1,721,036 research outputs found
Reassessment of the largest Pleistocene rhinocerotine Rhinoceros platyrhinus (Mammalia, Rhinocerotidae) from the Upper Siwaliks (Siwalik Hills, India)
No full textWe describe and figure a well-preserved, large skull of a rhinoceros, NHMUK 36661, collected in 1860 from Upper Siwalik deposits. This specimen can be referred to Rhinoceros platyrhinus. Comparison with the type material of R. platyrhinus revealed that several specimens previously referred to this taxon, including the lectotype, should instead be assigned to Rhinoceros sp. (potentially R. sivalensis or R. unicornis). Therefore, we here provide new detailed cranial and dental characters for R. platyrhinus, which is currently known only by a few specimens collected from a restricted area of northern India. We suggest that the generic name Punjabitherium erected for R. platyrhinus represents a junior synonym of Rhinoceros due to the morphological affinities of NHMUK 36661 with R. unicornis. A principal component analysis and a cluster analysis confirmed the morphological similarities between R. platyrhinus and R. unicornis. Rhinoceros platyrhinus represents the largest rhinocerotine species in Eurasia and is characterized by a long skull and high-crowned teeth, suggesting that it was a grazer rather than a mixed feeder such as R. unicornis. This is supported by a cluster analysis on the upper teeth. The progressive increase in aridity from ca. 12 Ma to Recent in northern India could have affected the dietary regime of R. platyrhinus towards to a more grazer-like diet
Did the Late Pleistocene climatic changes influence evolutionary trends in body size of the red deer? The study case of the Italian Peninsula
No full textVariations in the body size of red deer (Cervus elaphus) have been reported by several authors from several European fossiliferous localities for the Late Pleistocene and Holocene. Recently, several contributions focused on body size variation of red deer populations from the Italian Peninsula. Evolutionary trends of phenotypic traits may follow distinct tempos and modes of evolution such as Brownian, Ornstein-Uhlenbeck, stasis or random walk. Here, we investigated which evolutionary model better explained the temporal trend in body size of C. elaphus ssp. from the Italian Peninsula using modern statistical tools. We also tested the potential relationships between climate change and geographical variation through the Late Pleistocene. Our sample includes 1090 specimens from several peninsular Italian localities. For each specimen, we extracted the Size Variation Index calculated on postcranial elements. We found that stasis was the model better explaining the body size evolution in C. elaphus. We also found a nonsignificant interaction between body size and climate, whereas we detected a significant relationship with geography. We hypothesized that the red deer phenotypical plasticity was able to mitigate the selective constraints driven by climatic changes and geographical variability through the Late Pleistocene and Holocene, therefore returning a no neat variation in body size
(2006) - Eocene Neochelys (Podocnemidae, Pleurodira, Testudinata) of Italy and their palaeobiogeography
No full textEvolutionary trends and stasis in carnassial teeth of European Pleistocene wolf Canis lupus (Mammalia, Canidae)
No full textThe evolutionary trends of tooth size in quaternary carnivores support an almost direct association with climate. However, phenotypic trait may follow distinct tempo and mode of evolution such as Brownian, Ornstein-Uhlenbeck or random walk. Here, we investigated the morphometric variations and evolutionary trends in the carnassial teeth size of the European wolf (Canis lupus) by means of modern statistical tools. Recent contributions highlighted linear increase trend in tooth size through the Pleistocene, but those differences in time have not been tested using modern statistical strategies. Examining a wide sample of linear measurements of carnassials of extinct and extant wolves (486 M1 and 491 P4), we tested which evolutionary model (random walk, stasis, Ornstein-Uhlenbeck) better explains the dimensional pattern of teeth through time at the continental scale and at the regional scale (France and Italy). Our results clearly show different models for the carnassials of C. lupus. Lower and upper carnassials for the entire sample of C. lupus are characterized by a directional trend, whereas Italian and French subsets show a random fluctuation of carnassials size through time. The carnassials dimensions are not directly correlated with the climate changes during the Middle-Late Pleistocene and Holocene, but they are possibly correlated with spread of the cold mega-fauna in Europe, and thus with the changes in the dietary regime
Phase II trial of gemcitabine plus carboplatin for urothelial transitional cell carcinoma (UTCC) in advanced or metastatic stage
No full textMechanical performance of ceratopsian lower jaws: New insight revealed by finite element analysis
No full text
Males resemble females: Re-evaluating sexual dimorphism in Protoceratops andrewsi (Neoceratopsia, Protoceratopsidae).
No full textBackground
Protoceratops andrewsi(Neoceratopsia, Protoceratopsidae) is a well-known dinosaur from the Upper Cretaceous of Mongolia. Some previous workers hypothesized sexual dimorphism in the cranial shape of this taxon, using qualitative and quantitative observations. In
particular, width and height of the frill as well as the development of a nasal horn have been hypothesized as potentially sexually dimorphic.
Methodology/Principal Findings
Here, we reassess potential sexual dimorphism in skulls of Protoceratops andrewsiby applying two-dimensional geometric morphometrics to 29 skulls in lateral and dorsal views. Principal Component Analyses and nonparametric MANOVAs recover no clear separation between hypothetical “males” and
“females” within the overall morphospace. Males and females
thus possess similar overall cranial morphologies. No differences in size between
“males” and “females” are recovered using nonparametric ANOVAs.
Conclusions/Significance
Sexual dimorphism within Protoceratops andrewsiis not strongly supported by our results, as previously proposed by several authors. Anatomical traits such as height and width of the frill, and skull size thus may not be sexually dimorphic. Based on PCA for a data set focusing on the rostrum and associated ANOVA results, nasal horn height is the only feature with potential dimorphism. As a whole, most purported dimorphic variation is probably primarily the result of ontogenetic cranial shape changes as well as intraspecific cranial variation independent of sex
Macroevolutionary patterns in cranial and lower jaw shape of ceratopsian dinosaurs (dinosauria, ornithischia). phylogeny, morphological integration, and evolutionary rates
Full text linkOrganisms: Ceratopsians were herbivorous, beaked dinosaurs, ranging from 1 m to 9 m in body length, usually four-footed, and with a bony frill that extended backwards from the cranium over the nape of the neck. Known from Asia, Europe, and North America, they appeared in the Late Jurassic and persisted until the end of the Late Cretaceous.
Questions: Which evolutionary processes drive the phenotypic evolution of skulls and lower jaws within Ceratopsia? What is the degree of morphological integration between the skull and lower jaw, and between the snout and frill among clades? Finally, are there any morphological evolution rate shifts across the ceratopsian phylogeny?
Data: Photographs from 121 ceratopsian skulls and 122 lower jaws in lateral view, both from original photos and published pictures. Fifty-five ceratopsian species are represented in the sample.
Methods: We investigated cranial and lower jaw shape changes across ceratopsians applying two-dimensional geometric morphometrics. We also investigated the morphological variation of the snout and the frill. Using phylogenetic generalized least squares regression, we estimated the degree of phylogenetic signal in size and shape data, as well as in the shape-size relationship. We performed phenotypic evolutionary rate analysis on shape data to describe phenotypic shifts across the phylogeny. Using a rarefied version of Escoufier's RV coefficient, we tested morphological integration between skulls and lower jaws, and between snouts and frills. Finally, we explored the potential link between cranial and frill shape evolution in ceratopsians and the radiation of angiosperms using a linear regression model.
Results: Skull, snout, and frill shapes differ among clades (with the exception of leptoceratopsids and protoceratopsids). Lower jaws show distinct morphologies among groups. Size and shape changes are phylogenetically structured. The frill drives the morphological variation of the skull, co-varying much more with the lower jaw than with the snout. The frill appears to evolve to co-vary better with the lower jaw in the more morphologically derived clades than in basal ones. A significant linear relationship does exist between cranial shape and angiosperm occurrences, suggesting the hypothesis that the frill evolved in response to changes in dietary compositions associated with the turnover between gymnosperms and angiosperms during the Cretaceous. Significant negative shifts in evolutionary rates characterize skull, snout, frill, and lower jaw shapes, corresponding to nodes where psittacosaurids diverge from other taxa. In contrast, a significant positive shift in skull and snout shape rate of evolution characterizes the clade Ceratopsoidea.
Conclusion: The frill is the main driving force in the overall cranial shape within Ceratopsia and evolved secondarily to better co-vary with the lower jaw to produce a more efficient masticatory apparatus. The changes in frill shape are correlated with the angiosperm diversification that occurred in the Cretaceous and thus correlated with changes in diet. Ceratopsians exhibit a slowdown in the phenotypic evolutionary rate in the Early Cretaceous and an acceleration of the phenotypic rate in the Late Cretaceous
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