Formation of sedimentary layers of white clay, Tamilnadu, India

Fossil site for wood fossils, Tamilnadu, India

Fossil site in Kerala, 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

Mars May Have Supported Life: Martian Underground Could Contain Clues to Life’s Origins

January 21st, 2013 Riffin

Minerals found in the subsurface of Mars, a zone of more than three miles below ground, make for the strongest evidence yet that the red planet may have supported life, according to research “Groundwater activity on Mars and implications for a deep biosphere,” published in Nature Geoscience on January 20, 2013.

This view of layered rocks on the floor of McLaughlin Crater shows sedimentary rocks that contain spectroscopic evidence for minerals formed through interaction with water. (Credit: NASA/JPL-Caltech/Univ. of Arizona)

This view of layered rocks on the floor of McLaughlin Crater shows sedimentary rocks that contain spectroscopic evidence for minerals formed through interaction with water. (Credit: NASA/JPL-Caltech/Univ. of Arizona)

Up to half of all life on Earth consists of simple microorganisms hidden in rocks beneath the surface and for some time, scientists have suggested that the same may be true for Mars. Now this theory has been supported by new research, which suggests that the ingredients for life have been present in the Martian subsurface for much of the planet’s history.

When meteorites strike the surface of Mars, they act like natural probes, bringing up rocks from far beneath the surface. Recent research has shown that many of the rocks brought up from the Martian subsurface contain clays and minerals whose chemical make-up has been altered by water, an essential element to support life. Some deep craters on Mars also acted as basins where groundwater likely emerged to produce lakes.

McLaughlin Crater, described in this study, is one such basin that contains clay and carbonate minerals formed in an ancient lake on Mars. The fluids that formed these minerals could carry clues to as to whether the subsurface contained life.

“We don’t know how life on Earth formed but it is conceivable that it originated underground, protected from harsh surface conditions that existed on early Earth. Due to plate tectonics, however, the early geological record of Earth is poorly preserved so we may never know what processes led to life’s origin and early evolution,” said Dr Joseph Michalski, lead author and planetary geologist at the Natural History Museum in London. “Exploring these rocks on Mars, where the ancient geologic record is better preserved than on Earth, would be like finding a stack of pages that have been ripped out of Earth’s geological history book. Whether the Martian geologic record contains life or not, analysis of these types of rocks would certainly teach us a tremendous amount about early chemical processes in the solar system.”

Co-author Deanne Rogers, Assistant Professor in the Department of Geosciences at Stony Brook University used data from the Thermal Emission Spectrometer aboard NASA’s Mars Global Surveyor and the Thermal Emission Imaging System aboard the Mars Odyssey orbiter to detect and identify minerals that proved to be consistent with a sustained aqueous environment on the floor of the McLaughlin Crater.

“Our understanding of Mars is changing very rapidly with all of the new mission data,” said Professor Rogers. “There have been several recent observations and models that have pointed to the possibility of a vast store of groundwater in the Martian past, and perhaps present. So you might expect that deep basins such as McLaughlin, which intersect the upwelling groundwater table, would contain evidence of this water. And this study found that evidence.”

Current exploration of Mars focuses on investigating surface processes because sedimentary rocks are most likely to provide the best chance evidence for habitability. Evidence suggests, however, that the Martian surface environment has been quite inhospitable to life for billions of years. In future missions, scientists could choose to target rocks related to the surface or subsurface, or perhaps do both by targeting areas where sedimentary rocks formed from subsurface fluids.

Michalski concludes: ‘In this paper, we present a strong case for exploring the subsurface, as well as the surface. But I don’t personally think we should try to drill into the subsurface to look for ancient life. Instead, we can study rocks that are naturally brought to the surface by meteor impact and search in deep basins where fluids have come to the surface.’

Co-author Professor John Parnell, geochemist at the University of Aberdeen, commented, “This research has demonstrated how studies of Earth and Mars depend on each other. It is what we have observed of microbes living below the continents and oceans of Earth. They allow us to speculate on habitats for past life on Mars, which in turn show us how life on the early Earth could have survived. We know from Earth’s history that planets face traumatic conditions such as meteorite bombardment and ice ages, when the survival of life may depend on being well below ground. So it makes sense to search for evidence of life from that subsurface environment, in the geological records of both Earth and Mars. But it’s one thing to do that on Earth — we need to be clever in finding a way to do it on Mars.”

Additional co-authors of the study include: Javier Caudros, Researcher, Clay Mineralogy, Earth Sciences Department, Natural History Museum, London; Paul B. Niles, Planetary Scientist, NASA Johnson Space Center; and Shawn P. Wright, Postdoctoral Fellow in Geology, Auburn University.

Insect plugs gap in fossil record

January 20th, 2013 Riffin

One day 370 million years ago, a tiny larva plunged into a shrimp-infested swamp and drowned. Unearthed in modern-day Belgium, the humble bug could plug a giant gap in the fossil record.

Named Strudiella devonica, the eight-millimetre invertebrate – while in far from mint condition – is thought by researchers who published their findings in Nature to be the world’s oldest complete insect fossil.

“It has everything an insect should have: the legs, the antennae, the thorax and the abdomen,” said Andre Nel of France’s National History Museum, one of the authors of the study.

Evolutionary roots of the insect kingdom

Scientists until now had few if any confirmed insect fossils from between 385 and 325 million years ago, a period known as the Hexapoda Gap, William A. Shear of Hampden-Sydney College wrote in a comment that accompanied the study.

Strudiella devonica could significantly narrow that gap in the fossil record.

Strudiella devonica

Strudiella devonica

Based on molecular DNA studies, Nel says scientists had long expected to find insect life dating that far back, but the fossil find yields insight into the evolutionary roots of the insect kingdom.

“Insects are an extremely ancient group, but we know very little about the earliest among them,” he explained. “This find enables us to confirm our molecular dating, it’s a palaeontological marker.”

“Two fossilised mandibles account for the whole Devonian”

Nel said science “had a grand total of two fossilised mandibles from Scotland to account for the whole Devonian” – the geological period running from around 415 million to 360 million years ago.

From these isolated fossil fragments, some 400 million years old, fast-forward to a period known as the Carboniferous, 300 to 330 million years ago, and the fossil record teems with insects.

“In between this profusion of creatures of all kinds – cockroaches, dragonflies, grasshoppers – and the earliest specimens, we have nothing,” Nel explained.

“Yet it was precisely at this time that these animals started to diversify, even started to appear since their ancestors were aquatic insects,” he said.

Strong contender for insect, but caution urged

With its six-legged thorax, long single-branched antennae, triangular jaws and 10-segmented abdomen, tiny Strudiella devonica is a strong contender for an insect ID card, Shear argues.

But he also urges a degree of caution, stressing the study is based on interpretation of a single fossil in relatively poor condition.

“What would make it more certain? A better-preserved specimen, especially one that showed more clearly the appendages and mouthparts,” he said.

While the specimen itself does not have wings, the researchers believe that based on the shape of its mandibles – similar to those of a modern-day grasshopper – it is probably the larva of a winged animal.

If correct, that would also mean that winged insects originated much earlier than available fossils have suggested, Shear said.

The fossil was found in a rock slab in a quarry in Belgium, in a strata of very fine, slightly sandy clay – “probably a land animal that landed in a pond teeming with carnivorous shrimps and that miraculously escaped being devoured by them,” Nel said.

India’s first dinosaur fossil rediscovered

January 19th, 2013 Riffin

More than a century after it went missing, the fossil of what has been regarded as India’s first recorded dinosaur has been rediscovered in Kolkata, according to a top scientific journal.

The recovery of Titanosaurus Indicus, or the Indian Tital reptile, was possible due to a collaborative programme between the Geological Survey of India (GSI) and the University of Michigan, according to the latest issue of Current Science (Vol. 104, No. 1, Jan. 10, 2013, Pg. No. 34), brought out by the Bangalore-based Indian Academy of Sciences.

Titanosaurus Indicus

Titanosaurus Indicus

The missing dinosaur, untraceable for nearly a century, was finally found at the GSI headquarters in Kolkata, says the magazine.

The fossil was originally discovered by W.H. Sleeman in the Jabalpur area of central India in 1828.

However, it was only half a century later – in 1877 – that its importance came to light as a new genus and species of sauropod dinosaur known as Taitanosaurus Indicus, first identified by Richard Lydekker.

At that time, the world had identified only 115 dinosaur species or less than 10 percent of the 1,401 species known by 2004.

Passing safely through many hands for over half a century, it suddenly went missing though a cast of the specimen was in London’s Natural History Museum.

Later, in the early 1900s, many more discoveries of dinosaur fossils were made by scientists such as Charles Metley and Durgasankar Bhattacharji around the original site in Jabalpur excavated by Sleeman.

The magazine says there are many Indian dinosaur specimens that are missing, including both large and small specimens of sauropod and theropod dinosaurs.

Prime among the missing specimens include the head and skeletal parts of the stocky-limbed large Theropod Lametasaurus Indicus, Indosaurus Matleyi, Indosuchus Raptorius, parts of Jainosaurus Septentrionalis and the small Noasaurid Theropod Laevisuchus Indicus and many Theropod limb bones.

Scientists lament that the non-availability of these elements seriously hamper efforts to understand the evolutionary history of Indian dinosaurs and to decode their palaeobiogeographic connections to other southern landmasses.

However, it is not clear whether these missing specimens are lost or merely misplaced and whether it is better to retrieve the old bones or discover newer ones in the field.

The joint efforts by GSI and the University of Michigan have already started bearing fruit and several important specimens have been recovered from various places in existing storage sites, and new ones are being discovered from the field, the magazine says.

Scientists are hopeful that many more missing specimens may be recovered in the future which would help in the study of the evolutionary history of India and its past and present connections to other landmasses.

Australia’s Stampeding Dinosaurs Take a Dip: Largely Tracks of Swimming Rather Than Running Animals

January 18th, 2013 Riffin

Queensland paleontologists have discovered that the world’s only recorded dinosaur stampede is largely made up of the tracks of swimming rather than running animals.

The University of Queensland’s (UQ) PhD candidate Anthony Romilio led the study of thousands of small dinosaur tracks at Lark Quarry Conservation Park, central-western Queensland.

Mr Romilio says the 95-98 million-year-old tracks are preserved in thin beds of siltstone and sandstone deposited in a shallow river when the area was part of a vast, forested floodplain.

Hypothesized reconstruction of the small Lark Quarry trackmaker. (Credit: Illustration by Anthony Romilio, The University of Queensland)

Hypothesized reconstruction of the small Lark Quarry trackmaker. (Credit: Illustration by Anthony Romilio, The University of Queensland)

“Many of the tracks are nothing more than elongated grooves, and probably formed when the claws of swimming dinosaurs scratched the river bottom,” Romilio said.

“Some of the more unusual tracks include ‘tippy-toe’ traces — this is where fully buoyed dinosaurs made deep, near vertical scratch marks with their toes as they propelled themselves through the water.

“It’s difficult to see how tracks such as these could have been made by running or walking animals.

“If that was the case we would expect to see a much flatter impression of the foot preserved in the sediment.”

Mr Romilio said that similar looking swim traces made by different sized dinosaurs also indicated fluctuations in the depth of the water.

“The smallest swim traces indicate a minimum water depth of about 14 cm, while much larger ones indicate depths of more than 40 cm,” Mr Romilio said.

“Unless the water level fluctuated, it’s hard to envisage how the different sized swim traces could have been preserved on the one surface.

“Some of the larger tracks are much more consistent with walking animals, and we suspect these dinosaurs were wading through the shallow water.”

Mr Romilio said the swimming dinosaur tracks at Lark Quarry belonged to small, two-legged herbivorous dinosaurs known as ornithopods.

“These were not large dinosaurs,” Mr Romilio said.

“Some of the smaller ones were no larger than chickens, while some of the wading animals were as big as emus.”

The researchers interpreted the large spacing among many consecutive tracks to indicate that the dinosaurs were moving downstream, perhaps using the current of the river to assist their movements.

Given the likely fluctuations in water depth, the researchers assume the tracks were formed over several days, maybe even weeks.

Previous research had identified two types of small dinosaur tracks at Lark Quarry: long-toed tracks (called Skartopus) and short-toed tracks (called Wintonopus).

The UQ scientists found that just like you ‘shouldn’t judge a book by its cover’, you also ‘shouldn’t judge a track by its outline’.

“3D profiles of ‘Skartopus’ tracks reveal that they were made by a short-toed trackmaker dragging its toes through the sediment, thereby elongating the tracks,” explained Romilio.

“In this context, they are best interpreted as a just another variant of Wintonopus.”

Romilio’s supervisor and coauthor of the new paper, Dr Steve Salisbury, added that, “3D analysis of the Lark Quarry tracks has allowed us to greatly refine our understanding of what this site represents.

“It is also allowing us to learn more about how these dinosaurs moved and behaved in different environments,” Dr Salisbury said.

For the past 30 years, the tracks at Lark Quarry have be known as the world’s only record of a ‘dinosaur stampede’.

Previous research by Romilio and Salisbury in 2011 also showed the larger tracks at Lark Quarry were probably made by a herbivorous dinosaur similar to Muttaburrasaurus, and not a large theropod, as had previously been proposed.

“Taken together, these findings strongly suggest Lark Quarry does not represent a ‘dinosaur stampede’,” Romilio said.

“A better analogy for the site is probably a river crossing.”

Dr Salisbury said regardless of how it was interpreted, these findings took nothing away from the importance of the site.

“Lark Quarry is, and will always remain, one of Australia’s most important dinosaur tracksites,” Dr Salisbury said.

The new study was published in the January 2013 issue of Journal of Vertebrate Paleontology.

More information about dinosaur research at UQ can be found at: http://www.uq.edu.au/dinosaurs/

The Completeness of the Fossil Record of Mesozoic Birds: Implications for Early Avian Evolution

January 17th, 2013 Riffin

Many palaeobiological analyses have concluded that modern birds (Neornithes) radiated no earlier than the Maastrichtian, whereas molecular clock studies have argued for a much earlier origination. Here, we assess the quality of the fossil record of Mesozoic avian species, using a recently proposed character completeness metric which calculates the percentage of phylogenetic characters that can be scored for each taxon. Estimates of fossil record quality are plotted against geological time and compared to estimates of species level diversity, sea level, and depositional environment. Geographical controls on the avian fossil record are investigated by comparing the completeness scores of species in different continental regions and latitudinal bins.

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The two opinions on the timing of modern bird origins based on molecular clocks.

A) an origin 123 million years ago during the Aptian, modified from reference; B) an origin 135 million years ago during the Valanginian modified from reference .

Avian fossil record quality varies greatly with peaks during the Tithonian-early Berriasian, Aptian, and Coniacian–Santonian, and troughs during the Albian-Turonian and the Maastrichtian. The completeness metric correlates more strongly with a ‘sampling corrected’ residual diversity curve of avian species than with the raw taxic diversity curve, suggesting that the abundance and diversity of birds might influence the probability of high quality specimens being preserved. There is no correlation between avian completeness and sea level, the number of fluviolacustrine localities or a recently constructed character completeness metric of sauropodomorph dinosaurs. Comparisons between the completeness of Mesozoic birds and sauropodomorphs suggest that small delicate vertebrate skeletons are more easily destroyed by taphonomic processes, but more easily preserved whole. Lagerstätten deposits might therefore have a stronger impact on reconstructions of diversity of smaller organisms relative to more robust forms. The relatively poor quality of the avian fossil record in the Late Cretaceous combined with very patchy regional sampling means that it is possible neornithine lineages were present throughout this interval but have not yet been sampled or are difficult to identify because of the fragmentary nature of the specimens.

Citation: Brocklehurst N, Upchurch P, Mannion PD, O’Connor J (2012) The Completeness of the Fossil Record of Mesozoic Birds: Implications for Early Avian Evolution. PLoS ONE 7(6): e39056. doi:10.1371/journal.pone.0039056

Scientists reassemble the backbone of life with a particle accelerator synchrotron X-rays

January 16th, 2013 Riffin

Scientists have been able to reconstruct, for the first time, the intricate three-dimensional structure of the backbone of early tetrapods, the earliest four-legged animals. High-energy X-rays and a new data extraction protocol allowed the researchers to reconstruct the backbones of the 360 million year old fossils in exceptional detail and shed new light on how the first vertebrates moved from water onto land. The results are published 13 January 2013 in Nature.

The international team of scientists was led by Stephanie E. Pierce from The Royal Veterinary College in London and Jennifer A. Clack from the University of Cambridge. It also comprised scientists from Uppsala University (Sweden) and the European Synchrotron Radiation Facility ESRF in Grenoble (France).

The tetrapods are four-limbed vertebrates, which are today represented by amphibians, reptiles, birds and mammals. Around 400 million years ago, early tetrapods were the first vertebrates to make short excursions into shallower waters where they used their four limbs for moving around. How this happened and how they then transferred to land is a subject of intense debate among palaeontologists and evolution biologists.

This is an artist's impression of an Ichthyostega Tetrapod, with the cut-out showing the 3-D reconstruction of two vetrebrae from the study. - Julia Molna

This is an artist’s impression of an Ichthyostega Tetrapod, with the cut-out showing the 3-D reconstruction of two vetrebrae from the study. – Julia Molna

All tetrapods have a backbone, or vertebral column, which is a bony structure common to all other vertebrates including fish, from which tetrapods evolved. A backbone is formed from vertebrae connected in a row – from head to tail. Unlike the backbone of living tetrapods (e.g. humans), in which each vertebra is composed of only one bone, early tetrapods had vertebrae made up of multiple parts.

“For more than 100 years, early tetrapods were thought to have vertebrae composed of three sets of bones – one bone in front, one on top, and a pair behind. But, by peering inside the fossils using synchrotron X-rays we have discovered that this traditional view literally got it back-to-front,” says Stephanie Pierce who is the lead author of the publication.

For the analysis, the European Synchrotron Radiation Facility (ESRF) in France, where the three fossil fragments were scanned with X-rays, applied a data extraction method to reveal tiny details of fossil bones buried deep inside the rock matrix. The fossilised bones are embedded in rock so dense it absorbs most of the X-rays. “Without the new method, it would not have been possible to reveal the elements of the spine in three dimensions with a resolution of 30 micrometres” says Sophie Sanchez from University of Uppsala and ESRF who is a co-author of the publication.

In these high-resolution X-ray images, the scientists discovered that what was thought to be the first bone – known as the intercentrum – is actually the last in the series. And, although this might seem like a trivial oversight, this re-arrangement in vertebral structure has over-arching ramifications for the functional evolution of the tetrapod backbone.

Stephanie Pierce explains: “By understanding how each of the bones fit together we can begin to explore the mobility of the spine and test how it may have transferred forces between the limbs during the early stages of land movement”.

But, the findings didn’t end there. One of the animals – known as Ichthyostega – was also found to have an assortment of hitherto unknown skeletal features including a string of bones extending down the middle of its chest.

Jennifer Clack says: “These chest bones turned out to be the earliest evolutionary attempt to produce a bony sternum. Such a structure would have strengthened the ribcage of Ichthyostega, permitting it to support its body weight on its chest while moving about on land.”

This unexpected discovery supports recent work by Pierce and Clack that showed Ichthyostega probably moved by dragging itself across flat ground using synchronous ‘crutching’ motions of its front legs – much like that of a mudskipper or seal. Dr Pierce adds: “The results of this study force us to re-write the textbook on backbone evolution in the earliest limbed animals.”

“At the ESRF, the new data extraction protocol makes it possible to study fossils in dense and heavy rock in unprecedented detail. What we have seen today is only the beginning of more surprises to come,” concludes Sophie Sanchez.

Note: This story has been adapted from a news release issued by the European Synchrotron Radiation Facility

Low Extinction Rates Made California a Refuge for Diverse Plant Species

January 14th, 2013 Riffin

The remarkable diversity of California’s plant life is largely the result of low extinction rates over the past 45 million years, according to a new study published in the journal Evolution. Although many new species have evolved in California, the rate at which plant lineages gave rise to new species has not been notably higher in California than elsewhere, researchers found.

California has more than 5,500 native plant species, including these spring wildflowers on Coyote Ridge in Santa Clara County. (Credit: Jenn Yost)

California has more than 5,500 native plant species, including these spring wildflowers on Coyote Ridge in Santa Clara County. (Credit: Jenn Yost)

Botanists have long recognized California as a biodiversity hotspot. With more than 5,500 native plant species, 40 percent of which are “endemic” (occurring nowhere else), California has more species and more endemic species than any other U.S. state, and is more species rich than most other places on Earth. The new findings highlight the importance of California as a refuge for plant species that might have gone extinct in other regions during the climatic shifts that occurred in the distant past.

“It seems that California has been an important refuge for plant lineages for a long time,” said coauthor Kathleen Kay, assistant professor of ecology and evolutionary biology at the University of California, Santa Cruz. “These findings speak to the importance of protecting areas in California so that it can continue to be a refuge for biodiversity in the future.”

First author Lesley Lancaster, now at Lund University in Sweden, became interested in collaborating with Kay after taking a course from her as a graduate student at UC Santa Cruz. She and Kay developed the project together after Lancaster received a postdoctoral fellowship to study plant evolution at the National Center for Ecological Analysis and Synthesis at UC Santa Barbara.

“Because California has so many unique and relatively young plant species, it was long assumed by biogeographers and naturalists that high speciation rates were the cause of California’s biodiversity,” Lancaster said. “It turns out that these species have not arisen at a particularly high rate in California compared to elsewhere. Instead, features of California’s climate, topography, and latitude have preserved these species, allowing us to see them today, when they may have simply gone extinct if they had arisen elsewhere.”

Lancaster and Kay are the first to tackle the question using modern methods of phylogenetic analysis. They studied 16 different plant lineages that are well represented both within and outside of California, and each lineage includes California endemic species. Using DNA sequence data to reconstruct the evolutionary “family trees” of these lineages, plus fossil records to calibrate the dates when different branches of each tree diverged, they were able to estimate historical rates of speciation, extinction, and migration across the California border.

Some of the study’s key findings differ from long-standing ideas about the origins of California’s extraordinary species richness that were set forth in a landmark study published in 1978, “Origin and relationships of the California flora,” by Peter Raven and Daniel Axelrod. That classic work, which was based on analyses of fossil data and current distributions of plants, emphasized high speciation rates as an important contributor to high plant biodiversity in California.

Raven and Axelrod also hypothesized that the onset of the wet-winter, dry-summer Mediterranean climate in California 3 to 5 million years ago was a key factor that promoted high rates of speciation and led to the species richness that now characterizes California’s flora. All the regions of the world with a Mediterranean climate (California, the cape of Africa, Southwestern Australia, the west coast of Chile, and around the Mediterranean sea) are currently plant biodiversity hotspots, and California does have a large number of relatively young species.

Lancaster and Kay’s study, however, indicates that the onset of the Mediterranean climate did not affect speciation rates in California in most lineages. “Instead, low extinction rates over longer periods of time are responsible for species richness in California, and possibly in other Mediterranean regions as well,” Lancaster said. “All of these regions share characteristics that predate the onset of the Mediterranean climate and that may have favored species persistence in each of these localities.”

According to Kay, California’s topographical diversity probably has played a critical role in preserving species richness. “People have talked about the topography fostering speciation, and it does play a role in that, but it plays a bigger role in preventing extinction by creating different niches and allowing lots of species to coexist,” Kay said. “Topography also provides refuges, and the mountains are particularly important in preventing extinctions during times of climate change.”

In a changing climate, species living on mountains can stay in the same temperature regime by shifting their elevation, moving relatively short distances compared to species on flat land that would have to shift their latitude by hundreds of miles to stay in the same temperature range. California’s mountains are also important for their influence on precipitation, capturing the moisture in air masses coming off the Pacific Ocean, Kay said.

The new study did support several of Raven and Axelrod’s conclusions. For example, they had predicted that cold-adapted lineages would have lower rates of speciation in California than warm-adapted lineages, which Lancaster and Kay confirmed. They also proposed that the onset of the Mediterranean climate facilitated the immigration of desert-adapted plants. Lancaster and Kay found that desert-adapted plants colonized California more recently than other lineages, arriving on average around 5 to 6 million years ago, in comparison to an average of around 17 million years ago for non-desert lineages.

“We just don’t have a lot of evidence that the Mediterranean climate spurred speciation,” Kay said. “Our work shows that the causes of the diversity we see now are more ancient than the Mediterranean climate itself.”

In addition to topography, important features of California and other Mediterranean climate regions are their latitude and their location on the west coast of a continent, Lancaster said. Latitude is important because it allowed these regions to avoid glaciation during periods when global temperatures were cold and northern latitudes were covered in ice. During periods of global warmth, being situated where easterly air currents bring moisture onto the land from the ocean has kept these regions from becoming deserts.

“These regions are likely diverse because they are some of the only non-tropical regions to have been able to avoid historical periods of either desertification or glaciation,” Lancaster said.

Tropical Collapse in Early Triassic Caused by Lethal Heat: Extreme Temperatures Blamed for ‘Dead Zone’

January 13th, 2013 Riffin

Scientists have discovered why the ‘broken world’ following the worst extinction of all time lasted so long — it was simply too hot to survive.

The end-Permian mass extinction, which occurred around 250 million years ago in the pre-dinosaur era, wiped out nearly all the world’s species. Typically, a mass extinction is followed by a ‘dead zone’ during which new species are not seen for tens of thousands of years. In this case, the dead zone, during the Early Triassic period which followed, lasted for a perplexingly long period: five million years.

A paleogeographic reconstruction of the Early Triassic world (Smithian substage) around 252-247 million years ago, showing a ‘dead zone’ in the tropics. Marine reptiles (ichthyosaurs), terrestrial tetrapods and fish almost exclusively occurred in higher latitudes (>30 °N and >40 °S) with rare exceptions. (Credit: Yadong Sun, University of Leeds)

A paleogeographic reconstruction of the Early Triassic world (Smithian substage) around 252-247 million years ago, showing a ‘dead zone’ in the tropics. Marine reptiles (ichthyosaurs), terrestrial tetrapods and fish almost exclusively occurred in higher latitudes (>30 °N and >40 °S) with rare exceptions. (Credit: Yadong Sun, University of Leeds)

A study jointly led by the University of Leeds and China University of Geosciences (Wuhan), in collaboration with the University of Erlangen-Nurnburg (Germany), shows the cause of this lengthy devastation was a temperature rise to lethal levels in the tropics: around 50-60°C on land, and 40°C at the sea-surface.

Lead author Yadong Sun, who is based in Leeds while completing a joint PhD in geology, says: “Global warming has long been linked to the end-Permian mass extinction, but this study is the first to show extreme temperatures kept life from re-starting in Equatorial latitudes for millions of years.”

It is also the first study to show water temperatures close to the ocean’s surface can reach 40°C — a near-lethal value at which marine life dies and photosynthesis stops. Until now, climate modellers have assumed sea-surface temperatures cannot surpass 30°C. The findings may help us understand future climate change patterns.

The dead zone would have been a strange world — very wet in the tropics but with almost nothing growing. No forests grew, only shrubs and ferns. No fish or marine reptiles were to be found in the tropics, only shellfish, and virtually no land animals existed because their high metabolic rate made it impossible to deal with the extreme temperatures. Only the polar regions provided a refuge from the baking heat.

Before the end-Permian mass extinction, Earth had teemed with plants and animals including primitive reptiles and amphibians, and a wide variety of sea creatures including coral and sea lillies.

This broken world scenario was caused by a breakdown in global carbon cycling. In normal circumstances, plants help regulate temperature by absorbing Co2 and burying it as dead plant matter. Without plants, levels of Co2 can rise unchecked, which causes temperatures to increase.

The study, published Oct. 19 in the journal Science, is the most detailed temperature record of this study period (252-247 million years ago) to date.

Sun and his colleagues collected data from 15,000 ancient conodonts (tiny teeth of extinct eel-like fishes) extracted from two tonnes of rocks from South China. Conodonts form a skeleton using oxygen. The isotopes of oxygen in skeletons are temperature controlled, so by studying the ratio of oxygen isotopes in the conodonts he was able to detect temperature levels hundreds of millions of years ago.

Professor Paul Wignall from the School of Earth and Environment at the University of Leeds, one of the study’s co-authors, said: “Nobody has ever dared say that past climates attained these levels of heat. Hopefully future global warming won’t get anywhere near temperatures of 250 million years ago, but if it does we have shown that it may take millions of years to recover.”

The study is the latest collaboration in a 20-year research partnership between the University of Leeds and China University of Geosciences in Wuhan. It was funded by the Chinese Science Foundation.

Study Reveals Jurassic Ecosystems Were Similar to Modern: Animals Flourish Among Lush Plants

January 12th, 2013 Riffin

Typically researchers count the number of animal species discovered in a region to determine how many different types of animals once lived there. Scientists call that a measure of faunal richness.

Myers took a different approach. Using a traditional method typically used to estimate carbon dioxide in the ancient atmosphere, Myers instead applied it to estimate the amount of CO2 in ancient soils.

Nodules of ancient soil are fairly common in present day rock, forming as a result of seasonally dry conditions. They harden into mineralized clods, making them easy to spot and sample as they weather out of ancient soil profiles. (Credit: Myers)

Nodules of ancient soil are fairly common in present day rock, forming as a result of seasonally dry conditions. They harden into mineralized clods, making them easy to spot and sample as they weather out of ancient soil profiles. (Credit: Myers)

Measurements were taken from nodules of calcite that form in soil as a result of wet and dry seasons. These nodules take on the isotopic signature of the CO2 gas around them, which is a mixture derived from two sources: the atmosphere, which leaves a more positive isotopic signature, and plants decaying in the soil, which leave a more negative isotopic signature.

A higher volume of CO2 from plants indicates a lusher, wetter environment.

“There’s a lot more litter fall in an environment with a lot of plants, and that produces a lot of organic material in the soil, creating CO2. So we see more soil-produced CO2, displacing the atmospheric CO2. These are established relationships,” Myers said.

“Our method can be used to infer relative levels of richness for areas where soils have been preserved, but where fossils are lacking because conditions were unsuitable for their preservation,” he said.

The research demonstrates creative use of existing geological data, said co-author Tabor, an expert in ancient soil.

“Vertebrate paleontologists have been accumulating information about vertebrate fossils in the Jurassic for well over 100 years. In addition, geochemists have been systematically sampling the composition of ancient soils for several decades,” Tabor said. “In these respects, the data that are the foundation of this study are not extraordinary. What is remarkable, though, is combining the paleontology and geochemistry data to answer large-scale questions that extend beyond the data points — specifically, to answer questions about ancient ecosystems.”

Data from Morrison Formation, Central Africa and Portugal

Myers tested Upper Jurassic soil nodules collected from the Morrison Formation in the western United States. The formation extends from Montana to New Mexico and has been the source of many dinosaur fossil discoveries.

He also analyzed Upper Jurassic soil nodules from Portugal, another location well-sampled for dinosaur fossils. The region’s paleoclimate was broadly similar to that of the Morrison Formation.

In addition, Myers tested a small Upper Jurassic core sample from Central Africa, where there’s no evidence of any major terrestrial life. Unique minerals in the rocks indicate that the region had an arid environment during the Late Jurassic.

Based on their hypothesis, the researchers expected to see regional variations in plant productivity — the amount of new growth produced in an area over time, which is an indirect measure of the amount of plant life in an environment. Forests, savannas and deserts all have different amounts of plant productivity, although those specific ecosystems can’t be identified on the basis of plant productivity alone.

The researchers expected to see higher plant productivity for Portugal than for the Morrison Formation, with the lowest productivity in Central Africa.

“Essentially that’s what we found,” Myers said. “We understand it’s tenuous and not a trend, but few places in the world are well-sampled. However, it’s still a useful tool for places where all we have are the soil nodules, without well-preserved fauna.”

Soil nodules are fairly common, Myers said. They form as a result of seasonally dry conditions and may be preserved in all but the wettest environments. Since they harden into mineralized clods, they are easy to spot and sample as they weather out of ancient soil profiles.

CO2 in ancient calcite nodules offers key to ancient climate

From the analysis scientists can draw a more complete picture of the ancient landscape and climate in which prehistoric animals lived.

“The Jurassic is thought of as very warm, very wet, with lots of dinosaurs,” said Myers, research curator for SMU’s Shuler Museum of Paleontology. “But we see from our analysis that there was regional variability during the Late Jurassic in the climate and in the abundance of animals across the planet.”

The Late Jurassic extended from 160 million years ago to 145 million years ago.

Giant Fossil Predator Provides Insights Into the Rise of Modern Marine Ecosystem Structures

January 8th, 2013 Riffin

An international team of scientists has described a fossil marine predator measuring 8.6 meters in length (about 28 feet) recovered from the Nevada desert in 2010 as representing the first top predator in marine food chains feeding on prey similar to its own size.

A paper with their description will appear the week of Jan. 7, 2013 in the early electronic issue of Proceedings of the National Academy of Sciences.

Scientists who studied the fossil include lead author Dr. Nadia Fröbisch and Prof. Jörg Fröbisch (both at Museum für Naturkunde Leibniz-Institut für Evolutions- und Biodiversitätsforschung), Prof. P. Martin Sander (Steinmann Institute of Geology, Mineralogy, and Paleontology, Division of Paleontology, University of Bonn), Prof. Lars Schmitz (W. M. Keck Science Department, Claremont McKenna, Pitzer, and Scripps Colleges, Claremont, California) and Dr. Olivier Rieppel (The Field Museum, Chicago, Illinois).

 

Artist's impression of ichthyosaurs (prehistoric marine predators). (Credit: Art by Raul Martin © 2013 National Geographic Magazine. Reproduced with permission)

Artist’s impression of ichthyosaurs (prehistoric marine predators). (Credit: Art by Raul Martin © 2013 National Geographic Magazine. Reproduced with permission)

 

The 244-million-year-old fossil, named Thalattoarchon saurophagis (lizard-eating sovereign of the sea) is an early representative of the ichthyosaurs, a group of marine reptiles that lived at the same time as dinosaurs and roamed the oceans for 160 million years. It had a massive skull and jaws armed with large teeth with cutting edges used to seize and slice through other marine reptiles in the Triassic seas. Because it was a meta-predator, capable of feeding on animals with bodies similar in size to its own, Thalattoarchon was comparable to modern orca whales.

Remarkably, only eight million years prior to the appearance of Thalattoarchon, a severe extinction at the end of the Permian period killed as many as 80 to 96 percent of species in the Earth’s oceans. The rise of a predator such as Thalattoarchon documents the fast recovery and evolution of a modern ecosystem structure after the extinction.

“Everyday we learn more about the biodiversity of our planet including living and fossil species and their ecosystems” Dr. Fröbisch said. “The new find characterizes the establishment of a new and more advanced level of ecosystem structure. Findings like Thalattoarchon help us to understand the dynamics of our evolving planet and ultimately the impact humans have on today’s environment.”

“This discovery is a good example of how we study the past in order to illuminate the future,” said Dr. Rieppel of The Field Museum.

The ichthyosaur was recovered from what is today a remote mountain range in central Nevada. Most of the animal was preserved, including the skull (except the front of the snout), parts of the fins, and the complete vertebral column up to the tip of the tail. Supported by a grant from the National Geographic Society’s Committee for Research and Exploration, the team of paleontologists took three weeks to unearth the ichthyosaur and prepare it for its transport by helicopter and truck out of the field.

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