Paleontology

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Carbon and Oxygen Abundances in Cool Metal-rich Exoplanet Hosts: A Case Study of the C/O Ratio of 55 CancriAuthors:Johanna K. Teske, Katia Cunha, Simon C. Schuler, Caitlin A. Griffith and Verne V. SmithAbstract:The super-Earth exopla...
Carbon and Oxygen Abundances in Cool Metal-rich Exoplanet Hosts: A Case Study of the C/O Ratio of 55 CancriAuthors:Johanna K. Teske, Katia Cunha, Simon C. Schuler, Caitlin A. Griffith and Verne V. SmithAbstract:The super-Earth exoplanet 55 Cnc e, the smallest member of a five-planet system, has recently been observed to transit its host star. The radius estimates from transit observations, coupled with spectroscopic determinations of mass, provide constraints on its interior composition. The composition of exoplanetary interiors and atmospheres are particularly sensitive to elemental C/O ratio, which to first order can be estimated from the host stars. Results from a recent spectroscopic study analyzing the 6300A [O I] line and two C I lines suggest that 55 Cnc has a carbon-rich composition (C/O=1.12+/-0.09). However oxygen abundances derived using the 6300A [O I] line are highly sensitive to a Ni I blend, particularly in metal-rich stars such as 55 Cnc ([Fe/H]=0.34+/-0.18). Here, we further investigate 55 Cnc's composition by deriving the carbon and oxygen abundances from these and additional C and O absorption features. We find that the measured C/O ratio depends on the oxygen lines used. The C/O ratio that we derive based on the 6300A [O I] line alone is consistent with the previous value. Yet, our investigation of additional abundance indicators results in a mean C/O ratio of 0.78+/-0.08. The lower C/O ratio of 55 Cnc determined here may place this system at the sensitive boundary between protoplanetary disk compositions giving rise to planets with high ( greater than 0.8) versus low (less than 0.8) C/O ratios. This study illustrates the caution that must applied when determining planet host star C/O ratios, particularly in cool, metal-rich stars. pop sci write up.and another.
about 1 hour ago
Ants and bees are surprisingly more genetically related to each other than they are to social wasps such as yellow jackets and paper wasps, a team of University of California, Davis, scientists has discovered. The groundbreaking research...
Ants and bees are surprisingly more genetically related to each other than they are to social wasps such as yellow jackets and paper wasps, a team of University of California, Davis, scientists has discovered. The groundbreaking research is available online and will be published Oct. 21 in the print version of the journal Current Biology.Using state-of-the-art genome sequencing and bioinformatics, the researchers resolved a long-standing, unanswered evolutionary question. Scientists previously thought that ants and bees were more distantly related, with ants being closer to certain parasitoid wasps.Ants, bees and stinging wasps all belong to the aculeate (stinging) Hymenoptera clade — the insect group in which social behavior is most extensively developed, said senior author and ant specialist Phil Ward, professor of entomology at UC Davis.“Despite great interest in the ecology and behavior of these insects, their evolutionary relationships have never been fully clarified. In particular, it has been uncertain how ants — the world’s most successful social insects — are related to bees and wasps,” Ward said. “We were able to resolve this question by employing next-generation sequencing technology and advances in bioinformatics. This phylogeny, or evolutionary tree, provides a new framework for understanding the evolution of nesting, feeding and social behavior in Hymenoptera.”The collaborators included Ward, Assistant Professor Joanna Chiu, Assistant Professor Brian Johnson, graduate student Marek Borowiec and postdoctoral researcher Joel Atallah, all with the UC Davis Department of Entomology and Nematology; and visiting scientist Ernest K. Lee of the Sackler Institute for Comparative Genomics, American Museum of Natural History.“With a phylogeny or evolutionary progression that we think is reliable and robust, we can now start to understand how various morphological and/or behavioral traits evolved in these groups of insects, and even examine the genetic basis of these phenotypic changes,” Chiu said.Johnson, whose lab studies the genetics, behavior, evolution and health of honeybees, noted that the study showed that ants and bees are more closely related than previously thought.“This result should be important for future studies focused on eusocial evolution, as it suggests that morphology may not be a good indicator of evolutionary relatedness in these groups of organisms,” he said. Eusocial behavior is characterized by cooperative brood care, overlapping adult generations and division of labor.The scientists combined data from the transcriptome — showing which genes are active and being transcribed from DNA into RNA — and genomic (DNA) data from a number of species of ants, bees and wasps, including bradynobaenid wasps, a cuckoo wasp, a spider wasp, a scoliid wasp, a mud dauber wasp, a tiphiid wasp, a paper wasp and a pollen wasp; a velvet ant (wasp); a dracula ant; and a sweat bee, Lasioglossum albipes.Of particular interest was the finding that ants are a sister group to the Apoidea, a major group within Hymenoptera that includes bees and sphecid wasps (a family of wasps that includes digger wasps and mud daubers).The UC Davis results also provide a new perspective on lower Cretaceous fossil Cariridris bipetiolata, originally claimed to be the oldest fossil ant. Scientists later reinterpreted it to be a spheciform wasp.“Our discovery that ants and apoids are sister taxa helps to explain difficulty in the placement of Cariridris,” the authors wrote in the paper, “and suggests that it is best treated as a lineage close to the root of the ant-apoid tree, perhaps not assignable with certainty to either branch.”The scientists discovered that the ancestral aculeate wasp was likely an ectoparasitoid, which attacks and paralyzes a host insect and leaves its offspring nearby where they can attach to the outside of the host and feed from it.link.
about 2 hours ago
Over 80% of the world's ice-free land is at risk of profound ecosystem transformation by 2100, a new study reveals. "Essentially, we would be leaving the world as we know it," says Sebastian Ostberg of the Potsdam Institute for Climate I...
Over 80% of the world's ice-free land is at risk of profound ecosystem transformation by 2100, a new study reveals. "Essentially, we would be leaving the world as we know it," says Sebastian Ostberg of the Potsdam Institute for Climate Impact Research, Germany. Ostberg and collaborators studied the critical impacts of climate change on landscapes and have now published their results in Earth System Dynamics, an open access journal of the European Geosciences Union (EGU).The researchers state in the article that "nearly no area of the world is free" from the risk of climate change transforming landscapes substantially, unless mitigation limits warming to around 2 degrees Celsius above preindustrial levels.Ecosystem changes could include boreal forests being transformed into temperate savannas, trees growing in the freezing Arctic tundra or even a dieback of some of the world's rainforests. Such profound transformations of land ecosystems have the potential to affect food and water security, and hence impact human well-being just like sea level rise and direct damage from extreme weather events.The new Earth System Dynamics study indicates that up to 86% of the remaining natural land ecosystems worldwide could be at risk of major change in a business-as-usual scenario (see note). This assumes that the global mean temperature will be 4 to 5 degrees warmer at the end of this century than in pre-industrial times – given many countries' reluctance to commit to binding emissions cuts, such warming is not out of the question by 2100."The research shows there is a large difference in the risk of major ecosystem change depending on whether humankind continues with business as usual or if we opt for effective climate change mitigation," Ostberg points out.But even if the warming is limited to 2 degrees, some 20% of land ecosystems – particularly those at high altitudes and high latitudes – are at risk of moderate or major transformation, the team reveals.The researchers studied over 150 climate scenarios, looking at ecosystem changes in nearly 20 different climate models for various degrees of global warming. "Our study is the most comprehensive and internally consistent analysis of the risk of major ecosystem change from climate change at the global scale," says Wolfgang Lucht, also an author of the study and co-chair of the research domain Earth System Analysis at the Potsdam Institute for Climate Impact Research.link.
about 3 hours ago
Mammal disparity decreases during the Cretaceous angiosperm radiationAuthors:David M. Grossnickle and P. David PollyAbstract:Fossil discoveries over the past 30 years have radically transformed traditional views of Mesozoic mammal evolut...
Mammal disparity decreases during the Cretaceous angiosperm radiationAuthors:David M. Grossnickle and P. David PollyAbstract:Fossil discoveries over the past 30 years have radically transformed traditional views of Mesozoic mammal evolution. In addition, recent research provides a more detailed account of the Cretaceous diversification of flowering plants. Here, we examine patterns of morphological disparity and functional morphology associated with diet in early mammals. Two analyses were performed: (i) an examination of diversity based on functional dental type rather than higher-level taxonomy, and (ii) a morphometric analysis of jaws, which made use of modern analogues, to assess changes in mammalian morphological and dietary disparity. Results demonstrate a decline in diversity of molar types during the mid-Cretaceous as abundances of triconodonts, symmetrodonts, docodonts and eupantotherians diminished. Multituberculates experience a turnover in functional molar types during the mid-Cretaceous and a shift towards plant-dominated diets during the late Late Cretaceous. Although therians undergo a taxonomic expansion coinciding with the angiosperm radiation, they display small body sizes and a low level of morphological disparity, suggesting an evolutionary shift favouring small insectivores. It is concluded that during the mid-Cretaceous, the period of rapid angiosperm radiation, mammals experienced both a decrease in morphological disparity and a functional shift in dietary morphology that were probably related to changing ecosystems.
about 5 hours ago
Crustal shortening during the Paleoproterozoic: Can it be accommodated by paleomagnetic data?Author:Henry HallsAbstract:In the last 130 million years, perhaps as much as 2000 km of intra-continental shortening has taken place within Asia...
Crustal shortening during the Paleoproterozoic: Can it be accommodated by paleomagnetic data?Author:Henry HallsAbstract:In the last 130 million years, perhaps as much as 2000 km of intra-continental shortening has taken place within Asia during 10000 km of convergence between Siberia and India (with ?8000 km being accommodated by oceanic subduction). Given that Earth was hotter during the Paleoproterozoic, crustal shortening at this time may have been equally, if not more, significant compared to today, warranting a search of the paleomagnetic data base for any supporting evidence. Paleomagnetic data from units on either side of the Paleoproterozoic Trans Hudson orogen in Canada have been chosen because this orogen bears close similarity both in size and history to the India-Siberia one. The data do not prove, but can accommodate, continental crustal shortening between the Archean Slave and Superior Provinces of about 3000 ± 1000 km. The results allow crustal shortening to have been a significant component of continental collision in the Paleoproterozoic, an important issue in any re-assembly of Precambrian continents. If true, the present dimensions of Precambrian shields, may be significantly different compared to those existing in earlier times.
about 10 hours ago
Martínez, R. N., Apaldetti, C., Alcober, O. A., Colombi, C. E., Sereno, P. C., Fernandez, E., Santi Malnis, P., Correa, G. A., and D. Abelin. 2013. Vertebrate succession in the Ischigualasto Formation, Journal of Vertebrate Paleontology...
Martínez, R. N., Apaldetti, C., Alcober, O. A., Colombi, C. E., Sereno, P. C., Fernandez, E., Santi Malnis, P., Correa, G. A., and D. Abelin. 2013. Vertebrate succession in the Ischigualasto Formation, Journal of Vertebrate Paleontology, 32:sup1, 10-30, DOI: 10.1080/02724634.2013.818546 Abstract - The Upper Triassic (Carnian–Norian) Ischigualasto Formation has yielded a diverse vertebrate fauna that records the initial phase of dinosaur evolution. Radioisotopic dates from ash layers within the formation provide a chronostratigraphic framework, and stratigraphic and sedimetological studies have subdivided the formation into four members and three abundance-based biozones. We describe two new basal dinosauromorphs, an unnamed lagerpetid and a new silesaurid, Ignotosaurus fragilis, gen. et sp. nov., which increase to 29 the number of vertebrates in the Ischigualasto fauna. We provide a census of 848 fossil specimens representing 26 vertebrate taxa logged to stratigraphic intervals of 50 m. This temporally calibrated census shows that abundance and taxonomic diversity within the Ischigualasto Formation does not change suddenly but rather appears to gradually decline in response to climatic deterioration. The only abrupt shift in faunal composition occurs at the end of the second of three biozones, when the abundant cynodont Exaeretodon is replaced by the rare dicynodont Jachaleria.
about 20 hours ago
Finally this is published. Now if I can just get the Revueltosaurus monograph out all will be right in the Triassic world, right? Sereno, P. C., Martínez, R. N., and O. A. Alcober. 2013. Osteology of Eoraptor lunensis (Dinosauria, S...
Finally this is published. Now if I can just get the Revueltosaurus monograph out all will be right in the Triassic world, right? Sereno, P. C., Martínez, R. N., and O. A. Alcober. 2013. Osteology of Eoraptor lunensis (Dinosauria, Sauropodomorpha). Journal of Vertebrate Paleontology Memoir 12:83-179. Abstract - We describe the basal sauropodomorph Eoraptor lunensis, based on the nearly complete holotypic skeleton and referred specimens, all of which were discovered in the Cancha de Bochas Member of the Ischigualasto Formation in northwestern Argentina. The lightly built skull has a slightly enlarged external naris and a spacious antorbital fossa with a prominent, everted dorsal margin and internal wall lacking any pneumatic extensions into surrounding bones. The tall quadrate is lapped along its anterior margin by the long, slender ventral process of the squamosal, and the lower jaw has a mid-mandibular joint between a tongue-shaped splenial process and a trough in the angular. All but the posterior-most maxillary and dentary crowns have a basal constriction, and the marginal denticles are larger and oriented more vertically than in typical theropod serrations. Rows of rudimentary palatal teeth are present on the pterygoid. Vertebral centra are hollow, although not demonstrably pneumatized,and all long bones have hollow shafts. The radius and ulna are more robust, the manus proportionately shorter, and the manual unguals less recurved than in the contemporaneous basal theropod Eodromaeus murphi. An outstanding feature of the manus of Eoraptor is the twisted shaft of the first phalanx of the pollex, which deflects medially the tip of the ungual as in basal sauropodomorphs. The long bones of the hind limb have more robust shafts than those of Eodromaeus, although in both genera the tibia remains slightly longer than the femur.Resumen - Describimos el sauropodomorfo basal Eoraptor lunensis basados en el esqueleto prácticamente completo del holotipo y especímenes referidos, todos ellos descubiertos en el Miembro Cancha de Bochas de la Formaci ón Ischigualasto, en el noroeste de Argentina. El grácil cráneo tiene las narinas externas ligeramente agrandadas, una amplia fosa antorbital con un margen dorsal prominente y evertido, y ausencia de extensiones neumáticas en los huesos circundantes. El alto cuadrado presenta todo su margen anterior solapado por el delgado proceso ventral del escamoso y la mandíbula tiene una junta medial entre un proceso linguoide del esplenial y un canal en el angular. Todas las coronas dentarias y maxilares, menos las más posteriores, tienen una constricci ón basal y los dentículos marginales son largos y orientados más verticalmente que en el aserrado típico de los terópodos. El pterigoideo tiene filas de dientes palatales rudimentarios. Los centros de las vértebras son huecos, aunque no demostrablemente neumatizados, y todos los huesos largos tienen las di íafisis huecas. El radio y la ulna son más robustos, la mano proporcionalmente corta y los ungueales manuales menos recurvados que en el contemporáneo terópodo basal Eodromaeus murphi. Una característica sobresaliente de la mano de Eoraptor es la rotaci ón de la primera falange del pulgar, que desvía medialmente la punta del ungueal como en los sauropodomorfos basales. Los huesos largos de las piernas tienen di áfisis más robustas que aquellas de Eodromaeus, aunque en ambos géneros la tibia es ligeramente más larga que el fémur.
about 20 hours ago
about 21 hours ago
(history repeats itself) (or close enough) Army paratroopers gave up their tanks in 1997. Now they want them back.“The infantry needs more protection and more firepower,” says Col. Ed House, Army Training and Doctrine Command manager for...
(history repeats itself) (or close enough) Army paratroopers gave up their tanks in 1997. Now they want them back.“The infantry needs more protection and more firepower,” says Col. Ed House, Army Training and Doctrine Command manager for the infantry brigade combat team.Even in these times of deep budget cuts and a projected steep decline in purchases of military hardware, senior Army officials believe that a light tank is a high priority that should be funded. In a future war, they contend, Army airborne forces would parachute into a warzone equipped with only light weapons and might have to confront more heavily armed enemies.Army leaders understand that, after 12 years of war, the infantry brigades have a “capability gap,” House says in an interview from Fort Benning, Ga. “The forcible entry forces we put in harm’s way lack sufficient protected firepower platform.”The current plan is to provide the XVIII Airborne Corps — a fast-to-the-scene 911 force — a flotilla of light tanks that can be flown by C-130 cargo planes and parachuted into the warzone.Light tanks existed in the Army’s inventory from World War I until the end of the Cold War. Production of the 16-ton Sheridan ended in 1970 after approximately 1,700 vehicles were delivered to the Army. The last unit to operate the Sheridan was the 3d Battalion, 73d Armor Regiment of the 82d Airborne Division, which was inactivated in July 1997 following a wave of cost cutting. The Army considered buying a replacement for the Sheridan, the Armored Gun System, but that program was terminated after the Army had bought just six vehicles.House says the goal is to replicate the functions of 3-73 although he admits it will be hard to locate a modern version of the Sheridan. “The tough part of this is to find a vehicle that fits in the back of a C-130 and can descend by parachute,” he says. “The Sheridan did that pretty well back in the 1990s.”Training and Doctrine Command officials are scoping the market for existing vehicles that could perform a similar role as the Sheridan.Up to 140 candidates are being considered, says Col. Rocky Kmiecik, director of mounted requirements at the capabilities development and integration directorate.Even though tanks are tracked vehicles, the Army is open to wheeled alternatives. The vehicle has to be air droppable, must have enough ballistic protection against 14.5 mm and .50 caliber rounds, and be able to drive off road.link.
about 22 hours ago
Additional information at this link.
Additional information at this link.
about 23 hours ago