WFS News: Strange reptile fossil (Drepanosaurus) puzzles scientists

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A 200-million-year-old reptile is rewriting the rulebooks on how four-legged animals conquered the world.Newly discovered fossils suggest Drepanosaurus had huge hooked claws to dig insects from bark, much like today’s anteaters in the forests of Central and South America.Scientists say the creature defies the convention on how reptiles evolved and flourished.

Drepanosaurus ripped away tree bark with a massive claw to get at hidden insects

Drepanosaurus ripped away tree bark with a massive claw to get at hidden insects

Their research is published in the journal Current Biology.

The new fossils, found in a New Mexico quarry, suggest Drepanosaurus was the size of a cat and lived in the trees.It had a bird-like head on a chameleon-like body, but the most unusual feature was its forearms, said Dr Adam Pritchard, of Yale University, who led the research.

Massive arms

Drepanosaurus itself has extremely massive arms and forearms – very muscular,” he said.

“The index finger is much much larger than any of the other fingers and supports this gigantic claw, which is easily the most massive bone of the entire arm.”

The forelimbs of tetrapods are known for their versatility, used to walk, dig, fly or swim.However, the basic plan of the forelimb has stayed much the same throughout 375 million years of evolution.

“The arm of tetrapod animals almost always follows some very consistent rules,” Dr Pritchard said.

Melting pot

The US team made 3D reconstructions of the reptile based on micro-CT (computerised tomography) scans of dozens of bones.

Other fossils that have been unearthed were partly crushed, making interpretation difficult.

The Pygmy anteater has similar adaptations for digging

  The Pygmy anteater has similar adaptations for digging

“In your forearm, in the forearm of Tyrannosaurus rex, in the forearm of an elephant, you have two bones – the radius and the ulna, which manifest as these elongate, slender, parallel shafts,” he explained.

But the Drepanosaurus did not have these parallel bones.

“So all of these consistent patterns that we see across a huge range of tetrapods, regardless of their ecology, regardless of their ancestry, are violated by this animal,” Dr Pritchard said.

“On the one hand, it extends the bounds of what we think the arm of tetrapod animals – those four-footed animals in the world – is capable of in terms of its development, in terms of evolution.

“And, it is also remarkable in what it evidences about the ecology, the lifestyle of the animal, in that it seems to have quite independently developed adaptations that we see today in modern groups like anteaters.”

Palaeontologist Dr Nicholas Fraser, of National Museums Scotland said the Triassic period was a “melting pot of experimentation”.

“The unconventional rules in the Triassic,” he said.

“Here is another animal which is completely unconventional in the way it has got this system of bones in the limb to help it dig – those are massive claws too.”

Invaded land

Drepanosaurus disappeared at the end of the Triassic and did not lend its form to any future creatures.

“It was only useful in this one particular instance, where you have got a really specialised fossorial animal – a digger,” Dr Fraser said.

“But it is the first real departure like this in the basic ground plan that you see ever since the first tetrapods invaded land 365 million years ago.”

The researchers say they are continuing to excavate the quarries in New Mexico, with the hope of finding more discoveries.

“There’s a lot – especially in terms of the smaller animals in the fossil record – that has remained undiscovered,” said Dr Pritchard. “I don’t see an end to it.”

Source: Article By 

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WFS News: Triopticus shows dinosaurs copied body, skull shapes of distant relatives

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Iconic dinosaur shapes were present for at least a hundred million years on our planet in animals before those dinosaurs themselves actually appeared.

In a study in today’s (Sept. 22) issue of Current Biology, a multi-institutional team of paleontologists including Virginia Tech College of Science researcher Michelle Stocker have identified and named a new species of extinct reptile estimated to be 230 million years old — predating dinosaurs.

Called Triopticus primus — meaning the “First of Three Eyes” because the large natural pit in the top of its head lends the appearance of an “extra”eye — Triopticus bears an extremely thickened skull roof, just like the very distantly related pachycephalosaur dinosaurs that lived more than 100 million years later. And even more unexpected, many of the other extinct animals found with Triopticus resemble later dinosaurs as well.

“Triopticus is an extraordinary example of evolutionary convergence between the relatives of dinosaurs and crocodylians and later dinosaurs that is much more common than anyone ever expected,” Stocker said. “What we thought were unique body shapes in many dinosaurs actually evolved millions of years before in the Triassic Period, about 225 million years ago.”

Convergence — where distantly related animals evolve to look very similar to each other — is a widely-recognized phenomenon in evolutionary biology. A classic example of this is a bird wing and a bat wing — both animals use their wings for flight, but the inner details of those wings are different and evolved independently.

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The preserved remains of Triopticus (left) show the evolution of a thickened domed skull in the Triassic Period, 150 million years before the evolution of the famous dome-headed pachycephalosaur dinosaurs, such as Stegoceras (right). The background image shows the field site in Texas where Works Progress Administration crews in 1940 found the curious fossils of Triopticus. Credit: Virginia Tech

The preserved remains of Triopticus (left) show the evolution of a thickened domed skull in the Triassic Period, 150 million years before the evolution of the famous dome-headed pachycephalosaur dinosaurs, such as Stegoceras (right). The background image shows the field site in Texas where Works Progress Administration crews in 1940 found the curious fossils of Triopticus. Credit: Virginia Tech

Many of the other Triassic reptiles buried with Triopticus in the Otis Chalk fauna display structures that are easily recognized in later dinosaurs as well, such as the long snouts of Spinosaurus, the toothless beaks of ornithomimids, and the armor plates of ankylosaurs. Researchers said it is extremely rare to have so many diverse species in a single ancient community be converged upon over a broad swath of later geologic time.

“The Otis Chalk fauna is an amazing single snapshot of geologic time where you have this extraordinary range of animal body plans all present at the same time living together,” Stocker said. “Among the animals preserved in the Otis Chalk fauna, Triopticus exemplifies this phenomenon of body-shape convergence because its skull shape was repeated by very distantly-related dome-headed dinosaurs more than 100 million years later.”

Dinosaurs, like these distant cousins from the Triassic Period, are all reptiles. Reptiles rapidly evolved in terms of numbers of species soon after the greatest mass extinction of all time on Earth, at the end of the Permian Period.

“After the enormous mass extinction 250 million years ago, reptiles exploded onto the scene and almost immediately diversified into many different sizes and shapes. These early body shapes were later mimicked by dinosaurs,” said Sterling Nesbitt, an assistant professor of paleontology at Virginia Tech and co-author of the study. The mimicry in body shape appears to evolve only after the extinction of the first group of reptiles.

Researchers said an important component of the study involved the use of CT technology, more commonly associated with patients, not fossils.

The specimen underwent a detailed CT scan at The University of Texas at Austin in order to reconstruct the brain anatomy, which had been rotted away millions of years ago when the animal was fossilized.

“This project combines both old-school and high-tech approaches,” said co-author Lawrence Witmer of Ohio University’s Heritage College of Osteopathic Medicine. “Careful excavation and cleaning of the fossils showed the team that we had something special in Triopticus, but being able to peer inside the skull with X-ray CT scanning was a game-changer.”

Not only is the external skull shape of Triopticus eerily reminiscent of the dome-headed dinosaurs, the internal parts of its head followed suit.

“CT scanning showed us that the similarity of Triopticus with the much later dome-headed pachycephalosaur dinosaurs was more than skin deep, extending to the structure of the bone and even the brain.” Witmer said.

“With a combination of CT scans and fossil comparisons we were able to give this old fossil new life,” said Katharine Criswell, a co-author and doctoral student at the University of Chicago.

Complete details of what Triopticus primus looked like and how big it was are not yet known, though it was likely no bigger than an alligator. For now, researchers only have a fragment of skull. The remainder of the face and jaw, the vertebrae, and the rest of the skeleton is missing, either long lost to natural elements, waiting to be found in the field still, or inside a plaster jacket not yet opened at the lab at UT Austin.

Though many fossils are uncovered during long stints of dusty fieldwork in far-off places, the team’s discovery of this specimen — originally collected near Big Spring, Texas, by the Works Progress Administration in 1940 — happened in the Texas Vertebrate Paleontology Collections in 2010, where it had been lying in plain sight for 70 years.

It is not uncommon for new species to be found in fossil ‘libraries’ around the world. The Works Progress Administration, part of Franklin D. Roosevelt’s monumental effort to put Americans back to work at end the Great Depression, found so many fossils during its short span of work that they didn’t have time to clean all of them.

“We can gain new insights into the history of life because specimens like Triopticus have been curated into museum collections like the one at UT Austin,” said Matthew Brown, co-author and director of the Texas Vertebrate Paleontology Collections at The University of Texas at Austin. “These collections are the foundation of natural history research, and this new animal illustrates how exciting discoveries are continually made thanks to the forethought and investment of past generations. It will be fascinating to see what the students of tomorrow find next.”

Citation: 1.Current Biology, 2016 DOI:10.1016/j.cub.2016.07.066 , Virginia Tech. “Bizarre new species of extinct reptile shows dinosaurs copied body, skull shapes of distant relatives.” ScienceDaily. ScienceDaily, 22 September 2016. <www.sciencedaily.com/releases/2016/09/160922124308.htm>

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WFS News: Stalagmites may record past earthquakes

Stalagmites rising from the floor of a cave in southern Indiana may contain traces of past earthquakes in the region, according to a report published September 13 in the Bulletin of the Seismological Society of America.

The rock formations in Donnehue’s Cave, and others like them in local caves, could help scientists better understand the history of ancient seismic events in the Wabash Valley fault system of the Midwestern United States, said Samuel Panno, a University of Illinois and Illinois State Geological Survey researcher.

However, the stalagmites also contain traces of past climate events such as glacial flooding, and the BSSA study by Panno and his colleagues demonstrates the importance of untangling climate and seismic effects on stalagmite growth.

Stalagmites grow on cave floors from the accumulation of minerals that are precipitated from mineral-laden waters that drip from a cave ceiling. During this process, small to large stalactites that hang like icicles on the cave ceiling grow in the same manner. Earthquakes can leave their mark on stalagmites by shifting the ground in a way that changes the flow of the drip feeding the stalagmite — closing a crack through which the drip flowed, for instance, or knocking down a stalactite that fed a stalagmite.

“Then when you take a stalagmite and slice it down its middle the long way and open it up like a book,” Panno explained, “you can see these shifts in the axis of its growth.”

Using a variety of dating techniques to determine the age of the stalagmite and any surrounding sediments, scientists can then pinpoint the timing of these growth shifts and compare them to the timing of known earthquakes in an area.

This is a view of the upper passage of Donnehue's Cave showing a ceiling crevice filled with large stalactites, some feeding large stalagmites to the left. A thick flood deposit lies to the right. Credit: Sam Frushour

This is a view of the upper passage of Donnehue’s Cave showing a ceiling crevice filled with large stalactites, some feeding large stalagmites to the left. A thick flood deposit lies to the right.Credit: Sam Frushour

Among the four Donnehue stalagmites in the study, the research team found a twin stalagmite pair that had stopped growing around 100,000 years B.P. and then resumed growing at around 6000 years B.P., overlapping in time with a magnitude 7.1 to 7.3 earthquake in the area. Another younger stalagmite began growing around 1800 years B.P. — coinciding with a magnitude 6.2 earthquake — and showed later shifts in its growth axis that overlap with other seismic events in the nearby New Madrid Seismic Zone.

These older earthquakes are known from other studies of soil shaking triggered by earthquakes, called paleoliquefaction, in ancient sediments. But seismic signs contained within stalagmites could potentially extend the evidence for these historic and prehistoric earthquakes, Panno said.

“Most of the evidence for paleoearthquakes comes from liquefaction features that are fairly easy to date,” he noted. “The problem is that you are doing this in sediments that are usually on the order of several hundred to up to 20,000 years old, so to go beyond that, to get older and older earthquake signatures, we decided to look into caves.”

Stalagmite growth can also be affected by climate change, whether through drying up a drip source or through flooding that can block drip passages, or by smothering or dislodging growing stalagmites. Most of the stalagmites examined in the BSSA study were affected by climate-related events, Panno and his colleagues note.

For instance, some of the stalagmites show shifts in growth patterns that coincide with known episodes of flooding from the melting of glacial ice, and others contain thin layers of silt deposited by these floods. “We’re learning that you have to be really careful in where you sample these things, because the caves in southern Indiana, for example, tended to flood during the Pleistocene,” Panno said. “That flooding can move a stalagmite or knock down the stalactite feeding it and change its drip location.”

Panno is working with U.S. Geological Survey seismologist John Tinsley at other caves in the Midwestern U.S., including Indiana’s well-known tourist attraction Marengo Cave, to find other stalagmites, as well as related fallen stalactites that might bear signs of seismic history. They hope future studies will provide more solid evidence of how these formations could store information on the timing, magnitude and origin of past earthquake activity.

Citation: Seismological Society of America. “Stalagmites in Indiana cave may record past earthquakes.” ScienceDaily. ScienceDaily, 12 September 2016. <www.sciencedaily.com/releases/2016/09/160912132306.htm>.

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WFS News: Laser used to unlock mysteries of fossils

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A researcher from the University of Cambridge is on the Bonavista Peninsula to get a better understanding of what’s left some of the oldest organisms in the history of life on earth.Paleontologist Emily Mitchell is using a hand-held laser to map thousands of large, complex fossils — dating from about 560 million years ago — along the coastline in Little Catalina.

Paleontologist Emily Mitchell from the University of Cambridge next to a fractofusus fossil at Watern Cove, Mistaken Point. (Submitted by Emily Mitchell)

Paleontologist Emily Mitchell from the University of Cambridge next to a fractofusus fossil at Watern Cove, Mistaken Point. (Submitted by Emily Mitchell)

“They’re very complicated and they’re very large, they can be up to a metre long and they’re really, really weird-looking,” Mitchell told CBC Radio’s Central Morning Show.

“They don’t look like animals, and they don’t look like plants, and they don’t look like fungi or mushrooms and as a result it’s very hard to work out what they actually were.”

Mitchell said the fossils are “incredibly important.”

Emily Mitchell, as well as other researchers, are mapping fossils along the coastline in Little Catalina. (Submitted by Emily Mitchell)

Emily Mitchell, as well as other researchers, are mapping fossils along the coastline in Little Catalina. (Submitted by Emily Mitchell)

“This is the first time that we see large things that probably are the precursors to animals actually appearing.”

Mitchell shipped 150 kilograms of equipment from the U.K. in order to record the fossil surface, including a generator and the laser scanner which is mounted on a tripod with a mechanical arm.

“It records the fossil surface to very, very small detail, we can get .05 of a millimetre so that’s very, very small.”

That detail is important because the fossils are incredibly difficult to photograph.

A fractosusus fossil in Mistaken Point Ecological Reseve. (Submitted by Emily Mitchell)

A fractosusus fossil in Mistaken Point Ecological Reseve. (Submitted by Emily Mitchell)

“They’re not very deep into rock so photographs have to wait for the exact perfect light to capture them so it’s quite difficult and that perfect light can only last for half an hour an hour on some surfaces,” said Mitchell.

The equipment records the fossils, which are not allowed to be moved, exactly where they are on the rockface.

The laser can also capture the entire surface of the rock, and pick up details researchers wouldn’t necessarily be able to see at the site.

Months of work ahead

Mitchell’s specialty involves looking at the spatial positions of fossils.

“These creatures didn’t move around, so the place where they are on the rockface encapsulates their entire life history, so how they reproduced, how they interacted with neighbours and local environment,” she said.

By combining the scans and statistical analysis, researchers can compare the spatial positions of the fossils on the rock-face to modern organisms to work out biological facts, such as how they reproduced.Mitchell has a lot of work to do once she gets back to the lab.

This fossil scan from Little Catalina contains some Ivesheadiomorphs, fronds and holdfast discs. (Submitted by Emily Mitchell)

This fossil scan from Little Catalina contains some Ivesheadiomorphs, fronds and holdfast discs. (Submitted by Emily Mitchell)

“There’ll probably be a couple months of putting all the scans together and marking out all the fossils and then a couple more months at least before we start getting an idea of what the spatial patterns are and what they’re saying to us.”

During the three weeks spent in Newfoundland, Mitchell and her colleagues from Memorial University and the British Geological Survey will have mapped about 4000 fossils.

Mitchell said the combination of very large surfaces, unique species, and the oldest complex organisms in the fossil record make the area a “brilliant” place to do research.

This field season the team is working around Little Catalina and Mistaken Point.Mitchell said she plans to return next year to continue her research in Port Union, where a rare fossil discovery, coined Haootia quadriformis, was made in 2009

Source: Article by Maggie Gillis, CBC News

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WFS News: 3D Camouflage in a Psittacosaurus Dinosaur

After reconstructing the colour patterns of a well-preserved dinosaur from China, researchers from the University of Bristol have found that the long-lost species Psittacosaurus (meaning “parrot lizard,” a reference to its parrot-like beak) was light on its underside and darker on top.

Psittacosaurus sp. SMF R 4970, Whole Specimen (A) Specimen photographed under crossed polarized light. (B) Interpretative drawing, showing the distribution of pigment patterns, skin, and bones. Green indicates forelimb bones, blue indicates hindlimb bones, purple indicates sacral elements, red indicates cranial elements, and buff yellow indicates vertebral column.

Psittacosaurus sp. SMF R 4970, Whole Specimen
(A) Specimen photographed under crossed polarized light.
(B) Interpretative drawing, showing the distribution of pigment patterns, skin, and bones. Green indicates forelimb bones, blue indicates hindlimb bones, purple indicates sacral elements, red indicates cranial elements, and buff yellow indicates vertebral column.

This colour pattern, known as countershading, is a common form of camouflage in modern animals.The study published today in Current Biology led the researchers to conclude that Psittacosaurus most likely lived in an environment with diffuse light, such as in a forest, and has produced the most life-like reconstruction of a dinosaur ever created.

Dr Jakob Vinther from the Schools of Earth Sciences and Biological Sciences, said: “The fossil, which is on public display at the Senckenberg Museum of Natural History in Germany, preserves clear countershading, which has been shown to function by counter-illuminating shadows on a body, thus making an animal appear optically flat to the eye of the beholder.”

Details of Psittacosaurus sp. SMF R 4970, Photographed under Crossed Polarized Light Overview (A); tail region, showing countershading gradient (B); belly with lighter pigmentation (lower-left corner) and a dorsoventral pigmentation gradient (C); left forelimb with raised clusters of pigmented scales (D); left hindlimb preserving external disruptive patterns and striping on internal leg (E); head with patches of intensely pigmented integument (F); pigmented ischial callosity and cloacal region (G); integument associated with the right leg (H); detail of pigment patterns associated with the proximal tail region, dorsolateral surface (I); pigment patterns associated with the lateral torso (J); and pigment patterns associated with the distal tail region (K). Jb, jugal boss; Pfb, prefrontal boss. Scale bars represent 50 mm (B–G), 20 mm (H), and 10 mm (I–K).

Details of Psittacosaurus sp. SMF R 4970, Photographed under Crossed Polarized Light
Overview (A); tail region, showing countershading gradient (B); belly with lighter pigmentation (lower-left corner) and a dorsoventral pigmentation gradient (C); left forelimb with raised clusters of pigmented scales (D); left hindlimb preserving external disruptive patterns and striping on internal leg (E); head with patches of intensely pigmented integument (F); pigmented ischial callosity and cloacal region (G); integument associated with the right leg (H); detail of pigment patterns associated with the proximal tail region, dorsolateral surface (I); pigment patterns associated with the lateral torso (J); and pigment patterns associated with the distal tail region (K). Jb, jugal boss; Pfb, prefrontal boss. Scale bars represent 50 mm (B–G), 20 mm (H), and 10 mm (I–K).

Behavioural ecologist Professor Innes Cuthill from the School of Biological Sciences, added: “By reconstructing a life-size 3D model, we were able to not only see how the patterns of shading changed over the body, but also that it matched the sort of camouflage which would work best in a forested environment.”

Countershading most likely served to protect Psittacosaurus — an early relative of the triceratop — against predators that use patterns of shadow on an object to determine shape, just as humans do.

Model of Psittacosaurus Based on Skin and Pigmentation Patterns on SMF R 4970 Left lateral view (A), posterior view (B), right lateral view (C), and anterior view (D). See also Data S1 Data S1. 3D Photogrammetric Representation of Psittacosaurus, Related to Figure 3 and S2 Data S2. 3D Photogrammetric Representation of Psittacosaurus Indicating Preserved Regions, Related to Figure 3

Model of Psittacosaurus Based on Skin and Pigmentation Patterns on SMF R 4970
Left lateral view (A), posterior view (B), right lateral view (C), and anterior view (D). See also Data S1
Data S1. 3D Photogrammetric Representation of Psittacosaurus, Related to Figure 3 and S2
Data S2. 3D Photogrammetric Representation of Psittacosaurus Indicating Preserved Regions, Related to Figure 3

Dr Vinther realised that structures previously thought to be artifacts or dead bacteria in fossilized feathers were actually “melanosomes,” small structures that carry melanin pigments found in the feathers and skin of many animals.

In some well-preserved specimens, such as the Psittacosaurusthe researchers worked on in the new study, it’s possible to make out the patterns of preserved melanin without the aid of a microscope.

Professor Innes and colleagues at Bristol had also been exploring the distribution of countershading in modern animals. But it was no easy matter to apply the same principles to an extinct animal that had been crushed flat and fossilized.To explore this idea further they teamed up with local palaeoartist, Bob Nicholls in order to reconstruct the remarkable fossil in to a physical model which, they say, is the most scientifically accurate life-size model of a dinosaur with its real color patterns.

Days of careful studies of the fossil, taking measurements of the bones, studying the preserved scales and the pigment patterns, with input on muscle structure from Bristol palaeontologists Professor Emily Rayfield and Dr Stephan Lautenschlager, led to months of careful modelling of the dinosaur.

Testing Psittacosaurus Countershading in Natural Conditions (A–F) Gray colored cast without bristles attached, imaged under “closed habitat” conditions (A–C) and direct illumination (D–F). The model is shown as imaged in natural environment (A and D), masked (B and E), and in inverse color (C and F). (G and H) Predicted boundaries of rapid transition from dark to light skin for countershading in the diffuse illumination of closed habitats (blue) and of direct lighting in a sunny open habitat (orange). Stippled lines indicate 95% confidence intervals.

Testing Psittacosaurus Countershading in Natural Conditions
(A–F) Gray colored cast without bristles attached, imaged under “closed habitat” conditions (A–C) and direct illumination (D–F). The model is shown as imaged in natural environment (A and D), masked (B and E), and in inverse color (C and F).
(G and H) Predicted boundaries of rapid transition from dark to light skin for countershading in the diffuse illumination of closed habitats (blue) and of direct lighting in a sunny open habitat (orange). Stippled lines indicate 95% confidence intervals.

Bob Nicholls said: “Our Psittacosaurus was reconstructed from the inside-out. There are thousands of scales, all different shapes and sizes, and many of them are only partially pigmented. It was a painstaking process but we now have the best suggestion as to what this dinosaur really looked like.”

In order to investigate what environment the psittacosaur had evolved to live in, Dr Vinther, Bob Nicholls and Professor Cuthill took another cast of the model and painted it all grey.They then placed it in the Cretaceous plant section of Bristol Botanic Garden and photographed it under an open sky and underneath trees to see how the shadow was cast under those conditions.

By comparing the shadow to the pattern in the fossil they could then predict what environment the psittacosaur lived in.

Dr Vinther said: “We predicted that the psittacosaur must have lived in a forest. This demonstrates that fossil colour patterns can provide not only a better picture of what extinct animals looked like, but they can also give new clues about extinct ecologies and habitats.

“We were amazed to see how well these color patterns actually worked to camouflage this little dinosaur.”

Psittacosaurus, which Professor Cuthill describes as “both weird and cute, with horns on either side of its head and long bristles on its tail” lived in the early Cretaceous of China and has been found in the same rock strata where many feathered dinosaurs have been found.Those deposits also include evidence for a forest environment based on plant and wood fossils.

The researchers say that they’d now like to explore other types of camouflage in fossils and to use this evidence in understanding how predators could perceive the environment and to understand their role in shaping evolution and biodiversity.

Courtesy: University of Bristol. “What dinosaurs’ color patterns say about their habitat.” ScienceDaily. ScienceDaily, 16 September 2016. <www.sciencedaily.com/releases/2016/09/160916134251.htm

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WFS News: A Paleolatitude Calculator for Paleoclimate Studies

In the last decade, paleoclimatology has been amongst the most rapidly developing research fields within the Earth Sciences. Crucial information that can be derived from geological records include the relationships between atmospheric chemical composition and global temperature, meridional temperature gradients, and regional and global sea level change, as well as the response of the global exogenic system to perturbations in ocean acidity and oxygenation [1]. Such studies ultimately aim at improving projections of future climate and ecosystem changes resulting from human emissions of carbon and nutrients.

(A) Example of a plate circuit. The motion of India versus Eurasia cannot be directly constrained since these plates are bounded by a destructive plate boundary (trench). Relative motions between these plates can be reconstructed by restoring the opening history of the North Atlantic ocean between Eurasia and North America, the Central Atlantic Ocean between Africa and North America, and the Indian Ocean between India and Africa. With the relative positions of all these plates known through time, a paleomagnetic pole of one of these plates can be used to constrain all of these plates relative to the geodynamo. (B) schematic outline of plate and mantle motions and reference frames. Plates move relative to the mantle (plate tectonics), and plates and mantle together can undergo phases of motion relative to the liquid outer core (true polar wander). Both processes lead to motion of a rock record relative to the Earth’s spin axis, and hence both influence the angle of insolation that is relevant for paleoclimate study. Mantle reference frames A-C (see text for explanation of these frames) can only reconstruct plate motion relative to the mantle, but cannot reconstruct true polar wander. These frames are therefore used for analysis of geodynamics, but should not be used for paleoclimate studies. Instead, a paleomagnetic reference frame should be used. On geological timescales, the geodynamo coincides with the Earth’s spin axis. The orientation of the paleomagnetic field in a rock can be used to restore a rock record into its original paleolatitude relative to the spin axis. http://dx.doi.org/10.1371/journal.pone.0126946.g001

(A) Example of a plate circuit. The motion of India versus Eurasia cannot be directly constrained since these plates are bounded by a destructive plate boundary (trench). Relative motions between these plates can be reconstructed by restoring the opening history of the North Atlantic ocean between Eurasia and North America, the Central Atlantic Ocean between Africa and North America, and the Indian Ocean between India and Africa. With the relative positions of all these plates known through time, a paleomagnetic pole of one of these plates can be used to constrain all of these plates relative to the geodynamo. (B) schematic outline of plate and mantle motions and reference frames. Plates move relative to the mantle (plate tectonics), and plates and mantle together can undergo phases of motion relative to the liquid outer core (true polar wander). Both processes lead to motion of a rock record relative to the Earth’s spin axis, and hence both influence the angle of insolation that is relevant for paleoclimate study. Mantle reference frames A-C (see text for explanation of these frames) can only reconstruct plate motion relative to the mantle, but cannot reconstruct true polar wander. These frames are therefore used for analysis of geodynamics, but should not be used for paleoclimate studies. Instead, a paleomagnetic reference frame should be used. On geological timescales, the geodynamo coincides with the Earth’s spin axis. The orientation of the paleomagnetic field in a rock can be used to restore a rock record into its original paleolatitude relative to the spin axis.
http://dx.doi.org/10.1371/journal.pone.0126946.g001

A crucial aspect of paleoclimate reconstructions based on geological proxy data is a correct representation of paleogeography, notably continent-ocean configuration and latitude. Continent-ocean configuration partially determines the distribution of energy across the Earth’s surface via ocean and atmosphere circulation. To accurately reconstruct past climate change, it is therefore essential to accurately constrain the paleogeographical position of a geological record, sampled at a drill site or an exposed sedimentary section, at the moment of deposition. For instance, a measurable/reconstructable (paleo-)climate parameter that provides key information to compare with theory (i.e., climate models) is the meridional temperature gradient. Many of such paleotemperature gradients have been reconstructed, e.g., for the Eocene [25]. However, for proper interpretation and comparison to numerical model predictions, the precise position, paleolatitude, and geography of the study sites, as well as the uncertainty on such numbers, must be optimally constrained to assess e.g., solar insolation and its position relative to expected ocean and atmosphere circulation patterns that potentially cause regional variations.

To incorporate the effect of plate tectonic changes, the relative motions of plates are reconstructed using marine magnetic anomalies and fracture zones of the ocean floor. Widely used reconstructions in the paleoclimate community are for instance those of Hay and colleagues [6], Scotese [7], and Müller and colleagues [8]. Using these reconstructions, so-called relative plate motion chains [9] are built that incorporate the relative motions of present and former plates that are or were bounded by mid-ocean ridges.

Such relative plate motion chains, which may be closed into a plate circuit, may be a sufficient reference frame to study the kinematic evolution of a destructive plate boundary, such as the India-Asia plate boundary in the Himalaya. For many other studies, however, it is key to determine the position of the plate circuit relative to the Earth’s spin axis, or to the mantle. To this end, ‘absolute’ reference frames have been developed. Paleoclimate studies require knowledge of the location of a studied sedimentary archive during its deposition relative to the Earth’s spin axis, as this determined its position relative to the sun, and thus its climate.

Below, we illustrate that reference frames reconstructing plates relative to the mantle can considerably differ from frames reconstructing plates relative to the spin axis (perhaps as much as 15° (i.e. ~1650 km) in the Early Cenozoic [10] and more than 20° (>2200 km) in the Mesozoic [11]) due to a process known as ‘true polar wander’. These differences may become important at critical time intervals and specific locations on Earth, for instance close to 60° paleolatitude, where even slight differences in paleolatitude determine whether a given site was in easterly versus westerly winds [12] and it is thus essential to use a reference frame relative to the Earth’s spin axis.

The notion, and importance of using the appropriate reference frame for paleoclimate studies, however, seems somewhat underappreciated in the literature. Most paleoclimate studies do not specify the reference frame that is used to determine the paleolatitude. In more recent literature (e.g., [3]), reference is frequently made to freely online available Gplates reconstruction software [13]. This software package comes with a state-of-the-art relative global plate reconstruction [14], and as default a mantle reference frame [15], which is appropriate for geodynamic problems, but, as we will explain, not for paleoclimate studies. As a consequence, while the effects of the obliquity of the Earth axis that correspond to variations of ~2° are carefully taken into account, the potential uncertainty introduced by misplacement of a study site due to an inappropriate reference frame may be one order of magnitude larger for paleoclimate studies going far back into geological time.

In this paper, we summarize the procedures underlying plate tectonic reconstructions and reference frame generation, and identify which reference frames should be used for various Earth scientific problems. In addition, we describe and provide an online tool (available atwww.paleolatitude.org) that we developed to determine the paleolatitude within all major plates and plate fragments, allowing a user to determine the paleolatitude and associated error bars relative to the Earth’s spin axis, tailor-made for paleoclimate analyses of Jurassic and younger times. Finally, we will show a case study in Cenozoic global temperature reconstructions to illustrate the importance of using the appropriate reference frame, and the use of the provided paleolatitude calculator.

@WFS,World Fossil Society,Riffin T Sajeev,Russel T Sajeev

WFS News: Duck-billed dinosaur (hadrosaur) with 300 Teeth

Imagine how much dental care you’d need if you had 300 or more teeth packed together on each side of your mouth.

Tethyshadros insularis, a hadrosaur. Duck-billed dinosaurs (hadrosaurs), who lived in the Cretaceous period between 90 million and 65 million years ago, sported this unique dental system, which had never been fully understood until it was examined at the microscopic level Credit: © bepsphoto / Fotolia

Tethyshadros insularis, a hadrosaur. Duck-billed dinosaurs (hadrosaurs), who lived in the Cretaceous period between 90 million and 65 million years ago, sported this unique dental system, which had never been fully understood until it was examined at the microscopic level
Credit: © bepsphoto / Fotolia

Duck-billed dinosaurs (hadrosaurs), who lived in the Cretaceous period between 90 million and 65 million years ago, sported this unique dental system, which had never been fully understood until it was examined at the microscopic level through recent research conducted by Aaron LeBlanc, a University of Toronto Mississauga PhD candidate; his supervisor, Professor Robert Reisz, the University of Toronto Mississauga vice-dean, graduate, and colleagues at the Royal Ontario Museum and the Museum of the Rockies.

The hadrosaurid dental battery. a skull of the hadrosaurid Corythosaurus (ROM 00868). Image flipped for the figure. b histological thin section through the maxillary dental battery of a hadrosaurid (ROM 00696). c lingual view of the dental battery in the lower jaw. d histological thin section through the dentary dental battery of the hadrosaurid Prosaurolophus (ROM 3500). e occlusal surface of the dentary dental battery. f closeup image of the intersection between two dentary teeth in a battery, showing the infilling of sediment (white arrow) that holds them together. g closeup image of the intersection of two teeth along the occlusal surface of a dental battery showing the infilling of sediment that holds the two teeth together. For (b) and (d), lingual is to the left. d, dentary; en, enamel; mx, maxilla

The hadrosaurid dental battery. a skull of the hadrosaurid Corythosaurus (ROM 00868). Image flipped for the figure. b histological thin section through the maxillary dental battery of a hadrosaurid (ROM 00696). c lingual view of the dental battery in the lower jaw. d histological thin section through the dentary dental battery of the hadrosaurid Prosaurolophus (ROM 3500). e occlusal surface of the dentary dental battery. f closeup image of the intersection between two dentary teeth in a battery, showing the infilling of sediment (white arrow) that holds them together. g closeup image of the intersection of two teeth along the occlusal surface of a dental battery showing the infilling of sediment that holds the two teeth together. For (b) and (d), lingual is to the left. d, dentary; en, enamel; mx, maxilla

Rather than shedding teeth and replacing them with new ones like other reptiles, hadrosaurs’ mouths contain several parallel stacks of six or more teeth apiece, forming a “highly dynamic network” of teeth that was used to grind and shear tough plant material. Although hadrosaur teeth appear to be fused in place, LeBlanc and his colleagues show that the newest teeth were constantly pushed towards the chewing surface by a complex set of ligaments. When viewed under the microscope, the columns of teeth are not physically touching and are held together by the sand and mud that can get in between the teeth following the decay of the soft ligaments after the animals died.

The hadrosaurid dental battery. a skull of the hadrosaurid Corythosaurus (ROM 00868). Image flipped for the figure. b histological thin section through the maxillary dental battery of a hadrosaurid (ROM 00696). c lingual view of the dental battery in the lower jaw. d histological thin section through the dentary dental battery of the hadrosaurid Prosaurolophus (ROM 3500). e occlusal surface of the dentary dental battery. f closeup image of the intersection between two dentary teeth in a battery, showing the infilling of sediment (white arrow) that holds them together. g closeup image of the intersection of two teeth along the occlusal surface of a dental battery showing the infilling of sediment that holds the two teeth together. For (b) and (d), lingual is to the left. d, dentary; en, enamel; mx, maxilla

The hadrosaurid dental battery. a skull of the hadrosaurid Corythosaurus (ROM 00868). Image flipped for the figure. b histological thin section through the maxillary dental battery of a hadrosaurid (ROM 00696). c lingual view of the dental battery in the lower jaw. d histological thin section through the dentary dental battery of the hadrosaurid Prosaurolophus (ROM 3500). e occlusal surface of the dentary dental battery. f closeup image of the intersection between two dentary teeth in a battery, showing the infilling of sediment (white arrow) that holds them together. g closeup image of the intersection of two teeth along the occlusal surface of a dental battery showing the infilling of sediment that holds the two teeth together. For (b) and (d), lingual is to the left. d, dentary; en, enamel; mx, maxilla

“Hadrosaur teeth are actually similar to what we have because our teeth are not solidly attached to our jaws. Like us, hadrosaur teeth would have had some fine-scale mobility as they chewed thanks to this ligament system that suspended the teeth in place,” says Reisz.

As they reached the grinding surface, hadrosaur teeth were essentially dead, filled with hard tissue — unlike humans, whose teeth have an inner core filled with blood vessels and nerves.

“Since the teeth were already dead, they could be ground down to little nubbins,” Reisz says.

The internal anatomy of the hadrosaurid dental battery. a artist’s reconstruction of a portion of the maxillary dental battery, with cutaways in the transverse and coronal planes. For completely labeled reconstruction, see Additional file 3: Figure S2 (illustration by D. Dufault). b magnified image of the junction between primary alveolar bone and the remodelled bone of the jaw. c magnified image of the resorptive front created by the younger teeth within a vertical stack of teeth (direction of resorption indicated by black arrows). d magnified image of the attachment site between the teeth and wall of the socket (direction of periodontal ligament fibers indicated by black arrows). The birefringence in the cellular cementum is caused by the parallel orientations of the Sharpey’s fibers. e magnified image of the occlusal end of the dental battery in thin section showing teeth at various stages of wear. f image of a tooth within the battery in transverse section. ab, alveolar bone; ac, acellular cementum; cc, cellular cementum; de, dentine; en, enamel; Li, lingual; Me, mesial; pc, pulp cavity; ppc, plugged pulp cavity; rl, reversal line

The internal anatomy of the hadrosaurid dental battery. a artist’s reconstruction of a portion of the maxillary dental battery, with cutaways in the transverse and coronal planes. For completely labeled reconstruction, see Additional file 3: Figure S2 (illustration by D. Dufault). b magnified image of the junction between primary alveolar bone and the remodelled bone of the jaw. c magnified image of the resorptive front created by the younger teeth within a vertical stack of teeth (direction of resorption indicated by black arrows). d magnified image of the attachment site between the teeth and wall of the socket (direction of periodontal ligament fibers indicated by black arrows). The birefringence in the cellular cementum is caused by the parallel orientations of the Sharpey’s fibers. e magnified image of the occlusal end of the dental battery in thin section showing teeth at various stages of wear. f image of a tooth within the battery in transverse section. ab, alveolar bone; ac, acellular cementum; cc, cellular cementum; de, dentine; en, enamel; Li, lingual; Me, mesial; pc, pulp cavity; ppc, plugged pulp cavity; rl, reversal line

LeBlanc says this tooth structure — with its tough grinding surface — was “well-adapted to break down tough plant material for digestion,” through both shearing and grinding. This adaptation may have contributed to the hadrosaurs’ longevity and proliferation.

Reisz says that hadrosaurs had “probably the most complex dental system ever made.”

“It’s very elegant — not a single brick of teeth working as a solid unit,” he says. “It’s more like chain mail, providing flexibility as well as strength.”

LeBlanc notes that the duck-billed dinosaur has been known for over 150 years and its dental system has long been recognized as unique, but no one had taken a look inside it at the microscopic level previously. He created thin sections of entire dental assemblies from the upper and lower jaws, that he then ground down, polished and examined under a powerful microscope. Working with their museum colleagues, he and Reisz were also able to explore how hadrosaur teeth form in embryos and hatchlings, providing a more complete picture of this unique model of dental evolution and development.

“The amazing thing is how consistently these dental assemblies conform to our hypothesis of how the system works,” LeBlanc says. “Even in the youngest specimens, the same processes that maintained dental assemblies in the adults were visible.”

Citation: University of Toronto. “300 Teeth: Duck-billed dinosaurs would have been dentist’s dream.” ScienceDaily. ScienceDaily, 25 August 2016. <www.sciencedaily.com/releases/2016/08/160825120216.htm>

@WFS,World Fossil Society,Riffin T Sajeev,Russel T sajeev

WFS News: Snake eats lizard eats beetle, Fossil food chain examined

In cooperation with CONICET in Argentina, Senckenberg scientists examined a spectacular discovery from the UNESCO World Heritage site Messel Pit: A fossil snake in whose stomach a lizard can be seen, which in turn had consumed a beetle. The discovery of the approximately 48-million-year-old tripartite fossil food chain is unique for Messel; worldwide, only one single comparable piece exists. The study was recently published in Senckenberg’s scientific journal Palaeobiodiversity and Palaeoenvironments.

It is no secret that the Messel Pit is home to a plethora of fantastic fossils — but some of the findings are so sensational that they even awe veteran Messel researchers. “In the year 2009, we were able to recover a plate from the pit that shows an almost fully preserved snake,” says Dr. Krister Smith of the Department for Messel Research at the Senckenberg Research Institute in Frankfurt, and he continues, “And as if this was not enough, we discovered a fossilized lizard inside the snake, which in turn contained a fossilized beetle in its innards!”

Snake with lizard and beetle: The rare tripartite fossil food chain from the Messel Pit. Credit: © Springer Heidelberg

   Snake with lizard and beetle: The rare tripartite fossil food chain from the Messel Pit.Credit: © Springer Heidelberg

Fossil food chains are extremely rarely preserved; due to the excellent level of preservation at the fossil site, leaves and grapes from the stomach of a prehistoric horse, pollen grains in a bird’s intestinal tract and remains of insects in fossilized fish excrements had previously been discovered at Messel. “However, until now, we had never found a tripartite food chain — this is a first for Messel!” exclaims Smith elatedly. To this day, only one other example of such fossil preservation has been found worldwide — in a 280-million-year-old shark.

Using a high-resolution computer tomograph, Smith and his colleague Agustín Scanferla from Argentina were able to identify both the snake and the lizard to the species level. Smith comments, “The fossil snake is a member of Palaeophython fischeri; the lizard belongs to Geiseltaliellus maarius, which has only been found at Messel to date.”

a Interpretive drawing of SMF ME 11332a overlaid on a photograph. The lizard, Geiseltaliellus maarius (orange), is preserved in the stomach of the snake (white). The lizard was swallowed headfirst, and the tail does not appear to have been shed during the encounter with the snake. The position of the insect in the abdominal cavity of the lizard is indicated in outline (blue). All Rights Reserved. b, c CT reconstruction of the snake skull in right ventrolateral and left dorsolateral views, respectively. d CT reconstruction of mid-trunk vertebrae of the snake in dorsal view. e Photograph of mid-trunk vertebrae of the snake in ventral view. f Part of the string of vertebrae, to the same scale, comprising the holotype of Palaeopython fischeri (SMF ME 929), four trunk vertebrae in dorsal (left) and ventral (right) views (after Schaal 2004), showing the significant size difference between the holotype and the new specimen. Abbreviations: bo basioccipital, bs-ps basiparasphenoid, ec ectopterygoid, fr frontal, lm left mandible, mx maxilla, n nasal, p parietal, pfr prefrontal, pl palatine, pmx premaxilla, pt pterygoid, q quadrate, rm right mandible, so supraoccipital, st supratemporal. Published with kind permission of ©Krister T. Smith 2016

a Interpretive drawing of SMF ME 11332a overlaid on a photograph. The lizard, Geiseltaliellus maarius (orange), is preserved in the stomach of the snake (white). The lizard was swallowed headfirst, and the tail does not appear to have been shed during the encounter with the snake. The position of the insect in the abdominal cavity of the lizard is indicated in outline (blue). All Rights Reserved. b, c CT reconstruction of the snake skull in right ventrolateral and left dorsolateral views, respectively. d CT reconstruction of mid-trunk vertebrae of the snake in dorsal view. e Photograph of mid-trunk vertebrae of the snake in ventral view. f Part of the string of vertebrae, to the same scale, comprising the holotype of Palaeopython fischeri (SMF ME 929), four trunk vertebrae in dorsal (left) and ventral (right) views (after Schaal 2004), showing the significant size difference between the holotype and the new specimen. Abbreviations: bo basioccipital, bs-ps basiparasphenoid, ec ectopterygoid, fr frontal, lm left mandible, mx maxilla, n nasal, p parietal, pfr prefrontal, pl palatine, pmx premaxilla, pt pterygoid, q quadrate, rm right mandible, so supraoccipital, st supratemporal. Published with kind permission of ©Krister T. Smith 2016

The snake measures 103 centimeters in length and is thus significantly smaller than other specimens of this species, which can reach two meters or more. Smith therefore assumes that the fossil represents a juvenile of this relative of the modern-day boas.

The lizard measures approximately 20 centimeters from the head to the tip of its tail — and some of the snake’s ribs, which overlap the arboreal reptile, clearly indicate that the lizard is located inside the snake. Geiseltaliellus maarius was presumably equipped with a small sagittal crest. It had the ability to shed its tail in case of danger, but did not lose it when it fell prey to the snake. “Unfortunately, we were unable to unambiguously identify the beetle — it was not well enough preserved to do so,” adds the Messel researcher from Frankfurt.

a Photograph of the insect in the abdominal cavity of the lizard on the excavated side (now embedded in epoxy resin) of SMF ME 11332. Insect cuticle shimmers blue-green, indicating that structural colour is preserved. Cuticle was accentuated by drawing of contour and fading of surroundings. The insect is scarcely visible in the prepared specimen. b Scanning electron micrographs of gut tract contents of Geiseltaliellus maarius SMF ME 11380. Arrow points to the globule shown at higher magnification in c

a Photograph of the insect in the abdominal cavity of the lizard on the excavated side (now embedded in epoxy resin) of SMF ME 11332. Insect cuticle shimmers blue-green, indicating that structural colour is preserved. Cuticle was accentuated by drawing of contour and fading of surroundings. The insect is scarcely visible in the prepared specimen. b Scanning electron micrographs of gut tract contents of Geiseltaliellus maarius SMF ME 11380. Arrow points to the globule shown at higher magnification in c

Nonetheless, the small crawler offers insights into the previously barely known feeding behavior of these lizards from Messel: The stomachs of previously discovered reptiles only contained the remains of plants; the fact that the lizards also fed on insects indicates an omnivorous diet.

The unique discovery came from a layer dating to the Middle Eocene with an approximate age of 48 million years. “Since the stomach contents are digested relatively fast and the lizard shows an excellent level of preservation, we assume that the snake died no more than one to two days after consuming its prey and then sank to the bottom of the Messel Lake, where it was preserved,” explains Smith. Too bad for the snake — but a stroke of luck for science!

Courtesy: Senckenberg Research Institute and Natural History Museum. “Snake eats lizard eats beetle: Fossil food chain from the Messel Pit examined.” ScienceDaily. ScienceDaily, 7 September 2016. www.sciencedaily.com/releases/2016/09/160907082052.htm>

KeY: WFS,World Fossil Society,Riffin T Sajeev,Russel T Sajeev

WFS News: Jurassic ‘sea monster’ fossil emerges in Scotland

A Jurassic sea monster in all its prehistoric glory has finally re-emerged into the light after 50 years cooped up in a museum storage room in Scotland.

Nicknamed the Storr Lochs Monster, the newly revealed creature is actually an ichthyosaur, a kind of extinct swimming reptile that ruled the waves while the dinosaurs reigned over the land. Over their long history, ichthyosaurs evolved into enormous beasts akin to the whales of their day.This fossil, though not a giant, is a scientific prize, scientists say. At roughly 170 million years old, it lived during the Middle Jurassic, a somewhat mysterious period for paleontologists.

An artist's rendering of what the Storr Lochs monster looked like in the Jurassic period (Photo: Todd Marshall)

An artist’s rendering of what the Storr Lochs monster looked like in the Jurassic period
(Photo: Todd Marshall)

“The Middle Jurassic is one of the most poorly known times in the history of dinosaurs and in the history of other reptiles like ichthyosaurs,” says University of Edinburgh’s Steve Brusatte, part of the team examining the fossil. The “spectacular” find, he says, “has a lot of potential.”

It took two generations of one Scottish family to bring the Storr Lochs Monster into the spotlight. In 1966, Norrie Gillies, who ran the hydropower plant on Scotland’s Isle of Skye, was strolling the shore near the Storr Lochs power station when he spotted some bones sticking out of a rock.

Gillies had collected many small fossils, but “he realized (this) was on a different scale altogether,” says his son Allan Gillies, an engineer for SSE, the successor to his father’s employer. “It wasn’t the sort of thing you kept in your back yard.”

The fossil was taken to a storage facility belonging to what is now National Museums Scotland. But it was encased in rock harder than concrete, and extracting it would have taken substantial skill – and money. When Norrie Gillies died in 2011, his fossil still wore its stone shroud.A few years later, Allan Gillies read about Brusatte’s research and contacted the scientist about the big fossil found near the hydropower station. Perhaps, Gillies said, his employer would pay for the fossil’s liberation from the rock.

Fossil conservator Nigel Larkin examines the Storr Lochs fossil. (Photo: Uncredited)

Fossil conservator Nigel Larkin examines the Storr Lochs fossil. (Photo: Uncredited)

And so it proved. After removal of its stone cloak, the ichthyosaur has been revealed as a barrel-chested animal about as big as a bottle-nosed dolphin. The fossil was unveiled Monday in Scotland.

“The father found it, and the son really helped with the fundraising,” Brusatte says. He and his colleagues don’t yet know which species it is, but Brusatte suspects it hunted fish and squid and, like other ichthyosaurs of its time, had hundreds of teeth and enormous eyes, which would’ve helped it see through the gloom of the deep seas.

Other scientists are keen to see what the new fossil might reveal.

“This new ichthyosaur can and, I’m sure, will tell us a good few things about ichthyosaur paleobiology, and marine reptiles more generally,” says Benjamin Moon of Britain’s University of Bristol. Very little fossil material is known from that time period, he says, so this new specimen will help fill a gap.

The Storr Lochs Monster is not the only ichthyosaur to swim into the 21st century out of long hiding. A 20-inch baby ichthyosaur and the fossil of an ichthyosaur as long as a subcompact car have recently been turned up by Dean Lomax of Britain’sUniversity of Manchester, who has been scouring Britain’s small museums for overlooked sea monsters.

“I contact a museum and say, ‘I’m looking for ichthyosaur specimens,’” he says. “Sometimes you just get lucky.”

Courtesy: Article by Traci Watson, Special for USA TODAY.

Key: WFS,World Fossil Society,Riffin T Sajeev,Russel T Sajeev

WFS News: Oldest fossil life found in Greenland rocks

The reddish peaks in this 3.7-billion-year-old rock may be structures made by microbes in a shallow ocean—if so, they would be the earliest known evidence of life on Earth.A. Nutman et. al. Nature 536, 7618 (1 September 2016) © MacMillian Publisher Ltd.

Hints of oldest fossil life found in Greenland rocks

How long has Earth harbored life? Chemical signatures found in hardy microscopic crystals called zircons point to a beginning about 4.1 billion years ago. But finding fossilized remains of microbes—undoubtedly the creature of the day—is a far more difficult task. Now, scientists say they have identified fossilized microbial mats, called stromatolites, in Greenland that date to about 3.7 billion years ago—nearly 300 million years older than the previous fossil record holder. The find may help guide scientists searching for life on other planets.

“It’s pretty impressive that anything remotely like a stromatolite is being found [in these rocks],” says Abigail Allwood, a geologist with NASA’s Jet Propulsion Laboratory in Pasadena, California, who was not involved in the study. “It’s another opportunity for us to sharpen our skills and develop rigorous techniques for the search for life.”

Earth was a tempestuous place during the Archean Eon, the name geologists give to the planet’s second act, which lasted from about 4 billion to 2.5 billion years ago. At its start, Earth was just half-a-billion years old and still fiery with remnant heat from its formation. Volcanoes were abundant, and the planet was likely too hot for plate tectonics, which may not have existed for another few hundred million years. Asteroids bombarded its surface. The atmosphere was a heady brew of methane and ammonia, with no free oxygen. The sun was fainter, shining at only about 75% of its current brightness.

If any hardy life did manage to succeed during that time, finding its traces in the Archean rock record seems unlikely. There are few outcrops of Archean rock on Earth, and they tend to be heavily metamorphosed—twisted and deeply altered by heat and pressure. Yet there have been some lucky finds: evidence for 3.4-billion-year-old fossil cells on an ancient Australian shoreline and, famously, 3.4-billion-year-old stromatolites in western Australia’s Strelley Pool Chert, which Allwood identified in 2006.

But the oldest known rocks on Earth are in Greenland, where a formation known as the Isua supracrustal belt (ISB) dates to between 3.7 billion and 3.8 billion years old. Scientists have pored over the belt for signs of life, but until now found only indirect evidence—chemical signatures of carbon and sulfur isotopes that might have been the handiwork of microbes.

To find more direct evidence, scientists searched for rocks untouched—or at least less altered by—metamorphism. That’s a needle-in-a-haystack sort of hunt, but a team led by geologist Allen Nutman of the University of Wollongong in Australia reports online this week in Naturethat is has finally struck pay dirt, thanks to an unseasonably early spring rainfall that washed away the snow from a promising, largely unmetamorphosed ISB outcrop in Greenland.

“This region just happened to avoid strong changes just by luck,” says Martin Van Kranendonk, a geologist at the University of New South Wales, Kensington, in Australia and a co-author on the paper.

The new outcrops included two sites with distinctive shapes—cones and peaks made up of thin, regular internal layers. The shapes are set against a distinctive background in the rock with a different texture and chemical makeup, the team reports. Further analyses of rare-earth elements suggest that the rocks were deposited in shallow ocean waters—just like modern microbial mats made by bacteria living in today’s oceans. Taken together, the team says, the evidence points strongly to a microbial origin for the structures—and that would make them the oldest fossilized life yet discovered on Earth.

Allwood agrees that the shapes are suggestive and interesting. But, she cautions, “it’s a chalk and cheese comparison with the stromatolites of western Australia—which are controversial in themselves.” Convincing scientists that the 3.4-billion-year-old western Australia stromatolites were made by microbes was a “hard sell,” she says. But those structures are at least widespread, spread out across 10 kilometers of outcrop. The new discoveries are tiny, with few structures to study, she notes. And although the overall shapes of the stromatolites have survived—perhaps against all odds—many of the textural and chemical details within them have degraded significantly.

Still, Allwood says, the discovery offers a tantalizing new “biosignature” for scientists hunting for signs of past life—whether on Earth or elsewhere. On Mars, for example, scientists are unsure which sites have the best possible chance of finding life, a key target of space exploration vehicles like the Mars rover. Scientists had thought it unlikely that 3.7-billion-year-old rocks on Mars would have hosted life because the Red Planet—like Earth—was just coming out of a period of heavy asteroid bombardment. But if the Greenland structures are biological, Allwood says, they suggest life could have emerged in that time, and that standing bodies of shallow water would be the likeliest place to look. And because Mars lacks plate tectonics, its rocks haven’t been heavily metamorphosed by internal heat and pressure, as they were on Earth. Allwood says that means ancient signs of life might still linger.

@Riffin T Sajeev,Russel T sajeev

Associate Professor Vickie Bennett (left), Professor Allen Nutman (centre), and Dr Clark Friend (right), examining the rocks in Greenland. Credit: Courtesy of Yuri Amelin

Associate Professor Vickie Bennett (left), Professor Allen Nutman (centre), and Dr Clark Friend (right), examining the rocks in Greenland.Credit: Courtesy of Yuri Amelin

KeY: WFS,World Fossil Society,Riffin T Sajeev,Russel T sajeev