Papers by Leonardo Maiorino
Ceratopsidae represents one of the last and best-known radiations of non-avian dinosaurs. Intersp... more Ceratopsidae represents one of the last and best-known radiations of non-avian dinosaurs. Interspecific variation is well documented qualitatively with linear measurements, but little has been done to quantify shape differences in the frill that may indicate functional or evolutionary signals. In order to investigate shape change in the squamosal across Chasmosaurinae and Centrosaurinae, we applied geometric morphometrics to the outline of the squamosal for 155 specimens representing 27 ceratopsid species and Protoceratops spp. A Mantel test suggests that the shape of ceratopsid squamosals is highly constrained by phylogeny. MANOVA, ANOVA, and their phylogenetic versions suggest that an evolutionarily significant allometric signal exists between the two clades, but not within clades. Principal component analysis indicates that centrosaurines have a uniform squamosal shape, with the exceptions of Spinops and Diabloceratops. Even when accounting for phylogeny, the relationship between squamosal shape and size is significant. Mapping shape onto the phylogeny, we estimated ancestral shapes at nodes. The transition from the non-ceratopsid to ceratopsid condition is characterized by a squamosal with a wider angle between the infratemporal process and the caudoventral margin, and a more dorsoventrally elongated and caudally expanded blade. From root to tips, centrosaurine squamosals were found to be conservative, but exhibit a slight dorsoventral expansion and a narrow angle between the infratemporal process and the caudoventral margin in more derived taxa. Chasmosaurines, compared with centrosaurines, show a derived morphology, with a trend towards a blade that is strongly expanded dorsoventrally and with a narrower angle between the infratemporal process and the caudoventral margin.
Cat-like carnivorous mammals represent a relatively homogeneous group of species whose morphology... more Cat-like carnivorous mammals represent a relatively homogeneous group of species whose morphology appears constrained by exclusive adaptations for meat eating. We present the most comprehensive data set of extant and extinct cat-like species to test for evolutionary transformations in size, shape and mechanical performance, that is, von Mises stress and surface traction, of the mandible. Size and shape were both quantified by means of geometric morphometrics, whereas mechanical performance was assessed applying finite element models to 2D geometry of the mandible. Additionally, we present the first almost complete composite phylogeny of cat-like carnivorans for which well-preserved mandibles are known, including representatives of 35 extant and 59 extinct species of Felidae, Nimravidae, and Barbourofelidae. This phylogeny was used to test morphological differentiation, allometry, and covariation of mandible parts within and among clades. After taking phylogeny into account, we found that both allometry and mechanical variables exhibit a significant impact on mandible shape. We also tested whether mechanical performance was linked to morphological integration. Mechanical stress at the coronoid process is higher in sabertoothed cats than in any other clade. This is strongly related to the high degree of covariation within modules of sabertooths mandibles. We found significant correlation between integration at the clade level and per-clade averaged stress values, on both original data and by partialling out interclade allometry from shapes when calculating integration. This suggests a strong interaction between natural selection and the evolution of developmental and functional modules at the clade level. Downloaded from SYSTEMATIC BIOLOGY FIGURE 2. Phylogenetic tree comprehensive of all species considered in this work. Thicker lines indicate the observed stratigraphic range of taxa.
After the effect of phylogeny is statistically removed, cranial structures that are employed sole... more After the effect of phylogeny is statistically removed, cranial structures that are employed solely for mastication should covary the most with hypsodonty (high-crowned cheek teeth are termed 'hypsodont'). Such structures should also be the least phylogenetically constrained. A corollary: structures that are highly influenced by shared ancestry will exhibit greater morphological integration than those that are affected less.
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Papers by Leonardo Maiorino