America’s Ancient Hurricane Belt and the U.S.-Canada Equator
ScienceDaily (Nov. 15, 2012) — The recent storms that have battered settlements on the east coast of America may have been much more frequent in the region 450 million years ago, according to scientists.
New research pinpointing the positions of the Equator and the landmasses of the USA, Canada and Greenland, during the Ordovician Period 450 million years ago, indicates that the equator ran down the western side of North America with a hurricane belt to the east.
The hurricane belt would have affected an area covering modern day New York State, New Jersey and most of the eastern seaboard of the USA.
An international research team led by Durham University used the distribution of fossils and sediments to map the line of the Ordovician Equator down to southern California.
The study, published in the journal Geology,is the first to accurately locate and map the ancient Equator and adjacent tropical zones. Previous studies had fuelled controversy about the precise location of the ancient equator. The researchers say the new results show how fossils and sediments can accurately track equatorial change and continental shifts over time.
Co-lead author Professor David Harper, Department of Earth Sciences, said: “The equator, equatorial zones and hurricane belts were in quite different places in the Ordovician. It is likely that the weather forecast would have featured frequent hurricane-force storms in New York and other eastern states, and warmer, more tropical weather from Seattle to California.”
Since Polar Regions existed 450 million years ago, the scientists believe that there would have been similar climate belts to those of today.
The research team from Durham University and universities in Canada, Denmark and the USA, discovered a belt of undisturbed fossils and sediments -deposits of shellfish- more than 6000 km long stretching from the south-western United States to North Greenland. The belt also lacks typical storm-related sedimentary features where the deposits are disturbed by bad weather. The researchers say that this shows that the Late Ordovician equatorial zone, like the equatorial zone today, had few hurricane-grade storms.
In contrast, sedimentary deposits recorded on either side of the belt provide evidence of disturbance by severe storms. Hurricanes tend to form in the areas immediately outside of equatorial zones where temperatures of at least 260C combine with Earth’s rotation to create storms. The researchers believe that hurricane belts would probably have existed on either side of the ancient equator, within the tropics.
The position of the equatorial belt, defined by undisturbed fossil accumulations and sediments, is coincident with the Late Ordovician equator interpreted from magnetic records (taken from rocks of a similar age from the region). This provides both a precise equatorial location and confirms that Earth’s magnetic field operated much in the same way as it does today.
The scientists pieced together the giant jigsaw map using the evidence of the disturbed and undisturbed sedimentary belts together with burrows and shells. Using the findings from these multiple sites, they were able to see that North America sat on either side of the Equator.
Co-author Christian Rasmussen, University of Copenhagen, said: “The layers of the earth build up over time and are commonly exposed by plate tectonics. We are able to use these ancient rocks and their fossils as evidence of the past to create an accurate map of the Ordovician globe.”
Professor Harper added: “The findings show that we had the same climate belts of today and we can see where North America was located 450 million years ago, essentially on the Equator.”
“While the Equator has remained in approximately the same place over time, the landmasses have shifted dramatically over time through tectonic movements. The undisturbed fossil belt helps to locate the exact position of the ancient Laurentian landmass, now known as North America.”
The study is funded by the Danish Council for Independent Research.
New Ancient Shark Species Gives Insight Into Origin of Great White
ScienceDaily (Nov. 14, 2012) — The great white shark is one of the largest living predatory animals and a magnet for media sensationalism, yet its evolutionary history is as misunderstood as its role as a menace.
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Originally classified as a direct relative of megatooth sharks, the white shark’s evolutionary history has been debated by paleontologists for the last 150 years. In a study appearing in print and online today in the journal Palaeontology, University of Florida researchers name and describe an ancient intermediate form of the white shark, Carcharodon hubbelli, which shows the modern white shark likely descended from broad-toothed mako sharks. The study deviates from the white shark’s original classification as a relative of megatooth sharks such as the extinct Carcharocles megalodon, the largest carnivorous shark that ever lived.
Based on recalibrated dates of the excavation site in Peru, the study also concludes the new species was about 2 million years older than previously believed.
“We can look at white sharks today a little bit differently ecologically if we know that they come from a mako shark ancestor,” said lead author Dana Ehret, a lecturer at Monmouth University in New Jersey who conducted research for the study as a UF graduate student. “That 2-million-year pushback is pretty significant because in the evolutionary history of white sharks, that puts this species in a more appropriate time category to be ancestral or kind of an intermediate form of white shark.”
Most ancient shark species are named using isolated teeth, but analysis of C. hubbelli, also known as Hubbell’s white shark, was based on a complete set of jaws with 222 teeth intact and 45 vertebrae. The species was named for Gainesville resident Gordon Hubbell, a collector who recovered the fossils from a farmer who discovered them in the Pisco Formation of southern Peru in 1988. Hubbell donated the specimens to the Florida Museum of Natural History on the UF campus in December 2009.
“The impetus of this project was really the fact that Gordon Hubbell donated a majority of his fossil shark collection to the Florida Museum,” Ehret said. “Naming the shark in his honor is a small tip of the hat to all the great things he has done to advance paleontology.”
Ehret and co-authors published an initial study describing the shark specimens in the Journal of Vertebrate Paleontology in 2009, but dates for the site reflected information from a 1985 study about the Pisco Formation, he said. With Hubbell’s hand-drawn maps and descriptions of the landscape, researchers returned to the site and found the exact spot the fossils were discovered.
Scientists extracted more accurate age estimates from mollusk shells in the fossil horizon to determine the shark species was from the late Miocene, about 6.5 million years ago, rather than the early Pliocene, about 4.5 million years ago. The new dates will also be useful for better understanding other fossils found in the rich Pisco Formation, which include new whale, marine sloth and terrestrial vertebrate species.
“The thing that was remarkable to me was that these fossils came from right out in the desert and this was before GPS, so Dana had only an approximate notion of where it was,” said Florida Museum of Natural History Director Douglas Jones, a study co-author who conducted strontium isotope dating of the fossils. “But after a few days of looking, we were able to find this deposit and Dana found the rest of the missing shark’s teeth.”
Researchers determined Hubbell’s white shark was related to ancient broad-toothed mako sharks by comparing the physical shapes of shark teeth to one another. While modern white sharks have serrations on their teeth for consuming marine mammals, mako sharks do not have serrations because they primarily feed on fish. Hubbell’s white shark has coarse serrations indicative of a transition from broad-toothed mako sharks to modern white sharks.
These evolutionary relationships have been hypothesized for decades, and researchers who interpret modern white sharks as being more closely related to megatooth sharks say it is “a friendly disagreement,” according to Michael Gottfried, an associate professor in geological sciences at Michigan State University.
But shark expert David Ward, a research associate at the Natural History Museum, London, said “fewer people believe the big megatooth sharks are related to the great white sharks than believe the Earth is flat.”
“Everyone working within the field will be absolutely delighted to see this relationship formalized,” Ward said.
Study co-authors include Bruce MacFadden of the Florida Museum, Thomas DeVries of the Burke Museum of Natural History and Culture in Seattle, David Foster of UF and Rodolfo Salas-Gismondi of Museo de Historia Natural Javier Prado in Lima.
Oldest Fossil of Giant Panda Family Discovered
ScienceDaily (Nov. 14, 2012) — New fossils found in Spain are thought to be of the oldest recorded ancestor of the giant panda.
The fossils reveal the origins of this unique bear, as described in a paper published Nov. 14 in the open access journal PLOS ONE by Juan Abella and colleagues from the National Museum of Natural Sciences and the Catalan Institute of Paleontology, Spain.
The two 11.6 million-year-old fossil jaws and teeth were discovered in southwest Europe and represent a new genus likely to be the oldest known members of the giant panda family. The fossils bear the characteristics of a bear adapted to eating tough plant material like bamboo. The giant panda, native to certain parts of China, is the only living member of this unique bear family with these dietary habits.
Corresponding author Juan Abella adds: “The new genus we describe in this paper is not only the first bear recorded in the Iberian Peninsula, but also the first of the giant panda’s lineage.”
The Spanish Ministerio de Economı´a y Competitividad (CGL2011-28681, CGL2011-25754, and RYC-2009-04533 to DMA), the research group BSCH-UCM 910607, and the Generalitat de Catalunya (2009 SGR 754 GRC) supported this research. Fieldwork at ACM was funded by CESPA Gestio´n de Residuos, S.A.U.
Earliest Record of Mating Fossil Vertebrates: Nine Pairs of Fossilized Turtles Died While Mating 47 Million Years Ago
ScienceDaily (June 20, 2012) — The fossil record consists mostly of the fragmentary remains of ancient animals and plants. But some finds can provide spectacular insights into the life and environment of ancient organisms. The Messel Fossil Pit, a UNESCO world heritage site south of Frankfurt in western Germany, is well known for yielding fossils of unusual quality, including early horses complete with embryos and insects and birds with fossilized colors.
In the latest edition of Biology Letters, a group of scientists lead by Dr. Walter Joyce of the University of Tübingen announces the discovery at Messel of nine pairs of fossilized turtles that perished in the act of mating. Dr. Joyce, a geoscientist from the University of Tübingen, heads the discovery team which includes researchers from the Senckenberg Research Institute Frankfurt and the Hessische Landesmuseum Darmstadt.
“Scientists have collected tens of thousands of fossils at this site in recent decades,” notes co-author Dr. Stephan Schaal of the Senckenberg Naturmuseum in Frankfurt, “but only these turtles are known to occur in pairs, a total of nine so far.” Detailed analysis of the fossil material revealed that each pair consists of a female and male individual. More importantly, even though the males typically face away from the females, the tail of some male individuals can be found wrapped under the shell of the female. “There is no doubt in my mind,” says Dr. Joyce, “These animals died some 47 million years ago in the act of mating. No other vertebrates are known to have died during this important biological process and then been fossilized.”
Most scientists agree that the Messel Pit Fossil Site originated as a deep volcanic crater lake that preserved animals and plants that sank to its bottom, but some questions remain, such as whether the lake had poisonous surface or only subsurface waters. Modern relatives of the fossil turtles found at Messel have permeable skin that allows them to breathe and stay under water for a long time. However, this adaptation can become lethal if these turtles enter poisonous waters. The very fact that turtles were seeking to reproduce at Messel reveals that the surface waters of the volcanic lake supported a thriving biotope. Numerous turtles apparently died, however, when they accidentally sank into poisonous sub-surface waters while mating.
Ancient Giant Turtle Fossil Was Size of Smart Car
ScienceDaily (May 17, 2012) — Picture a turtle the size of a Smart car, with a shell large enough to double as a kiddie pool. Paleontologists from North Carolina State University have found just such a specimen — the fossilized remains of a 60-million-year-old South American giant that lived in what is now Colombia.
he turtle in question is Carbonemys cofrinii, which means “coal turtle,” and is part of a group of side-necked turtles known as pelomedusoides. The fossil was named Carbonemys because it was discovered in 2005 in a coal mine that was part of northern Colombia’s Cerrejon formation. The specimen’s skull measures 24 centimeters, roughly the size of a regulation NFL football. The shell which was recovered nearby — and is believed to belong to the same species — measures 172 centimeters, or about 5 feet 7 inches, long. That’s the same height as Edwin Cadena, the NC State doctoral student who discovered the fossil.
“We had recovered smaller turtle specimens from the site. But after spending about four days working on uncovering the shell, I realized that this particular turtle was the biggest anyone had found in this area for this time period — and it gave us the first evidence of giantism in freshwater turtles,” Cadena says.
Smaller relatives of Carbonemys existed alongside dinosaurs. But the giant version appeared five million years after the dinosaurs vanished, during a period when giant varieties of many different reptiles — including Titanoboa cerrejonensis, the largest snake ever discovered — lived in this part of South America. Researchers believe that a combination of changes in the ecosystem, including fewer predators, a larger habitat area, plentiful food supply and climate changes, worked together to allow these giant species to survive. Carbonemys’ habitat would have resembled a much warmer modern-day Orinoco or Amazon River delta.
In addition to the turtle’s huge size, the fossil also shows that this particular turtle had massive, powerful jaws that would have enabled the omnivore to eat anything nearby — from mollusks to smaller turtles or even crocodiles.
Thus far, only one specimen of this size has been recovered. Dr. Dan Ksepka, NC State paleontologist and research associate at the North Carolina Museum of Natural Sciences, believes that this is because a turtle of this size would need a large territory in order to obtain enough food to survive. “It’s like having one big snapping turtle living in the middle of a lake,” says Ksepka, co-author of the paper describing the find. “That turtle survives because it has eaten all of the major competitors for resources. We found many bite-marked shells at this site that show crocodilians preyed on side-necked turtles. None would have bothered an adult Carbonemys, though — in fact smaller crocs would have been easy prey for this behemoth.”
The paleontologists’ findings appear in the Journal of Systematic Palaeontology. Dr. Carlos Jaramillo from the Smithsonian Tropical Research Institute in Panama and Dr. Jonathan Bloch from the Florida Museum of Natural History contributed to the work. The research was funded by grants from the Smithsonian Institute and the National Science Foundation
Were Dinosaurs Undergoing Long-Term Decline Before Mass Extinction?
ScienceDaily (May 1, 2012) — Despite years of intensive research about the extinction of non-avian dinosaurs about 65.5 million years ago, a fundamental question remains: were dinosaurs already undergoing a long-term decline before an asteroid hit at the end of the Cretaceous? A study led by scientists at the American Museum of Natural History gives a multifaceted answer.
The findings, published online May 1 in Nature Communications, suggest that in general, large-bodied, “bulk-feeding” herbivores were declining during the last 12 million years of the Cretaceous. But carnivorous dinosaurs and mid-sized herbivores were not. In some cases, geographic location might have been a factor in the animals’ biological success.
“Few issues in the history of paleontology have fueled as much research and popular fascination as the extinction of non-avian dinosaurs,” said lead author Steve Brusatte, a Columbia University graduate student affiliated with the Museum’s Division of Paleontology. “Did sudden volcanic eruptions or an asteroid impact strike down dinosaurs during their prime? We found that it was probably much more complex than that, and maybe not the sudden catastrophe that is often portrayed.”
The research team, which includes Brusatte; Mark Norell, chair of the Museum’s Division of Paleontology; and scientists Richard Butler of Ludwig Maximilian University of Munich and Albert Prieto-M‡rquez from the Bavarian State Collection for Palaeontology, both in Germany, is the first to look at dinosaur extinction based on “morphological disparity”-the variability of body structure within particular groups of dinosaurs. Previous research was based almost exclusively on estimates of changes in the number of dinosaur species over time. However, it can be very difficult to do this accurately.
“By looking just at trends in taxonomic diversity, you get conflicting answers about the state of dinosaurs prior to extinction,” Brusatte said. “This is because the results can be biased by uneven sampling of the fossil record. In places where more rock and fossils were formed, like in America’s Great Plains, you’ll find more species. We wanted to go beyond a simple species count for this study.”
By looking at the change in biodiversity within a given dinosaur group over time, researchers can create a rough snapshot of the animals’ overall well-being. This is because groups that show an increase in variability might have been evolving into more species, giving them an ecological edge. On the other hand, decreasing variability might be a warning sign of extinction in the long term.
The researchers calculated morphological disparity for seven major dinosaur groups using databases that include wide-ranging characteristics about the intricate skeletal structure of nearly 150 different species.
“People often think of dinosaurs as being monolithic-we say ‘The dinosaurs did this, and the dinosaurs did that,'” Butler said. “But dinosaurs were hugely diverse. There were hundreds of species living in the Late Cretaceous, and these differed enormously in diet, shape, and size. Different groups were probably evolving in different ways and the results of our study show that very clearly.”
The researchers found that hadrosaurs and ceratopsids, two groups of large-bodied, bulk-feeding herbivores-animals that did not feed selectively-may have experienced a decline in biodiversity in the 12 million years before the dinosaurs ultimately went extinct. In contrast, small herbivores (ankylosaurs and pachycephalosaurs), carnivorous dinosaurs (tyrannosaurs and coelurosaurs), and enormous herbivores without advanced chewing abilities (sauropods) remained relatively stable or even slightly increased in biodiversity.
As a complication, hadrosaurs showed different levels of disparity in different locations. While declining in North America, the disparity of this dinosaur group seems to have been increasing in Asia during the latest Cretaceous.
“These disparity calculations paint a more nuanced picture of the final 12 million years of dinosaur history,” Brusatte said. “Contrary to how things are often perceived, the Late Cretaceous wasn’t a static ‘lost world’ that was violently interrupted by an asteroid impact. Some dinosaurs were undergoing dramatic changes during this time, and the large herbivores seem to have been mired in a long-term decline, at least in North America.”
In North America, extreme fluctuations of the inland Western Interior Sea and mountain building might have affected the evolution of dinosaurs in distinct ways from species on other continents. Therefore, the authors say, the North American record might not be representative of a global pattern, if one exists. They also note that there is no way to tell whether a declining dinosaur group would have survived if the asteroid had not struck Earth.
“Even if the disparity of some dinosaur clades or regional faunas were in decline, this does not automatically mean that dinosaurs were doomed to extinction,” Norell said. “Dinosaur diversity fluctuated throughout the Mesozoic, and small increases or decreases between two or three time intervals may not be noteworthy within the context of the entire 150-million-year history of the group.”
Funding for this study was provided by the National Science Foundation through the Division of Earth Sciences, the Division of Biological Infrastructure, a Graduate Research Fellowship, and a Doctoral Dissertation Improvement Grant; the German Research Foundation’s Emmy Noether Programme; the Alexander von Humboldt Foundation; the Charlotte and Walter Kohler Charitable Trust; the American Museum of Natural History; and Columbia University.
Mysterious ‘Monster’ Discovered by Amateur Paleontologist
ScienceDaily (Apr. 24, 2012) — For 70 years, academic paleontologists have been assisted by a dedicated corps of amateurs known as the Dry Dredgers. Recently, one amateur found a very large and very mysterious fossil that has the professionals puzzled.
Around 450 million years ago, shallow seas covered the Cincinnati region and harbored one very large and now very mysterious organism. Despite its size, no one has ever found a fossil of this “monster” until its discovery by an amateur paleontologist last year.
The fossilized specimen, a roughly elliptical shape with multiple lobes, totaling almost seven feet in length, will be unveiled at the North-Central Section 46th Annual Meeting of the Geological Society of America, April 24, in Dayton, Ohio. Participating in the presentation will be amateur paleontologist Ron Fine of Dayton, who originally found the specimen, Carlton E. Brett and David L. Meyer of the University of Cincinnati geology department, and Benjamin Dattilo of the Indiana University Purdue University Fort Wayne geosciences faculty.
Fine is a member of the Dry Dredgers, an association of amateur paleontologists based at the University of Cincinnati. The club, celebrating its 70th anniversary this month, has a long history of collaborating with academic paleontologists.
“I knew right away that I had found an unusual fossil,” Fine said. “Imagine a saguaro cactus with flattened branches and horizontal stripes in place of the usual vertical stripes. That’s the best description I can give.”
The layer of rock in which he found the specimen near Covington, Kentucky, is known to produce a lot of nodules or concretions in a soft, clay-rich rock known as shale.
“While those nodules can take on some fascinating, sculpted forms, I could tell instantly that this was not one of them,” Fine said. “There was an ‘organic’ form to these shapes. They were streamlined.”
Fine was reminded of streamlined shapes of coral, sponges and seaweed as a result of growing in the presence of water currents.
“And then there was that surface texture,” Fine said. “Nodules do not have surface texture. They’re smooth. This fossil had an unusual texture on the entire surface.”
For more than 200 years, the rocks of the Cincinnati region have been among the most studied in all of paleontology, and the discovery of an unknown, and large, fossil has professional paleontologists scratching their heads.
“It’s definitely a new discovery,” Meyer said. “And we’re sure it’s biological. We just don’t know yet exactly what it is.”
To answer that key question, Meyer said that he, Brett, and Dattilo were working with Fine to reconstruct a timeline working backward from the fossil, through its preservation, burial, and death to its possible mode of life.
“What things had to happen in what order?” Meyer asked. “Something caused a directional pattern. How did that work? Was it there originally or is it post-mortem? What was the burial event? How did the sediment get inside? Those are the kinds of questions we have.”
It has helped, Meyer said, that Fine has painstakingly reassembled the entire fossil. This is a daunting task, since the large specimen is in hundreds of pieces.
“I’ve been fossil collecting for 39 years and never had a need to excavate. But this fossil just kept going, and going, and going,” Fine said. “I had to make 12 trips, over the course of the summer, to excavate more material before I finally found the end of it.”
Even then he still had to guess as to the full size, because it required countless hours of cleaning and reconstruction to put it all back together.
“When I finally finished it was three-and-a-half feet wide and six-and-a-half feet long,” Fine said. “In a world of thumb-sized fossils that’s gigantic!”
Meyer, co-author of A Sea without Fish: Life in the Ordovician Sea of the Cincinnati Region, agreed that it might be the largest fossil recovered from the Cincinnati area.
“My personal theory is that it stood upright, with branches reaching out in all directions similar to a shrub,” Fine said. “If I am right, then the upper-most branch would have towered nine feet high. “
As Meyer, Brett and Dattilo assist Fine in studying the specimen, they have found a clue to its life position in another fossil. The mystery fossil has several small, segmented animals known as primaspid trilobites attached to its lower surface. These small trilobites are sometimes found on the underside of other fossilized animals, where they were probably seeking shelter.
“A better understanding of that trilobite’s behavior will likely help us better understand this new fossil,” Fine said.
Although the team has reached out to other specialists, no one has been able to find any evidence of anything similar having been found. The mystery monster seems to defy all known groups of organisms, Fine said, and descriptions, even pictures, leave people with more questions than answers.
The presentation April 24 is a “trial balloon,” Meyer said, an opportunity for the team to show a wide array of paleontologists what the specimen looks like and to collect more hypotheses to explore.
“We hope to get a lot of people stopping by to offer suggestions,” he said.
In the meantime, the team is playing around with potential names. They are leaning toward “Godzillus.”
Evidence for a Geologic Trigger of the Cambrian Explosion
ScienceDaily (Apr. 18, 2012) — The oceans teemed with life 600 million years ago, but the simple, soft-bodied creatures would have been hardly recognizable as the ancestors of nearly all animals on Earth today.
Then something happened. Over several tens of millions of years — a relative blink of an eye in geologic terms — a burst of evolution led to a flurry of diversification and increasing complexity, including the expansion of multicellular organisms and the appearance of the first shells and skeletons.
The results of this Cambrian explosion are well documented in the fossil record, but its cause — why and when it happened, and perhaps why nothing similar has happened since — has been a mystery.
New research shows that the answer may lie in a second geological curiosity — a dramatic boundary, known as the Great Unconformity, between ancient igneous and metamorphic rocks and younger sediments.
“The Great Unconformity is a very prominent geomorphic surface and there’s nothing else like it in the entire rock record,” says Shanan Peters, a geoscience professor at the University of Wisconsin-Madison who led the new work. Occurring worldwide, the Great Unconformity juxtaposes old rocks, formed billions of years ago deep within Earth’s crust, with relatively young Cambrian sedimentary rock formed from deposits left by shallow ancient seas that covered the continents just a half billion years ago.
Named in 1869 by explorer and geologist John Wesley Powell during the first documented trip through the Grand Canyon, the Great Unconformity has posed a longstanding puzzle and has been viewed — by Charles Darwin, among others — as a huge gap in the rock record and in our understanding of Earth’s history.
But Peters says the gap itself — the missing time in the geologic record — may hold the key to understanding what happened.
In the April 19 issue of the journal Nature, he and colleague Robert Gaines of Pomona College report that the same geological forces that formed the Great Unconformity may have also provided the impetus for the burst of biodiversity during the early Cambrian.
“The magnitude of the unconformity is without rival in the rock record,” Gaines says. “When we pieced that together, we realized that its formation must have had profound implications for ocean chemistry at the time when complex life was just proliferating.”
“We’re proposing a triggering mechanism for the Cambrian explosion,” says Peters. “Our hypothesis is that biomineralization evolved as a biogeochemical response to an increased influx of continental weathering products during the last stages in the formation of the Great Unconformity.”
Peters and Gaines looked at data from more than 20,000 rock samples from across North America and found multiple clues, such as unusual mineral deposits with distinct geochemistry, that point to a link between the physical, chemical, and biological effects.
During the early Cambrian, shallow seas repeatedly advanced and retreated across the North American continent, gradually eroding away surface rock to uncover fresh basement rock from within the crust. Exposed to the surface environment for the first time, those crustal rocks reacted with air and water in a chemical weathering process that released ions such as calcium, iron, potassium, and silica into the oceans, changing the seawater chemistry.
The basement rocks were later covered with sedimentary deposits from those Cambrian seas, creating the boundary now recognized as the Great Unconformity.
Evidence of changes in the seawater chemistry is captured in the rock record by high rates of carbonate mineral formation early in the Cambrian, as well as the occurrence of extensive beds of glauconite, a potassium-, silica-, and iron-rich mineral that is much rarer today.
The influx of ions to the oceans also likely posed a challenge to the organisms living there. “Your body has to keep a balance of these ions in order to function properly,” Peters explains. “If you have too much of one you have to get rid of it, and one way to get rid of it is to make a mineral.”
The fossil record shows that the three major biominerals — calcium phosphate, now found in bones and teeth; calcium carbonate, in invertebrate shells; and silicon dioxide, in radiolarians — appeared more or less simultaneously around this time and in a diverse array of distantly related organisms.
The time lag between the first appearance of animals and their subsequent acquisition of biominerals in the Cambrian is notable, Peters says. “It’s likely biomineralization didn’t evolve for something, it evolved in response to something — in this case, changing seawater chemistry during the formation of the Great Unconformity. Then once that happened, evolution took it in another direction.” Today those biominerals play essential roles as varied as protection (shells and spines), stability (bones), and predation (teeth and claws).
Together, the results suggest that the formation of the Great Unconformity may have triggered the Cambrian explosion.
“This feature explains a lot of lingering questions in different arenas, including the odd occurrences of many types of sedimentary rocks and a very remarkable style of fossil preservation. And we can’t help but think this was very influential for early developing life at the time,” Gaines says.
Far from being a lack of information, as Darwin thought, the gaps in the rock record may actually record the mechanism as to why the Cambrian explosion occurred in the first place, Peters says.
“The French composer Claude Debussy said, ‘Music is the space between the notes.’ I think that is the case here,” he says. “The gaps can have more information, in some ways, about the processes driving Earth system change, than the rocks do. It’s both together that give the whole picture.”
The work was supported by the National Science Foundation
Duck-Billed Dinosaurs Endured Long, Dark Polar Winters
ScienceDaily (Apr. 11, 2012) — Duck-billed dinosaurs that lived within Arctic latitudes approximately 70 million years ago likely endured long, dark polar winters instead of migrating to more southern latitudes, a recent study by researchers from the University of Cape Town, Museum of Nature and Science in Dallas and Temple University has found.
The researchers published their findings, “Hadrosaurs Were Perennial Polar Residents,” in the April issue of the journal The Anatomical Record: Advances in Integrative Anatomy and Evolutionary Biology.
Anthony Fiorillo, a paleontologist at the Museum of Nature and Science, excavated Cretaceous Period fossils along Alaska’s North Slope. Most of the bones belonged to Edmontosaurus, a duck-billed herbivore, but some others such as the horned dinosaur Pachyrhinosaurus were also found.
Fiorillo hypothesized that the microscopic structures of the dinosaurs’ bones could show how they lived in polar regions. He enlisted the help of Allison Tumarkin-Deratzian, an assistant professor of earth and environmental science, who had both expertise and the facilities to create and analyze thin layers of the dinosaurs’ bone microstructure.
Another researcher, Anusuya Chinsamy-Turan, a professor of zoology at the University of Cape Town, was independently pursuing the same analysis of Alaskan Edmontosaurus fossils. When the research groups discovered the similarities of their studies, they decided to collaborate and combine their data sets to provide a larger sampling. Half of the samples were tested and analyzed at Temple; the rest were done in South Africa.
“The bone microstructure of these dinosaurs is actually a record of how these animals were growing throughout their lives,” said Tumarkin-Deratzian. “It is almost similar to looking at tree rings.”
What the researchers found was bands of fast growth and slower growth that seemed to indicate a pattern.
“What we found was that periodically, throughout their life, these dinosaurs were switching how fast they were growing,” said Tumarkin-Deratzian. “We interpreted this as potentially a seasonal pattern because we know in modern animals these types of shifts can be induced by changes in nutrition. But that shift is often driven by changes in seasonality.”
The researchers questioned what was causing the dinosaurs to be under stress at certain times during the year: staying up in the polar region and dealing with reduced nutrition during the winter or migrating to and from lower latitudes during the winter.
They did bone microstructure analysis on similar duck-billed dinosaur fossils found in southern Alberta, Canada, but didn’t see similar stress patterns, implying that those dinosaurs did not experience regular periodic seasonal stresses. “We had two sets of animals that were growing differently,” said Tumarkin-Deratzian.
Since the Alaska fossils had all been preserved in the same sedimentary horizon, Fiorillo examined the geology of the bonebeds in Alaska where the samples were excavated and discovered that these dinosaurs had been preserved in flood deposits.
“They are very similar to modern flood deposits that happen in Alaska in the spring when you get spring melt water coming off the Brooks Mountain Range,” said Fiorillo. “The rivers flood down the Northern Slope and animals get caught in these floods, particularly younger animals, which appear to be what happened to these dinosaurs.
“So we know they were there at the end of the dark winter period, because if they were migrating up from the lower latitudes, they wouldn’t have been there during these floods,” he said.
“It is fascinating to realize how much of information is locked in the bone microstructure of fossil bones,” said Chinsamy-Turan. “It’s incredible to realize that we can also tell from these 70 million-year-old bones that the majority of the polar hadrosaurs died just after the winter season.”
The study was funded through a grant from the National Science Foundation.
The Viking journey of mice and men
ScienceDaily (Mar. 19, 2012) — House mice (Mus musculus) happily live wherever there are humans. When populations of humans migrate the mice often travel with them. New research published in BioMed Central’s open access journal BMC Evolutionary Biology has used evolutionary techniques on modern day and ancestral mouse mitochondrial DNA to show that the timeline of mouse colonization matches that of Viking invasion.
During the Viking age (late 8th to mid 10th century) Vikings from Norway established colonies across Scotland, the Scottish islands, Ireland, and Isle of Man. They also explored the north Atlantic, settling in the Faroe Islands, Iceland, Newfoundland and Greenland. While they intentionally took with them domestic animals such as horses, sheep, goats and chickens they also inadvertently carried pest species, including mice.
A multinational team of researchers from the UK, USA, Iceland, Denmark and Sweden used techniques designed to characterize genetic similarity, and hence the relatedness of one population, or one individual, with another, to determine a mouse colonization timeline. Modern samples of mouse DNA were collected and compared to ancient samples dating mostly from the 10th to the 12th century. Samples of house mouse DNA were collected from nine sites in Iceland, Narsaq in Greenland, and four sites near the Viking archaeological site, L’Anse aux Meadows, in Newfoundland. The ancient samples came from the Eastern and Western settlements in Greenland and four archaeological sites in Iceland.
Analysis of mouse mitochondrial DNA showed that house mice (M. m. domesticus) hitched a lift with the Vikings, in the early 10th century, into Iceland, either from Norway or the northern part of the British Isles. From Iceland the mice continued their journey on Viking ships to settlements in Greenland. However, while descendants of these stowaways can still be found in Iceland, the early colonizers in Greenland have become extinct and their role has been filled by interloping Danish mice (M. m. musculus) brought by a second wave of European human immigrants.
Dr Eleanor Jones (affiliated with the University of York and Uppsala University) explained, “Human settlement history over the last 1000 years is reflected in the genetic sequence of mouse mitochondrial DNA. We can match the pattern of human populations to that of the house mice.” Prof Jeremy Searle, from Cornell University, continued, “Absence of traces of ancestral DNA in modern mice can be just as important. We found no evidence of house mice from the Viking period in Newfoundland. If mice did arrive in Newfoundland, then like the Vikings, their presence was fleeting and we found no genetic evidence of it.”