns of morphospace occupation. Phylogeny imposes a primary signal upon which a secondary ecological signal is imprinted. Evolutionary patterns in skull metrics, taken with functional landmarks, allow testing of trends and the development of new hypotheses concerning both shape and biomechanics.

Animals↗
PubMed2001

Geometric morphometrics of corpus callosum and subcortical structures in the fetal-alcohol-affected brain.

BACKGROUND: Although experienced clinicians have been diagnosing fetal alcohol syndrome (FAS) for nearly 30 years, the rest of the spectrum of fetal alcohol damage is not being classified effectively. This article describes a quantification of neuroanatomical structure that may supply a useful discriminator of prenatal brain damage from alcohol. It is demonstrated in a data set of adults of both sexes. METHODS: Ninety adults (45 males) were examined by magnetic resonance imaging (MRI). These subjects were group-matched for age and ethnicity across three diagnoses: FAS, fetal alcohol effects (FAE), and normals. All FAS and FAE were heavily alcohol-exposed in utero; normals were not. From T(1)-weighted MR brain images, we extracted 3D morphometric representations of shape for 33-landmark point configurations and 40-point outlines of the corpus callosum along its midline (a slightly nonplanar structure). RESULTS: There are striking differences between exposed and unexposed in the statistical distributions of these two shapes. The differences are better characterized by excess variance in the exposed group than by any change in average landmark or outline shape. For each sex, combining the callosal outline data with the landmark data leads to a powerful quadratic discriminator of exposed from unexposed. The discriminating features include the relationship of brain stem to diencephalon, and localized variabilities of callosal outline shape, but not diagnosis (FAS vs. FAE). CONCLUSIONS: Statistical analysis of brain shape is a powerful new source of information relevant to fetal alcohol spectrum nosology and etiology. Patients with FAS and FAE do not differ in these brain shape features, but both differ from the unexposed. The aspects of brain shape that are especially variable may be entailed in the underlying neuroteratogenetic mechanisms.

Adolescent↗
PubMed2006

Hominin lower second premolar morphology: evolutionary inferences through geometric morphometric analysis.

Mandibular premolars are increasingly used in taxon-specific diagnostic analyses of hominins. Among the principal difficulties in these evaluations is the absence of discrete, discernible, and comparable anatomical structures for rigorous quantitative assessment. Previous research has addressed either internal crown surface features (such as cusps and fossae) or the morphology of the crown outline. In the present paper, we integrate both types of information in the examination of morphological variation of lower P4s (n = 96) among various fossil hominin species with an emphasis on genus Homo. We use a set of 34 2D landmarks combining coordinate data from four classical dental landmarks on the occlusal surface and 30 sliding semilandmarks of the crown outline. Our results indicate that external shape variation is closely related to the configuration of the occlusal morphological features and influenced by dental size. The external and internal shapes of P4 are polymorphic but still useful in depicting a primitive-derived gradient. The primitive pattern seems to have been an asymmetrical contour with a mesially displaced metaconid, development of a bulging talonid, and a broad occlusal polygon. The trend toward dental reduction during the Pleistocene produced different morphological variants with a reduced occlusal polygon and decreased lingual occlusal surface in later Homo species. Homo heidelbergensis/neanderthalensis have fixed plesiomorphic traits in high percentages, whereas in modern humans a symmetrical outline with a centered metaconid and talonid reduction evolved.

Animals↗
PubMed2002

Morphospatial analysis of soft-tissue profile in patients with Class II Division 1 malocclusion treated using twin block appliances: geometric morphometrics.

OBJECTIVES: To study soft-tissue profile changes in patients treated with twin block appliances (TBA) for the correction of Class II division 1 malocclusion. The null hypothesis is that soft-tissue profiles do not show any significant improvements associated with TBA treatment. DESIGN: Longitudinal, retrospective. SETTING AND SAMPLE POPULATION: Scotland, UK, using lateral cephalographs of 46 consecutive, prepubertal children (aged 9-11 years) and 55 adolescents (aged 12-14 years) obtained from an orthodontic practice. EXPERIMENTAL VARIABLE: The prepubertal children underwent = 13 months of TBA treatment, while the adolescents underwent = 22 months of treatment. OUTCOME MEASURES: Configurations of 13 digitized homologous landmarks of pre- and post-treatment soft-tissue facial profiles were compared using cephalometry, Euclidean distance matrix analysis (EDMA) and thin plate spline (TPS) analysis. RESULTS: Cephalometry showed that height increases associated with the TBA were in the labiomental areas, and the most significant height decreases were seen in the lip regions. The results of EDMA also indicated significant changes (P < 0.05). The distance between the lips decreased by >5%, with increases in length in the labiomental region. The TPS analysis showed the soft-tissues of the mandibular complex being displaced anteroinferiorly, with anterior displacement of the landmarks of the lip region. These changes showed that the lips were brought into closer proximity with each other, permitting a functional oral seal. Moreover, the labiomental groove became less pronounced, reflecting the underlying dento-alveolar correction. CONCLUSION: Demonstrable improvements in soft-tissue facial profile may be associated with TBA treatment.

Adolescent↗
PubMed2003

Effects of the headgear-activator Teuscher appliance in the treatment of Class II Division 1 malocclusion: a geometric morphometric study.

OBJECTIVES: To test the hypothesis that there are no gender differences in the outcomes of patients with class II malocclusion treated with the headgear-activator Teuscher appliance (HATA). DESIGN: Retrospective, longitudinal SETTING AND SAMPLE POPULATION: Puerto Rico and Scotland, UK. Thirty-one patients requiring correction of class II division 1 malocclusions. EXPERIMENTAL VARIABLE: Male and female patients treated using HATA. OUTCOME MEASURES: Mean pre- and post-treatment parameters derived from cephalometry subjected to t-tests, and finite-element scaling analysis (FESA), which localizes and quantifies differences between mean pre- and post-treatment configurations. RESULTS: Post-treatment, cephalometry showed that for both males and females, angle SNA decreased, SNB increased, and lower facial heights increased significantly (p < 0.01). For the female post-treatment configuration, FESA revealed large size increases (approximately 20%) located in the inter-maxillary region, the ramus and mandibular body, and around the nasal and mental regions. Conversely, the lip region was diminished (approximately 20%). Similarly, male post-treatment showed size increases located in the inter-maxillary region that extended into the nasal region and the mandibular body (approximately 10-15%), and around the chin (15%). The lip region was diminished (approximately 5%). CONCLUSION: In the attainment of a normal occlusion, both male and female patients treated for class II malocclusions using HATA exhibit antero-posterior restraint of the maxilla, improvements in the mandible maintaining facial height, and lip changes commensurate with improvements in the soft tissue profile.

Activator Appliances↗
PubMed2000

Ability of geometric morphometric methods to estimate a known covariance matrix.

Landmark-based morphometric methods must estimate the amounts of translation, rotation, and scaling (or, nuisance) parameters to remove nonshape variation from a set of digitized figures. Errors in estimates of these nuisance variables will be reflected in the covariance structure of the coordinates, such as the residuals from a superimposition, or any linear combination of the coordinates, such as the partial warp and standard uniform scores. A simulation experiment was used to compare the ability of the generalized resistant fit (GRF) and a relative warp analysis (RWA) to estimate known covariance matrices with various correlations and variance structures. Random covariance matrices were perturbed so as to vary the magnitude of the average correlation among coordinates, the number of landmarks with excessive variance, and the magnitude of the excessive variance. The covariance structure was applied to random figures with between 6 and 20 landmarks. The results show the expected performance of GRF and RWA across a broad spectrum of conditions. The performance of both GRF and RWA depended most strongly on the number of landmarks. RWA performance decreased slightly when one or a few landmarks had excessive variance. GRF performance peaked when approximately 25% of the landmarks had excessive variance. In general, both RWA and GRF performed better at estimating the direction of the first principal axis of the covariance matrix than the structure of the entire covariance matrix. RWA tended to outperform GRF when > approximately 75% of the coordinates had excessive variance. When < 75% of the coordinates had excessive variance, the relative performance of RWA and GRF depended on the magnitude of the excessive variance; when the landmarks with excessive variance had standard deviations (sigma) > or = 4 sigma minimum, GRF regularly outperformed RWA.

Analysis of Variance↗