Background. Previous quantitative studies on Bauruemys elegans (Suárez, 1969) shell variation, as well as the taphonomic interpretation of its type locality, have suggested that all specimens collected in this locality may have belonged to the same population. We rely on this hypothesis in a morphometric study of the skull. Also, we tentatively assessed the eating preference habits differentiation that might be explained as due to ontogenetic changes. Methods. We carried out an ANOVA testing 29 linear measurements from 21 skulls of B. elegans taken by using a caliper and through images, using the ImageJ software. A Principal Components Analysis (PCA) was performed with 27 measurements (excluding total length and width characters; =raw data) in order to visualize the scatter plots based on the form variance only. Then, a PCA was carried out using ratios of length and width of each original measurement to assess shape variation among individuals. Finally, original measurements were log-transformed to describe allometries over ontogeny. Results. No statistical differences were found between caliper and ImageJ measurements. The first three PCs of the PCA with raw data comprised 70.2% of the variance. PC1 was related to size variation and all others related to shape variation. Two specimens plotted outside the 95% ellipse in PC1~PC2 axes. The first three PCs of the PCA with ratios comprised 64% of the variance. When considering PC1~PC2, all specimens plotted inside the 95% ellipse. In allometric analysis, five measurements were positively allometric, 19 were negatively allometric and three represent truly negative allometry. Many bones of the posterior and the lateral emarginations lengthen due to increasing size, while jugal and the quadratojugal decrease in width. Discussion. ImageJ is useful in replacing caliper since there was no statistical differences. Yet, iterative imputation is more appropriate to deal with missing data in PCA. Some specimens show small differences in form and shape. Form differences were interpreted as occuring due to ontogeny, whereas shape differences are related to feeding changes during growth.
In this study, 21 skull bones of Metoposaurus krasiejowensis from the Late Triassic of Poland were investigated histologically. Dermal bones show a diploë structure, with an ornamented external surface. The ridges consist of mostly well vascularized parallelfibered bone; the valleys are built of an avascular layer of lamellar bone. The thick middle region consists of cancellous bone, with varying porosity. The thin and less vascularized internal cortex consists of parallel-fibered bone. The numerous Sharpey's fibers and ISF are present in all bones. The cyclicity of growth is manifested as an alternation of thick, avascular annuli and high vascularized zones as well as a sequence of resting lines. The detailed histological framework of dermal bones varies even within a single bone; this seems to be related to the local biomechanical loading of the particular part of the skull. The dynamic processes observed during the ornamentation creation indicate that the positions of the ridges and grooves change during growth and could be a specific adaptation to changing biomechanical conditions and stress distribution during bone development. In the supratemporal, the cementing lines show that the remodeling process could be involved in the creations of sculpture. The common occurrence of ISF suggests that metaplastic ossification plays an important role during cranial development. Endochondral bones preserved the numerous remains of calcified cartilage. This indicates that ossification follows a pattern known for stereospondyl intercentra, with relatively slow ossification of the trabecular part and late development of the periosteal cortex. The large accumulation of Sharpey's fibers in the occipital condyles indicates the presence of strong muscles and ligaments connecting the skull to the vertebral column.
Background. Previous quantitative studies on Bauruemys elegans (Suárez, 1969) shell variation, as well as the taphonomic interpretation of its type locality, have suggested that all specimens collected in this locality may have belonged to the same population. We rely on this hypothesis in a morphometric study of the skull. Also, we tentatively assessed the eating preference habits differentiation that might be explained as due to ontogenetic changes. Methods. We carried out an ANOVA testing 29 linear measurements from 21 skulls of B. elegans taken by using a caliper and through images, using the ImageJ software. A Principal Components Analysis (PCA) was performed with 27 measurements (excluding total length and width characters; =raw data) in order to visualize the scatter plots based on the form variance only. Then, a PCA was carried out using ratios of length and width of each original measurement to assess shape variation among individuals. Finally, original measurements were log-transformed to describe allometries over ontogeny. Results. No statistical differences were found between caliper and ImageJ measurements. The first three PCs of the PCA with raw data comprised 70.2% of the variance. PC1 was related to size variation and all others related to shape variation. Two specimens plotted outside the 95% ellipse in PC1~PC2 axes. The first three PCs of the PCA with ratios comprised 64% of the variance. When considering PC1~PC2, all specimens plotted inside the 95% ellipse. In allometric analysis, five measurements were positively allometric, 19 were negatively allometric and three represent truly negative allometry. Many bones of the posterior and the lateral emarginations lengthen due to increasing size, while jugal and the quadratojugal decrease in width. Discussion. ImageJ is useful in replacing caliper since there was no statistical differences. Yet, iterative imputation is more appropriate to deal with missing data in PCA. Some specimens show small differences in form and shape. Form differences were interpreted as occuring due to ontogeny, whereas shape differences are related to feeding changes during growth.
Background. Piramys auffenbergi was described as an emydine turtle based on a well-preserved skull retrieved from late Miocene deposits exposed on Piram Island, India. The description and figures provided in the original publication are vague and do not support assignment to Emydinae. This taxon has mostly been ignored by subsequent authors. Material & Methods. We reexamine the holotype specimen and provide an extensive description and diagnosis for Piramys auffenbergi and included this taxon in a global character-taxon matrix for Pleurodira. Results. The presence of a processus trochlearis pterygoidei conclusively shows pleurodiran affinities for Piramys auffenbergi. Inclusion of this taxon in a phylogenetic analysis retrieves it within Stereogenyini and as sister to the Asian taxa Shweboemys pilgrimi and Brontochelys gaffneyi. Discussion. Our reexamination of the holotype of Piramys auffenbergi confidently rejects the original assessment of this taxon as an emydine testudinoid and conclusively shows affinities with the pleurodiran clade Stereogenyini instead. Even though most taxa from this lineage are thought to be coastal turtles, all Asian stereogenyines were collected from continental deposits, suggesting a more diverse paleoecology for the group.
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