WFS

Formation of sedimentary layers of white clay, Tamilnadu, India

Fossil site for wood fossils, Tamilnadu, India

Fossil site in Kerala, India

Fossil wood park maintained by geological survey of India at Tamilnadu

Cretaceous fossil sites india

Fossils in rack:-Cyad

Fossils in rack:-echiniderms

Fossils in rack:-Rastellum sp

Pre-historic seabed, Cretaceous period

Sea Temperatures Less Sensitive to CO2 13 Million Years Ago

January 7th, 2013

Riffin

In the modern global climate, higher levels of carbon dioxide (CO₂) in the atmosphere are associated with rising ocean temperatures. But the seas were not always so sensitive to this CO₂ “forcing,” according to a new report. Around 5 to 13 million years ago, oceans were warmer than they are today — even though atmospheric carbon dioxide concentrations were considerably lower.

The unusual mismatch between sea temperatures and CO₂ levels during this time period hints that the relationship between climate and carbon dioxide hasn’t always been the same as it is today, said Petra Dekens, assistant professor of geosciences and a co-author of the new study published in the journal Nature.

Pre historic ocean

“There was a transition, from the Earth’s climate system being not as sensitive to changes in atmospheric carbon dioxide to becoming more sensitive to these changes,” Dekens said. “What’s interesting is that we can see this transition happening within the last 13 million years.”

The connection between modern-day ocean warming and increased levels of atmospheric carbon dioxide produced by human activities has been confirmed in numerous studies, many of them collected in the most recent report of the Intergovernmental Panel on Climate Change.

Recent reconstructions of carbon dioxide levels for the late Miocene time period (roughly 5 to 13 million years ago) suggest that CO₂ concentrations for the period were only 200-350 parts per million. Modern CO₂ concentrations, by contrast, are around 390 parts per million.

The study’s lead author, Jonathan P. LaRiviere at the University of California, Santa Cruz, and colleagues including Dekens, sought information on late-Miocene ocean temperatures to analyze alongside the Miocene CO₂ reconstructions.

They used an organic compound called unsaturated alkenone as their “fossil thermometers.” The compound is produced by tiny phytoplankton and preserved in cores of ocean sediment drawn from the mid-latitude Pacific Ocean basin. Ratios of the compound preserve a record of the water temperature in which the plankton lived.

These data provide the first evidence, Dekens said, that late Miocene sea surface temperatures were significantly warmer than today across a large swath of the North Pacific. The research team found that sea surface temperatures appeared to be highest in the early part of the late Miocene (around 12 to 13 million years ago), and gradually cooled throughout the late Miocene.

The researchers also looked at changes in the late Miocene thermocline, or the ocean layer where warmer, shallow waters meet colder, deeper waters. By comparing oxygen isotope data retrieved from a variety of fossil plankton species that thrive at different ocean depths, they found that the depth of the thermocline has been growing shallow over the past 13 million years.

It is possible, Dekens and colleagues suggest, that changes in the thermocline played some role in creating the warmer waters of the late Miocene — even as carbon dioxide concentrations stayed relatively low. The depth of the thermocline affects the mixing and circulation of colder and warmer ocean waters, which can in turn affect ocean temperature and atmospheric temperatures in a complex feedback cycle. “We would like to have more records from different regions,” Dekens said, “to see if this change in the depth of the thermocline was a global change.”

The thermocline might have grown shallow, the researchers say, as massive ocean waterways opened and closed with the shifting of tectonic plates. These changes would have remodeled ocean basins and the major patterns of ocean circulation.

One major waterway that began to close during the period was the Central American Seaway, an ancient body of water separating North and South America. The seaway was later closed by the volcanic creation of the Panama isthmus.

The study published in the June 7 issue of Nature. LaRiviere and Dekens’ co-authors include A. Christina Ravelo and Heather L. Ford of the University of California, Santa Cruz; Allison Crimmons of the U.S. Environmental Protection Agency; Mitch Lyle of Texas A&M University; and Michael W. Wara of Stanford Law School.

Fossil scars capture dinosaur headbutts

January 6th, 2013

Riffin

With domed heads and thick, bony skull protuberances, pachycephalosaurids are well known by seven-year-olds and palaeontologists alike. The dinosaurs are thought to have used their thick domes to headbutt each other, perhaps as part of courtship behaviour. But whereas children recreating these vicious displays simply ram plastic models of the animals together in a straight line, a study now suggests that pachycephalosaurs may have bashed one another in a number of different ways.

Pachycephalosaurids could attack each other with their dome-shaped skulls in a variety of ways.
Ryan Steiskal

The work, presented this week at the Society of Vertebrate Paleontology’s annual meeting in Raleigh, North Carolina, started with just one pachycephalosaur fossil. “We were looking at a dome and noticed these lesions that looked like they were from injuries,” explains Joseph Peterson, a palaeontologist at the University of Wisconsin in Oshkosh. He wondered whether the fossilized injury was one of a kind — or whether such lesions were common. To find out, Peterson and his colleague Collin Dischler started examining more domes.

Together, they were able to look at 102 domes from fossil collections around the world. Of these, 23 had lesions. Fascinated by the presence of so many injuries, Peterson and Dischler produced a three-dimensional computer model of a pachycephalosaur skull and mapped injuries onto it.

They noted that the shape of the dome differed from fossil to fossil, and that the placement of the injuries depended on the shape of the skull. Skulls with low domes tended to have injuries at the front, whereas skulls with higher domes had lesions evenly distributed between the front and back.

Living proof

The finding hinted that the pachycephalosaurs with differently shaped skulls were bumping heads in different ways. To find out what those ways were, the researchers considered the butting of sheep, goats and bison.

“The lesions we were seeing were strikingly similar to those that we often see on the skulls of modern mammals that ram heads,” says Peterson.

The team found that bighorn sheep (Ovis canadensis) charge each other head on; that mountain goats (Oreamos americanus) bump one another in the flanks; and that bison (Bison bison) wrestle with their horns. On the basis of these examples, Peterson and Dischler speculate that the high-domed pachycephalosaurs with parietal injuries were side-bumping like mountain goats, and that the frontal injuries are indicative of bison-like wrestling.

“It could be that we are seeing two different species bashing in different ways, but it could also be a single dinosaur species where juveniles and adults exhibit different bashing behaviours,” says Andrew Farke, a palaeontologist at the Raymond Alf Museum of Palaeontology in Claremont, California.

Bone to pick

Some palaeontologists disagree that pachycephalosaurs rammed one another at all, and there is much scepticism over whether the lesions really are ‘butt prints’.

“It is an intriguing study but after examining one of these ‘injuries’ I found it hard to rule out the possibility that this might have simply been the skull being chipped after death,” says Bruce Rothschild, a palaeo-osteopathologist at the University of Kansas in Lawrence.

Farke is confident that the debate will soon be resolved. “A look at skull bone microstructure should determine if the lesion sites actually suffered trauma,” he says.

Whatever the outcome, seven-year-olds will undoubtedly keep on bashing.

Nature doi:10.1038/nature.2012.11624

Origin of Photosynthesis Revealed by a ‘Living Fossil’

January 5th, 2013

Riffin

Recently, the complete genome of a glaucophyte alga (Cyanophora paradoxa) has been unraveled by an international consortium led by Dr. Debashish Bhattacharya from Rutgers University (USA). From the University of Freiburg, Dr. Stefan Rensing and Aikaterini Symeonidi (Faculty of Biology), contributed to the analysis of the genome by performing classification and phylogenomic analyses of the encoded transcription factors as well as by checking for and removing genomic contaminations.

Illustration of alga cyanophora paradoxa. (Credit: Susanne Ruemmele, Bhattacharya Lab)

The results are published in the current issue of the journal Science.

Todays plants and algae, which form the base of many food chains, contain little green reactors (plastids) that transform gaseous carbon dioxide to sugar by means of photosynthesis. The genome of the early diverging alga C. paradoxa provides conclusive evidence for the fact that more than one billion years ago plastids were acquired in a single evolutionary event, through so-called primary endosymbiosis. The present day plastids we find in land plants, red and green algae and in the glaucophyte algae, such a C. paradoxa, can all be traced back to that single crucial event, enabling eukaryotes to gain energy from sunlight.

The relatively small (~70Mbp) genome was sequenced and analysed by a team of 30 scientists from six countries. Since it represents the earliest lineage to branch off from what became today’s land plants, it is expected to be of high value for many future comparative genomics studies.

Asteroid impact Wiped out the ‘Obamadon’

January 4th, 2013

Riffin

The asteroid collision widely thought to have killed the dinosaurs also led to extreme devastation among snake and lizard species, according to new research — including the extinction of a newly identified lizard Yale and Harvard scientists have named Obamadon gracilis.

“The asteroid event is typically thought of as affecting the dinosaurs primarily,” said Nicholas R. Longrich, a postdoctoral associate with Yale’s Department of Geology and Geophysics and lead author of the study. “But it basically cut this broad swath across the entire ecosystem, taking out everything. Snakes and lizards were hit extremely hard.”

New research indicates that the asteroid collision widely thought to have killed the dinosaurs also led to extreme devastation among snake and lizard species. (Credit: © revers_jr / Fotolia)

The study was scheduled for online publication the week of Dec. 10 in the Proceedings of the National Academy of Sciences.

Earlier studies have suggested that some snake and lizard species (as well as many mammals, birds, insects and plants) became extinct after the asteroid struck Earth 65.5 million years ago, on the edge of the Yucatan Peninsula. But the new research argues that the collision’s consequences were far more serious for snakes and lizards than previously understood. As many as 83 percent of all snake and lizard species died off, the researchers said — and the bigger the creature, the more likely it was to become extinct, with no species larger than one pound surviving.

The results are based on a detailed examination of previously collected snake and lizard fossils covering a territory in western North America stretching from New Mexico in the southwestern United States to Alberta, Canada. The authors examined 21 previously known species and also identified nine new lizards and snakes.

They found that a remarkable range of reptile species lived in the last days of the dinosaurs. Some were tiny lizards. One snake was the size of a boa constrictor, large enough to take the eggs and young of many dinosaur species. Iguana-like plant-eating lizards inhabited the southwest, while carnivorous lizards hunted through the swamps and flood plains of what is now Montana, some of them up to six feet long.

“Lizards and snakes rivaled the dinosaurs in terms of diversity, making it just as much an ‘Age of Lizards’ as an ‘Age of Dinosaurs,'” Longrich said.

The scientists then conducted a detailed analysis of the relationships of these reptiles, showing that many represented archaic lizard and snake families that disappeared at the end of the Cretaceous, following the asteroid strike.

One of the most diverse lizard branches wiped out was the Polyglyphanodontia. This broad category of lizards included up to 40 percent of all lizards then living in North America, according to the researchers. In reassessing previously collected fossils, they came across an unnamed species and called it Obamadon gracilis. In Latin, odon means “tooth” and gracilis means “slender.”

“It is a small polyglyphanodontian distinguished by tall, slender teeth with large central cusps separated from small accessory cusps by lingual grooves,” the researchers write of Obamadon, which is known primarily from the jaw bones of two specimens. Longrich said the creature likely measured less than one foot long and probably ate insects.

He said no one should impute any political significance to the decision to name the extinct lizard after the recently re-elected U.S. president: “We’re just having fun with taxonomy.”

The mass (but not total) extinction of snakes and lizards paved the way for the evolution and diversification of the survivors by eliminating competitors, the researchers said. There are about 9,000 species of lizard and snake alive today. “They didn’t win because they were better adapted, they basically won by default, because all their competitors were eliminated,” Longrich said.

Co-author Bhart-Anjan S. Bhullar, a doctoral student in organismic and evolutionary biology at Harvard University, said: “One of the most important innovations in this work is that we were able to precisely reconstruct the relationships of extinct reptiles from very fragmentary jaw material. This had tacitly been thought impossible for creatures other than mammals. Our study then becomes the pilot for a wave of inquiry using neglected fossils and underscores the importance of museums like the Yale Peabody as archives of primary data on evolution — data that yield richer insights with each new era of scientific investigation.”

Jacques A. Gauthier, professor of geology and geophysics at Yale and curator of vertebrate paleontology and vertebrate zoology, is also an author.

The paper is titled “Mass Extinction of Lizards and Snakes at the Cretaceous-Paleogene Boundary.” The National Science Foundation and the Yale Institute for Biospheric Studies supported the research.

Research Reveals New Information On the Evolution of Dinosaur Senses

January 3rd, 2013

Riffin

An international team of scientists, including PhD student Stephan Lautenschlager and Dr Emily Rayfield of the University of Bristol, found that the senses of smell, hearing and balance were well developed in therizinosaurs and might have affected or benefited from an enlarged forebrain. These findings came as a surprise to the researchers as exceptional sensory abilities would be expected from predatory and not necessarily from plant-eating animals.

Fossil skull of the Cretaceous therizinosaur Erlikosaurus andrewsi (Credit: Image by Emily Rayfield, University of Bristol)

Therizinosaurs are an unusual group of theropod dinosaurs which lived between 145 and 66 million years ago. Members of this group had evolved into up to 7m (23ft) large animals, with more than 50cm (20in) long, razor-sharp claws on their forelimbs, elongated necks and a coat of primitive, down-like feathers along their bodies. Although closely related to carnivorous dinosaurs such as Tyrannosaurus rex and Velociraptor, and in spite of their bizarre appearance, therizinosaurs were probably peaceful herbivores.

Inspired by this paradox, the international team of palaeontologists decided to take the first close look inside the heads of these enigmatic dinosaurs.

They studied the brain and inner ear anatomy of therizinosaurs using high-resolution CT scanning and 3D computer visualisation to find out more about their sensory and cognitive capabilities and how these had evolved with the transition from meat- to plant-eating.

The focus of the study was the skull of Erlikosaurus andrewsi — a 3-4m (10-13ft) therizinosaur, which lived more than 90 million years ago in what is now Mongolia.

Lead author, Stephan Lautenschlager of Bristol’s School of Earth Sciences said: “Our results suggest that therizinosaurs would have used their well-developed sensory repertoire to their advantage which, for herbivorous animals, must have played an important role in foraging, in the evasion of predators or in social complexity.

“This study sheds a new light on the evolution of dinosaur senses and shows it is more complex than we thought.”

Co-author, Professor Lindsay Zanno of the North Carolina Museum of Natural History and the North Carolina State University agrees: “Once you’ve evolved a good sensory toolkit, it’s probably worth hanging on to, whether you’re hunting or being hunted.”

Fellow author Lawrence Witmer, Chang Professor of Paleontology at the Ohio University Heritage College of Osteopathic Medicine said: “Of course the actual brain tissue is long gone from the fossil skulls but we can use CT scanning to visualize the cavity that the brain once occupied and then generate 3D computer renderings of the olfactory bulbs and other brain parts.”

This study has important ramifications for our understanding of how sensory function evolved in different dinosaur groups and whether it was developed as a response to their environment or simply inherited by their ancestors. In particular, in the light of the transition from dinosaurs to birds, these results should prove to be very interesting.

Evidence Contradicts Idea That Starvation Caused Saber-Tooth Cat Extinction

December 28th, 2012

Riffin

In the period just before they went extinct, the American lions and saber-toothed cats that roamed North America in the late Pleistocene were living well off the fat of the land.

That is the conclusion of the latest study of the microscopic wear patterns on the teeth of these great cats recovered from the La Brea tar pits in southern California. Contrary to previous studies, the analysis did not find any indications that the giant carnivores were having increased trouble finding prey in the period before they went extinct 12,000 years ago.

The results, published on Dec. 26 in the scientific journal PLOS ONE, contradicts previous dental studies and presents a problem for the most popular explanations for the Megafaunal (or Quaternary) extinction when the great cats, mammoths and a number of the largest mammals that existed around the world disappeared.

Sabertoothed cats were not limited by food in California during the late Pleistocene. (Credit: Mauricio Anton/ DeSantis LRG, Schubert BW, Scott JR, Ungar PS (2012) Implications of Diet for the Extinction of Saber-Toothed Cats and American Lions. PLoS ONE 7(12): e52453. doi:10.1371/journal.pone.0052453)

“The popular theory for the Megafaunal extinction is that either the changing climate at the end of the last Ice Age or human activity — or some combination of the two — killed off most of the large mammals,” said Larisa DeSantis, assistant professor of earth and environmental sciences at Vanderbilt, who headed the study. “In the case of the great cats, we expect that it would have been increasingly difficult for them to find prey, especially if had to compete with humans. We know that when food becomes scarce, carnivores like the great cats tend to consume more of the carcasses they kill. If they spent more time chomping on bones, it should cause detectable changes in the wear patterns on their teeth.”

In 1993, Blaire Van Valkenburgh at UCLA published a paper on tooth breakage in large carnivores in the late Pleistocene. Analyzing teeth of American lions, saber-tooth cats, dire wolves and coyotes from La Brea, she found that they had approximately three times the number of broken teeth of contemporary predators and concluded, .” ..these findings suggest that these species utilized carcasses more fully and likely competed more intensely for food than present-day large carnivores.”

The latest study uses a new technique, called dental microwear texture analysis (DMTA), developed by co-author Peter Ungar at the University of Arkansas. It uses a confocal microscope to produce a three-dimensional image of the surface of a tooth. The image is then analyzed for microscopic wear patterns. Chowing down on red meat produces small parallel scratches. Chomping on bones adds larger, deeper pits. Previous methods of dental wear analysis relied on researchers to identify and count these different types of features. DMTA relies on automated software and is considered more accurate because it reduces the possibility of observer bias.

DeSantis and Ungar, with the assistance of Blaine Schubert from East Tennessee State University and Jessica Scott from the University of Arkansas, applied DMTA to the fossil teeth of 15 American lions (Panthera atrox) and 15 saber-tooth cats (Smilodon fatalis) recovered from the La Brea tar pits in Los Angeles.

Their analysis revealed that the wear pattern on the teeth of the American lion most closely resembled those of the present-day cheetah, which actively avoids bones when it feeds. Similarly, the saber-tooth cat’s wear pattern most closely resembled those of the present-day African lion, which indulges in some bone crushing when it eats. (This differs from a previous microwear study using a different technique that concluded saber-tooth cats avoided bone to a far greater extent.)

The researchers examined how these patterns changed over time by selecting specimens from tar pits of different ages, ranging from about 35,000 to 11,500 years ago. They did not find any evidence that the two carnivores increased their “utilization” of carcasses throughout this period. If anything, their analysis suggests that the proportion of the carcasses that both kinds of cats consumed actually declined toward the end.

The researchers acknowledge the high rate of tooth breakage reported in the previous study, but they argue that it is more likely the result of increased breakage when taking down prey instead of when feeding.

“Teeth can break from the stress of chewing bone but they can also break when the carnivores take down prey,” DeSantis pointed out. Species like hyenas that regularly chew and crack bones of their kills are as likely to break the rear teeth they use for chewing as their front canines. Species like the cheetah, however, which avoid bones during feeding are twice as likely to break canines than rear teeth. This suggests that they are more likely to break canines when pulling down prey.

The researchers report that previous examinations of the jaws of the American lions and saber-tooth cats from this period found that they have more than three times as many broken canines and interpret this as additional evidence that supports their conclusion that most of the excess tooth breakage occurred during capture instead of feeding.

In addition, the researchers argue that the large size of the extinct carnivores and their prey can help explain the large number of broken teeth. The saber-toothed cats were about the size of today’s African lion and the American lion was about 25 percent larger. The animals that they preyed upon likely included mammoths, four-ton giant ground sloths and 3,500-pound bison.

Larger teeth break more easily than smaller teeth. So larger carnivores are likely to break more canine teeth when attempting to take down larger prey, the researchers argue. They cite a study that modeled the strength of canine teeth that found the canines of a predator the size of fox can support more than seven times its weight before breaking while a predator the size of lion can only support about four times its weight and the curved teeth of the saber-toothed cats can only support about twice its weight.

“The net result of our study is to raise questions about the reigning hypothesis that “tough times” during the late Pleistocene contributed to the gradual extinction of large carnivores,” DeSantis summarized. “While we can not determine the exact cause of their demise, it is unlikely that the extinction of these cats was a result of gradually declining prey (due either to changing climates or human competition) because their teeth tell us that these cats were not desperately consuming entire carcasses, as we had expected, and instead seemed to be living the ‘good life’ during the late Pleistocene, at least up until the very end.”

Multicellular Fossils Point to Life On Land ?

December 27th, 2012

Riffin

Ancient multicellular fossils long thought to be ancestors of early marine life are remnants of land-dwelling lichen or other microbial colonies, says University of Oregon scientist Gregory J. Retallack, who has been studying fossil soils of South Australia.

Ediacaran (pronounced EDI-akran) fossils date to 542-635 million years ago. They’ve been considered fossil jellyfish, worms and sea pens, but are preserved in ways distinct from marine invertebrate fossils. The fossils — first discovered in 1946 in Australia’s Ediacara Hills — are found in iron-colored impressions similar to plant fossils and microbes in fossil soils.

Dickinsonia fossils in South Australia, shown here, were likely formed by lichen or other microbial consortia, not from marine invertebrates or giant protists as previously theorized. (Credit: Courtesy of Greg Retallack)

Retallack, a native of Australia, examined ancient Ediacaran soils with an array of state-of-the-art chemical and microscopic techniques, including an electron microprobe and scanning electron microscope in the UO’s CAMCOR Microanalytical Facility headed by John Donovan and rock-analysis technology in the UO’s stable isotope laboratory of Ilya Bindeman.

The soils with fossils, Retallack writes in his study, “are distinguished by a surface called ‘old elephant skin,’ which is best preserved under covering sandstone beds.” The healed cracks and lumpy appearance of sandy “old elephant skin” are most like the surface of microbial soil crusts in modern deserts.

“This discovery has implications for the tree of life, because it removes Ediacaran fossils from the ancestry of animals,” said Retallack, professor of geological sciences and co-director of paleontological collections at the UO’s Museum of Natural and Cultural History. His evidence, mostly gathered from a site in the Flinders Ranges, is presented in a paper placed online ahead of print by the journal Nature.

“These fossils have been a first-class scientific mystery,” he said. “They are the oldest large multicellular fossils. They lived immediately before the Cambrian evolutionary explosion that gave rise to familiar modern groups of animals.”

Retallack studied numerous Ediacaran fossils and determined that the diversity reflects a preference by the ancient organisms for “unfrozen, low salinity soils, rich in nutrients, like most terrestrial organisms.” Thus the fossils in Australia’s iconic red-rock ranges, he concludes, were landlubbers. In his closing paragraph, Retallack outlines implications for a variety of other Edicaran fossils, that could have been lichens, other microbial consortia, fungal fruiting bodies, slime molds, flanged pedestals of biological soil crusts, and even casts of needle ice.

Ediacaran fossils, he said, represent “an independent evolutionary radiation of life on land that preceded by at least 20 million years the Cambrian evolutionary explosion of animals in the sea.” Increased chemical weathering by large organisms on land may have been needed to fuel the demand of nutrient elements by Cambrian animals. Independent discoveries of Cambrian fossils comparable with Ediacaran ones is evidence, he said, that even in the Cambrian, more than 500 million years ago, life on land may have been larger and more complex than life in the sea.

Retallack leaves open the possibility that some Ediacaran fossils found elsewhere in the world may not be land-based in origin, writing in his conclusion that the many different kinds of these fossils need to be tested and re-evaluated.

“The key evidence for this new view is that the beds immediately below the cover sandstones in which they are preserved were fossil soils,” he said. “In other words the fossils were covered by sand in life position at the top of the soils in which they grew. In addition, frost features and chemical composition of the fossil soils are evidence that they grew in cold dry soils, like lichens in tundra today, rather than in tropical marine lagoons.”

Fossil soils are usually recognized from root traces, soil horizons and soil structures, but in rocks of Ediacaran age, before the advent of rooted plants, only the second two criteria can be used to recognize fossil soils. Ediacaran fossil soils, Retallack said, represent ecosystems less effective at weathering than the modern array of ecosystems, so that soil horizons and soil structures are not as well developed as they are in modern soils.

“The research conducted by Dr. Retallack helps to unravel the mystery of very ancient life on Earth,” said Kimberly Andrews Espy, UO vice president for research and innovation, and dean of the graduate school. “It also serves as an example of how technology, some of it developed at the University of Oregon, can be used to analyze materials from anywhere in the world.”

The American Chemical Society’s Petroleum Research Fund supported the fieldwork.

First Freshwater Mosasaur Discovered

December 26th, 2012

Riffin

A new mosasaur species discovered in Hungary is the first known example of this group of scaled reptiles to have lived in freshwater river environments similar to modern freshwater dolphins.

The research is published Dec. 19 in the open-access journal PLOS ONE by Laszlo Makadi from the Hungarian Natural History Museum, Hungary and colleagues from the University of Alberta, Canada and MTA-ELTE Lendület Dinosaur Research Group, Hungary.

The First Freshwater Mosasauroid (Upper Cretaceous, Hungary) and a New Clade of Basal Mosasauroids.The First Freshwater Mosasauroid (Upper Cretaceous, Hungary) and a New Clade of Basal Mosasauroids.

The species lived about 84 million years ago, the largest specimens reached about 20 feet in length, and belongs to a family called ‘mosasaurs’, conventionally thought of as gigantic finned marine lizards, similar and perhaps even related to present day monitor lizards. The researchers discovered several fossils of the new species, ranging from small juveniles to large adults that suggest that this species had limbs like a terrestrial lizard, a flattened, crocodile-like skull, and a tail unlike other known members of the mosasaur family.

The fossils were recovered from an open-pit mine in the Bakony Hills of Western Hungary, which were once flood-plains. According to the study, this is the first known mosasaur that lived in freshwater, and only the second specimen of a mosasaur to have been found in rocks that were not once deposited in the ocean. Makadi says, “The evidence we provide here makes it clear that similar to some lineages of cetaceans, mosasaurs quickly adapted to a variety of aquatic environments, with some groups re- invading available niches in freshwater habitats. The size of Pannoniasaurus makes it the largest known predator in the waters of this paleo-environment.”

Even in the modern world, scaly reptiles in the aquatic world are extremely rare. Only a few species live in the water, and even fewer, like marine iguanas and sea kraits, live in the oceans. The new species described here probably adapted to freshwater environments similarly to river dolphins, such as those now inhabiting the Amazon, Ganges and Yangtze rivers.

Evolution of Early Life:Paleo-Ocean Chemistry answers

December 24th, 2012

Riffin

A research team led by biogeochemists at the University of California, Riverside has tested a popular hypothesis in paleo-ocean chemistry, and proved it false.

The fossil record indicates that eukaryotes — single-celled and multicellular organisms with more complex cellular structures compared to prokaryotes, such as bacteria — show limited morphological and functional diversity before 800-600 million years ago. Many researchers attribute the delayed diversification and proliferation of eukaryotes, which culminated in the appearance of complex animals about 600 million years ago, to very low levels of the trace metal zinc in seawater.

As it is for humans, zinc is essential for a wide range of basic cellular processes. Zinc-binding proteins, primarily located in the cell nucleus, are involved in the regulation of gene transcription.

Eukaryotes have increasingly incorporated zinc-binding structures during the last third of their evolutionary history and still employ both early- and late-evolving zinc-binding protein structures. Zinc is, therefore, of particular importance to eukaryotic organisms. And so it is not a stretch to blame the 1-2-billion-year delay in the diversification of eukaryotes on low bioavailability of this trace metal.

But after analyzing marine black shale samples from North America, Africa, Australia, Asia and Europe, ranging in age from 2.7 billion years to 580 million years old, the researchers found that the shales reflect high seawater zinc availability and that zinc concentrations during the Proterozoic (2.5 billion to 542 million years ago) were similar to modern concentrations. Zinc, the researchers posit, was never biolimiting.

Study results appear online Dec. 23 in Nature Geoscience.

“We argue that the concentration of zinc in ancient marine black shales is directly related to the concentrations of zinc in seawater and show that zinc is abundant in these rocks throughout Earth’s history,” said Clint Scott, the first author of the research paper and a former UC Riverside graduate student. “We found no evidence for zinc biolimitation in seawater.”

Scott, now a research geologist with the U.S. Geological Survey, explained that the connection between zinc limitation and the evolution of eukaryotes was based largely on the hypothesis that Proterozoic oceans were broadly sulfidic. Under broadly sulfidic conditions, zinc should have been scarce because it would have rapidly precipitated in the oceans, he explained.

“However, a 2011 research paper in Nature also published by our group at UCR demonstrated that Proterozoic oceans were more likely broadly ferruginous — that is, low in oxygen and iron-rich — and that sulfidic conditions were more restricted than previously thought,” said Scott, who performed the research in the lab of Timothy Lyons, a professor of biogeochemistry and the principal investigator of the research project.

The research team argues that ferruginous deep oceans, combined with large hydrothermal fluxes of zinc via volcanic activity on the seafloor, maintained high levels of dissolved zinc throughout the oceans and provided a relatively stable marine reservoir of the trace metal over the past 2.7 billion years.

“The key challenge in understanding the early evolution of life is recognizing the environmental conditions under which that life first appeared and diversified,” Lyons said. “We have taken a very direct approach that specifically tracks the availability of essential micronutrients, and, to our surprise, zinc supplies in ancient seawater were much higher and less variable than previously imagined.

“We can imagine for the first time,” he quipped, “that zinc supplements were not on the shopping lists of our early eukaryotic ancestors, and so we better find another reason to explain the mysterious delay in their rise in the ocean.”

Scott, who graduated with a doctoral degree in geological sciences from UCR in 2009, and Lyons were joined in the study by Noah J. Planavsky, a former UCR graduate student in Lyons’ lab; Chris L. Dupont at the J. Craig Venter Institute, La Jolla, Calif.; Brian Kendall and Ariel D. Anbar at Arizona State University; Benjamin C. Gill at Virginia Polytechnic Institute and State University and also a former member of the Lyons lab; Leslie J. Robbins and Kurt O. Konhauser at the University of Alberta, Canada; Kathryn F. Husband and Simon W. Poulton at the University of Leeds, United Kingdom; Gail L. Arnold at the Max Planck Institute for Marine Microbiology, Germany; Boswell A. Wing at McGill University, Canada; and Andrey Bekker at the University of Manitoba, Canada.

The idea for the study was a direct consequence of the 2011 Nature paper by Planavsky, Scott, Lyons and others that challenged the hypothesis of broadly sulfidic oceans.

The international collaboration received funding for the study from numerous sources. In the U.S., funding came from the National Science Foundation, the NASA Astrobiology Institute and the Agouron Institute.

New Study Sheds Light On Dinosaur Size

December 23rd, 2012

Riffin

Dinosaurs were not only the largest animals to roam the Earth — they also had a greater number of larger species compared to all other back-boned animals — scientists suggest in a new paper published in the journal PLOS ONE.

The researchers, from Queen Mary, University of London, compared the size of the femur bone of 329 different dinosaur species from fossil records. The length and weight of the femur bone is a recognised method in palaeontology for estimating a dinosaur’s body mass.

They found that dinosaurs follow the opposite pattern of body size distribution as seen in other vertebrate species. For example, within living mammals there tends to be few larger species, such as elephants, compared to smaller animals, such as mice, which have many species. The evidence from fossil records implies that in contrast there were many species of larger dinosaurs and few small species.

Frequency distribution of species body size for eight different animal groups

Dr David Hone from Queen Mary’s School of Biological and Chemical Sciences, explains: “What is remarkable is that this tendency to have more species at a bigger size seemed to evolve quite early on in dinosaurian evolution around the Late Triassic period, 225 million years ago, raising questions about why they got to be so big.

“Our evidence supports the hypothesis that young dinosaurs occupied a different ecological niche to their parents so they weren’t in competition for the same sources of food as they ate smaller plants or preyed on smaller size animals. In fact, we see modern crocodiles following this pattern — baby crocodiles start by feeding off insects and tadpoles before graduating onto fish and then larger mammals.”

Dr Eoin Gorman, also from Queen Mary’s School of Biological and Chemical Sciences added: “There is growing evidence that dinosaurs produced a large number of offspring, which were immediately vulnerable to predation due to their smaller size. It was beneficial for the herbivores to grow to large size as rapidly as possible to escape this threat, but the carnivores had sufficient resources to live optimally at smaller sizes.

“These differences are reflected in our analyses and also offer an explanation why other groups do not follow a similar pattern. Several modern-day vertebrate groups are almost entirely carnivorous, while many of the herbivores are warm-blooded, which limits their size.”