scholarly journals Three-dimensional geometric morphometric studies of modern human occipital variation

PLoS ONE ◽  
2021 ◽  
Vol 16 (1) ◽  
pp. e0245445
Author(s):  
Yameng Zhang ◽  
Lynne A. Schepartz
Keyword(s):  
Three Dimensional ◽  
Principal Component ◽  
Modern Human ◽  
Foramen Magnum ◽  
European Ancestry ◽  
Shape Variation ◽  
Geometric Morphometric ◽  
Phylogenetic Studies ◽  
Males And Females ◽  
Ct Data

Objectives To investigate three-dimensional morphological variation of the occipital bone between sexes and among populations, to determine how ancestry, sex and size account for occipital shape variation and to describe the exact forms by which the differences are expressed. Methods CT data for 214 modern crania of Asian, African and European ancestry were compared using 3D geometric morphometrics and multivariate statistics, including principal component analysis, Hotelling’s T2 test, multivariate regression, ANOVA, and MANCOVA. Results Sex differences in average occipital morphology are only observed in Europeans, with males exhibiting a pronounced inion. Significant ancestral differences are observed among all samples and are shared by males and females. Asian and African crania have smaller biasterionic breadths and flatter clivus angles compared to Europeans. Asian and European crania are similar in their nuchal and occipital plane proportions, nuchal and occipital angles, and lower inion positions compared to Africans. Centroid size significantly differs between sexes and among populations. The overall allometry, while significant, explains little of the shape variation. Larger occipital bones were associated with a more curved occipital plane, a pronounced inion, a narrower biasterionic breadth, a more flexed clivus, and a lower and relatively smaller foramen magnum. Conclusions Although significant shape differences were observed among populations, it is not recommended to use occipital morphology in sex or population estimation as both factors explained little of the observed variance. Other factors, relating to function and the environment, are suggested to be greater contributors to occipital variation. For the same reason, it is also not recommended to use the occiput in phylogenetic studies.

scholarly journals A developmentally descriptive method for quantifying shape in gastropod shells

2020 ◽  
Vol 17 (163) ◽  
pp. 20190721
Author(s):  
J. Larsson ◽  
A. M. Westram ◽  
S. Bengmark ◽  
T. Lundh ◽  
R. K. Butlin
Keyword(s):  
Empirical Studies ◽  
Three Dimensional ◽  
Shell Shape ◽  
Large Set ◽  
Littorina Saxatilis ◽  
Shape Variation ◽  
Gastropod Shell ◽  
Geometric Morphometric ◽  
Wide Range ◽  
Descriptive Method

The growth of snail shells can be described by simple mathematical rules. Variation in a few parameters can explain much of the diversity of shell shapes seen in nature. However, empirical studies of gastropod shell shape variation typically use geometric morphometric approaches, which do not capture this growth pattern. We have developed a way to infer a set of developmentally descriptive shape parameters based on three-dimensional logarithmic helicospiral growth and using landmarks from two-dimensional shell images as input. We demonstrate the utility of this approach, and compare it to the geometric morphometric approach, using a large set of Littorina saxatilis shells in which locally adapted populations differ in shape. Our method can be modified easily to make it applicable to a wide range of shell forms, which would allow for investigations of the similarities and differences between and within many different species of gastropods.

scholarly journals Individual variation of the masticatory system dominates 3D skull shape in the herbivory-adapted marsupial wombats

2019 ◽  
Author(s):  
Vera Weisbecker ◽  
Thomas Guillerme ◽  
Cruise Speck ◽  
Emma Sherratt ◽  
Hyab Mehari Abraha ◽  
...  
Keyword(s):  
Individual Variation ◽  
Principal Component ◽  
Individual Variability ◽  
Shape Variation ◽  
Mandibular Ramus ◽  
Geometric Morphometric ◽  
Skull Shape ◽  
Marsupial Species ◽  
Masticatory System ◽  
The Individual

AbstractBackgroundWithin-species skull shape variation of marsupial mammals is widely considered low and strongly size-dependent (allometric), possibly due to developmental constraints arising from the altricial birth of marsupials. However, species whose skulls are impacted by strong muscular stresses – particularly those produced through mastication of tough food items – may not display such intrinsic patterns very clearly because of the known plastic response of bone to muscle activity of the individual. In such cases, shape variation should not be dominated by allometry; ordination of shape in a geometric morphometric context through principal component analysis (PCA) should reveal main variation in areas under masticatory stress (incisor region/zygomatic arches/mandibular ramus); but this main variation should emerge from high individual variability and thus have low eigenvalues.ResultsWe assessed the evidence for high individual variation through 3D geometric morphometric shape analysis of crania and mandibles of thre species of grazing-specialized wombats, whose diet of tough grasses puts considerable strain on their masticatory system. As expected, we found little allometry and low Principal Component 1 (PC1) eigenvalues within crania and mandibles of all three species. Also as expected, the main variation was in the muzzle, zygomatic arches, and masticatory muscle attachments of the mandibular ramus. We then implemented a new test to ask if the landmark variation reflected on PC1 was reflected in individuals with opposite PC1 scores and with opposite shapes in Procrustes space. This showed that correspondence between individual and ordinated shape variation was limited, indicating high levels of individual variability in the masticatory apparatus.DiscussionOur results are inconsistent with hypotheses that skull shape variation within marsupial species reflects a constraint pattern. Rather, they support suggestions that individual plasticity can be an important determinant of within-species shape variation in marsupials (and possibly other mammals) with high masticatory stresses, making it difficult to understand the degree to which intrinsic constraint act on shape variation at the within-species level. We conclude that studies that link micro- and macroevolutionary patterns of shape variation might benefit from a focus on species with low-impact mastication, such as carnivorous or frugivorous species.

Phenotypic variation of south-western Atlantic clam Mactra isabelleana (Bivalvia: Mactridae)

2012 ◽  
Vol 93 (2) ◽  
pp. 511-517 ◽  
Author(s):  
Javier H. Signorelli ◽  
Federico Márquez ◽  
Guido Pastorino
Keyword(s):  
Principal Component ◽  
Shell Shape ◽  
Physical Parameters ◽  
Buenos Aires Province ◽  
Shape Variation ◽  
Geometric Morphometric ◽  
Western Atlantic ◽  
Canonical Variates Analysis ◽  
Canonical Variates ◽  
Geometric Morphometric Method

The phenotypic shell shape variation of Mactra isabelleana was tested using the geometric morphometric method. Four localities were sampled along the Río de la Plata estuary and the coast of Buenos Aires province. Principal component analysis and canonical variates analysis of the first principal components were performed to reveal the shell variation and differences among localities, respectively. The specimens from different microhabitats mostly overlapped, although differences in shape were observed in the development of the umbo, the enlargement of the dorsoventral axes and the elongation of the posterior end. The ecological and physical parameters that could influence shell shape variation are discussed.

Software Support for Advanced Cephalometric Analysis in Orthodontics

2011 ◽  
pp. 926-948
Author(s):  
Demetrios J. Halazonetis
Keyword(s):  
Volume Rendering ◽  
Diagnostic Procedure ◽  
Principal Component ◽  
Cephalometric Analysis ◽  
Synergic Effect ◽  
Software Support ◽  
Geometric Morphometric ◽  
Ct Technology ◽  
Ct Data ◽  
Procrustes Superimposition

Cephalometric analysis has been a routine diagnostic procedure in Orthodontics for more than 60 years, traditionally employing the measurement of angles and distances on lateral cephalometric radiographs. Recently, advances in geometric morphometric (GM) methods and computed tomography (CT) hardware, together with increased power of personal computers, have created a synergic effect that is revolutionizing the cephalometric field. This chapter starts with a brief introduction of GM methods, including Procrustes superimposition, Principal Component Analysis, and semilandmarks. CT technology is discussed next, with a more detailed explanation of how the CT data are manipulated in order to visualize the patient’s anatomy. Direct and indirect volume rendering methods are explained and their application is shown with clinical cases. Finally, the Viewbox software is described, a tool that enables practical application of sophisticated diagnostic and research methods in Orthodontics.

Skull morphological variation in a British stranded population of false killer whale (Pseudorca crassidens): a three-dimensional geometric morphometric approach

2022 ◽  
pp. 119-132
Author(s):  
Deborah Vicari ◽  
Richard C. Sabin ◽  
Richard P. Brown ◽  
Olivier Lambert ◽  
Giovanni Bianucci ◽  
...  
Keyword(s):  
Sexual Dimorphism ◽  
Morphological Variation ◽  
Killer Whale ◽  
Three Dimensional ◽  
Anatomical Landmarks ◽  
Geometric Morphometric ◽  
False Killer Whale ◽  
Sexual Shape Dimorphism ◽  
Males And Females ◽  
Pseudorca Crassidens

The false killer whale (Pseudorca crassidens (Owen, 1846)) is a globally distributed delphinid that shows geographical differentiation in its skull morphology. We explored cranial morphological variation in a sample of 85 skulls belonging to a mixed sex population stranded in the Moray Firth, Scotland, in 1927. A three-dimensional digitizer (Microscribe 2GX) was used to record 37 anatomical landmarks on the cranium and 25 on the mandible to investigate size and shape variation and to explore sexual dimorphism using geometric morphometric. Males showed greater overall skull size than females, whereas no sexual dimorphism could be identified in cranial and mandibular shape. Allometric skull changes occurred in parallel for both males and females, supporting the lack of sexual shape dimorphism for this particular sample. Also, fluctuating asymmetry did not differ between crania of males and females. This study confirms the absence of sexual shape dimorphism and the presence of a sexual size dimorphism in this false killer whale population.

scholarly journals The use of the geometric morphometric method to illustrate shape difference in the skulls of different-aged horses

2020 ◽  
Vol 44 (3-4) ◽  
pp. 137-145
Author(s):  
Tiziana Liuti ◽  
Padraic M. Dixon
Keyword(s):  
Age Groups ◽  
Nasal Bone ◽  
Principal Component ◽  
Age Group ◽  
Shape Variation ◽  
Geometric Morphometric ◽  
Biological Studies ◽  
Potential Applications ◽  
Variation Explained ◽  
Ethmoid Sinuses

Abstract The geometric morphometrics method (GMM) is a technique to study scale and shape relationships of structures using Cartesian geometric coordinates rather than linear, areal (of area), or volumetric variables. GMM has been of great value in many biological studies, but does not appear to have been used to examine equine skulls. In this exploratory study, twenty-nine normal equine heads of three different age groups: <5 years old (N = 9), 6–15 years old (N = 10) and > 16 years old (N = 10) were examined. Computed tomography (CT) bone window DICOM images were reconstructed into isosurfaces (3-dimensional contoured surfaces), onto which landmarks were added using Stratovan Checkpoint® software. Data from 29 landmarks were analysed using MorphoJ analysis, which applies a Procrustes fit, prior to reducing data dimensionality through principal component (PC) analysis. PCs with and without allometry were considered. Allometric shape described by PC1 accounted for 27% of variance. Loading pertaining to: the pterygoid process, bilaterally; caudal aspect of hard palate; tip of nasal bone; ethmoid sinuses, bilaterally; caudal aspect of the ventral conchal bulla, bilaterally and caudal aspect of the vomer bone suggest that these anatomical structures are predictive of age group. When allometric effects (shape variation explained by size) were removed, PC1 was unable to distinguish horses by age group. Allometric shape differences could distinguish the youngest versus the two older age groups. The potential applications of GMM in equine diagnostic imaging are wide ranging and include the investigation of changes in the equine skull with respect to genetics and characterisation of conformation-related diseases affecting the teeth, jaws and sinonasal compartments.

scholarly journals Phylogeny and adaptation shape the teeth of insular mice

2016 ◽  
Vol 283 (1824) ◽  
pp. 20152820 ◽  
Author(s):  
Ronan Ledevin ◽  
Pascale Chevret ◽  
Guila Ganem ◽  
Janice Britton-Davidian ◽  
Emilie A. Hardouin ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Size Variation ◽  
Wood Mouse ◽  
Relative Role ◽  
Resource Exploitation ◽  
Shape Variation ◽  
Geometric Morphometric ◽  
Competition Level ◽  
History Of

By accompanying human travels since prehistorical times, the house mouse dispersed widely throughout the world, and colonized many islands. The origin of the travellers determined the phylogenetic source of the insular mice, which encountered diverse ecological and environmental conditions on the various islands. Insular mice are thus an exceptional model to disentangle the relative role of phylogeny, ecology and climate in evolution. Molar shape is known to vary according to phylogeny and to respond to adaptation. Using for the first time a three-dimensional geometric morphometric approach, compared with a classical two-dimensional quantification, the relative effects of size variation, phylogeny, climate and ecology were investigated on molar shape diversity across a variety of islands. Phylogeny emerged as the factor of prime importance in shaping the molar. Changes in competition level, mostly driven by the presence or absence of the wood mouse on the different islands, appeared as the second most important effect. Climate and size differences accounted for slight shape variation. This evidences a balanced role of random differentiation related to history of colonization, and of adaptation possibly related to resource exploitation.

Head shape analysis of National Football League Players

2021 ◽  
pp. 175433712110206
Author(s):  
Gwansik Park ◽  
Lee F Gabler ◽  
Ann M Bailey ◽  
Nathan Z Dau ◽  
Chris Sherwood ◽  
...  
Keyword(s):  
Shape Analysis ◽  
National Football League ◽  
Sagittal Plane ◽  
Three Dimensional ◽  
Principal Component ◽  
Shape Variation ◽  
Head Shape ◽  
Two Factors ◽  
Football Helmets ◽  
Statistical Shape

Understanding the size and shape variations of the head is important to the design of football helmets used to mitigate the risk of head injury. Current guidelines for selecting helmets use only the circumference of the player’s head to determine an appropriate size that may not offer the best fit and protection for every player. The goal of this study was to quantify key measurements of head shape to sufficiently characterize variability among players in the National Football League (NFL), focusing on the shape variation of the cranial region. Statistical shape analysis was performed on three-dimensional head scans of 87 contemporary NFL players to identify key features of head shape variability among the players’ heads. The principal component analysis revealed two factors that explained 87% of the head shape variance: (1) height and length of the head in the sagittal plane and (2) prominent back of the head with an oval shape in the transverse plane versus prominent forehead with a round shape. Four head shape measurements (circumference, length, breadth, and height) were then defined and quantified to describe the first two principal components. This information can facilitate improvements in the design of football helmets.

scholarly journals Subspecies and sexual craniofacial size and shape variations in Japanese macaques (Macaca fuscata)

2018 ◽  
Author(s):  
Wataru Yano ◽  
Naoko Egi ◽  
Tomo Takano ◽  
Naomichi Ogihara
Keyword(s):  
Macaca Fuscata ◽  
Japanese Macaque ◽  
Three Dimensional ◽  
Principal Component ◽  
Shape Space ◽  
Size Difference ◽  
Shape Variation ◽  
Three Dimensional Model ◽  
Temporal Fossa ◽  
Size And Shape

AbstractIn order to investigate craniofacial size and three-dimensional shape variations independently in the Japanese macaque (Macaca fuscata) we used a geometric morphometries technique. A total of 55 specimens were CT scanned to generate a three-dimensional model of each cranium, and 57 landmarks were digitized to analyze the craniofacial shape variation in the Japanese macaque. The results showed that four intra-specific groups, consisting of two subspecies and the two sexes, differed in both size and shape space. In size, the cranium of the Macaca fuscata yakui (MFY) was smaller than that of Macaca fuscata fuscata (MFF) in both sexes, and female crania were smaller than male crania in both subspecies. Shape sexual dimorphisms in both subspecies were detected in the first axis of principal component analysis and were related to a relatively broad orbit, smaller neurocranium, enlarged snout, and broader temporal fossa in males. The shape differences between subspecies showed different features than those between sexes. Male subspecies shape differences were detected in the first and third axes, while those for females were in the first and second axes. Subspecies shape differences common to both sexes were a narrower orbit, relatively small neurocranium, longer snout, and postorbital constriction in MFY. Male MFY was specifically characterized by a more anterior and superior direction of snout protrusion. In contrast, female MFY showed an inferior direction of snout protrusion. Female MFY also had a taller orbit. With regard to the relationship between size and shape differences, shape sexual dimorphism for each subspecies was positively associated with size difference, but there was no such association between subspecies in either sex. Size does not seem to play an important role in subspeciation of Macaca fuscata.

scholarly journals Geometric morphometry of pupae to identify four medically important flies (Order: Diptera) in Thailand

2019 ◽  
Vol 20 (6) ◽  
Author(s):  
TANAWAT CHAIPHONGPACHARA ◽  
PATCHARAPRON TUBSAMUT
Keyword(s):  
Fourier Coefficients ◽  
Principal Component ◽  
Future Application ◽  
Size Analysis ◽  
Size Estimation ◽  
Shape Variation ◽  
Elliptic Fourier Analysis ◽  
Geometric Morphometric ◽  
Significance Level ◽  
Geometric Morphometry

Abstract. Chaiphongpachara T, Tubsamut P. 2019. Geometric morphometry of pupae to identify four medically important flies (Order: Diptera) in Thailand. Biodiversitas 20: 1504-1509. In this study, we evaluated an outline-based geometric morphometric (GM) approach for species identification from pupae of four common flies medically important in Thailand, Chrysomya megacephala, Lucilia cuprina, Musca domestica, and Boettcherisca nathani. For size estimation, mean perimeter length was used. For shape analysis, Elliptic Fourier Analysis was performed to produce the contour shape variables, which was calculated as Normalised Elliptic Fourier coefficients. Then, principal component analysis was performed on the Normalized Fourier coefficients for discriminant analysis, and used to estimate pupal shape variation among the species. The difference in size and shape between the fly species was analyzed using a non-parametric test based on 1000 permutations after Bonferroni correction for the significance level (p < 0.05). In the size analysis, the mean perimeter length for pupae of B. nathani was the largest (20.35 mm) followed by C. megacephala (14.73 mm), while that for M. domestica was the smallest (11.82 mm). The size differences were statistically significant between all species (p < 0.05). The contour shapes of all pupae were significantly different among all species. The results of this study can be used as a basis for the future application of GM to identify other types of flies via their pupae.

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