scholarly journals Automated Detection of 3D Landmarks for the Elimination of Non-Biological Variation in Geometric Morphometric Analyses

2015 ◽  
Author(s):  
Deepali Aneja ◽  
Siddharth R. Vora ◽  
Esra D. Camci ◽  
Linda G. Shapiro ◽  
Timothy C. Cox
Keyword(s):  
Biological Variation ◽  
Automated Detection ◽  
Geometric Morphometric ◽  
Morphometric Analyses ◽  
3D Landmarks

scholarly journals Effects of taphonomic deformation on geometric morphometric analysis of fossils: a study using the dicynodont Diictodon feliceps (Therapsida, Anomodontia)

PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e9925
Author(s):  
Christian F. Kammerer ◽  
Michol Deutsch ◽  
Jacqueline K. Lungmus ◽  
Kenneth D. Angielczyk
Keyword(s):  
Sexual Dimorphism ◽  
Phylogenetic Signal ◽  
Principal Component ◽  
Biological Variation ◽  
Biological Information ◽  
Geometric Morphometric ◽  
Uniform Shear ◽  
Geological Processes ◽  
Morphometric Analyses ◽  
True Position

Taphonomic deformation, the distortion of fossils as a result of geological processes, poses problems for the use of geometric morphometrics in addressing paleobiological questions. Signal from biological variation, such as ontogenetic trends and sexual dimorphism, may be lost if variation from deformation is too high. Here, we investigate the effects of taphonomic deformation on geometric morphometric analyses of the abundant, well known Permian therapsid Diictodon feliceps. Distorted Diictodon crania can be categorized into seven typical styles of deformation: lateral compression, dorsoventral compression, anteroposterior compression, “saddle-shape” deformation (localized collapse at cranial mid-length), anterodorsal shear, anteroventral shear, and right/left shear. In simulated morphometric datasets incorporating known “biological” signals and subjected to uniform shear, deformation was typically the main source of variance but accurate “biological” information could be recovered in most cases. However, in empirical datasets, not only was deformation the dominant source of variance, but little structure associated with allometry and sexual dimorphism was apparent, suggesting that the more varied deformation styles suffered by actual fossils overprint biological variation. In a principal component analysis of all anomodont therapsids, deformed Diictodon specimens exhibit significant dispersion around the “true” position of this taxon in morphospace based on undistorted specimens. The overall variance associated with deformation for Anomodontia as a whole is minor, and the major axes of variation in the study sample show a strong phylogenetic signal instead. Although extremely problematic for studying variation in fossil taxa at lower taxonomic levels, the cumulative effects of deformation in this study are shown to be random, and inclusion of deformed specimens in higher-level analyses of morphological disparity are warranted. Mean morphologies of distorted specimens are found to approximate the morphology of undistorted specimens, so we recommend use of species-level means in higher-level analyses when possible.

scholarly journals Morphological diversity in tenrecs (Afrosoricida, Tenrecidae): comparing tenrec skull diversity to their closest relatives

2015 ◽  
Author(s):  
Sive Finlay ◽  
Natalie Cooper
Keyword(s):  
Quantitative Analysis ◽  
Quantitative Methods ◽  
Morphological Diversity ◽  
Lateral View ◽  
Ecological Niches ◽  
Diverse Group ◽  
Geometric Morphometric ◽  
Skull Shape ◽  
Morphometric Analyses ◽  
The Family

Morphological diversity is often studied qualitatively. However, to truly understand the evolution of exceptional diversity, it is important to take a quantitative approach instead of relying on subjective, qualitative assessments. Here, we present a quantitative analysis of morphological diversity in a Family of small mammals, the tenrecs (Afrosoricida, Tenrecidae). Tenrecs are often cited as an example of an exceptionally morphologically diverse group. However, this assumption has not been tested quantitatively. We use geometric morphometric analyses of skull shape to test whether tenrecs are more morphologically diverse than their closest relatives, the golden moles (Afrosoricida, Chrysochloridae). Tenrecs occupy a wider range of ecological niches than golden moles so we predict that they will be more morphologically diverse. Contrary to our expectations, We find that tenrec skulls are only more morphologically diverse than golden moles when measured in lateral view. Furthermore, similarities among the species-rich Microgale tenrec Genus appear to mask higher morphological diversity in the rest of the Family. These results reveal new insights into the morphological diversity of tenrecs and highlight the importance of using quantitative methods to test qualitative assumptions about patterns of morphological diversity.

On the morphospace of eurypterine sea scorpions

2021 ◽  
pp. 1-6
Author(s):  
Russell D. C. BICKNELL ◽  
Lisa AMATI
Keyword(s):  
New Taxa ◽  
Compound Eye ◽  
Developmental Changes ◽  
Apex Predators ◽  
Geometric Morphometric ◽  
Eye Morphology ◽  
Morphometric Analyses ◽  
Ontogenetic Trajectories ◽  
Landmark Analyses ◽  
Shape Data

ABSTRACT Eurypterids (sea scorpions) are a group of extinct, marine euchelicerates that have an extensive Palaeozoic record. Despite lacking a biomineralised exoskeleton, eurypterids are abundantly preserved within select deposits. These collections make statistical analyses comparing the morphology of different genera possible. However, eurypterid shape has not yet been documented with modern geometric morphometric tools. Here, we summarise the previous statistical assessments of eurypterid morphology and expand this research by presenting landmark and semi-landmark analyses of 115 eurypterid specimens within the suborder Eurypterina. We illustrate that lateral compound eye morphology and position drives specimen placement in morphospace and separates proposed apex predators from more generalist forms. Additionally, evidence for size clusters in Eurypterus that may reflect ontogeny is uncovered. We highlight the use of geometric morphometric analyses in supporting the naming of new taxa and demonstrate that these shape data represent a novel means of understanding inter-generic ontogenetic trajectories and uncovering developmental changes within the diverse euarthropod group.

scholarly journals Geometric Morphometric Analyses Support Incorporating the Goshen Point Type into Plainview

2019 ◽  
Vol 85 (1) ◽  
pp. 171-181 ◽  
Author(s):  
Briggs Buchanan ◽  
Mark Collard ◽  
Michael J. O'Brien
Keyword(s):  
Recent Work ◽  
Social Dynamics ◽  
Spatiotemporal Variation ◽  
Single Type ◽  
Geometric Morphometric ◽  
Morphometric Analyses ◽  
Morphometric Methods ◽  
Point Type

Recent work has demonstrated that Goshen points overlap in time with another group of unfluted lanceolate points from the Plains, Plainview points. This has raised the question of whether the two types should be kept separate or consolidated into a single type. We sought to resolve this issue by applying geometric morphometric methods to a sample of points from well-documented Goshen and Plainview assemblages. We found that their shapes were statistically indistinguishable, which indicates that Goshen and Plainview points should be assigned to the same type. Because Plainview points were recognized before Goshen points, it is the latter type name that should be dropped. Sinking Goshen into Plainview allows us to move beyond taxonomic issues and toward understanding both the spatiotemporal variation that exists among Plainview assemblages and what it can tell us about the adaptations and social dynamics of Plainview groups.

scholarly journals Do island populations differ in size and shape compared to mainland counterparts?

2019 ◽  
Vol 101 (2) ◽  
pp. 373-385 ◽  
Author(s):  
Sergio Ticul Álvarez-Castañeda ◽  
Laura A Nájera-Cortazar
Keyword(s):  
Geometric Morphometric ◽  
Island Populations ◽  
Terrestrial Vertebrates ◽  
Skull Shape ◽  
Skull Size ◽  
Morphometric Analyses ◽  
Interpopulation Variation ◽  
Pocket Mouse ◽  
Shape Analyses ◽  
Insular Populations

Abstract Adaptation and evolution of terrestrial vertebrates inhabiting islands have been the topic of many studies, particularly those seeking to identify trends or patterns in body size in mammals, albeit not necessarily in shape, in relation to mainland populations. The spiny pocket mouse, Chaetodipus spinatus, is distributed in the Baja California peninsula and its surrounding islands. Insular populations became isolated ~12,000 due to changes in sea level; these populations’ matrilinear (mitochondrial) DNA shows minor interpopulation variation. We tested the hypothesis that adaptation and evolution in these island populations involve variation in both skull size and skull shape (using geometric morphometrics) relative to mainland populations, rather than only in size as previously assumed. A total of 363 specimens from 15 insular and peninsular populations were used in analysis of the skull length and geometric morphometric analyses. Our findings revealed significant differences related to skull size among population. The skull shape analyses showed two significantly different morphotypes: one for all island specimens and one for all mainland samples. Our analyses support the hypothesis that insular populations may not only vary in size relative to mainland populations, but may also show variations in shape, regardless of differing conditions across islands.

scholarly journals Local domestication or diffusion? Insights into viticulture in Greece from Neolithic to Archaic times, using geometric morphometric analyses of archaeological grape seeds

2021 ◽  
Vol 125 ◽  
pp. 105263 ◽  
Author(s):  
Clémence Pagnoux ◽  
Laurent Bouby ◽  
Soultana Maria Valamoti ◽  
Vincent Bonhomme ◽  
Sarah Ivorra ◽  
...  
Keyword(s):  
Grape Seeds ◽  
Geometric Morphometric ◽  
Morphometric Analyses

Phylogeny explains better than ecology or body size the variation of the first lower molar in didelphid marsupials

Mammalia ◽  
2017 ◽  
Vol 81 (2) ◽  
Author(s):  
Luíza Z. Magnus ◽  
Nilton Cáceres
Keyword(s):  
Body Size ◽  
Phylogenetic Relationship ◽  
Phylogenetic Signal ◽  
The Body ◽  
Male Body ◽  
Environmental Pressures ◽  
Geometric Morphometric ◽  
Morphometric Analyses ◽  
Lower Molar ◽  
Better Than

AbstractTribosphenic molars are considered great innovations in mammals and are related to several structures and variables that can explain adaptation. The aim of this study was to investigate the importance of body size and habitat relation, using a phylogenetic approach, in the first lower molar shape in didelphid marsupials. Geometric morphometric analyses of the lower molar’s shape were performed on 261 specimens, 130 females and 131 males, covering 14 genera and 37 species of the Didelphidae family. The molar conformation showed a larger talonid in relation to the trigonid in more arboreal genera, and narrower and longer molars in genera with a larger body size. Phylogeny was the variable with the highest explanation for both females and males (16.17% and 9.02%, respectively). The body size was significant in males, presenting an important influence on molar shape, while the body size in females was not significant when phylogenetic relationship was controlled for. In both sexes, habitat presents a strong effect of phylogeny, with no direct effect on molar shape. Didelphid molar shape is another result of its phylogenetic history and does not respond very much to environmental pressures. Male body size influences molar shape in didelphids, even in the presence of a strong phylogenetic signal.

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