This was made for me last night. It was rather good, but whatever you do, forgo a second helping. Its far, far too rich and fatty. I asked for some mint tea to go with it. Its probably what saved me. Excellent, delicious meat though.
Monday, July 30, 2012
Thursday, July 26, 2012
Paleoecology and geochemistry of Early Triassic (Spathian) microbial mounds and implications for anoxia following the end-Permian mass extinction
1. Pedro J. Marenco (a)
2. Julie M. Griffin (a)
3. Margaret L. Fraiser (b)
4. Matthew E. Clapham (c)
a. Department of Geology, Bryn Mawr College, Bryn Mawr, Pennsylvania 19010, USA
b. Department of Geosciences, University of Wisconsin–Milwaukee, Milwaukee, Wisconsin 53201, USA
c. Department of Earth and Planetary Sciences, University of California–Santa Cruz, Santa Cruz, California 95064, USA
Large microbialite mounds (1–2 m in height) have previously been reported from two units within the Spathian section of the Virgin Limestone Member of the Moenkopi Formation at Lost Cabin Spring, Nevada (United States). Previous investigations led to the interpretation that the mounds were formed under anoxic and alkaline conditions that suppressed metazoan grazers and delayed the biotic recovery from the end-Permian mass extinction. Here we report low organic carbon and total sulfur abundances throughout the section that suggest that anoxia was not prevalent during deposition. We also report that the upper mound-bearing unit contains stromatolite-sponge patch reefs in which mutual encrustation between stromatolites and sponges contributed to the building of a reef framework. The stromatolite-sponge patch reefs contain discrete burrows within stromatolitic laminations, suggesting that there was sufficient oxygen for grazing during the formation of the upper unit mounds. The enhanced ecological complexity of the upper unit mounds leads us to conclude that the mounds represent the transition to biotic recovery following the end-Permian mass extinction.
Mulling here still.
Wednesday, July 25, 2012
Scientists have discovered a potential cause of Earth's "icehouse climate" cooling trend of the past 45 million years. It has everything to do with the chemistry of the world's oceans.
"Seawater chemistry is characterized by long phases of stability, which are interrupted by short intervals of rapid change," says geoscientist Ulrich Wortmann of the University of Toronto, lead author of a paper reporting the results and published this week in the journal Science.
"We've established a new framework that helps us better interpret evolutionary trends and climate change over long periods of time. The study focuses on the past 130 million years, but similar interactions have likely occurred through the past 500 million years."
Wortmann and co-author Adina Paytan of the University of California Santa Cruz point to the collision between India and Eurasia approximately 50 million years ago as one example of an interval of rapid change.
This collision enhanced dissolution of the most extensive belt of water-soluble gypsum on Earth, stretching from Oman to Pakistan and well into western India. Remnants of the collision are exposed in the Zagros Mountains in western Iran.
The dissolution or creation of such massive gypsum deposits changes the sulfate content of the ocean, say the scientists, affecting the amount of sulfate aerosols in the atmosphere and thus climate.
"We propose that times of high sulfate concentrations in ocean water correlate with global cooling, just as times of low concentrations correspond with greenhouse [warmer] periods," says Paytan.
"When India and Eurasia collided, it caused dissolution of ancient salt deposits, which resulted in drastic changes in seawater chemistry."
That may have led to the end of the Eocene epoch--the warmest period of the modern-day Cenozoic era--and the transition from a greenhouse to an icehouse climate. "It culminated in the beginning of the rapid expansion of the Antarctic ice sheet," says Paytan.
Canada's Natural Sciences and Engineering Research Council supports Wortmann's research and the U.S. National Science Foundation (NSF) supports Paytan research.
"Abrupt changes in seawater composition are a new twist in our understanding of the links among ocean chemistry, plate tectonics, climate and evolution," says Candace Major, program director in NSF's Division of Ocean Sciences.
To make the discovery, the researchers combined past seawater sulfur composition data collected by Paytan with Wortmann's recent discovery of the strong link between marine sulfate concentrations and carbon and phosphorus cycling.
They found that seawater sulfate reflects huge changes in the accumulation and weathering of gypsum, which is the mineral form of hydrated calcium sulfate.
"While it's been known for a long time that gypsum deposits can be formed and destroyed rapidly, the effect of these processes on seawater chemistry has been overlooked," says Wortmann.
"The idea represents a paradigm shift in our understanding of how ocean chemistry changes over time, and how these changes are linked with climate."
Monday, July 23, 2012
A Whole-Cell Computational Model Predicts Phenotype from Genotype
1. Jonathan R. Karr (a)
2. Jayodita C. Sanghvi (b)
3. Derek N. Macklin (b)
4. Miriam V. Gutschow (b)
5. Jared M. Jacobs (b)
6. Benjamin Bolival (b)
7. Nacyra Assad-Garcia (c)
8. John I. Glass (c)
9. Markus W. Covert (b, *)
a. Graduate Program in Biophysics, Stanford University, Stanford, CA 94305, USA
b. Department of Bioengineering, Stanford University, Stanford, CA 94305, USA
c. J. Craig Venter Institute, Rockville, MD 20850, USA
*. Correspondence: firstname.lastname@example.org
* An entire organism is modeled in terms of its molecular components
* Complex phenotypes can be modeled by integrating cell processes into a single model
* Unobserved cellular behaviors are predicted by model of M. genitalium
* New biological processes and parameters are predicted by model of M. genitalium
Understanding how complex phenotypes arise from individual molecules and their interactions is a primary challenge in biology that computational approaches are poised to tackle. We report a whole-cell computational model of the life cycle of the human pathogen Mycoplasma genitalium that includes all of its molecular components and their interactions. An integrative approach to modeling that combines diverse mathematics enabled the simultaneous inclusion of fundamentally different cellular processes and experimental measurements. Our whole-cell model accounts for all annotated gene functions and was validated against a broad range of data. The model provides insights into many previously unobserved cellular behaviors, including in vivo rates of protein-DNA association and an inverse relationship between the durations of DNA replication initiation and replication. In addition, experimental analysis directed by model predictions identified previously undetected kinetic parameters and biological functions. We conclude that comprehensive whole-cell models can be used to facilitate biological discovery.
First off, this is a VERY first step. Don't expect a human cell to be simulated very soon. Ours are far, far more complicated. Given a full run on our biggest current system using the same methods, you could "only" do something a thousand times more complicated, at best.
Even so, this is something impressive.
Friday, July 20, 2012
I hate having this one languish because of the issues of moving the XenoPermian forward. Its simply too gorgeous to NOT share. What happens when the dicynodonts adapt to the ocean? Well, Zach's walrodont. Redone by Raven and Scott.
This will be subsumed into a greater walrodont post, but that will be a while coming. The next real post (which is half written and fully illustrated) is on another anomodont's descendants.
Thursday, July 19, 2012
This was a beach that I went to a lot when I was a kid prior to moving to Los Alamos, NM. I visited a few times after but not in 25+ years. Its changed. A lot. The Geo geeks must love the exposed bits. lol.
ok. Geo Geeking here:
From here (PDF).
ok. Geo Geeking here:
Overall grain size of lower unit becomes finer in northwest part of map area, and at Bartlett Canyon, lower unit has been previously interpreted to grade westward into marine sandstone of the upper Eocene and lowermost Oligocene (Refugian) Gaviota Formation (Weaver and Kleinpell, 1963; Howard, 1995). However, correlation of lower Sespe beds with Gaviota in this area is questionable due to fault complications (as noted in Weaver and Kleinpell, 1963) and because unequivocal marine, fossil-bearing interbeds were not observed within the lower unit during our mapping. Possibly the lower Sespe transition into the Gaviota is confined to the small area where the lower conglomerate and sandstone unit pinches out in Glen Annie Canyon. The locally gradational nature of the basal Sespe contact with the underlying Coldwater Sandstone is consistent with a late Eocene age for part or all of the lower conglomerate and sandstone unit.
From here (PDF).
Wednesday, July 18, 2012
A new study indicates that mass extinctions affect the pace of evolution, not just in the immediate aftermath of catastrophe, but for millions of years to follow. The study’s authors, University of Chicago’s Andrew Z. Krug and David Jablonski, will publish their findings in the August issue of the journal Geology.
Scientists expected to see an evolutionary explosion immediately following a mass extinction, but Krug and Jablonski’s findings go far beyond that.
“There’s some general sense that the event happens, there’s some aftermath and then things return to normal,” said Krug, a research scientist in geophysical sciences at UChicago. But in reality, Krug said, “Things don’t return to what they were before. They operate at a different pace, sometimes more rapidly, other times more slowly. Evolutionary rates shift, and that shift is permanent until the next mass extinction.”
Krug and Jablonski’s suggestion that the potential for rapid speciation and expansion of survivors and new groups of organisms in the “emptier” world following a mass extinction “is a reasonable possibility as one source of rate change,” said paleontologist Richard Bambach of the Smithsonian Museum of Natural History, who was not directly involved in the UChicago study.
The long-term evolutionary patterns of species diversification following mass extinctions are poorly understood. Paleontologists have extensively debated whether diversity has increased over the last 251 million years, which followed the most devastating mass extinction in Earth history, Bambach said.
“There’s been a lot of talk about the evolutionary role of mass extinctions, but it’s like the weather. Everyone talks about it, but no one does much about it,” Jablonski joked.
“No one has really thought about it in terms of these downstream dynamics, once the smoke has cleared and ecosystems have found a new equilibrium, for want of a better word. But the wonderful thing is that when they find a new equilibrium, it’s a different evolutionary pace from the one that prevailed for the preceding 50 million years. The survivors of the mass extinction, or the world they inherited, is so different from what went before that the rate of evolution is permanently changed.”
Krug and Jablonski’s research builds upon the work of UChicago’s David Raup, the Sewell L. Avery Distinguished Service Professor Emeritus in Geophysical Sciences, and Michael Foote, professor in Geophysical Sciences.
In 1978, Raup published a method for determining the extinction rate of organisms. His method involved monitoring the survivorship of a group of organisms that had all originated during a specific time period and quantifying when they disappeared. It would be like collecting census data for all individuals born on Jan. 1, 1899, tracking their longevity, then finding that the 1918 influenza epidemic had produced a spike in this group’s mortality.
Foote followed up in 2001, showing that Raup’s method worked equally well for determining origination rates as it did for extinction rates. One simply needed to use the method in reverse, tracking the time since origination of a group of co-occurring lineages as opposed to the time until extinction. Now comes Krug and Jablonski’s latest study, finding that the evolutionary “birth rate” was also reset at major catastrophes. “It’s very Chicago-esque,” Jablonski said.
Have to wait for the August Geology to appear before I can link to the paper. Press release link.
Tuesday, July 17, 2012
Recent excavations, sediment coring and mapping by a multi-university team led by the University of Cincinnati at the pre-Columbian city of Tikal, a paramount urban center of the ancient Maya, have identified new landscaping and engineering feats, including the largest ancient dam built by the Maya of Central America.
That dam – constructed from cut stone, rubble and earth – stretched more than 260 feet in length, stood about 33 feet high and held about 20 million gallons of water in a man-made reservoir.
These findings on ancient Maya water and land-use systems at Tikal, located in northern Guatemala, are scheduled to appear this week in the Proceedings of the National Academy of Sciences (PNAS) in an article titled "Water and Sustainable Land Use at the Ancient Tropical City of Tikal, Guatemala." The research sheds new light on how the Maya conserved and used their natural resources to support a populous, highly complex society for over 1,500 years despite environmental challenges, including periodic drought.
The paper is authored by Vernon Scarborough, UC professor of anthropology; Nicholas Dunning, UC professor of geography; archaeologist Kenneth Tankersley, UC assistant professor of anthropology; Christopher Carr, UC doctoral student in geography; Eric Weaver, UC doctoral student in geography; Liwy Grazioso of the Universidad de San Carlos de Guatemala; Brian Lane, former UC master's student in anthropology now pursuing doctoral studies at the University of Hawaii; John Jones, associate professor of anthropology, Washington State University; Palma Buttles, technical staff senior member, SEI Carnegie Mellon University; Fred Valdez, professor of anthropology, University of Texas-Austin; and David Lentz, UC professor of biology.
Starting in 2009, the UC team was the first North American group permitted to work at the Tikal site core in more than 40 years.
Detailed in the latest findings by the UC-led efforts are
* The largest ancient dam built by the ancient Maya of Central America
* Discussion on how reservoir waters were likely released
* Details on the construction of a cofferdam needed by the Maya to dredge one of the largest reservoirs at Tikal
* The presence of ancient springs linked to the initial colonization of Tikal
* Use of sand filtration to cleanse water entering reservoirs
* A "switching station" that accommodated seasonal filling and release of water
* Finding of the deepest, rock-cut canal segment in the Maya lowlands
According to UC's Scarborough, "The overall goal of the UC research is to better understand how the ancient Maya supported a population at Tikal of perhaps 60,000 to 80,000 inhabitants and an estimated population of five million in the overall Maya lowlands by AD 700."
He added, "That is a much higher number than is supported by the current environment. So, they managed to sustain a populous, highly complex society for well over 1,500 years in a tropical ecology. Their resource needs were great, but they used only stone-age tools and technology to develop a sophisticated, long-lasting management system in order to thrive."
Water collection and storage were critical in the environment where rainfall is seasonal and extended droughts not uncommon. And so, the Maya carefully integrated the built environment – expansive plazas, roadways, buildings and canals – into a water-collection and management system. At Tikal, they collected literally all the water that fell onto these paved and/or plastered surfaces and sluiced it into man-made reservoirs. For instance, the city's plastered plaza and courtyard surfaces and canals were canted in order to direct and retain rainwater runoff into these tanks.
In fact, by the Classic Period (AD 250-800), the dam (called the Palace Dam) identified by the UC-led team was constructed to contain the waters that were now directed from the many sealed plaster surfaces in the central precinct. It was this dam on which the team focused its latest work, completed in 2010. This gravity dam presents the largest hydraulic architectural feature known in the Maya area. In terms of greater Mesoamerica, it is second in size only to the huge Purron Dam built in Mexico's Tehuacan Valley sometime between AD 250-400.
Said Scarborough, "We also termed the Palace Dam at Tikal the Causeway Dam, as the top of the structure served as a roadway linking one part of the city to another. For a long time, it was considered primarily a causeway, one that tourists coming to the site still use today. However, our research now shows that it did double duty and was used as an important reservoir dam as well as a causeway."
Another discovery by the UC-led team: To help purify water as it sluiced into the reservoir tanks via catchment runoff and canals, the Maya employed deliberately positioned "sand boxes" that served to filter the water as it entered into the reservoirs. "These filtration beds consisted of quartz sand, which is not naturally found in the greater Tikal area. The Maya of Tikal traveled at least 20 miles (about 30 kilometers) to obtain the quartz sand to create their water filters. It was a fairly laborious transportation effort. That speaks to the value they placed on water and water management," said UC's Nicholas Dunning.
Monday, July 16, 2012
Origin and evolution of carnivorism in the Ascomycota (fungi)
1. Ence Yang (a)
2. Lingling Xu (a,b)
3. Ying Yang (a)
4. Xinyu Zhang (a)
5. Meichun Xiang (a)
6. Chengshu Wang (c)
7. Zhiqiang An (d, *)
8. Xingzhong Liu (a, *)
a. State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China
b. College of Biotechnology, Xi'an University of Arts and Science, Xi'an 710065, China
c. Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China
d. Brown Foundation Institute of Molecular Medicine, University of Texas Health Science Center at Houston, Houston, TX 77030
*. To whom correspondence may be addressed. E-mail: email@example.com or firstname.lastname@example.org.
Carnivorism is one of the basic life strategies of fungi. Carnivorous fungi possess the ability to trap and digest their preys by sophisticated trapping devices. However, the origin and development of fungal carnivorism remains a gap in evolution biology. In this study, five protein-encoding genes were used to construct the phylogeny of the carnivorous fungi in the phylum Ascomycota; these fungi prey on nematodes by means of specialized trapping structures such as constricting rings and adhesive traps. Our analysis revealed a definitive pattern of evolutionary development for these trapping structures. Molecular clock calibration based on two fossil records revealed that fungal carnivorism diverged from saprophytism about 419 Mya, which was after the origin of nematodes about 550–600 Mya. Active carnivorism (fungi with constricting rings) and passive carnivorism (fungi with adhesive traps) diverged from each other around 246 Mya, shortly after the occurrence of the Permian–Triassic extinction event about 251.4 Mya. The major adhesive traps evolved around 198–208 Mya, which was within the time frame of the Triassic–Jurassic extinction event about 201.4 Mya. However, no major carnivorous ascomycetes divergence was correlated to the Cretaceous–Tertiary extinction event, which occurred more recently (about 65.5 Mya). Therefore, a causal relationship between mass extinction events and fungal carnivorism evolution is not validated in this study. More evidence including additional fossil records is needed to establish if fungal carnivorism evolution was a response to mass extinction events.
No time & link. Perhaps they ought to consider whether or not the KT Extinction was uniquely different than the PT/TJ and whether or not that might have some important bits.
Friday, July 13, 2012
A new study of Oregon's Paisley Caves confirms that humans used the site as early as 12,450 radiocarbon years ago, and the projectile points they left behind were of the "Western Stemmed" tradition and not Clovis – which suggests parallel technological development of early inhabitants to the Americas.
The study, published this week in the journal Science, could have a major impact on theories of how the Western Hemisphere was populated. The research was funded by multiple organizations, including the National Science Foundation.
Lead author Dennis Jenkins, from the University of Oregon, and second author Loren Davis, from Oregon State University, were part of a large multidisciplinary team that spent much of the past two years combing through deposits and collecting more than 100 high-precision radiocarbon dates from Paisley Caves, located in south-central Oregon's Summer Lake basin.
What cemented the authors' findings was a thorough examination of the stratigraphy in the caves, which confirmed that coprolites containing human DNA were definitely associated with layers of sediment ranging in age from 2,295 to 12,450 years ago – and were not contaminated by humans or animals at later dates. The researchers last year also found additional Western Stemmed projectile points.
"The Western Stemmed and Clovis traditions include different technological strategies," said Davis, an associate professor of anthropology in OSU's School of Language, Culture and Society. "The Western Stemmed artifacts from Paisley Caves are at least as old – and may predate – the oldest confirmed Clovis sites, indicating that the peopling of the Americas was at least technologically divergent, if not genetically divergent."
The projectile points were found in deposits dating back to 11,070 to 11,340 radiocarbon years ago, and thus were not quite as old as the oldest coprolites. But DNA from coprolites of that era was similar to that found in the oldest coprolites, Davis pointed out. "They were from the same genetic group," he said.
The difference in technology between Clovis and Western Stemmed projectile points revolves around how they were attached to spears, which relates to the strategy of finding and shaping pieces of rock in the first place. Clovis artifacts have a distinct notch at the base, where a piece has been removed. The tool builder starts with a large rock and reduces it considerably.
Western Stemmed points and Clovis points primarily differ in the construction of their hafting portions, Davis said. Stemmed points bear constricted bases, while the hafting element of a Clovis point is thinned through the removal of a large flake from the base. Western Stemmed points are also often made by modifying smaller flakes in a different way than Clovis peoples manufactured their spear points.
"These two approaches to making projectile points were really quite different," Davis said, "and the fact that Western Stemmed point-makers fully overlap, or even pre-date Clovis point makers likely means that Clovis peoples were not the sole founding population of the Americas."
Clovis technology has only been found in the New World, while Western Stemmed technology can be related to archaeological patterns seen in northeastern Asia.
"We seem to have two different traditions co-existing in the United States that did not blend for a period of hundreds of years," said the University of Oregon's Jenkins.
Past studies of Paisley Caves also have reported on human coprolites with ancient DNA, but questions arose about whether those samples could have been contaminated, and whether they were found in context with artifacts from the same era. So the researchers did an exhaustive examination of the stratigraphy, which is one of Davis' specialties.
Davis conducted microscopic analysis of the soil structure using a petrographic microscope to eliminate signs of liquid – such as water or urine from humans or animals – moving downward through the soil. The team also carefully analyzed the silt lens where the stem points were found and bracketed above and below those layers to see if radiocarbon dates synchronized.
"The stemmed points were in great context," Davis said. "There is no doubt that they were in primary context, associated with excellent radiocarbon dates."
The earliest models for peopling of the Americas suggest that the first inhabitants arrived from Asia via a land bridge at the end of the last Ice Age and fanned out across the continent. However, those models can't explain the presence of two separate and distinct stone tool technologies at the end of the last glacial period.
"Given these recent results from Paisley Caves, it's clear that we need to come up with some better models," Davis said.
Thursday, July 12, 2012
Before her death in December 2010, Nieves López Martínez, palaeontologist of the Complutense University of Madrid, was working on the research of dinosaur eggs with a very peculiar characteristic: an ovoid, asymmetrical shape. Together with Enric Vicens, palaeontologist of the Universitat Autònoma de Barcelona, the two scientists conducted an exhaustive analysis of their discovery, recently published in the journal Palaeontology.
The new type of dinosaur egg has been given the scientific name of Sankofa pyrenaica. The eggs were discovered in the Montsec area of Lleida, in two sites located on either side of the Terradets pass.
The South Pyrenean area is rich in dinosaur egg sites, most of which correspond to sauropod eggs from the upper Cretaceous, dating back more than 70 million years ago. During that period, the area was a coastal area full of beaches and deltas which won land from the sea through sediment accumulation. Sand and mud from that period gave way, millions of years later, to the sandstone and marl where dinosaur remains now can be found. On the beach ridges and flat coastal lands is where a large group of dinosaurs laid their eggs.
The sites where the discoveries were made correspond to the upper Cretaceous, between the Campanian and Maastrichtian periods, some 70 to 83 million years ago. The fossils found belong to small eggs measuring some 7 centimetres tall and 4 cm wide, while the eggshell was on average 0.27mm thick. Most of the eggs found were broken in small fragments, but scientists also discovered more or less complete eggs, which can be easily studied in sections. The eggs found at the sites all belong to the same species. The main difference when compared to other eggs from the same period is their asymmetrical shape, similar to that of chicken eggs. The more complete samples clearly show an oval form rarely seen in eggs from the upper Cretaceous period and similar to modern day eggs.
Their shape is a unique characteristic of theropod eggs from the upper Cretaceous period and suggests a connection with bird eggs. Non avian dinosaur eggs are symmetrical and elongated. Asymmetry in bird eggs is associated to the physiology of birds: they take on this shape given the existence of only one oviduct which can form only one egg at a time. In this case the isthmus, the region in the oviduct creating the eggshell membrane, is what gives the egg its asymmetrical shape. Thanks to this shape, the wider end contains a bag of air which allows the bird to breathe in the last stages of its development. This evolutionary step was still relatively underdeveloped in dinosaurs.
Thus, the egg discovered by UCM and UAB researchers in certain manners represents the missing link between dinosaurs and birds. Only one other egg, discovered in Argentina and corresponding to a primitive bird from the same period, has similar characteristics. The discover represents proof in favour of the hypothesis that non avian theropods, the dinosaurs of the Cretaceous period, and birds could have had a common ancestor.
Link. Someone have a link to a paper? This is "just" a PR, really.
Wednesday, July 11, 2012
A volcanic eruption some 579 million years ago buried and fossilized a "nursery" of the some of the world's earliest animals, British scientists say.
Researchers from the universities of Oxford and Cambridge, in collaboration with the Memorial University of Newfoundland, discovered more than 100 fossils in Newfoundland rocks of what are believed to be "baby" rangeomorphs, bizarre frond-shaped organisms that lived 580 million to 550 million years ago that were unlike any creature alive today,
The fossils are evidence of life from the mysterious Ediacaran period, 635 million to 542 million years ago, in which the first animals -- complex multi cellular organisms -- appeared, an Oxford release reported Monday.
Exactly where rangeomorphs, often described as "fern-like," fit in the tree of life is unclear, the researchers said.
They are not thought to be plants but may not have had all of the characteristics of animals, they said.
"The fossilized 'babies' we found are all less than three centimeters (1 inch) long and are often as small as six millimeters (0.2 inches), many times smaller than the 'parent' forms, seen in neighboring areas, which can reach up to two meters (6 feet) in length," Oxford researcher Martin Brasier said.
"We think that, around 579 million years ago, an underwater 'nursery' of baby Ediacaran fronds was overwhelmed, Pompeii-style, by an ash fall from a volcanic eruption on a nearby island that smothered and preserved them for posterity."
Tuesday, July 10, 2012
Survival, but…! New Tales of ‘Dead Clade Walking’ from Austral and Boreal Post-K–T Assemblages
1. J Stillwell (a,*)
2. E Håkansson
a. Applied Palaeontology and Basin Studies Group, School of Geosciences, Monash University, Clayton, Vic 3800, Australia Centre for Evolutionary
*. Author to contact: Jeffrey.Stilwell@sci.monash.edu.au
Our knowledge of postmass extinction biotic trajectories is at the mercy of available data and detailed research on the governing factors of differential extinction/survivorship patterns of fossil biotas. Some taxa managed—barely—to survive major extinction events, but only for the short-term, becoming extinct at variable times in the following geologic stage, having succumbed to myriad natural forces generated by severe paleoenvironmental perturbations. These ‘Dead Clade Walking’ (DCW) organisms should be included in investigations on the resultant effects of the extinction bottleneck and subsequent rebound phase(s). Significantly, even though the ‘big five’ mass extinctions of the Phanerozoic are distinguished primarily by their overwhelming intensities, their magnitudes—and thus importance for shaping the present-day biosphere—have been systematically underestimated, when time frames including immediate, post-apocalyptic DCW taxa are included in survivorship/extinction analyses. Our research from recent studies of Austral and Boreal invertebrates and vertebrates in relation to the Cretaceous–Tertiary (K–T) boundary provides alluring new evidence of the DCW phenomenon, including the short-term survivorship of ammonoid cephalopods and possible non-avian dinosaurs into the dawn of the Cenozoic.
Link. Cenozoic dinosaurs live on.
Monday, July 02, 2012
A new species of feathered dinosaur discovered in southern Germany is further changing the perception of how predatory dinosaurs looked. The fossil of Sciurumimus albersdoerferi, which lived about 150 million years ago, provides the first evidence of feathered theropod dinosaurs that are not closely related to birds. The fossil is described in a paper published in the Proceedings of the National Academy of Sciences today.
"This is a surprising find from the cradle of feathered dinosaur work, the very formation where the first feathered dinosaur Archaeopteryx was collected over 150 years ago," said Mark Norell, chair of the Division of Palaeontology at the American Museum of Natural History and an author on the new paper along with researchers from Bayerische Staatssammlung für Paläontologie und Geologie and the Ludwig Maximilians University.
Theropods are bipedal, mostly carnivorous dinosaurs. In recent years, scientists have discovered that many extinct theropods had feathers. But this feathering has only been found in theropods that are classified as coelurosaurs, a diverse group including animals like T. rex and birds. Sciurumimus—identified as a megalosaur, not a coelurosaur— is the first exception to this rule. The new species also sits deep within the evolutionary tree of theropods, much more so than coelurosaurs, meaning that the species that stem from Sciurumimus are likely to have similar characteristics.
"All of the feathered predatory dinosaurs known so far represent close relatives of birds," said palaeontologist Oliver Rauhut, of the Bayerische Staatssammlung für Paläontologie und Geologie. "Sciurumimus is much more basal within the dinosaur family tree and thus indicates that all predatory dinosaurs had feathers."
The fossil, which is of a baby Sciurumimus, was found in the limestones of northern Bavaria and preserves remains of a filamentous plumage, indicating that the whole body was covered with feathers. The genus name of Sciurumimus albersdoerferi refers to the scientific name of the tree squirrels, Sciurus, and means "squirrel-mimic"—referring to the especially bushy tail of the animal. The species name honors the private collector who made the specimen available for scientific study.
"Under ultraviolet light, remains of the skin and feathers show up as luminous patches around the skeleton," said co-author Helmut Tischlinger, from the Jura Museum Eichstatt.
Sciurumimus is not only remarkable for its feathers. The skeleton, which represents the most complete predatory dinosaur ever found in Europe, allows a rare glimpse at a young dinosaur. Apart from other known juvenile features, such as large eyes, the new find also confirmed other hypotheses.
"It has been suggested for some time that the lifestyle of predatory dinosaurs changed considerably during their growth," Rauhut said. "Sciurumimus shows a remarkable difference to adult megalosaurs in the dentition, which clearly indicates that it had a different diet."
Wow. This is cool!