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Jacques A Gauthier - One of the best experts on this subject based on the ideXlab platform.
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a transitional snake from the late Cretaceous Period of north america
Nature, 2012Co-Authors: Nicholas R Longrich, Bhartanjan S Bhullar, Jacques A GauthierAbstract:Snakes are the most diverse group of lizards, but their origins and early evolution remain poorly understood owing to a lack of transitional forms. Several major issues remain outstanding, such as whether snakes originated in a marine or terrestrial environment and how their unique feeding mechanism evolved. The Cretaceous Coniophis precedens was among the first Mesozoic snakes discovered, but until now only an isolated vertebra has been described and it has therefore been overlooked in discussions of snake evolution. Here we report on previously undescribed material from this ancient snake, including the maxilla, dentary and additional vertebrae. Coniophis is not an anilioid as previously thought a revised phylogenetic analysis of Ophidia shows that it instead represents the most primitive known snake. Accordingly, its morphology and ecology are critical to understanding snake evolution. Coniophis occurs in a continental floodplain environment, consistent with a terrestrial rather than a marine origin; furthermore, its small size and reduced neural spines indicate fossorial habits, suggesting that snakes evolved from burrowing lizards. The skull is intermediate between that of lizards and snakes. Hooked teeth and an intramandibular joint indicate that Coniophis fed on relatively large, soft-bodied prey. However, the maxilla is firmly united with the skull, indicating an akinetic rostrum. Coniophis therefore represents a transitional snake, combining a snake-like body and a lizard-like head. Subsequent to the evolution of a serpentine body and carnivory, snakes evolved a highly specialized, kinetic skull, which was followed by a major adaptive radiation in the Early Cretaceous Period. This pattern suggests that the kinetic skull was a key innovation that permitted the diversification of snakes.
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A transitional snake from the Late Cretaceous Period of North America
Nature, 2012Co-Authors: Nicholas R Longrich, Bhartanjan S Bhullar, Jacques A GauthierAbstract:Snakes are the most diverse group of lizards^ 1 , but their origins and early evolution remain poorly understood owing to a lack of transitional forms. Several major issues remain outstanding, such as whether snakes originated in a marine^ 2 , 3 , 4 or terrestrial^ 5 , 6 environment and how their unique feeding mechanism evolved^ 1 , 7 , 8 . The Cretaceous Coniophis precedens was among the first Mesozoic snakes discovered^ 9 , but until now only an isolated vertebra has been described^ 9 , 10 and it has therefore been overlooked in discussions of snake evolution. Here we report on previously undescribed material^ 11 from this ancient snake, including the maxilla, dentary and additional vertebrae. Coniophis is not an anilioid as previously thought^ 11 ; a revised phylogenetic analysis of Ophidia shows that it instead represents the most primitive known snake. Accordingly, its morphology and ecology are critical to understanding snake evolution. Coniophis occurs in a continental floodplain environment, consistent with a terrestrial rather than a marine origin; furthermore, its small size and reduced neural spines indicate fossorial habits, suggesting that snakes evolved from burrowing lizards. The skull is intermediate between that of lizards and snakes. Hooked teeth and an intramandibular joint indicate that Coniophis fed on relatively large, soft-bodied prey. However, the maxilla is firmly united with the skull, indicating an akinetic rostrum. Coniophis therefore represents a transitional snake, combining a snake-like body and a lizard-like head. Subsequent to the evolution of a serpentine body and carnivory, snakes evolved a highly specialized, kinetic skull, which was followed by a major adaptive radiation in the Early Cretaceous Period. This pattern suggests that the kinetic skull was a key innovation that permitted the diversification of snakes. Previously undescribed material from the maxilla, dentary and spine of the Cretaceous Coniophis precedens shows that it is the most primitive known snake. Fossils of snakes are extremely rare, and the resulting shortage of information has fuelled a heated debate over the origins of this distinctive group. Did they evolve in the sea? Or on land, as suggested by remains of the primitive Cretaceous snake Najash ? A study of the long-neglected remains of the snake Coniophis , originally described by famous dinosaur-hunter Othniel C. Marsh in 1892, has come up with some facts that favour a land-based genesis for snakes. Coniophis was a terrestrial species, with a snake-like body but a primitive, lizard-like head. This suggests that early snakes were burrowers that achieved their elongate form before evolving the characteristic highly mobile skull of modern snakes.
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A transitional snake from the Late Cretaceous Period of North America
Nature, 2012Co-Authors: Nicholas R Longrich, Bhartanjan S Bhullar, Jacques A GauthierAbstract:Fossils of snakes are extremely rare, and the resulting shortage of information has fuelled a heated debate over the origins of this distinctive group. Did they evolve in the sea? Or on land, as suggested by remains of the primitive Cretaceous snake Najash ? A study of the long-neglected remains of the snake Coniophis , originally described by famous dinosaur-hunter Othniel C. Marsh in 1892, has come up with some facts that favour a land-based genesis for snakes. Coniophis was a terrestrial species, with a snake-like body but a primitive, lizard-like head. This suggests that early snakes were burrowers that achieved their elongate form before evolving the characteristic highly mobile skull of modern snakes. Previously undescribed material from the maxilla, dentary and spine of the Cretaceous Coniophis precedens shows that it is the most primitive known snake. Snakes are the most diverse group of lizards^ 1 , but their origins and early evolution remain poorly understood owing to a lack of transitional forms. Several major issues remain outstanding, such as whether snakes originated in a marine^ 2 , 3 , 4 or terrestrial^ 5 , 6 environment and how their unique feeding mechanism evolved^ 1 , 7 , 8 . The Cretaceous Coniophis precedens was among the first Mesozoic snakes discovered^ 9 , but until now only an isolated vertebra has been described^ 9 , 10 and it has therefore been overlooked in discussions of snake evolution. Here we report on previously undescribed material^ 11 from this ancient snake, including the maxilla, dentary and additional vertebrae. Coniophis is not an anilioid as previously thought^ 11 ; a revised phylogenetic analysis of Ophidia shows that it instead represents the most primitive known snake. Accordingly, its morphology and ecology are critical to understanding snake evolution. Coniophis occurs in a continental floodplain environment, consistent with a terrestrial rather than a marine origin; furthermore, its small size and reduced neural spines indicate fossorial habits, suggesting that snakes evolved from burrowing lizards. The skull is intermediate between that of lizards and snakes. Hooked teeth and an intramandibular joint indicate that Coniophis fed on relatively large, soft-bodied prey. However, the maxilla is firmly united with the skull, indicating an akinetic rostrum. Coniophis therefore represents a transitional snake, combining a snake-like body and a lizard-like head. Subsequent to the evolution of a serpentine body and carnivory, snakes evolved a highly specialized, kinetic skull, which was followed by a major adaptive radiation in the Early Cretaceous Period. This pattern suggests that the kinetic skull was a key innovation that permitted the diversification of snakes.
John A. Tarduno - One of the best experts on this subject based on the ideXlab platform.
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Hum from the quiet zone
Nature Geoscience, 2012Co-Authors: John A. TardunoAbstract:During the middle of the Cretaceous Period, the polarity of Earth's magnetic field remained stable. A magnetic survey of oceanic crust formed during that time, however, suggests that the field intensity was surprisingly variable.
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Geomagnetism: Hum from the quiet zone
Nature Geoscience, 2012Co-Authors: John A. TardunoAbstract:During the middle of the Cretaceous Period, the polarity of Earth's magnetic field remained stable. A magnetic survey of oceanic crust formed during that time, however, suggests that the field intensity was surprisingly variable.
Nicholas R Longrich - One of the best experts on this subject based on the ideXlab platform.
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a transitional snake from the late Cretaceous Period of north america
Nature, 2012Co-Authors: Nicholas R Longrich, Bhartanjan S Bhullar, Jacques A GauthierAbstract:Snakes are the most diverse group of lizards, but their origins and early evolution remain poorly understood owing to a lack of transitional forms. Several major issues remain outstanding, such as whether snakes originated in a marine or terrestrial environment and how their unique feeding mechanism evolved. The Cretaceous Coniophis precedens was among the first Mesozoic snakes discovered, but until now only an isolated vertebra has been described and it has therefore been overlooked in discussions of snake evolution. Here we report on previously undescribed material from this ancient snake, including the maxilla, dentary and additional vertebrae. Coniophis is not an anilioid as previously thought a revised phylogenetic analysis of Ophidia shows that it instead represents the most primitive known snake. Accordingly, its morphology and ecology are critical to understanding snake evolution. Coniophis occurs in a continental floodplain environment, consistent with a terrestrial rather than a marine origin; furthermore, its small size and reduced neural spines indicate fossorial habits, suggesting that snakes evolved from burrowing lizards. The skull is intermediate between that of lizards and snakes. Hooked teeth and an intramandibular joint indicate that Coniophis fed on relatively large, soft-bodied prey. However, the maxilla is firmly united with the skull, indicating an akinetic rostrum. Coniophis therefore represents a transitional snake, combining a snake-like body and a lizard-like head. Subsequent to the evolution of a serpentine body and carnivory, snakes evolved a highly specialized, kinetic skull, which was followed by a major adaptive radiation in the Early Cretaceous Period. This pattern suggests that the kinetic skull was a key innovation that permitted the diversification of snakes.
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A transitional snake from the Late Cretaceous Period of North America
Nature, 2012Co-Authors: Nicholas R Longrich, Bhartanjan S Bhullar, Jacques A GauthierAbstract:Snakes are the most diverse group of lizards^ 1 , but their origins and early evolution remain poorly understood owing to a lack of transitional forms. Several major issues remain outstanding, such as whether snakes originated in a marine^ 2 , 3 , 4 or terrestrial^ 5 , 6 environment and how their unique feeding mechanism evolved^ 1 , 7 , 8 . The Cretaceous Coniophis precedens was among the first Mesozoic snakes discovered^ 9 , but until now only an isolated vertebra has been described^ 9 , 10 and it has therefore been overlooked in discussions of snake evolution. Here we report on previously undescribed material^ 11 from this ancient snake, including the maxilla, dentary and additional vertebrae. Coniophis is not an anilioid as previously thought^ 11 ; a revised phylogenetic analysis of Ophidia shows that it instead represents the most primitive known snake. Accordingly, its morphology and ecology are critical to understanding snake evolution. Coniophis occurs in a continental floodplain environment, consistent with a terrestrial rather than a marine origin; furthermore, its small size and reduced neural spines indicate fossorial habits, suggesting that snakes evolved from burrowing lizards. The skull is intermediate between that of lizards and snakes. Hooked teeth and an intramandibular joint indicate that Coniophis fed on relatively large, soft-bodied prey. However, the maxilla is firmly united with the skull, indicating an akinetic rostrum. Coniophis therefore represents a transitional snake, combining a snake-like body and a lizard-like head. Subsequent to the evolution of a serpentine body and carnivory, snakes evolved a highly specialized, kinetic skull, which was followed by a major adaptive radiation in the Early Cretaceous Period. This pattern suggests that the kinetic skull was a key innovation that permitted the diversification of snakes. Previously undescribed material from the maxilla, dentary and spine of the Cretaceous Coniophis precedens shows that it is the most primitive known snake. Fossils of snakes are extremely rare, and the resulting shortage of information has fuelled a heated debate over the origins of this distinctive group. Did they evolve in the sea? Or on land, as suggested by remains of the primitive Cretaceous snake Najash ? A study of the long-neglected remains of the snake Coniophis , originally described by famous dinosaur-hunter Othniel C. Marsh in 1892, has come up with some facts that favour a land-based genesis for snakes. Coniophis was a terrestrial species, with a snake-like body but a primitive, lizard-like head. This suggests that early snakes were burrowers that achieved their elongate form before evolving the characteristic highly mobile skull of modern snakes.
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A transitional snake from the Late Cretaceous Period of North America
Nature, 2012Co-Authors: Nicholas R Longrich, Bhartanjan S Bhullar, Jacques A GauthierAbstract:Fossils of snakes are extremely rare, and the resulting shortage of information has fuelled a heated debate over the origins of this distinctive group. Did they evolve in the sea? Or on land, as suggested by remains of the primitive Cretaceous snake Najash ? A study of the long-neglected remains of the snake Coniophis , originally described by famous dinosaur-hunter Othniel C. Marsh in 1892, has come up with some facts that favour a land-based genesis for snakes. Coniophis was a terrestrial species, with a snake-like body but a primitive, lizard-like head. This suggests that early snakes were burrowers that achieved their elongate form before evolving the characteristic highly mobile skull of modern snakes. Previously undescribed material from the maxilla, dentary and spine of the Cretaceous Coniophis precedens shows that it is the most primitive known snake. Snakes are the most diverse group of lizards^ 1 , but their origins and early evolution remain poorly understood owing to a lack of transitional forms. Several major issues remain outstanding, such as whether snakes originated in a marine^ 2 , 3 , 4 or terrestrial^ 5 , 6 environment and how their unique feeding mechanism evolved^ 1 , 7 , 8 . The Cretaceous Coniophis precedens was among the first Mesozoic snakes discovered^ 9 , but until now only an isolated vertebra has been described^ 9 , 10 and it has therefore been overlooked in discussions of snake evolution. Here we report on previously undescribed material^ 11 from this ancient snake, including the maxilla, dentary and additional vertebrae. Coniophis is not an anilioid as previously thought^ 11 ; a revised phylogenetic analysis of Ophidia shows that it instead represents the most primitive known snake. Accordingly, its morphology and ecology are critical to understanding snake evolution. Coniophis occurs in a continental floodplain environment, consistent with a terrestrial rather than a marine origin; furthermore, its small size and reduced neural spines indicate fossorial habits, suggesting that snakes evolved from burrowing lizards. The skull is intermediate between that of lizards and snakes. Hooked teeth and an intramandibular joint indicate that Coniophis fed on relatively large, soft-bodied prey. However, the maxilla is firmly united with the skull, indicating an akinetic rostrum. Coniophis therefore represents a transitional snake, combining a snake-like body and a lizard-like head. Subsequent to the evolution of a serpentine body and carnivory, snakes evolved a highly specialized, kinetic skull, which was followed by a major adaptive radiation in the Early Cretaceous Period. This pattern suggests that the kinetic skull was a key innovation that permitted the diversification of snakes.
Gilles Ramstein - One of the best experts on this subject based on the ideXlab platform.
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Existence of an ice cap during the mid-Cretaceous Period (120–90 Ma): an AGCM investigation
Annals of Glaciology, 1997Co-Authors: Gilles Ramstein, Frédéric Fluteau, Valérie Masson-delmotteAbstract:Many questions remain concerning whether or not an ice cap existed during the mid-Cretaceous Period (120–90 Ma). Other than data and observations from ice-rafted materials, atmospheric general circulation models (AGCMs) may be appropriate tools to investigate whether changes in atmospheric composition, land-sea distribution, or oceanic circulation (used as boundary conditions to constrain the model), provide the climatic conditions that enable ice caps to be formed. This study uses an AGCM developed by the Laboratoire de Météorologie Dynamique (LMD) to perform a set of numerical sensitivity experiments to investigate plate tectonics (land–sea distribution and orography), CO2 partial pressure in the atmosphere and changes in prescribed sea-surface temperatures. The main goals are to quantify the effect of each forcing factor on the increase of Northern Hemisphere high-latitude temperatures, and to investigate whether combining these factors produce temperatures that would allow the ice-sheet formation.
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Existence of an ice cap during the mid-Cretaceous Period (120–90 Ma): an AGCM investigation
Annals of Glaciology, 1997Co-Authors: Gilles Ramstein, Frédéric Fluteau, V. MassonAbstract:Many questions remain concerning whether or not an ice cap existed during the mid-Cretaceous Period (120–90 Ma). Other than data and observations from ice-rafted materials, atmospheric general circulation models (AGCMs) may be appropriate tools to investigate whether changes in atmospheric composition, land-sea distribution, or oceanic circulation (used as boundary conditions to constrain the model), provide the climatic conditions that enable ice caps to be formed. This study uses an AGCM developed by the Laboratoire Météorologie Dynamique (LMD) to perform a set of numerical sensitivity experiments to investigate plate tectonics (land-sea distribution and orography), CO2 partial pressure in the atmosphere and changes in prescribed sea-surface temperatures. The main goals are to quantify the effect of each forcing factor on the increase of Northern Hemisphere high-latitude temperatures, and to investigate whether combining these factors produce temperatures that would allow the ice-sheet formation.
Bartolomeu C. Viana - One of the best experts on this subject based on the ideXlab platform.
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Spectroscopic studies of the fish fossils (Cladocyclus gardneri and Vinctifer comptoni) from the Ipubi Formation of the Cretaceous Period.
Spectrochimica acta. Part A Molecular and biomolecular spectroscopy, 2015Co-Authors: F.e. Sousa Filho, J.h. Da Silva, B.t.o. Abagaro, Gilberto Dantas Saraiva, Olga Alcântara Barros, Antônio Álamo Feitosa Saraiva, Bartolomeu C. Viana, Paulo T.c. FreireAbstract:Fossils are mineralized remains or traces from animals, plants and other organisms aged to about 10(8)years. The chemical processes of fossilization are dated back from old geological Periods on Earth. The understanding of these processes and the structure of the fossils are one of the goals of paleontology and geology in the sedimentary environments. Many researches have tried to unveil details about special kinds of biological samples; however, a lack of data is noticed for various other specimens. This study reports the investigations through infrared spectroscopy, X-ray fluorescence and X-ray diffraction measurements for two types of fish fossils from the Cretaceous Period. The sample of Cladocyclus gardneri and Vinctifer comptoni fossils were collected from the Ipubi Formation, being one of the less studied, among the formations that constitute the important Santana group in the Araripe Basin, Brazil. The results obtained through different techniques, showed that the C. gardneri fish fossil contains hydroxyapatite and calcite as constituents whereas its rock matrix was formed by calcite, quartz and pyrite. Regarding the V. comptoni, the measurements confirmed the presence of hydroxyapatite in the fossil and its rock matrix gypsum, pyrite, quartz and calcite. The above scientific data contributed to the understanding the fossil formation in the Ipubi Formation, an important environment of the Cretaceous Period, which is rich in well-preserved fossils from different species.
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Spectroscopic studies of wood fossils from the Crato Formation, Cretaceous Period
Spectrochimica acta. Part A Molecular and biomolecular spectroscopy, 2013Co-Authors: J.h. Da Silva, Paulo T.c. Freire, B.t.o. Abagaro, J.a.f. Silva, Gilberto Dantas Saraiva, F.j. De Lima, Olga Alcântara Barros, Renan Alfredo Machado Bantim, Antônio Álamo Feitosa Saraiva, Bartolomeu C. VianaAbstract:Abstract In this work we study two types of wood fossils (Gymnosperms, Araucariaceae) from the Crato Formation of Araripe Basin in Brazil, from the Cretaceous Period. The samples were characterized by Raman and infrared spectroscopies, X-ray diffraction and scanning electron microscopy. The results obtained by different techniques showed that although the rocks surrounding the fossils have predominantly the same constitution – calcite – however, the formation processes of these types of wood fossils are quite different. One of the fossils, denominated as light wood, is predominantly composed of gypsum, while the other fossil, the dark wood, is rich in amorphous carbon, possibly the kerogen type. Implications relative to the environment where the plants lived millions years ago are also given. Finally, the results highlight the constitution of one of the most important paleontological sites of the Cretaceous Period in the South America.