The Experts below are selected from a list of 294 Experts worldwide ranked by ideXlab platform
Claire E Terhune - One of the best experts on this subject based on the ideXlab platform.
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a 3 d geometric morphometric study of intraspecific variation in the Ontogeny of the temporal bone in modern homo sapiens
Journal of Human Evolution, 2013Co-Authors: Heather F Smith, Terrence B Ritzman, Erik Otarolacastillo, Claire E TerhuneAbstract:Abstract This study addresses how the human temporal bone develops the population-specific pattern of morphology observed among adults and at what point in Ontogeny those patterns arise. Three-dimensional temporal bone shape was captured using 15 landmarks on ontogenetic series of specimens from seven modern human populations. Discriminant function analysis revealed that population-specific temporal bone morphology is evident early in Ontogeny, with significant shape differences among many human populations apparent prior to the eruption of the first molar. As early as five years of age, temporal bone shape reflects population history and can be used to reliably sort populations, although those in closer geographic proximity and molecular affinity are more likely to be misclassified. The deviation of cold-adapted populations from this general pattern of congruence between temporal bone morphology and genetic distances, identified in previous work, was confirmed here in adult and subadult specimens, and was revealed to occur earlier in Ontogeny than previously recognized. Significant differences exist between the ontogenetic trajectories of some pairs of populations, but not among others, and the angles of these trajectories do not reflect genetic relationships or final adult temporal bone size. Significant intrapopulation differences are evident early in Ontogeny, with differences becoming amplified by divergent trajectories in some groups. These findings elucidate how the congruence between adult human temporal bone morphology and population history develops, and reveal that this pattern corresponds closely to that described previously for facial Ontogeny.
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Postnatal temporal bone Ontogeny in Pan, Gorilla, and Homo, and the implications for temporal bone Ontogeny in Australopithecus afarensis
American Journal of Physical Anthropology, 2013Co-Authors: Claire E Terhune, William H. Kimbel, Charles A. LockwoodAbstract:Assessments of temporal bone morphology have played an important role in taxonomic and phylogenetic evaluations of fossil taxa, and recent three-dimensional analyses of this region have supported the utility of the temporal bone for testing taxonomic and phylogenetic hypotheses. But while clinical analyses have examined aspects of temporal bone Ontogeny in humans, the Ontogeny of the temporal bone in non-human taxa is less well documented. This study examines ontogenetic allometry of the temporal bone in order to address several research questions related to the pattern and trajectory of temporal bone shape change during Ontogeny in the African apes and humans. We further apply these data to a preliminary analysis of temporal bone Ontogeny in Australopithecus afarensis. Three-dimensional landmarks were digitized on an ontogenetic series of specimens of Homo sapiens, Pan troglodytes, Pan paniscus, and Gorilla gorilla. Data were analyzed using geometric morphometric methods, and shape changes throughout Ontogeny in relation to size were compared. Results of these analyses indicate that, despite broadly similar patterns, African apes and humans show marked differences in development of the mandibular fossa and tympanic portions of the temporal bone. These findings indicate divergent, rather than parallel, postnatal ontogenetic allometric trajectories for temporal bone shape in these taxa. The pattern of temporal bone shape change with size exhibited by A. afarensis showed some affinities to that of humans, but was most similar to extant African apes, particularly Gorilla. Am J Phys Anthropol 151:630–642, 2013. © 2013 Wiley Periodicals, Inc.
Mark E. Olson - One of the best experts on this subject based on the ideXlab platform.
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wood Ontogeny as a model for studying heterochrony with an example of paedomorphosis in moringa moringaceae
Systematics and Biodiversity, 2007Co-Authors: Mark E. OlsonAbstract:Abstract Modern studies of heterochrony in plants have focused mostly on determinate organs or annuals, leaving long‐lived plants unstudied. Wood offers remarkable access to the issue, because Ontogeny during the life of a woody plant is recorded by changes in cell attributes from the inner wood to the outermost wood. An example is provided, examining vessel element Ontogeny in an explicitly phylogenetic context to infer paedomorphosis in the evolution of tuberous shrubs, represented by Moringa longituba (Moringaceae, the drumstick tree family), from an arborescent ancestral‐type Ontogeny represented by sister taxon M. ruspoliana. Two main difficulties with the use of wood in heterochrony studies are identified and their implications are discussed: (1) Some variable must be chosen against which to plot ontogenetic data; time, either observed directly or inferred from growth rings can be used, but stem diameter may be an acceptable or more informative alternative; (2) ‘Onset’ and ‘terminal’ ontogenetic ref...
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ontogenetic origins of floral bilateral symmetry in moringaceae brassicales
American Journal of Botany, 2003Co-Authors: Mark E. OlsonAbstract:: Floral morphology of the 13 species of Moringa ranges from actinomorphic flowers with little hypanthium to highly zygomorphic flowers with well-developed hypanthia. Scanning electron and light microscopy were used to identify ontogenetic differences among two actinomorphic and eight zygomorphic species. All species show traces of zygomorphy between petal organogenesis and anther differentiation. At late organogenesis, zygomorphy is manifest by one petal being larger than the others, slight unidirectional maturation of the anthers, and in many species, some staminodes may be missing. At organ differentiation and beyond, the actinomorphic species show a trend toward increasing actinomorphy, whereas the zygomorphic features of early Ontogeny are progressively accentuated throughout the Ontogeny of the zygomorphic species. Because of the early traces of zygomorphy throughout the family, Ontogeny in Moringa does not resemble that known from the sister taxon Caricaceae, which has flowers that are actinomorphic throughout Ontogeny. Great intraspecific variation was found in floral plan in the actinomorphic-flowered species in contrast to the zygomorphic species. Each of the main clades in the family is distinguished by at least one feature of floral Ontogeny. In general, ontogenetic differences that are congruent with deeper phylogenetic splits tend to occur earlier in Ontogeny than those congruent with more recent divergences.
Heather F Smith - One of the best experts on this subject based on the ideXlab platform.
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a 3 d geometric morphometric study of intraspecific variation in the Ontogeny of the temporal bone in modern homo sapiens
Journal of Human Evolution, 2013Co-Authors: Heather F Smith, Terrence B Ritzman, Erik Otarolacastillo, Claire E TerhuneAbstract:Abstract This study addresses how the human temporal bone develops the population-specific pattern of morphology observed among adults and at what point in Ontogeny those patterns arise. Three-dimensional temporal bone shape was captured using 15 landmarks on ontogenetic series of specimens from seven modern human populations. Discriminant function analysis revealed that population-specific temporal bone morphology is evident early in Ontogeny, with significant shape differences among many human populations apparent prior to the eruption of the first molar. As early as five years of age, temporal bone shape reflects population history and can be used to reliably sort populations, although those in closer geographic proximity and molecular affinity are more likely to be misclassified. The deviation of cold-adapted populations from this general pattern of congruence between temporal bone morphology and genetic distances, identified in previous work, was confirmed here in adult and subadult specimens, and was revealed to occur earlier in Ontogeny than previously recognized. Significant differences exist between the ontogenetic trajectories of some pairs of populations, but not among others, and the angles of these trajectories do not reflect genetic relationships or final adult temporal bone size. Significant intrapopulation differences are evident early in Ontogeny, with differences becoming amplified by divergent trajectories in some groups. These findings elucidate how the congruence between adult human temporal bone morphology and population history develops, and reveal that this pattern corresponds closely to that described previously for facial Ontogeny.
Erik Otarolacastillo - One of the best experts on this subject based on the ideXlab platform.
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a 3 d geometric morphometric study of intraspecific variation in the Ontogeny of the temporal bone in modern homo sapiens
Journal of Human Evolution, 2013Co-Authors: Heather F Smith, Terrence B Ritzman, Erik Otarolacastillo, Claire E TerhuneAbstract:Abstract This study addresses how the human temporal bone develops the population-specific pattern of morphology observed among adults and at what point in Ontogeny those patterns arise. Three-dimensional temporal bone shape was captured using 15 landmarks on ontogenetic series of specimens from seven modern human populations. Discriminant function analysis revealed that population-specific temporal bone morphology is evident early in Ontogeny, with significant shape differences among many human populations apparent prior to the eruption of the first molar. As early as five years of age, temporal bone shape reflects population history and can be used to reliably sort populations, although those in closer geographic proximity and molecular affinity are more likely to be misclassified. The deviation of cold-adapted populations from this general pattern of congruence between temporal bone morphology and genetic distances, identified in previous work, was confirmed here in adult and subadult specimens, and was revealed to occur earlier in Ontogeny than previously recognized. Significant differences exist between the ontogenetic trajectories of some pairs of populations, but not among others, and the angles of these trajectories do not reflect genetic relationships or final adult temporal bone size. Significant intrapopulation differences are evident early in Ontogeny, with differences becoming amplified by divergent trajectories in some groups. These findings elucidate how the congruence between adult human temporal bone morphology and population history develops, and reveal that this pattern corresponds closely to that described previously for facial Ontogeny.
Nigel C Hughes - One of the best experts on this subject based on the ideXlab platform.
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the development of the silurian trilobite aulacopleura koninckii reconstructed by applying inferred growth and segmentation dynamics a case study in paleo evo devo
Frontiers in Ecology and Evolution, 2017Co-Authors: Nigel C Hughes, Paul S Hong, Giuseppe FuscoAbstract:Fossilized growth series provide rare glimpses into the development of ancient organisms, illustrating descriptively how size and shape changed through Ontogeny. Occasionally fossil preservation is such that it is feasible to test alternative possibilities about how ancient development was regulated. Here we apply inferred developmental parameters pertaining to size, shape, and segmentation in the abundant and well-preserved 429 Myr old trilobite Aulacopleura koninckii that we have investigated previously to reconstruct the post-embryonic Ontogeny of this ancient arthropod. Our published morphometric analyses associated with model testing have shown that: specification of the adult number of trunk segments (polymorphic in this species) was determined precociously in Ontogeny; that growth regulation was targeted (i.e., compensatory), such that each developmental stage exhibited comparable variance in size and shape; and that growth gradients operating along the main body axis, both during juvenile and adult Ontogeny, resulted from a form of growth control based on positional specification. While such developmental features are common among extant organisms, our results represent the oldest evidence for them within Metazoa. Herein, the novel reconstruction of the development of A. koninckii permits visualization of patterns of relative and absolute growth and segmentation as never before possible for a fossilized arthropod Ontogeny. By conducting morphometric analysis of appropriate data sets it is thus possible to move beyond descriptive ontogenetic studies and to address questions of high interest for evolutionary developmental biology using data from fossils, which can help elucidate both how developmental processes themselves evolve and how they affect the evolution of organismal body patterning. By extending similar analyses to other cases of exceptional preservation of fossilized Ontogeny, we can anticipate beginning to realize the research program of “paleo-evo-devo”.
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growth and variation in the silurian proetide trilobite aulacopleura konincki and its implications for trilobite palaeobiology
Lethaia, 1995Co-Authors: Nigel C Hughes, Ralph E ChapmanAbstract:Morphometric analysis of growth in Aulacopleura konincki reveals several important features: (1) morphological variability is approximately constant throughout growth, increasing slightly in later Ontogeny; (2) shape is more tightly constrained than the numbers of postcephalic segments, which can be quite variable; and (3) a major ontogenetic transition occurs at glabellar lengths of about 1.7 mm. This transition divides the Ontogeny into two distinct growth phases, is smooth rather than abrupt, and is expressed as changes in growth trajectories, especially in the pygidium. The transition is not strictly correlated with the number of thoracic or pygidial segments. These results suggest a re-evaluation of the concepts of meraspid and holaspid growth stages in A. konincki, using growth trajectories rather than thoracic segment number to define the stages. Developmental flexibility in holaspid segment numbers in this phylogenetically advanced trilobite suggests that environmental factors, rather than phylogenetic constraint, may explain variations in segment production patterns within some advanced Trilobita.Morphometrics, trilobites, Ontogeny, variability, segmentation, Silurian, Czech Republic.
