Prehistoric predators tangled across land, sea

About 210 million years ago when the supercontinent of Pangea was starting to break up and dog-sized dinosaurs were hiding from nearly everything, entirely different kinds of reptiles called phytosaurs and rauisuchids were at the top of the food chain.

It was widely believed the two top predators didn’t interact much as the former was king of the water, and the latter ruled the land. But those ideas are changing, thanks largely to the contents of a single bone.

Teeth from phytosaurs, a reptile from the Triassic Period about 210 million years ago in what is now the western United States. The blue tooth on the left is a 3-D printed replica of a tooth embedded in the thigh bone of a rauisuchid, another Triassic period carnivore. The details of the tooth were digitally extracted using CT scans. Credit: Virginia Tech

Teeth from phytosaurs, a reptile from the Triassic Period about 210 million years ago in what is now the western United States. The blue tooth on the left is a 3-D printed replica of a tooth embedded in the thigh bone of a rauisuchid, another Triassic period carnivore. The details of the tooth were digitally extracted using CT scans.
Credit: Virginia Tech

In a paper published online in September in the German journal Naturwissenschaften, Stephanie Drumheller of the University of Tennessee and Michelle Stocker and Sterling Nesbitt, vertebrate paleontologists with the Virginia Tech’s Department of Geosciences, present evidence the two creatures not only interacted, but did so on purpose.

“Phytosaurs were thought to be dominant aquatic predators because of their large size and similarity to modern crocodylians,” said Stocker, “but we were able to provide the first direct evidence they targeted both aquatic and large terrestrial prey.”

The evidence? A tooth. Not just any tooth, but the tooth of a phytosaur lodged in the thigh bone of a rauisuchid, a creature about 25 feet long and 4 feet high at the hip. The tooth lay broken off and buried about two inches deep in bone, and then healed over, indicating the rauisuchid survived the attack.

“Finding teeth embedded directly in fossil bone is very, very rare,” Drumheller said. “This is the first time it’s been identified among phytosaurs, and it gives us a smoking gun for interpreting this set of bite marks.”

The researchers came across the bone by chance at the University of California Museum of Paleontology in Berkeley.

“It was remarkable we were able to reconstruct a part of an ancient food web from over 210 million years ago from a few shallow marks and a tooth in a bone,” said Nesbitt. “It goes to show how careful observation can lead to important discoveries even when you’re not seeking those answers.

“We came across this bone and realized pretty quickly we had something special,” Nesbitt said. “There are many bones that get dug up, not all are immediately processed, prepared, and studied. No one had recognized the importance of this specimen before but we were able to borrow it and make our study.”

The large rauisuchid thigh bone at the center of the research has the tooth of the attacker, which the researchers recreated using CT scans and a 3-D printer. Multiple bite marks indicate the creature was preyed upon at least twice over the course of its life, by phytosaurs.

“This research will call for us to go back and look at some of the assumptions we’ve had in regard to the Late Triassic ecosystems,” Stocker said. “The distinctions between aquatic and terrestrial distinctions were over-simplified and I think we’ve made a case that the two spheres were intimately connected.”

Drilling Into an Active Earthquake Fault

Three University of Michigan geologists are participating in an international effort to drill nearly a mile beneath the surface of New Zealand this fall to bring back rock samples from an active fault known to generate major earthquakes.

The goal of the Deep Fault Drilling Project is to better understand earthquake processes by sampling the Alpine Fault, which is expected to trigger a large event in the coming decades.

“We’re trying to understand why some faults are more earthquake-prone than others, and that requires fundamental knowledge about the processes at work,” said Ben van der Pluijm, the Bruce R. Clark Collegiate Professor of Geology in the U-M Department of Earth and Environmental Sciences.

An aerial view of the Alpine Fault at Gaunt Creek, where the Deep Fault Drilling Project is scheduled to begin next month. Three University of Michigan geologists are participating in the $2.5 million international project, which will drill nearly a mile beneath the surface and return rock samples from an active fault known to generate major earthquakes. Credit: Photo by Ben van der Pluijm

An aerial view of the Alpine Fault at Gaunt Creek, where the Deep Fault Drilling Project is scheduled to begin next month. Three University of Michigan geologists are participating in the $2.5 million international project, which will drill nearly a mile beneath the surface and return rock samples from an active fault known to generate major earthquakes.
Credit: Photo by Ben van der Pluijm

Van der Pluijm and two of his EES colleagues — doctoral student Austin Boles and research scientist Anja Schleicher — are part of the team scheduled to start the two-month drilling project early next month. Schleicher will spend October at the site, and Boles will be there for about six weeks starting in early November.

It will be only the second science project to drill deep into an active earthquake fault and return samples. Several years ago, scientists drilled a nearly 2-mile-deep hole into California’s San Andreas Fault. Van der Pluijm was a member of that team, as well.

“I hope we find something different this time, a different rock signature that contrasts with what we saw at the San Andreas,” he said.

The goal is to drill 0.8 miles (1.3 kilometers) into the 530-mile-long Alpine Fault, which marks the boundary between the Australian and Pacific tectonic plates, on New Zealand’s South Island. Though most of the movement along the fault is lateral rather than vertical, the fault is responsible for lifting the Southern Alps, the rugged mountain range featured in the “Lord of the Rings” movies.

Earthquakes occur on the Alpine Fault every 200 to 400 years at magnitudes of 7.5 to 8.0, with an average time between successive large earthquakes of about 330 years. Though earthquakes of that size that originate at shallow depths are capable of tremendous damage, the region is sparsely populated.

The last Alpine Fault quake occurred in 1717, and the probability of another big one occurring there in the next 50 years has been calculated at about 28 percent. So the $2.5 million Deep Fault Drilling Project presents a rare opportunity to collect and analyze samples from a major fault before it breaks.

The task for van der Pluijm and his colleagues is to analyze the possible role of clay minerals and friction melting in the fault zone. Radiometric dating, X-ray studies and isotopic-analysis techniques will be used to determine how much clay is in the rock samples and when those clays formed, as well as the likely source of the water that helped produce them.

“The information we can extract from these clays is remarkably rich,” said Boles, who will use data from the New Zealand study in his doctoral dissertation. “These clay minerals are a key tool that we can use to better understand the physical and chemical processes happening in an active fault.”

Clay minerals can help reduce friction and heat generation along a fault, lubricating it so that pressure is released through steady, relatively small and nondestructive “creeping” motions rather than the periodic violent jolts known as earthquakes.

Creeping motions were observed along the portion of the San Andreas Fault drilled by scientists several years ago. Temperatures in that fault were relatively low, and clay-rich rocks from the active zone were returned to the surface.

“We think that clays are a significant player in making faults less earthquake-prone,” van der Pluijm said. “We know that the section of the Alpine Fault we’ll be drilling has a history of producing large earthquakes. So finding little clay and, instead, evidence for frictional melting in the rock would better fit the large-earthquake scenario. That would be a fantastic breakthrough.”

In addition to sampling the fault during the two-month drilling program, researchers will install permanent pressure, temperature and seismic-monitoring sensors in the borehole.

The U-M researchers are hoping to obtain a rock sample about the volume of a baseball from deep within the Alpine Fault. That would be plenty to complete their various studies, which are funded by the National Science Foundation and the International Continental Scientific Drilling Program.

“Getting the right samples is more important than the amount,” van der Pluijm said. “Returning samples to the surface from depth is always a challenge, but I’m confident that it will work.”

Dinosaur family tree gives clues on the evolution of birds

The most comprehensive family tree of meat-eating dinosaurs ever created is enabling scientists to discover key details of how birds evolved from them.

The study, published in the journal Current Biology, shows that the familiar anatomical features of birds — such as feathers, wings and wishbones — all first evolved piecemeal in their dinosaur ancestors over tens of millions of years.

Researchers examined the evolutionary links between ancient birds and their closest dinosaur relatives, by analyzing the anatomical make-up of more than 850 body features in 150 extinct species, and used statistical techniques to analyze their findings and assemble a detailed family tree. Credit: Steve Brusatte

Researchers examined the evolutionary links between ancient birds and their closest dinosaur relatives, by analyzing the anatomical make-up of more than 850 body features in 150 extinct species, and used statistical techniques to analyze their findings and assemble a detailed family tree.
Credit: Steve Brusatte

However, once a fully functioning bird body shape was complete, an evolutionary explosion began, causing a rapid increase in the rate at which birds evolved. This led eventually to the thousands of avian species that we know today.

A team of researchers, led by the University of Edinburgh (UK) and including Swarthmore College Associate Professor of Statistics Steve C. Wang, examined the evolutionary links between ancient birds and their closest dinosaur relatives. They did this by analyzing the anatomical make-up of more than 850 body features in 150 extinct species and used statistical techniques to analyze their findings and assemble a detailed family tree.

Based on their findings from fossil records, researchers say the emergence of birds some 150 million years ago was a gradual process, as some dinosaurs became more bird-like over time. This makes it very difficult to draw a dividing line on the family tree between dinosaurs and birds.

Findings from the study support a controversial theory proposed in the 1940s that the emergence of new body shapes in groups of species could result in a surge in their evolution.

“The evolution of birds from their dinosaur ancestors was a landmark in the history of life,” says Wang. “This process was so gradual that if you traveled back in time to the Jurassic, you’d find that the earliest birds looked indistinguishable from many other dinosaurs.”

Wang invented a novel statistical method that was able to take advantage of new kinds of data from the fossil record, which reached the conclusion that early birds had a high rate of evolution. He adds that “birds as we know them evolved over millions of years, accumulating small shifts in shape and function of the skeleton. But once all these pieces were in place to form the archetypal bird skeleton, birds then evolved rapidly, eventually leading to the great diversity of species we know today.”

“There was no moment in time when a dinosaur became a bird, and there is no single missing link between them, ” says Steve Brusatte of the University of Edinburgh’s School of GeoSciences, who led the study. “What we think of as the classic bird skeleton was pieced together gradually over tens of millions of years. Once it came together fully, it unlocked great evolutionary potential that allowed birds to evolve at a super-charged rate.”

The work was supported by the European Commission, National Science Foundation, the University of Edinburgh, Swarthmore College’s Research Fund, Swarthmore College’s James Michener Faculty Fellowship, Columbia University, and the American Museum of Natural History.

New explanation for origin of plate tectonics?

The mystery of what kick-started the motion of our earth’s massive tectonic plates across its surface has been explained by researchers at the University of Sydney.

“Earth is the only planet in our solar system where the process of plate tectonics occurs,” said Professor Patrice Rey, from the University of Sydney’s School of Geosciences.

“The geological record suggests that until three billion years ago the Earth’s crust was immobile so what sparked this unique phenomenon has fascinated geoscientists for decades. We suggest it was triggered by the spreading of early continents then eventually became a self-sustaining process.”

Professor Rey is lead author of an article on the findings published in Nature on Wednesday, 17 September.

The other authors on the paper are Nicolas Flament, also from the School of Geosciences and Nicolas Coltice, from the University of Lyon.

There are eight major tectonic plates that move above Earth’s mantle at rates up to 150 millimetres every year.

The image shows a snapshot from the film after 45 million years of spreading. The pink is the region where the mantle underneath the early continent has melted, facilitating its spreading, and the initiation of the plate tectonic process. Credit: Patrice Rey, Nicolas Flament and Nicolas Coltice

The image shows a snapshot from the film after 45 million years of spreading. The pink is the region where the mantle underneath the early continent has melted, facilitating its spreading, and the initiation of the plate tectonic process.
Credit: Patrice Rey, Nicolas Flament and Nicolas Coltice

In simple terms the process involves plates being dragged into the mantle at certain points and moving away from each other at others, in what has been dubbed ‘the conveyor belt’.

Plate tectonics depends on the inverse relationship between density of rocks and temperature.

At mid-oceanic ridges, rocks are hot and their density is low, making them buoyant or more able to float. As they move away from those ridges they cool down and their density increases until, where they become denser than the underlying hot mantle, they sink and are ‘dragged’ under.

But three to four billion years ago, Earth’s interior was hotter, volcanic activity was more prominent and tectonic plates did not become cold and dense enough to spontaneously sank.

“So the driving engine for plate tectonics didn’t exist,” said Professor Rey said.

“Instead, thick and buoyant early continents erupted in the middle of immobile plates. Our modelling shows that these early continents could have placed major stress on the surrounding plates. Because they were buoyant they spread horizontally, forcing adjacent plates to be pushed under at their edges.”

“This spreading of the early continents could have produced intermittent episodes of plate tectonics until, as the Earth’s interior cooled and its crust and plate mantle became heavier, plate tectonics became a self-sustaining process which has never ceased and has shaped the face of our modern planet.”

The new model also makes a number of predictions explaining features that have long puzzled the geoscience community.

Rhinorex condrupus :Hadrosaur with huge nose discovered

Call it the Jimmy Durante of dinosaurs — a newly discovered hadrosaur with a truly distinctive nasal profile. The new dinosaur, named Rhinorex condrupus by paleontologists from North Carolina State University and Brigham Young University, lived in what is now Utah approximately 75 million years ago during the Late Cretaceous period.

Rhinorex, which translates roughly into “King Nose,” was a plant-eater and a close relative of other Cretaceous hadrosaurs like Parasaurolophus and Edmontosaurus. Hadrosaurs are usually identified by bony crests that extended from the skull, although Edmontosaurus doesn’t have such a hard crest (paleontologists have discovered that it had a fleshy crest). Rhinorex also lacks a crest on the top of its head; instead, this new dinosaur has a huge nose.

Terry Gates, a joint postdoctoral researcher with NC State and the North Carolina Museum of Natural Sciences, and colleague Rodney Sheetz from the Brigham Young Museum of Paleontology, came across the fossil in storage at BYU. First excavated in the 1990s from Utah’s Neslen formation, Rhinorex had been studied primarily for its well-preserved skin impressions. When Gates and Sheetz reconstructed the skull, they realized that they had a new species.

“We had almost the entire skull, which was wonderful,” Gates says, “but the preparation was very difficult. It took two years to dig the fossil out of the sandstone it was embedded in — it was like digging a dinosaur skull out of a concrete driveway.”

The newly discovered hadrosaur, Rhinorex condrupus, has a truly distinctive nasal profile. Credit: Terry Gates

The newly discovered hadrosaur, Rhinorex condrupus, has a truly distinctive nasal profile.
Credit: Terry Gates

Based on the recovered bones, Gates estimates that Rhinorex was about 30 feet long and weighed over 8,500 lbs. It lived in a swampy estuarial environment, about 50 miles from the coast. Rhinorex is the only complete hadrosaur fossil from the Neslen site, and it helps fill in some gaps about habitat segregation during the Late Cretaceous.

“We’ve found other hadrosaurs from the same time period but located about 200 miles farther south that are adapted to a different environment,” Gates says. “This discovery gives us a geographic snapshot of the Cretaceous, and helps us place contemporary species in their correct time and place. Rhinorex also helps us further fill in the hadrosaur family tree.”

When asked how Rhinorex may have benefitted from a large nose Gates said, “The purpose of such a big nose is still a mystery. If this dinosaur is anything like its relatives then it likely did not have a super sense of smell; but maybe the nose was used as a means of attracting mates, recognizing members of its species, or even as a large attachment for a plant-smashing beak. We are already sniffing out answers to these questions.”

climate events in Earth’s history may require reappraisal

A recent study of the global carbon cycle offers a new perspective of Earth’s climate records through time. Scientists at the University of Miami (UM) Rosenstiel School of Marine and Atmospheric Science suggest that one of the current methods for interpreting ancient changes in the concentration of carbon dioxide in the atmosphere and oceans may need to be re-evaluated.

The UM Rosenstiel School researchers measured the abundance of carbon-12 and carbon-13 isotopes in both the organic matter and carbonate sediments found in a nearly 700-meter marine sediment core from the Great Bahama Bank. The analyses showed a change to lower amounts of the rare isotope of carbon (carbon-13) in both the organic and inorganic materials as a result of several periods of sub-aerial exposure during the Pleistocene ice ages, which took place over the past two million years.

This photo shows roots casts observed between 131-132 meters below the mud pit. These casts are situated 0.2 meters below the subaerial exposure surface (not shown). Root casts are the darker grey irregular shapes observed in the photo with round, unfilled pore spaces. Scale bar on the right are 1 cm increments. Credit: UM Rosenstiel School of Marine and Atmospheric Science

This photo shows roots casts observed between 131-132 meters below the mud pit. These casts are situated 0.2 meters below the subaerial exposure surface (not shown). Root casts are the darker grey irregular shapes observed in the photo with round, unfilled pore spaces. Scale bar on the right are 1 cm increments.
Credit: UM Rosenstiel School of Marine and Atmospheric Science

“Without geological context, classical interpretations of this dataset would suggest that there was a significant change in global carbon cycling, or a very large change in the concentration of atmospheric CO2 during the past five-million years,” said Amanda Oehlert, UM Rosenstiel School alumna and lead author of the study. “These findings show how important it is to understand the geological context of carbon isotope records.”

Scientists refer to the global carbon cycle as the natural processes by which carbon is cycled through the different components of Earth, including the mantle, atmosphere, plants, the oceans, and sediments.

The results showed that post-depositional changes in sediments could cause carbonate and organic values to covary through time, a process that had never been observed before, and has been considered impossible. The new findings suggest that similar trends in carbon isotopes values through time do not always provide conclusive information about the amount of CO2¬† — in the atmosphere or how carbon was cycled through the atmosphere and oceans.

Current scientific theory suggests that post-depositional physical, chemical, or biological processes produce contrasting carbonate and organic carbon isotope records. Currently, carbon isotope records of carbonate and organic material that show the same trends through time, or those that are highly correlated, are considered accurate records of changes in the global carbon cycle and concentrations of CO2 in the atmosphere and oceans.

“The observation that simultaneous changes in the amount of carbon-13 in carbonate and organic carbon isotope records can be caused by post-depositional changes is in direct contrast to current interpretations of these paired records,” said Oehlert. “These findings highlight the importance of understanding where and how the sediments and organic matter were originally produced, how they were transported to the sea floor, and what physical, chemical or biological changes may have happened to them after they were deposited.”

Scientists evaluate how the global carbon cycle changes through time by studying accumulations of carbonate skeletons and organic matter produced by marine organisms. Understanding the dynamics of the global carbon cycle is fundamental to estimations of atmospheric CO2, and consequently, how Earth’s climate may have changed through geologic history.

Rukwatitan bisepultus : new species of titanosaurian

Ohio University paleontologists have identified a new species of titanosaurian, a member of the large-bodied sauropods that thrived during the final period of the dinosaur age, in Tanzania. Although many fossils of titanosaurians have been discovered around the globe, especially in South America, few have been recovered from the continent of Africa.

The new species, named Rukwatitan bisepultus, was first spotted by scientists embedded in a cliff wall in the Rukwa Rift Basin of southwestern Tanzania. Using the help of professional excavators and coal miners, the team unearthed vertebrae, ribs, limbs and pelvic bones over the course of two field seasons.

An artistic rendering of a deceased Rukwatitan bisepultus individual in the initial floodplain depositional setting from which the holotypic skeleton was recovered. Credit: Mark Witton, University of Portsmouth

An artistic rendering of a deceased Rukwatitan bisepultus individual in the initial floodplain depositional setting from which the holotypic skeleton was recovered.
Credit: Mark Witton, University of Portsmouth

CT scans of the fossils, combined with detailed comparisons with other sauropods, revealed unique features that suggested an animal that was different from previous finds — including those from elsewhere in Africa, according to a study the team published today in the Journal of Vertebrate Paleontology.

“Using both traditional and new computational approaches, we were able to place the new species within the family tree of sauropod dinosaurs and determine both its uniqueness as a species and to delineate others species with which it is most closely related,” said lead author Eric Gorscak, a doctoral student in biological sciences at Ohio University.

Rukwatitan bisepultus lived approximately 100 million years ago during the middle of the Cretaceous Period. Titanosaurian sauropods, the group that includes Rukwatitan, were herbivorous dinosaurs known for their iconic large body sizes, long necks and wide stance. Although not among the largest of titanosaurians, Rukwatitan is estimated to have a forelimb reaching 2 meters and may have weighed as much as several elephants.

The dinosaur’s bones exhibit similarities with another titanosaurian, Malawisaurus dixeyi, previously recovered in Malawi. But the two southern African dinosaurs are distinctly different from one another, and, most notably, from titanosaurians known from northern Africa, said co-author Patrick O’Connor, a professor of anatomy in the Ohio University Heritage College of Osteopathic Medicine.

The fossils of middle Cretaceous crocodile relatives from the Rukwa Rift Basin also exhibit distinctive features when compared to forms from elsewhere on the continent.

“There may have been certain environmental features, such as deserts, large waterways and/or mountain ranges, that would have limited the movement of animals and promoted the evolution of regionally distinct faunas,” O’Connor said. “Only additional data on the faunas and paleo environments from around the continent will let us further test such hypotheses.”

In addition to providing new data about species evolution in sub-Saharan Africa, the study also contributes to fleshing out the global portrait of titanosaurians, which lived in habitats across the globe through the end of the Cretaceous Period. Their rise in diversity came in the wake of the decline of another group of sauropods, the diplodocoids, which include the dinosaur Apatosaurus, the researchers noted. Scientists have found fossils for more than 30 titanosaurians in South America compared to just four in Africa.

“Much of what we know regarding titanosaurian evolutionary history stems from numerous discoveries in South America — a continent that underwent a steady separation from Africa during the first half of the Cretaceous Period,” Gorscak said. “With the discovery of Rukwatitan and study of the material in nearby Malawi, we are beginning to fill a significant gap from a large part of the world.”

Co-authors on the study are Nancy Stevens, a professor in the Ohio University Heritage College of Osteopathic Medicine, and Eric Roberts, a senior lecturer in the James Cook University of Australia.

The study was funded by the National Science Foundation, the National Geographic Society, the Ohio University Heritage College of Osteopathic Medicine and the Ohio University Office of the Vice President for Research and Creative Activity.

Scientists report first semiaquatic dinosaur, Spinosaurus: Massive predator was more than 9 feet longer than largest T. rex

Scientists are unveiling what appears to be the first truly semiaquatic dinosaur, Spinosaurus aegyptiacus. New fossils of the massive Cretaceous-era predator reveal it adapted to life in the water some 95 million years ago, providing the most compelling evidence to date of a dinosaur able to live and hunt in an aquatic environment. The fossils also indicate that Spinosaurus was the largest known predatory dinosaur to roam Earth, measuring more than nine feet longer than the world’s largest Tyrannosaurus rex specimen.

These findings, to be published Sept. 11 in the journal Science online at the Science Express website, are also featured in the October National Geographic magazine cover story available online Sept. 11. In addition, Spinosaurus will be the subject of a new exhibition at the National Geographic Museum, opening Sept. 12, as well as a National Geographic/NOVA special airing on PBS Nov. 5 at 9 p.m.

An international research team — including paleontologists Nizar Ibrahim and Paul Sereno from the University of Chicago; Cristiano Dal Sasso and Simone Maganuco from the Natural History Museum in Milan, Italy; and Samir Zouhri from the Universit√© Hassan II Casablanca in Morocco — found that Spinosaurus developed a variety of previously unknown aquatic adaptations.

The researchers came to their conclusions after analyzing new fossils uncovered in the Moroccan Sahara and a partial Spinosaurus skull and other remains housed in museum collections around the world as well as historical records and images from the first reported Spinosaurus discovery in Egypt more than 100 years ago. According to lead author Ibrahim, a 2014 National Geographic Emerging Explorer, “Working on this animal was like studying an alien from outer space; it’s unlike any other dinosaur I have ever seen.”

The aquatic adaptations of Spinosaurus differ significantly from earlier members of the spinosaurid family that lived on land but were known to eat fish. These adaptations include:

  • Small nostrils located in the middle of the skull. The small size and placement of the nostrils farther back on the skull allowed Spinosaurus to breathe when part of its head was in water.
  • Neurovascular openings at the end of the snout. Similar openings on crocodile and alligator snouts contain pressure receptors that enable them to sense movement in water. It’s likely these openings served a comparable function in Spinosaurus.
  • Giant, slanted teeth that interlocked at the front of the snout. The conical shape and location of the teeth were well-suited for catching fish.
  • A long neck and trunk that shifted the dinosaur’s center of mass forward. This made walking on two legs on land nearly impossible, but facilitated movement in water.
  • Powerful forelimbs with curved, blade-like claws. These claws were ideal for hooking or slicing slippery prey.
  • A small pelvis and short hind legs with muscular thighs. As in the earliest whales, these adaptations were for paddling in water and differ markedly from other predatory dinosaurs that used two legs to move on land.
  • Particularly dense bones lacking the marrow cavities typical to predatory dinosaurs. Similar adaptations, which enable buoyancy control, are seen in modern aquatic animals like king penguins.
  • Strong, long-boned feet and long, flat claws. Unlike other predators, Spinosaurus had feet similar to some shorebirds that stand on or move across soft surfaces rather than perch. In fact, Spinosaurus may have had webbed feet for walking on soft mud or paddling.
  • Loosely connected bones in the dinosaur’s tail. These bones enabled its tail to bend in a wave-like fashion, similar to tails that help propel some bony fish.
  • Enormous dorsal spines covered in skin that created a gigantic “sail” on the dinosaur’s back. The tall, thin, blade-shaped spines were anchored by muscles and composed of dense bone with few blood vessels. This suggests the sail was meant for display and not to trap heat or store fat. The sail would have been visible even when the animal entered the water.

More than a century ago, German paleontologist Ernst Freiherr Stromer von Reichenbach first discovered evidence of Spinosaurus in the Egyptian Sahara. Sadly, all of Stromer’s fossils were destroyed during the April 1944 Allied bombing of Munich, Germany. Ibrahim, however, was able to track down Stromer’s surviving notes, sketches and photos in archives and at the Stromer family castle in Bavaria to supplement Stromer’s surviving publications.

The new Spinosaurus fossils were discovered in the Moroccan Sahara along desert cliffs known as the Kem Kem beds. This area was once a large river system, stretching from present-day Morocco to Egypt. At the time, a variety of aquatic life populated the system, including large sharks, coelacanths, lungfish and crocodile-like creatures, along with giant flying reptiles and predatory dinosaurs.

The most important of the new fossils, a partial skeleton uncovered by a local fossil hunter, was spirited out of the country. As a result, critical information about the context of the find was seemingly lost, and locating the local fossil hunter in Morocco was nearly impossible. Remarked Ibrahim, “It was like searching for a needle in a desert.” After an exhaustive search, Ibrahim finally found the man and confirmed the site of his original discovery.

To unlock the mysteries of Spinosaurus, the team created a digital model of the skeleton with funding provided by the National Geographic Society. The researchers CT scanned all of the new fossils, which will be repatriated to Morocco, complementing them with digital recreations of Stromer’s specimens. Missing bones were modeled based on known elements of related dinosaurs.

According to Maganuco, “We relied upon cutting-edge technology to examine, analyze and piece together a variety of fossils. For a project of this complexity, traditional methods wouldn’t have been nearly as accurate.”

The researchers then used the digital model to create an anatomically precise, life-size 3-D replica of the Spinosaurus skeleton. After it was mounted, the researchers measured Spinosaurus from head to tail, confirming their calculation that the new skeleton was longer than the largest documented Tyrannosaurus by more than 9 feet.

According to Sereno, head of the University of Chicago’s Fossil Lab, “What surprised us even more than the dinosaur’s size were its unusual proportions. We see limb proportions like this in early whales, not predatory dinosaurs.”

Added Dal Sasso, “In the last two decades, several finds demonstrated that certain dinosaurs gave origins to birds. Spinosaurus represents an equally bizarre evolutionary process, revealing that predatory dinosaurs adapted to a semiaquatic life and invaded river systems in Cretaceous North Africa.”

The life-size skeletal replica will be the centerpiece of a new exhibition at the National Geographic Museum in Washington, D.C., titled “Spinosaurus: Lost Giant of the Cretaceous.” The exhibition, which runs from Sept. 12, 2014, to April 12, 2015, brings to life the story of Spinosaurus, from Stromer’s original discoveries to the dedicated efforts of the international research team working to unlock its secrets.

For more information on this interactive, multimedia experience developed in collaboration with UChicagoTech, the university’s Center for Technology Development & Ventures, visit ngmuseum.org.

The global search to uncover the Spinosaurus skeleton and its mysteries will also be featured in a National Geographic/NOVA special, “Bigger Than T.rex,” airing on PBS Nov. 5, 2014, at 9 p.m.

Other authors of the Science paper are David Martill, University of Portsmouth, United Kingdom; Matteo Fabbri, University of Bristol, United Kingdom; Nathan Myhrvold, Intellectual Ventures; and Dawid Iurino, Sapienza Università di Roma in Italy. Important contributors to the making of the digital Spinosaurus include Tyler Keillor, Lauren Conroy and Erin Fitzgerald of the Fossil Lab at the University of Chicago.

Mantle plumes crack continents

In some parts of the Earth, material rises upwards like a column from the boundary layer of Earth’s core and the lower mantle to just below Earth’s crust hundreds of kilometres above. Halted by the resistance of the hard crust and lithospheric mantle, the flow of material becomes wider, taking on a mushroom-like shape. Specialists call these magma columns “mantle plumes” or simply “plumes.”

In some parts of the Earth, material rises upwards like a column from the boundary layer of Earth's core and the lower mantle to just below Earth's crust hundreds of kilometres above. Credit: "Lower Mantle Superplume" by Brews ohare - Own work. Licensed under Creative Commons Attribution-Share Alike 3.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Lower_Mantle_Superplume.PNG#mediaviewer/File:Lower_Mantle_Superplume.PNG

In some parts of the Earth, material rises upwards like a column from the boundary layer of Earth’s core and the lower mantle to just below Earth’s crust hundreds of kilometres above.

Are mantle plumes responsible for the African rift system?

Geologists believe that plumes are not just responsible for creating volcanoes outside of tectonically active areas — they can also break up continents. The scientists offer the Danakil Depression (the lowlands in the Ethiopia-Eritrea-Djibouti triangle) as an example of this. This “triple junction” is extremely tectonically and volcanically active. Geologists believe that the so-called Afar plume is rising up below it and has created a rift system that forks into the Red Sea, the Gulf of Aden and Africa’s Great Rift Valley. However, the sheer length of time required, geologically speaking, for this process to take place, means that nobody is able to confirm or disprove with absolute certainty that the force of a plume causes continental breakup.

Simulations becoming more realistic

Evgueni Burov, a Professor at the University of Paris VI, and Taras Gerya, Professor of Geophysics at ETH Zurich, have now taken a step closer to solving this geological mystery with a new computer model. Their paper has recently been published in the journal Nature. The two researchers conducted numerical experiments to reproduce the Earth’s surface in high-resolution 3D.

These simulations show that the rising flow of material is strong enough to cause continental breakup if the tectonic plate is under (weak) tensile stress. “The force exerted by a plume on a plate is actually too weak to break it up,” says Gerya. In experiments using simple models, the researchers allowed the plumes to hit an unstressed plate, which did not cause it to break, but merely formed a round hump. However, when the geophysicists modelled the same process with a plate under weak tensile stress, it broke apart, forming a crevice and rift system like the ones found around the world.

“The process can be compared to a taut piece of plastic film. Weak, pointed force is enough to tear the film, but if the film is not pulled taut, it is extremely difficult to tear.” This mechanism has already been proposed in the past as a possible model for explaining continental breakup, but had never been outlined in plausible terms before now.

First high-resolution simulations

“We are the first to create such a high-resolution model which demonstrates how a plume interacts with a plate under tensile stress,” says Gerya. Fast and powerful computers and stable algorithms programmed by the scientists themselves were required for the simulations. The researchers benefited from technical advances made and experience accumulated by the ETH professor in this field over the past ten years.

In the model, the deformations are created quickly from a geological point of view. Rift systems several kilometres deep and more than a thousand kilometres long can form after “just” two million years. The processes are therefore up to ten times faster than tectonic processes such as subduction and 50 times faster than the Alpine orogeny, for example.

Disputed idea

The idea of mantle plumes is widely disputed, with some researchers denying that they even exist. “I think it is much more likely that they do exist,” says Gerya. As is often the case in geology, especially when researching Earth’s interior, such processes and phenomena like the existence of plumes cannot be observed directly. Furthermore, the periods over which geological processes take place are far too long for humans to experience first-hand. “So far, we have only been able to observe the effects that plumes have on the Earth’s surface and on the propagation of seismic waves in the Earth’s interior.”

The scientists are therefore reliant on good, realistic models that show the processes in a geological time lapse. How realistic the calculated simulations are depends on the parameters used. The plume-plate interaction model incorporated physical laws, the characteristics of materials in the Earth’s crust and mantle, and temperature and pressure conditions. “We know the rules, but humans generally lack the intuition to identify how they interact on geological timescales.”

How good is the fossil record?

Methods have been developed to try to identify and correct for bias in the fossil record but new research from the Universities of Bristol and Bath, suggests many of these correction methods may actually be misleading.

The study, led by Dr Alex Dunhill, formerly at the Universities of Bristol and Bath and now at the University of Leeds, explored the rich and well-studied fossil record of Great Britain. Professional geological work has been done in the British Isles for over 200 years and the British Geological Survey (dating from the 1830s) has amassed enormous, detailed knowledge of every inch of the rocks and fossils of the islands.

A map showing the geology of Great Britain spanning the past 550 million years. Credit: Dr Alex Dunhill

A map showing the geology of Great Britain spanning the past 550 million years.
Credit: Dr Alex Dunhill

Together with collaborators from the Universities of Bristol and Bergen, Dr Dunhill compared biodiversity through the last 550 million years of the British fossil record against a number of geological and environmental factors including the area of sedimentary rock, the number of recorded fossil collections and the number of named geological ‘formations’. All of these measures have been used as yardsticks against which the quality of the fossil record can be assessed — but the new study casts doubt on their usefulness.

Dr Dunhill said: “We suspected that the similar patterns displayed by the rock and fossil records were due to external factors rather than the number of fossils being simply dictated by the amount of accessible rock. Our work shows this is true. Factors such as counts of geological formations and collections cannot be used to correct biodiversity in the fossil record.”

The study benefits from the application of advanced mathematical techniques that not only identify whether two data sets correlate, but also whether one drives the other.

The results show that out of all the geological factors, only the area of preserved rock drives biodiversity. Therefore, the other geological factors — counts of fossil collections and geological formations — are not independent measures of bias in the fossil record.

Co-author, Bjarte Hannisdal from the University of Bergen, said: “We can learn more by analysing old data in new ways, than by analysing new data in old ways.”

This discovery fundamentally alters the way we view the diversity of life through time. It shows that both the preservation of rock and the preservation of fossils were probably driven by external environmental factors like climate change and sea level. This better explains the similarities between the rock and fossil records, as both responding to the same external factors. The alternative idea, that rock preservation was driving the fossil record is now strongly queried by this study. Perhaps the record of biodiversity in the fossil record is more accurate than previously feared.

Professor Michael Benton from the University of Bristol, another co-author of the study, said: “Palaeontologists are right to be cautious about the quality of the fossil record, but perhaps some have been too cautious. The sequence of fossils in the rocks more or less tells us the story of the history of life, and we have sensible ways of dealing with uncertainty. Some recent work on ‘correcting’ the fossil record by using formation counts may produce nonsense results.”

The research is published in Nature Communications.