1,720,996 research outputs found
Arothron: R Functions for Geometric Morphometrics Analyses
No full text<p>Tools for Geometric Morphometrics</p>
Arothron: R Functions for Geometric Morphometrics Analyses
No full textTools for Geometric Morphometric
Arothron: R Functions for Geometric Morphometrics Analyses
No full text<p>Tools for Geometric Morphometrics</p>
Advances in virtual morphometrics: a new approach to generate 2D and 3D surface outlines on virtual specimens
No full textPalaeoanthropology and Bioarchaeology make extensive use of outline-based morphometrics and this approach can be used to ex-tract information from several sources. 2D outlines are usually generated from teeth or lithic tools, as well as from skulls or longbones profiles, and this method is widespread in the study of human evolution [1, 2]. In many cases, the generation of outlines is avaluable alternative to traditional linear measurements or 2D landmark-based geometric morphometrics. 2D outlines are conven-tionally acquired through photography, a procedure prone to parallax errors . In recent years, the use of virtual collections increasedremarkably due to the availability of novel imaging techniques, such as CT-scanning, laser scanning and photogrammetry. anksto these new virtual environments, current methodological approaches can be improved and new techniques can be developed. Wepresent here a method to generate 2D and 3D outlines of complex specimens from a 3D surface model. e 3D contours recreatethe patterns of maximal breadth of the object outline. e procedure has been developed in the R statistical environment and usesα-shape approach and Bézier curves to generate the outlines. α-shape formalises the concept of “shape” for spatial point sets in com-putational geometry : a α-shape is built by connecting all the pairs of points lying on a circle which is not touching or overlappingany other point of the set. Bézier curves are used to approximate curves by generating a set of points through a polynomial fitting.Only three landmarks are needed to apply the method: these points define a reference plane to project all the vertices of the 3Dmodel onto. A α-shape is then obtained from the projected vertices and a Bézier approximation is used to generate evenly spacedlandmarks lying on the outline. e 3D outline is generated by bringing each point of the α-shape back on the surface model; aBézier curve is then calculated. is method allows high precision and reproducibility in outline generation and can be applied onboth skeletal and lithic material. 3D contours generated with this method consent to address new questions on functional trendsin skeletal morphology or in material culture, enhancing the morphometric approach on the study of human evolution
Arothron: Geometric Morphometrics Analyses
No full text<p>Tools for geometric morphometric analysis. The package includes tools of virtual anthropology to align two not articulated parts belonging to the same specimen and to build virtual cavities as endocast. In addition, we supply functions to import and export the coordinates of landmarks and 3D paths into 'landmarkAscii' and 'am' format files.</p>
Surface smoothing, decimation, and their effects on 3D biological specimens
No full textObjective
Smoothing and decimation filters are commonly used to restore the realistic appearance of virtual biological specimens, but they can cause a loss of topological information of unknown extent. In this study, we analyzed the effect of smoothing and decimation on a 3D mesh to highlight the consequences of an inappropriate use of these filters.
Materials and methods
Topological noise was simulated on four anatomical regions of the virtual reconstruction of an orangutan cranium. Sequential levels of smoothing and decimation were applied, and their effects were analyzed on the overall topology of the 3D mesh and on linear and volumetric measurements.
Results
Different smoothing algorithms affected mesh topology and measurements differently, although the influence on the latter was generally low. Decimation always produced detrimental effects on both topology and measurements. The application of smoothing and decimation, both separate and combined, is capable of recovering topological information.
Conclusion
Based on the results, objective guidelines are provided to minimize information loss when using smoothing and decimation on 3D meshes
Investigating locomotion from cranial base morphology and foramen magnum position in primates and hominins
No full textPrimates exhibit high variability in their locomotion. The main pattern adopted by each species is strictly connected to the surroundings
in which it moves and is part of its ecological niche. The way a primate moves influences its morphological evolution,
with limb proportions and long bone morphology often used as proxies for locomotion. Nonetheless, other skeletal structures
may have been involved in important locomotory adaptations during primate evolution. The skull base provides a substrate for the
growth of the brain and interlaces the neurocranium and the face. Also, it is directly connected to the vertebral column, which is
pivotal for locomotion. This cranial district, as well as the relative position of the foramen magnum along the cranial base, are often
found in literature as crucial elements for the comprehension of locomotion in fossil hominins [1,2,3]. In this study we adopted a
Geometric Morphometric approach to investigate the capability of the cranial base morphology in discriminating between different
locomotory patterns in a broad sample of living primates, modern humans and fossil hominins. The dataset consists of 308 adult
specimens (males and females), for a total of 74 species. The sample is made of 3D surfaces obtained by computerized tomography.
The 3D landmark configuration used for the analysis consists of 17 landmarks which synthesize the morphology of the whole cranial
base. Three additional landmarks were acquired (prostion, left orbital and opistocranion) in order to capture the position of the
foramen magnum along the Frankfurt plane. We tested for the multivariate correlation between cranial base shape/size, foramen
magnum position and locomotor categories . The observed correlations were corrected for the effect of phylogenetic relatedness.
The results showed that the shape of the cranial base and the position of the foramen magnum are not suitable for distinguishing
between different types of locomotion in primates, while the cranial base size exhibited a clear discriminating power, likely due to
the ecological importance of body size in primates. When modern humans and fossil hominins were included in the sample, the
same correlations did not appear clear, probably due to the small sample of bipedal species. Further studies including other fossil
hominins will help to clarify the results. This study suggests that cranial base morphology may have evolved as a non-specialised
structure in primates and is probably the result of the multiple connections it has in the skeleton. In addition, the occipital bone
and the position of the foramen magnum may not be as informative as previously thought for the interpretation of locomotion in
fossil hominins
Morphological integration and modularity in the cranium of extant and fossil Hominoidea. A 3D geometric morphometric approach
No full textWe report the results of a 3D geometric-morphometric analysis performed on the face (23 landmarks) and cranial base (17 landmarks) of 315 specimens belonging to extant Hominoidea (Homo, Pan, Gorilla, Pongo, and various genera of Hylobatidae) and 16 fossil specimens of Australopithecus, Paranthropus and Homo
A lynx natural brain endocast from Ingarano (Southern Italy; Late Pleistocene). Taphonomic, Morphometric and Phylogenetic approaches
Full text linkA natural brain endocast from the Late Pleistocene site of Ingarano (Apulia, Southern Italy) has
been investigated in detail using CT scanning, image processing techniques and Geometric Morphometrics
to obtain information about the taxonomy and taphonomy of the specimen. Based on its
characteristically felid shape, we compared several measurements of the endocast with those of the
brains of living Felidae, with a special emphasis on Panthera pardus, Lynx lynx and Felis silvestris
earlier reported from the same locality. The applied combination of techniques revealed that this
specimen is morphometrically closest to the brains of lynxes, and so can be reported as the first
natural endocranial cast of Late Pleistocene Lynx sp. In addition, CT scanning of the Ingarano endocast
allowed us to reconstruct the early stages of its taphonomy (i.e., the process of infilling of
the braincase with the sediment)
- …
