The Effects of Cranial Orientation on Forensic Frontal Sinus Identification as Assessed by Outline Analyses

The utility of frontal sinuses for personal identification is widely recognized, but potential factors affecting its reliability remain uncertain. Deviations in cranial position between antemortem and postmortem radiographs may affect sinus appearance. This study investigates how slight deviations in orientations affect sinus size and outline shape and potentially impact identification. Frontal sinus models were created from CT scans of 21 individuals and digitally oriented to represent three clinically relevant radiographic views. From each standard view, model orientations were deviated at 5° intervals in horizontal, vertical, and diagonal (e.g., left-up) directions (27 orientations per individual). For each orientation, sinus dimensions were obtained, and outline shape was assessed by elliptical Fourier analyses and principal component (PC) analyses. Wilcoxon sign rank tests indicated that sinus breadth remained relatively stable (p > 0.05), while sinus height was significantly affected with vertical deviations (p < 0.006). Mann–Whitney U tests on Euclidean distances from the PC scores indicated consistently lower intra- versus inter-individual distances (p < 0.05). Two of the three orientations maintained perfect (100%) outline identification matches, while the third had a 98% match rate. Smaller and/or discontinuous sinuses were most problematic, and although match rates are high, practitioners should be aware of possible alterations in sinus variables when conducting frontal sinus identifications.

Journeys Through Shape and Time: Palaeobiology of Cenozoic New Zealand Spissatella and Eucrassatella (Bivalvia, Crassatellidae)

<p>A novel, highly-integrated approach combining morphometric, stratocladistic and sclerochronological methods has been applied to two genera of New Zealand Cenozoic crassatellid bivalve (Family Crassatellidae): Spissatella Finlay, 1926 and Eucrassatella Iredale, 1924. This study builds on previous work on Spissatella that demonstrated their amenability to shape analysis and provided a foundation for evolutionary studies of the group. The taxonomy of these crassatellids has been in need of revision; a number of changes to generic placement having been proposed in recent publications without redescription. These bivalves are character-depauperate and known only from fossil material within New Zealand, making them challenging subjects for the phylogenetic analysis that would, ideally, inform taxonomic revision. Geometric morphometric methods have been used to characterise the morphological variation of the study group in terms of shape. Landmarks/semilandmarks that capture internal hard-part morphology and external shell shape, have been compared with internal landmarks only, outline shape semilandmarks only, and outline shape Fourier transform methods, and are shown to best combine comprehensive coverage of total shell form with high correct reassignment of individuals to taxa in multidimensional morphospace. Procrustes-superimposed landmark/semilandmark configurations have been ordinated using Principal Components Analysis (PCA), and PCA plots have been used to compare the shape variation of each species. The independance in morphospace of Spissatella n. sp. C from S. trailli and S. clifdenensis has been established. Covariation of internal morphology and shell-shape has been interpreted as supporting the interdependance of shell and body/mantle proposed by Stasek (1963). PCA scores have been combined with traditional morphological characters and stratigraphic data to produce a phylogenetic tree using stratocladistics, a form of parsimony-based analysis which seeks to minimise combined morphological and stratigraphic debt. This technique also assesses the placement of taxa in ancestral positions on internal nodes of the tree. Combining discretised morphometric data with stratigraphic and morphological data in a single analysis has been shown to produce a more resolved tree than analyses based only on continuous morphometric data. The new analyses demonstrate paraphyly of both Eucrassatella and Spissatella as previously recognised. A taxonomic revision of the studied taxa has been undertaken, incorporating information from both morphometric and phylogenetic studies. Spissatella subobesa and S. maudensis are referred to Eucrassatella. Spissatella discrepans is synonymised with S. acculta. Triplicitella n. gen. and S.maxwelli n. sp. are described. Oxygen isotope analysis has been employed to show that shell-banding in these species is, on average, likely to have been laid down annually. Using this information, the longitudinal dataset of outlines from Crampton & Maxwell (2000) has been recalibrated to use chronological age rather than size to compare shape across taxa, and investigate heterochrony in twelve pairs of species representing either ancestor-descendant, sister-group or lineage-segment relationships. All of the heterochronic processes sensu Gould (1977), namely progenesis, neoteny, acceleration and hypermorphosis, as well as proportioned dwarfism and proportioned gigantism, are identified as having affected evolution within this clade.</p>

Journeys Through Shape and Time: Palaeobiology of Cenozoic New Zealand Spissatella and Eucrassatella (Bivalvia, Crassatellidae)

<p>A novel, highly-integrated approach combining morphometric, stratocladistic and sclerochronological methods has been applied to two genera of New Zealand Cenozoic crassatellid bivalve (Family Crassatellidae): Spissatella Finlay, 1926 and Eucrassatella Iredale, 1924. This study builds on previous work on Spissatella that demonstrated their amenability to shape analysis and provided a foundation for evolutionary studies of the group. The taxonomy of these crassatellids has been in need of revision; a number of changes to generic placement having been proposed in recent publications without redescription. These bivalves are character-depauperate and known only from fossil material within New Zealand, making them challenging subjects for the phylogenetic analysis that would, ideally, inform taxonomic revision. Geometric morphometric methods have been used to characterise the morphological variation of the study group in terms of shape. Landmarks/semilandmarks that capture internal hard-part morphology and external shell shape, have been compared with internal landmarks only, outline shape semilandmarks only, and outline shape Fourier transform methods, and are shown to best combine comprehensive coverage of total shell form with high correct reassignment of individuals to taxa in multidimensional morphospace. Procrustes-superimposed landmark/semilandmark configurations have been ordinated using Principal Components Analysis (PCA), and PCA plots have been used to compare the shape variation of each species. The independance in morphospace of Spissatella n. sp. C from S. trailli and S. clifdenensis has been established. Covariation of internal morphology and shell-shape has been interpreted as supporting the interdependance of shell and body/mantle proposed by Stasek (1963). PCA scores have been combined with traditional morphological characters and stratigraphic data to produce a phylogenetic tree using stratocladistics, a form of parsimony-based analysis which seeks to minimise combined morphological and stratigraphic debt. This technique also assesses the placement of taxa in ancestral positions on internal nodes of the tree. Combining discretised morphometric data with stratigraphic and morphological data in a single analysis has been shown to produce a more resolved tree than analyses based only on continuous morphometric data. The new analyses demonstrate paraphyly of both Eucrassatella and Spissatella as previously recognised. A taxonomic revision of the studied taxa has been undertaken, incorporating information from both morphometric and phylogenetic studies. Spissatella subobesa and S. maudensis are referred to Eucrassatella. Spissatella discrepans is synonymised with S. acculta. Triplicitella n. gen. and S.maxwelli n. sp. are described. Oxygen isotope analysis has been employed to show that shell-banding in these species is, on average, likely to have been laid down annually. Using this information, the longitudinal dataset of outlines from Crampton & Maxwell (2000) has been recalibrated to use chronological age rather than size to compare shape across taxa, and investigate heterochrony in twelve pairs of species representing either ancestor-descendant, sister-group or lineage-segment relationships. All of the heterochronic processes sensu Gould (1977), namely progenesis, neoteny, acceleration and hypermorphosis, as well as proportioned dwarfism and proportioned gigantism, are identified as having affected evolution within this clade.</p>

Tales of schizomid tails: patterns in schizomid flagellum shape from elliptical Fourier analysis

The arachnid order Schizomida is a relatively understudied group of soil-dwelling predators found on all continents except Antarctica. While efforts to understand their biology are growing, there is still much to know about them. A curious aspect of their morphology is the male flagellum, a sexually dimorphic, tail-like structure which differs in shape across the order and functions in their courtship rituals. The flagellar shape is important for taxonomic classification, yet few efforts have been made to examine shape diversity across the group. Using elliptical Fourier analysis, a type of geometric morphometrics based on outline shape, we quantified shape differences across a combined nearly 550 outlines in the dorsal and lateral views, categorizing them based on genus, family, biogeographic realm, and habitat, with special emphasis on Caribbean and Cuban fauna. We tested for allometric relationships, differences in disparity based on locations and sizes in morphospace among these categories, and for clusters of shapes in morphospace. We found multiple differences in all categories despite apparent overlaps in morphospace, evolutionary allometry, and evidence for discrete clusters in some flagellum shapes. This study can serve as a foundation for further study on the evolution, diversification, and taxonomic utility of the male flagellum.

A new species of Epithemia Kützing (Bacillariophyceae, Rhopalodiales) from the Mula river, Western Ghats, India, with comments on the phylogenetic position of Rhopalodia and Epithemia

A new species, Epithemia agharkarii sp. nov., is described from the Mula River, Western Ghats, India. The new species is described based on light and scanning electron microscopy; it is characterized by having lanceolate to slightly elliptical valves with rounded apices and being 16–38 μm long and 12.5–17.5 μm wide. Based on morphology, especially the atypical position of the raphe, it is similar to E. reicheltii. The new species is differentiated from the latter by the valve outline, shape of the apices, specific position of the raphe and breadth. We discuss the possible phylogenetic position of these two taxa and recent proposals related to the classification of Rhopalodia and Epithemia.

The impact of hybridization on upper first molar shape in robust capuchins (Sapajus nigritus x S. libidinosus)

To better understand the impact of hybridization on development and morphology, I analyze an understudied phenotype in hybrid morphology research: tooth shape. I apply a 2D geometric morphometric approach to compare variation in first upper molar cusp tip positions and crown outline shape among 31 crested capuchins (Sapajus nigritus), 37 bearded capuchins (S. libidinosus), and 44 hybrids (S. nigritus x S. libidinosus). A principal components analysis shows that group membership accounts for a significantly greater proportion of variance along the first major axis of M1 shape variation than does allometry. While most hybrids have S. nigritus-like M1s, several possess a transgressive M1 shape not observed in either parental species. Procrustes distances are greater in hybrids compared to the parental capuchins, and two-block partial least squares analyses show that hybrids exhibit weaker integration between cusp tip positions and crown outline shape. These results demonstrate that hybridization generates novel M1 shapes and support the hypothesis that destabilized development results in elevated phenotypic variance in hybrids. Further studies of dental shape in hybrid primates will generate important data for on-going efforts to detect potential hybrids in the hominin fossil record and to understand the evolutionary outcomes of anthropogenic hybridization.

Quantifying shell outline variability in extant and fossil Laqueus (Brachiopoda: Terebratulida): are outlines good proxies for long-looped brachidial morphology and can they help us characterize species?

Extant and extinct terebratulide brachiopod species have been defined primarily on the basis of morphology. What is the fidelity of morphological species to biological species? And how can we test this fidelity with fossils? Taxonomically and phylogenetically, the most informative internal feature in the brachiopod suborder Terebratellidina is the geometrically complex long-looped brachidium, which is highly fragile and only rarely preserved in the fossil record. Given this, it is essential to test other sources of morphological data, such as valve outline shape, when trying to recognize and identify species. We analyzed valve outlines and brachidia in the genus Laqueus to explore the utility of shell shape in discriminating extant and fossil species. Using geometric morphometric methods, we quantified valve outline variability using elliptical Fourier methods and tested whether long-looped brachidial morphology correlates with shell outline shape. We then built classification models based on machine learning algorithms using outlines as shape variables to predict fossil species’ identities. Our results demonstrate that valve outline shape is significantly correlated with long-looped brachidial shape and that even relatively simple outlines are sufficiently morphologically distinct to enable extant Laqueus species to be identified, validating current taxonomic assignments. These are encouraging results for the study and delimitation of fossil terebratulide species, and their recognition as biological species. In addition, machine learning algorithms can be successfully applied to help solve species recognition and delimitation problems in paleontology, especially when morphology can be characterized quantitatively and analyzed statistically.

Detecting Phylogenetic Signal and Adaptation in Papionin Cranial Shape by Decomposing Variation at Different Spatial Scales

Phylogenetic reconstruction based on morphometric data is hampered by homoplasies. For example, many similarities in cranial form between primate taxa more strongly reflect ecological similarities rather than phylogenetic relatedness. However, the way in which the different cranial bones constitute cranial form is, if at all, of less functional relevance and thus largely hidden from selection. We propose that these “constructional details” are better indicators of phylogenetic history than any large-scale shape feature or raw form variable. Within a geometric morphometric context, we show how to analyze the relative extent of bones independently of differences in overall shape. We also show how to decompose total shape variation into small-scale and large-scale shape variation. We apply both methods to the midsagittal cranial morphology of papionin monkeys, which are well known for the discrepancy between morphological similarities and phylogenetic relationships. We study phylogenetic signal and functional adaptation using a molecular phylogeny and contextual data on feeding ecology and locomotor behavior. As expected, total cranial shape, bone outline shape, and large-scale shape features were only weakly associated with phylogenetic distance. But the relative bone contributions and small-scale shape features were both highly correlated with phylogenetic distances. By contrast, the association with ecological and behavioral variables was strongest for the outline shape and large-scale shape features. Studies of morphological adaptation and phylogenetic history thus profit from a decomposition of shape variation into different spatial scales.