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

Counting calories in the fossil record: How the biology of our modern ocean evolved

March 27th, 2014

Riffin

Starting about 250 million years ago, at the end of the Permian period, brachiopod groups disappeared in large numbers, along with 90 percent of the planet’s species. Today, only a few groups, or genera, of brachiopods remain. “Most people won’t be familiar with brachiopods. They’re pretty rare in the modern ocean,” said Jonathan Payne, a paleobiologist at Stanford University.

Meanwhile, bivalves flourished, diversifying into a staggering variety of shapes and sizes, and spread from marine to freshwater habitats. “After the end-Permian mass extinction, we find far fewer brachiopods and a lot more bivalves,” said Payne, who is an associate professor in the Department of Geological & Environmental Sciences.

Why one group of shelled animals thrived while the other barely survived is one of the great mysteries in paleontology. A popular theory, based on diversity and abundance data from the fossil record for the two groups, is that bivalves simply outcompeted brachiopods. But a new study by Payne and other researchers that looks at the issue from an energy standpoint paints a different picture. Their findings, published online on March 26 in the journal Proceedings of the Royal Society B, show that, despite being fewer in number, ancient bivalves were already consuming as much food as brachiopods, and that modern bivalves consume vastly more.

“Brachiopods and bivalves used about same amount of food during Paleozoic, but bivalve food intake has increased by a factor of 100 since then,” Payne said. “There’s no way that increase is the result of bivalves simply displacing brachiopods. Even if bivalves had entirely supplanted brachiopods, their metabolism would have only doubled.”

Payne and his collaborators reached their conclusions after conducting a comprehensive search of scientific literature and recording the body sizes of more than 6,000 ancient and modern genera of bivalves and brachiopods. Some of the fossils dated back to the Cambrian era, more than 500 million years ago. Five undergraduate students and high school interns spent an entire summer on the task.

Fossil records like the one used in the current study can also provide clues about how the biological makeup of the modern ocean evolved, Payne said. “If scientists want to know how evolution works, one of the best ways is to study changes in animal shape over Earth’s history,” he added. “By moving from form to function as we have done in this study, fossils give us a very direct way of comparing how ancient ecosystems worked compared to their modern counterparts.”

From body size to metabolic rate

Once the body sizes of the different genera were known, the team was ready to estimate each one’s metabolic rate. To do this, they used available data about the ratio between shell size and living, or “soft,” tissue in modern bivalves and brachiopods to calculate the soft tissue amounts, and by extension the metabolic rates, of the extinct genera.

The results of their study showed that like their modern descendants, ancient brachiopods possessed relatively little soft tissue and would have had low metabolic rates compared to ancient bivalves. “It turns out that even though brachiopod and bivalve shells are about the same size, if you open up a brachiopod shell, there’s a lot less meat inside,” Payne said. “That’s one reason that we eat bivalves, and not brachiopods. There also aren’t there many brachiopods around, and some of them may be toxic to humans.”

The new finding indicates that, from a metabolic standpoint at least, brachiopods didn’t dominate the Paleozoic. At best, they split their ocean kingdom with bivalves. “Our study is unique in that it provides a deep time perspective of how life arose, and in this case declined as well, because of how these two group differentially use energy,” said study coauthor Craig McClain, an oceanographer at the National Evolutionary Synthesis Center (NESCent) in Durham, NC. “Today’s ocean reflects these evolutionary stories of the past. We can look at the modern oceans and see the end of the story-lots of bivalves and few brachiopods-but now we know more about the introduction and climax of the narrative.”

Unlucky brachiopods

So if bivalves weren’t responsible for the brachiopods fall from glory, then what was? It’s likely, Payne said, that brachiopods were just unlucky. The evolutionary strategies that made them successful for hundreds of millions of years simply no longer worked or were even detrimental in the face of the environmental changes wrought by the End Permian extinction. “We think that about 250 million years ago, a series of large volcanic eruptions in Siberia ejected something on the order of 6 million kilometers of basalt rock. That’s enough to cover all of Western Europe in a quarter-mile deep layer of basalt,” Payne said.

When the scalding volcanic rock rained back to surface and penetrated the Earth’s upper crust, it heated other rocks, causing them to release large amounts of gas, including the greenhouse gas carbon dioxide. This catastrophic chain reaction would have altered the chemistry of the oceans, increasing their acidity. Brachiopods would have been particularly hard hit by the change, Payne said. “Bivalves have gills and an active circulatory system, while brachiopods don’t. That means that in general, bivalves are more effective at regulating their internal chemistries relative to the external environment.”

Bivalves would have also been in a better position to take advantage of the new food sources that became available as life recovered from the mass extinction event. More creatures were becoming mobile, and brachiopods, which are largely stationary and filter feed on floating organic debris, would have been less able to capitalize on this shift. Meanwhile, bivalves such as clams were becoming more proficient at moving around by quickly opening and closing their shells or using their muscular foot to burrow. Increased mobility gave bivalves an edge not only over brachiopods, but likely other organisms as well, such as microbes. “What we see is that more mobile organisms tend to be better in the post-Paleozoic,” Payne said.

The new findings cast the fate of the two groups in a new light: Bivalves didn’t outcompete brachiopods by getting better at obtaining the food sources that the two groups shared. Rather, their physiological differences enabled them to branch out and take advantage of other food resources in ways that brachiopods simply couldn’t follow.

J. L. Payne, N. A. Heim, M. L. Knope, C. R. McClain. Metabolic dominance of bivalves predates brachiopod diversity decline by more than 150 million years. Proceedings of the Royal Society B: Biological Sciences, 2014; 281 (1783): 20133122 DOI: 10.1098/rspb.2013.3122

Computer models solve geologic riddle millions of years in the making

March 25th, 2014

Riffin

An international team of scientists that included USC’s Meghan Miller used computer modeling to reveal, for the first time, how giant swirls form during the collision of tectonic plates — with subduction zones stuttering and recovering after continental fragments slam into them.

The team’s 3D models suggest a likely answer to a question that has long plagued geologists: why do long, curving mountain chains form along some subduction zones — where two tectonic plates collide, pushing one down into the mantle?

Based on the models, the researchers found that parts of the slab that is being subducted sweep around behind the collision, pushing continental material into the mountain belt.

With predictions confirmed by field observations, the 3D models show a characteristic pattern of intense localized heating, volcanic activity and fresh sediments that remained enigmatic until now.

Computer model of typical mantle flow patterns.
Credit: Courtesy of Louis Moresi/Monash University

“The new model explains why we see curved mountains near colliding plates, where material that has been scraped off of one plate and accreted on another is dragged into a curved path on the continent,” Miller said.

Miller collaborated with lead author Louis Moresi from Monash University and his colleagues Peter Betts (also from Monash) and R. A. Cayley from the Geological Survey of Victoria in Australia. Their research was published online by Nature on March 23.

Their research specifically looked at the ancient geologic record of Eastern Australia, but is also applicable to the Pacific Northwest of the United States, the Mediterranean, and southeast Asia. Coastal mountain ranges from Northern California up to Alaska were formed by the scraping off of fragment of the ancient Farallon plate as it subducted beneath the North American continent. The geology of the Western Cordillera (wide mountain belts that extend along all of North America) fits the predictions of the computer model.

“The amazing thing about this research is that we can now interpret arcuate-shaped geological structures on the continents in a whole new way,” Miller said. “We no longer need to envision complex motions and geometries to explain the origins of ancient or modern curved mountain belts.”

The new results from this research will help geologists interpret the formation of ancient mountain belts and may prove most useful as a template to interpret regions where preservation of evidence for past collisions is incomplete — a common, and often frustrating, challenge for geologists working in fragmented ancient terrains.

Moresi was funded by the Australian Research Council and Miller was funded by NSF CAREER award.

Fern Fossil Contains Unique chromosomes

March 23rd, 2014

Riffin

Researchers from Lund University and the Swedish Museum of Natural History have made a unique discovery in a well-preserved fern that lived 180 million years ago. Both undestroyed cell nuclei and individual chromosomes have been found in the plant fossil, thanks to its sudden burial in a volcanic eruption.

The well-preserved fossil of a fern from the southern Swedish county of Skåne is now attracting attention in the research community. The plant lived around 180 million years ago, during the Jurassic period, when Skåne was a tropical region where the fauna was dominated by dinosaurs, and volcanoes were a common feature of the landscape. The fossilised fern has been studied using different microscopic techniques, X-rays and geochemical analysis. The examinations reveal that the plant was preserved instantaneously, before it had started to decompose. It was buried abruptly under a volcanic lava flow.

“The preservation happened so quickly that some cells have even been preserved during different stages of cell division,” said Vivi Vajda, Professor of Geology at Lund University.

Thanks to the circumstances of the fern’s sudden death, the sensitive components of the cells have been preserved. The researchers have found cell nuclei, cell membranes and even individual chromosomes. Such structures are extremely rare finds in fossils, observed Vivi Vajda.

“This naturally leads us to think that there must be more to discover. It isn’t hard to imagine what else could be encapsulated in the lava flows at Korsaröd in Skåne,” said Vivi Vajda.

This is a fern fossil.
Credit: Benjamin Bomfleur

Professor Vajda has carried out the study with two researchers from the Swedish Museum of Natural History, Benjamin Bomfleur and Stephen McLoughlin. The fern belonged to the family Osmundaceae, Royal Ferns. In modern times, royal ferns grow in the wild in Sweden and are also a common garden plant. Living representatives of this family are very similar in appearance to the Jurassic fossil, which suggests that only limited evolutionary change has taken place over the millennia. By comparing the size of the cell nuclei in the fossilised plant with its living relatives, the researchers have been able to show that the royal ferns have outstanding evolutionary stability.

“Royal Ferns look essentially the same now as they did during the Jurassic Period, and are therefore an excellent example of what we call a living fossil,” said Vivi Vajda.

Professor Vajda has also dated the rocks surrounding the fossil by studying pollen and spores preserved in these rocks. Their analysis revealed that the lava flows are around 180 million years old, from the early Jurassic Period. These results have considerably refined previous radiometric dating conducted on nearby volcano cones. In addition, the research study shows that spores from royal ferns, as well as pollen from coniferous trees, including cypress and cycad, are found in large quantities in the volcanic rock. This is evidence of varied vegetation and a hot, humid climate at the time when the area was engulfed by a disastrous volcanic eruption.

The unique fern fossil was collected in the 1960s, near Korsaröd in central Skåne, by farmer Gustav Andersson who donated the fossil to the Swedish Museum of Natural History. The fossil remained forgotten in the museum’s collections for over 40 years before it came to the attention of the researchers. The research findings have now been published in the latest issue of the journal Science.

After major earthquake, silence: Dynamic stressing of a global system of faults results in rare seismic silence

March 21st, 2014

Riffin

In the global aftershock zone that followed the major April 2012 Indian Ocean earthquake, seismologists noticed an unusual pattern — a dynamic “stress shadow,” or period of seismic silence when some faults near failure were temporarily rendered incapable of a large rupture.

The magnitude (M) 8.6 earthquake, a strike-slip event at intraoceanic tectonic plates, caused global seismic rates of M≥4.5 to spike for several days, even at distances tens of thousands of kilometers from the mainshock site. But beginning two weeks after the mainshock, the rate of M≥6.5 seismic activity subsequently dropped to zero for the next 95 days.

Why did this rare period of quiet occur?

In a paper published today in the Bulletin of the Seismological Society of America (BSSA), Fred Pollitz of the U.S. Geological Survey and co-authors suggests that the Indian Ocean earthquake caused short-term dynamic stressing of a global system of faults. Across the planet, there are faults that are “close to failure” and ready to rupture. It may be, suggests Pollitz and his colleagues, that a large quake encourages short-term triggering of these close-to-failure faults but also relieves some of the stress that has built up along these faults. Large magnitude events would not occur until tectonic movement loads stress back on to the faults at the ready-to-fail levels they reached before the main shock.

Using a statistical model of global seismicity, Pollitz and his colleagues show that a transient seismic perturbation of the size of the April 2012 global aftershock would inhibit rupture in 88 percent of their possible M≥6.5 earthquake fault sources over the next 95 days, regardless of how close they were to failure beforehand.

This surprising finding, say the authors, challenges the previously held notion that dynamic stresses can only increase earthquake rates rather than inhibit them. But there are still mysteries about this process; for example, the global rate of M≥4.5 and M≥5.5 shocks did not decrease along with the larger shocks.

Source: Seismological Society of America. “After major earthquake, silence: Dynamic stressing of a global system of faults results in rare seismic silence.” ScienceDaily. ScienceDaily, 11 March 2014. <www.sciencedaily.com/releases/2014/03/140311124319.htm>.

Oldest fossil evidence of modern African venomous snakes found in Tanzania

March 20th, 2014

Riffin

Ohio University scientists have found the oldest definitive fossil evidence of modern, venomous snakes in Africa, according to a new study published March 19 in the journal PLOS ONE.

The newly discovered fossils demonstrate that elapid snakes — such as cobras, kraits and sea snakes — were present in Africa as early as 25 million years ago, said lead author Jacob McCartney, a postdoctoral researcher in the Ohio University Heritage College of Osteopathic Medicine. He’s part of a team that has been examining the Rukwa Rift Basin of Tanzania over the last decade to understand environmental change through time in the East African Rift System.

Elapids belong to a larger group of snakes known as colubroids, active foragers that use a variety of methods, including venom, to capture and kill prey.

Colubroid fossils are documented as early as 50 million years ago. But they weren’t expected to constitute such a large part of the African snake fauna 25 million years ago, as they became dominant in Europe and North America much later.

“In the Oligocene epoch, from about 34 to 23 million years ago, we would have expected to see a fauna dominated by booid snakes, such as boas and pythons. These are generally ‘sit and wait’ constricting predators that hide and ambush passing prey,” McCartney said.

In fact, the recent study includes a description of the oldest evidence of African booid snakes, he said. The researchers have named this new species Rukwanyoka holmani; the genus name combines the Rukwa region name with the Swahili word for snake, and the species name is in honor of J. Alan Holman, a paleontologist and mentor.

Scientists have found the oldest definitive fossil evidence of modern, venomous snakes in Africa.
Credit: Image courtesy of Ohio University

However, the team was surprised to discover that the fauna actually revealed more colubroids than booids. That higher-than-expected concentration of colubroid snakes suggests that the local environment became more open and seasonally dry — and, in turn, more hospitable to these active foraging types of snakes that don’t require cover to hide and ambush prey — at an earlier time in Africa than in most other parts of the world, as documented in previous studies.

“This finding gives further strength to the idea that tectonic activity in the East African Rift has helped to shape animal habitats in fascinating ways,” said Nancy Stevens, an associate professor of biomedical sciences at Ohio University and co-author of the study. “The fossils suggest a fundamental shift toward more active and potentially venomous snakes that could exert very different pressures on the local fauna.”

More fossils from additional locations should indicate whether colubroid snakes dominated all of Africa during the Oligocene or just the local region around the Rukwa Rift, McCartney said.

The study published in PLOS ONE describes eight different types of fossil snakes from the Rukwa Rift (five colubroid and three booid), with vertebrae ranging in length from 2.6 mm to just over 5 mm.

A Diminutive New Tyrannosaur from the Top of the World

March 19th, 2014

Riffin

Tyrannosaurid theropods were dominant terrestrial predators in Asia and western North America during the last of the Cretaceous. The known diversity of the group has dramatically increased in recent years with new finds, but overall understanding of tyrannosaurid ecology and evolution is based almost entirely on fossils from latitudes at or below southern Canada and central Asia. Remains of a new, relatively small tyrannosaurine were recovered from the earliest Late Maastrichtian (70-69Ma) of the Prince Creek Formation on Alaska’s North Slope. Cladistic analyses show the material represents a new tyrannosaurine species closely related to the highly derived Tarbosaurus+Tyrannosaurus clade. The new taxon inhabited a seasonally extreme high-latitude continental environment on the northernmost edge of Cretaceous North America. The discovery of the new form provides new insights into tyrannosaurid adaptability, and evolution in an ancient greenhouse Arctic.

: Relative size of Nanuqsaurus hoglundi.
Silhouettes showing approximate sizes of representative theropods. A, Nanuqsaurus hoglundi, based on holotype, DMNH 21461. B, Tyrannosaurus rex, based on FMNH PR2081. C, Tyrannosaurus rex, based on AMNH 5027. D, Daspletosaurus torosus, based on FMNH PR308; E, Albertosaurus sarcophagus, based on TMP 81.10.1; F, Troodon formosus, lower latitude individual based on multiple sources and size estimates; G, Troodon sp., North Slope individual based on extrapolation from measurements of multiple dental specimens [47]. Scale bar equals 1 m.
doi:10.1371/journal.pone.0091287.g008

Nanuqsaurus hoglundi, holotype, DMNH 21461. A
. Reconstruction of a generalized tyrannosaurine skull, with preserved elements of holotype shown in white. Arrow points to autapomorphic, reduced, first two dentary teeth. B–E. Photographs and interpretive line drawings of right maxilla piece in medial (B, C); and dorsal (D, E) views. F–I. Photographs and interpretive line drawings of partial skull roof in dorsal (F, G); and rostrolateral (H, I) views. J–M, partial left dentary in lateral (J); medial (K); dorsal (L) views; and close-up of mesial alveoli in dorsal (M) views. Abbreviations: a, alveolus, with number indicating position in tooth row; d, dentary tooth, with number indicating position in tooth row; f, frontal; gr, orbital groove; lac.f, lacrimal facet of frontal; l.f, left frontal; na, nasal contact surface; oif, oral intramandibular foramen; p, parietal; po.f, postorbital facet of frontal; prf.f, prefrontal facet of frontal;. r.f, right frontal; ri, ridge separating sockets in nasal articulation of maxilla; rpf, rostral process of frontal between prefrontal and lacrimal facets; rsp, rostral spur of parietal; sac, sagittal crest; so, socket for nasal articulation of maxilla; stf; supratemporal fossa. Gray fill indicates missing bone or broken bone surfaces and cracks. Scale bar in A equals 10 cm. Scale bars in B–L equal 5 cm. Scale bar in M equals 1 cm.
doi:10.1371/journal.pone.0091287.g003

Nanuqsaurus hoglundi, holotype DMNH 21461, CT slice through partial left dentary.
Parasagittal CT scan slice through the partial left dentary shows several replacement teeth remaining in alveoli. This slice shows parts of cross-sections through replacement teeth in the first and second alveoli, verifying their identity. Abbreviations: a, alveolus, with number indicating position in tooth row; d3, base of partially erupted third dentary tooth, r, replacement tooth (unerupted), with number indicating position in tooth row.
doi:10.1371/journal.pone.0091287.g005

Citation: Fiorillo AR, Tykoski RS (2014) A Diminutive New Tyrannosaur from the Top of the World. PLoS ONE 9(3): e91287. doi:10.1371/journal.pone.0091287 Editor: Peter Dodson, University of Pennsylvania, United States

‘Steak-knife’ teeth reveal ecology of oldest land predators

March 18th, 2014

Riffin

The first top predators to walk on land were not afraid to bite off more than they could chew, a University of Toronto Mississauga study has found.

Graduate student and lead author Kirstin Brink along with Professor Robert Reisz from U of T Mississauga’s Department of Biology suggest that Dimetrodon, a carnivore that walked on land between 298 million and 272 million years ago, was the first terrestrial vertebrate to develop serrated ziphodont teeth.

According to the study published in Nature Communications, ziphodont teeth, with their serrated edges, produced a more-efficient bite and would have allowed Dimetrodon to eat prey much larger than itself.

While most meat-eating dinosaurs possessed ziphodont teeth, fossil evidence suggests serrated teeth first evolved in Dimetrodon some 40 million years earlier than theropod dinosaurs.

“Technologies such as scanning electron microscope (SEM) and histology allowed us to examine these teeth in detail to reveal previously unknown patterns in the evolutionary history of Dimetrodon,” Brink said.

The four-meter-long Dimetrodon was the top of the terrestrial food chain in the Early Permian Period and is considered to be the forerunner of mammals.

This is a Dimetrodon skull with histological thin section tooth detail by Danielle Dufault.
Credit: Danielle Dufault

According to Brink and Reisz’s research, Dimetrodon had a diversity of previously unknown tooth structures and were also the first terrestrial vertebrate to develop cusps — teeth with raised points on the crown, which are dominant in mammals.

The study also suggests ziphodont teeth were confined to later species of Dimetrodon, indicating a gradual change in feeding habits.

“This research is an important step in reconstructing the structure of ancient complex communities,” Reisz said.

“Teeth tell us a lot more about the ecology of animals than just looking at the skeleton.”

“We already know from fossil evidence which animals existed at that time but now with this type of research we are starting to piece together how the members of these communities interacted.”

Brink and Reisz studied the changes in Dimetrodon teeth across 25 million years of evolution.

The analysis indicated the changes in tooth structure occurred in the absence of any significant evolution in skull morphology. This, Brink and Reisz suggest, indicates a change in feeding style and trophic interactions.

“The steak knife configuration of these teeth and the architecture of the skull suggest Dimetrodon was able to grab and rip and dismember large prey,” Reisz said.

“Teeth fossils have attracted a lot of attention in dinosaurs but much less is known about the animals that lived during this first chapter in terrestrial evolution.”

Journal Reference:

Kirstin S. Brink, Robert R. Reisz. Hidden dental diversity in the oldest terrestrial apex predator Dimetrodon. Nature Communications, 2014; 5 DOI: 10.1038/ncomms4269

Cotylocara macei: A New Fossil Species shows evidence of echolocation

March 16th, 2014

Riffin

Research led by an anatomy professor at New York Institute of Technology College of Osteopathic Medicine indicates that echolocation — the sonar-like system based on high-frequency vocalizations and their echoes — was present in a 28-million-year old relative of modern-day toothed whales, dolphins, and porpoises.

Associate Professor Jonathan Geisler led the study of a new fossil species, Cotylocara macei, discovered near Charleston, SC. His findings, together with those of co-authors Matthew Colbert (University of Texas at Austin) and James Carew (College of Charleston), were published online today in the journal Nature.

“The most important conclusion of our study involves the evolution of echolocation and the complex anatomy that underlies this behavior,” said Geisler. “This was occurring at the same time that whales were diversifying in terms of feeding behavior, body size, and relative brain size.”

Toothed whales, dolphins, and porpoises produce their high-frequency vocalizations through a constricted area in the nasal passages below the blowhole, while all other mammals, including humans, produce sounds in the larynx. The sound-producing mechanism in toothed whales is complex, with large muscles, air pockets, and bodies of fat all packed into a small area in the face.

Scientists have long-studied how complex adaptations evolve, and new fossil discoveries often reveal that adaptations evolve in a step-wise fashion, often over long periods of geologic time.

The skull of the 28-million-year-old Cotylocara macei. Its anatomy and density variation indicate that this early toothed whale used echolocation to find its prey.
Credit: James Carew and Mitchell Colgan

Geisler said their study of the skull of Cotylocara macei has led them to conclude that this whale echolocated.

“Its dense bones and air sinuses would have helped this whale focus its vocalizations into a probing beam of sound, which likely helped it find food at night or in muddy water ocean waters,” said Geisler.

NYIT’s College of Osteopathic Medicine’s whale evolution website includes a new page on Cotylocara.

After detailed comparisons with living and fossil whales, Geisler and his colleagues determined that Cotylocara belonged to an extinct family of whales that split off from other whales at least 32 million years ago. Their new discovery, when viewed in the context of the entire toothed whale family tree, implies that a rudimentary form of echolocation evolved in the common ancestor of Cotylocara and other toothed whales, between 35 and 32 million years ago. Once it evolved, the fossil record indicates that there was a progressive increase in size and complexity in the air sacs and muscles that controlled the sound generating apparatus in the face.

Cotylocara had some unique features, says Geisler, including a deep cavity on the top of its head (leading to its name, loosely translated as “cavity head”) for an air sinus that that stored air while diving and may have reflected sound generated in the face. There is also a radar-dish-like shelf of bone around the nasal openings that could have reflected sound and improved its echolocation ability.

“The anatomy of the skull is really unusual. I’ve not seen anything like this in any other whale, living or extinct” Geisler said.

New fossil species reveals parental care of young from 450 million years ago

March 15th, 2014

Riffin

A portrait of prehistoric parenthood captured deep in the fossil record has been uncovered by an international team of scientists led by University of Leicester geologist Professor David Siveter.

The ‘nursery in the sea’ has revealed a species new to science — with specimens preserved incubating their eggs together with probable hatched individuals. As a result, the team has named the new species Luprisca incuba after Lucina, goddess of childbirth, and alluding to the fact that the fossils are ancient and in each case the mother was literally sitting on her eggs.

The find, published in the journal Current Biology, provides conclusive evidence of a reproductive and brood-care strategy conserved for at least 450 million years. It also represents the oldest confirmed occurrence of ostracods in the fossil record.

Professor Siveter, Emeritus Professor of Palaeontology at the University of Leicester, said: “This a very rare and exciting find from the fossil record. Only a handful of examples are known where eggs are fossilized and associated with the parent. This discovery tells us that these ancient tiny marine crustaceans took particular care of their brood in exactly the same way as their living relatives.”

This is the ostracod Luprisca incuba, showing limbs and eggs, from 450 million-year old-rocks of New York State, USA.
Credit: Siveter, David J., Tanaka, G., Farrell, C. Ú., Martin, M.J., Siveter, Derek J & Briggs, D.E.G.

The team from the UK, USA and Japan has discovered a new and scientifically important species of a fossil ostracod- an animal group related to shrimps, lobsters and crabs — in mudstone rocks from New York State, USA, dating back to the Ordovician period of geological time. Ostracods are tiny crustaceans known from thousands of living species in oceans to rivers, lakes and ponds today and from countless fossil shells.

The newly discovered fossils are two to three millimetres long and are especially informative because they are exceptionally well preserved, complete with not only the shell but also the soft parts of the animal that in all but very rare cases are lost to the fossil record. Limbs and in some specimens a clutch of eggs are present within the bivalved shell, enabling the scientists to identify and gender such specimens. These anatomical features were preserved in the mineral pyrite, which facilitated the use of x-ray techniques to reveal morphological details hidden within the shells and the rock.

Professor Siveter, of the University of Leicester’s Department of Geology, together with researchers from the universities of Yale and Kansas, USA, Oxford, UK, and the Japan Agency of Marine Science and Technology, discovered the tiny arthropods.

The ostracods lived, together with other invertebrate animals such as trilobites, in poorly oxygenated conditions in a sea bordering the margins of the ancient North American continent. Professor Siveter said that, like their modern relatives, the ostracods were probably capable of swimming near the sea bed and obtained their food by scavenging and hunting.

First animals oxygenated Earth’s oceans, study suggests

March 10th, 2014

Riffin

The evolution of the first animals may have oxygenated Earth’s oceans — contrary to the traditional view that a rise in oxygen triggered their development.

New research led by the University of Exeter contests the long held belief that oxygenation of the atmosphere and oceans was a pre-requisite for the evolution of complex life forms.

The study, published in the journal Nature Geoscience, builds on the recent work of scientists in Denmark who found that sponges — the first animals to evolve — require only small amounts of oxygen.

Professor Tim Lenton of the University of Exeter, who led the new study, said: “There had been enough oxygen in ocean surface waters for over 1.5 billion years before the first animals evolved, but the dark depths of the ocean remained devoid of oxygen. We argue that the evolution of the first animals could have played a key role in the widespread oxygenation of the deep oceans. This in turn may have facilitated the evolution of more complex, mobile animals.”

The researchers considered mechanisms by which the deep ocean could have been oxygenated during the Neoproterozoic Era (from 1,000 to 542 million years ago) without requiring an increase in atmospheric oxygen.

Crucial to determining oxygen levels in the deep ocean is the balance of oxygen supply and demand. Demand for oxygen is created by the sinking of dead organic material into the deep ocean. The new study argues that the first animals reduced this supply of organic matter — both directly and indirectly.

Sponges feed by pumping water through their bodies, filtering out tiny particles of organic matter from the water, and thus helping oxygenate the shelf seas that they live in. This naturally selects for larger phytoplankton — the tiny plants of the ocean — which sink faster, also reducing oxygen demand in the water.

By oxygenating more of the bottom waters of shelf seas, the first filter-feeding animals inadvertently increased the removal of the essential nutrient phosphorus in the ocean. This in turn reduced the productivity of the whole ocean ecosystem, suppressing oxygen demand and thus oxygenating the deep ocean.

Sponges were the first animals to evolve and may have helped drive oceanic oxygenation in the Neoproterozoic through their active pumping and filter-feeding activities.
Credit: Nicholas J. Butterfield

A more oxygen-rich ocean created ideal conditions for more mobile animals to evolve, because they have a higher requirement for oxygen. These included the first predatory animals with guts that started to eat one another, marking the beginning of a modern marine biosphere, with the type of food webs we are familiar with today.

Professor Lenton added: “The effects we predict suggest that the first animals, far from being a passive response to rising atmospheric oxygen, were the active agents that oxygenated the ocean around 600 million years ago. They created a world in which more complex animals could evolve, including our very distant ancestors.”

Professor Simon Poulton of the University of Leeds, who is a co-author of the study, added: ″This study provides a plausible mechanism for ocean oxygenation without the requirement for a rise in atmospheric oxygen. It therefore questions whether the long-standing belief that there was a major rise in atmospheric oxygen at this time is correct. We simply don’t know the answer to this at present, which is ultimately key to understanding how our planet evolved to its current habitable state. Geochemists need to come up with new ways to decipher oxygen levels on the early Earth.″