Brain of Ampelosaur from Cuenca (Spain) Revealed
Jan. 23, 2013 — Scientists have made a 3D reconstruction of the remains of ampelosaur, found in 2007 in the site of Lo Hueco (Cuenca). The fossils are about 70 million years old (Late Cretaceous).
Up to now, only one species of the genus was known, Ampelosaurus atacis, which was discovered in France. The differences between the Spanish and the French fossils do not rule out that they could represent distinct species.
The researcher from the National Museum of Natural Sciences (CSIC) Fabien Knoll, who has conducted the investigation, considers that “more fossils are necessary to establish that we are dealing with a new species.” For this reason, the team has identified the specimen as Ampelosaurus sp., which leaves open its specific identity.
Little evolved brain
The ampelosaur pertains to the sauropod group, large-sized dinosaurs that settled widely during the Mesozoic Era (which began 253 million years ago and ended 66 million years ago). More precisely, it is a titanosaur, a group of plant eating animals that were dominant during the last half of the Cretaceous (last period of the Mesozoic). The first sauropods appeared about 160 million years earlier than the ampelosaur.
However, despite being the product of a long evolution, the brain of the ampelosaur does not show any notable development. Knoll explains: “This saurian may have reached 15 m in length; nonetheless its brain was not in excess of 8 cm.” According to the CSIC researcher: “Increase in brain size was not favored in the course of sauropod evolution.”
Another of the characteristics yielded by the reconstruction of the Cuenca ampelosaur brain is the small size of the inner ear. According to Knoll: “This may suggest that the ampelosaur would not have been adapted to quickly move either its eyes or its head and neck.”
In January of 2012, Knoll conducted the investigation that led to the reconstruction of another sauropod, Spinophorosaurus nigeriensis. The simulation in 3D of its brain revealed that that species, in contrast to what the study of the ampelosaur braincase demonstrated, presented a fairly well-developed inner ear.
According to the one of the researchers, “It is quite enigmatic that sauropods show such a diverse inner ear morphology whereas they have a very homogenous body shape; more investigation is definitely required.”
A Relative from the Tianyuan Cave: Humans Living 40,000 Years Ago Likely Related to Many Present-Day Asians and Native Americans
Jan. 21, 2013 — Ancient DNA has revealed that humans living some 40,000 years ago in the area near Beijing were likely related to many present-day Asians and Native Americans.
An international team of researchers including Svante Pääbo and Qiaomei Fu of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, sequenced nuclear and mitochondrial DNA that had been extracted from the leg of an early modern human from Tianyuan Cave near Beijing, China. Analyses of this individual’s DNA showed that the Tianyuan human shared a common origin with the ancestors of many present-day Asians and Native Americans. In addition, the researchers found that the proportion of Neanderthal and Denisovan-DNA in this early modern human is not higher than in people living in this region nowadays.
Humans with morphology similar to present-day humans appear in the fossil record across Eurasia between 40,000 and 50,000 years ago. The genetic relationships between these early modern humans and present-day human populations had not yet been established. Qiaomei Fu, Matthias Meyer and colleagues of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, extracted nuclear and mitochondrial DNA from a 40,000 year old leg bone found in 2003 at the Tianyuan Cave site located outside Beijing. For their study the researchers were using new techniques that can identify ancient genetic material from an archaeological find even when large quantities of DNA from soil bacteria are present.
The researchers then reconstructed a genetic profile of the leg’s owner. “This individual lived during an important evolutionary transition when early modern humans, who shared certain features with earlier forms such as Neanderthals, were replacing Neanderthals and Denisovans, who later became extinct,” says Svante Pääbo of the Max Planck Institute for Evolutionary Anthropology, who led the study.
The genetic profile reveals that this early modern human was related to the ancestors of many present-day Asians and Native Americans but had already diverged genetically from the ancestors of present-day Europeans. In addition, the Tianyuan individual did not carry a larger proportion of Neanderthal or Denisovan DNA than present-day people in the region. “More analyses of additional early modern humans across Eurasia will further refine our understanding of when and how modern humans spread across Europe and Asia,” says Svante Pääbo.
Parts of the work were carried out in a new laboratory jointly run by the Max Planck Society and the Chinese Academy of Sciences in Beijing.
Earliest Sea Cow Ancestors Originated in Africa, Lived in Fresh Water
Jan. 16, 2013 — A new fossil discovered in Tunisia represents the oldest known ancestor of modern-day sea cows, supporting the African origins of these marine mammals. The find is described in research published January 16 in the open access journal PLOS ONE by Julien Benoit and colleagues from the University of Science and Technology in Montpellier, France.
Some fossils of sea cow ancestors have been found in Jamaica, but the Tunisian fossil is more primitive and pre-dates these, revealing an older ancestor for sea cows that emerged at the same time as other modern mammals. Unlike whales and dolphins, the evolutionary origins of the sea cow family have been obscure.
They share an ancestor with elephants, and it is thought that their oldest relatives were terrestrial animals that gradually adapted to an aquatic life. The last common ancestor of the two species may have lived in freshwater swamps well before the time that the new species described in this study lived.
Though this specimen may not have been the common link between modern day sea cows and elephants, the authors’ analyses suggest that this new species lived in fresh water, not sea waters.
Paleo-Ocean Chemistry: New Data Challenge Old Views About Evolution of Early Life
Dec. 23, 2012 — A research team led by biogeochemists at the University of California, Riverside has tested a popular hypothesis in paleo-ocean chemistry, and proved it false.
The fossil record indicates that eukaryotes — single-celled and multicellular organisms with more complex cellular structures compared to prokaryotes, such as bacteria — show limited morphological and functional diversity before 800-600 million years ago. Many researchers attribute the delayed diversification and proliferation of eukaryotes, which culminated in the appearance of complex animals about 600 million years ago, to very low levels of the trace metal zinc in seawater.
As it is for humans, zinc is essential for a wide range of basic cellular processes. Zinc-binding proteins, primarily located in the cell nucleus, are involved in the regulation of gene transcription.
Eukaryotes have increasingly incorporated zinc-binding structures during the last third of their evolutionary history and still employ both early- and late-evolving zinc-binding protein structures. Zinc is, therefore, of particular importance to eukaryotic organisms. And so it is not a stretch to blame the 1-2-billion-year delay in the diversification of eukaryotes on low bioavailability of this trace metal.
But after analyzing marine black shale samples from North America, Africa, Australia, Asia and Europe, ranging in age from 2.7 billion years to 580 million years old, the researchers found that the shales reflect high seawater zinc availability and that zinc concentrations during the Proterozoic (2.5 billion to 542 million years ago) were similar to modern concentrations. Zinc, the researchers posit, was never biolimiting.
Study results appear online Dec. 23 in Nature Geoscience.
“We argue that the concentration of zinc in ancient marine black shales is directly related to the concentrations of zinc in seawater and show that zinc is abundant in these rocks throughout Earth’s history,” said Clint Scott, the first author of the research paper and a former UC Riverside graduate student. “We found no evidence for zinc biolimitation in seawater.”
Scott, now a research geologist with the U.S. Geological Survey, explained that the connection between zinc limitation and the evolution of eukaryotes was based largely on the hypothesis that Proterozoic oceans were broadly sulfidic. Under broadly sulfidic conditions, zinc should have been scarce because it would have rapidly precipitated in the oceans, he explained.
“However, a 2011 research paper in Nature also published by our group at UCR demonstrated that Proterozoic oceans were more likely broadly ferruginous — that is, low in oxygen and iron-rich — and that sulfidic conditions were more restricted than previously thought,” said Scott, who performed the research in the lab of Timothy Lyons, a professor of biogeochemistry and the principal investigator of the research project.
The research team argues that ferruginous deep oceans, combined with large hydrothermal fluxes of zinc via volcanic activity on the seafloor, maintained high levels of dissolved zinc throughout the oceans and provided a relatively stable marine reservoir of the trace metal over the past 2.7 billion years.
“The key challenge in understanding the early evolution of life is recognizing the environmental conditions under which that life first appeared and diversified,” Lyons said. “We have taken a very direct approach that specifically tracks the availability of essential micronutrients, and, to our surprise, zinc supplies in ancient seawater were much higher and less variable than previously imagined.
“We can imagine for the first time,” he quipped, “that zinc supplements were not on the shopping lists of our early eukaryotic ancestors, and so we better find another reason to explain the mysterious delay in their rise in the ocean.”
Scott, who graduated with a doctoral degree in geological sciences from UCR in 2009, and Lyons were joined in the study by Noah J. Planavsky, a former UCR graduate student in Lyons’ lab; Chris L. Dupont at the J. Craig Venter Institute, La Jolla, Calif.; Brian Kendall and Ariel D. Anbar at Arizona State University; Benjamin C. Gill at Virginia Polytechnic Institute and State University and also a former member of the Lyons lab; Leslie J. Robbins and Kurt O. Konhauser at the University of Alberta, Canada; Kathryn F. Husband and Simon W. Poulton at the University of Leeds, United Kingdom; Gail L. Arnold at the Max Planck Institute for Marine Microbiology, Germany; Boswell A. Wing at McGill University, Canada; and Andrey Bekker at the University of Manitoba, Canada.
The idea for the study was a direct consequence of the 2011 Nature paper by Planavsky, Scott, Lyons and others that challenged the hypothesis of broadly sulfidic oceans.
The international collaboration received funding for the study from numerous sources. In the U.S., funding came from the National Science Foundation, the NASA Astrobiology Institute and the Agouron Institute.
Researchers Find First Evidence of Ice Age Wolves in Nevada
Dec. 13, 2012 — A University of Nevada, Las Vegas research team recently unearthed fossil remains from an extinct wolf species in a wash northwest of Las Vegas, revealing the first evidence that the Ice Age mammal once lived in Nevada.
The metapodial, or foot bone, was uncovered late last year by UNLV geologist Josh Bonde during a survey of the Upper Las Vegas Wash. They have now confirmed that the bone comes from a dire wolf.
The discovery site is near the proposed Tule Springs Fossil Beds National Monument, a fossil-rich area known for its diversity and abundance of Ice Age animal remains. Scientists estimate the fossil to be 10,000 to 15,000 years old during the Late Pleistocene period.
“Dire wolves are known to have lived in almost all of North America south of Canada, but their historical presence in Nevada has been absent until now,” said Bonde, a UNLV geology professor. He was a Ph.D. student at the university when he discovered the bone.
“The Tule Springs area has turned up many species, but it’s exciting to fill in another part of the map for this animal and reveal a bit more about the Ice Age ecosystem in Southern Nevada.”
The dire wolf, a larger relative of the gray wolf, was present in much of North and South America for more than a million years. Scientists theorize that competition from other wolf species and a possible food scarcity led to its extinction roughly 10,000 years ago.
Foot bones of the extinct dire wolf are difficult to distinguish from those of the gray wolf. Researchers conclude bone is likely from a dire wolf because of the abundance of dire wolf fossils―and scarcity of gray wolf fossils―in similar-aged excavation sites throughout the Southwest.
Fossil remains of dire wolves are abundant in the La Brea tar pits and have been found in other Southwestern states. Many of the same species of Ice Age animals found at La Brea have also been recovered in the Las Vegas Valley, including Columbian mammoths, camels, horses, bison, and ground sloths.
“This discovery helps flesh out Southern Nevada’s Pleistocene ecosystem and shows that there are still important discoveries to be made in the Upper Las Vegas Wash,” said UNLV geology professor Steve Rowland, a collaborator with Bonde on the study of local Ice Age fossils. “To understand why certain species became extinct and others did not, we need to learn as much as possible about predatory habits and which species were especially sensitive to changes in the environment.”
The announcement comes on the heels of a recent discovery in the same wash of a saber-tooth cat by researchers from the San Bernardino County Museum. Like dire wolves, saber-tooth cats were Pleistocene predators that had been conspicuously absent from the Southern Nevada fossil record.
According to Rowland, Tule Springs was a spring-fed, swampy area during periods of the Late Pleistocene, an ideal spot for plant-eating animals and their carnivorous predators.
The recent discoveries come exactly 50 years after scientists conducted a ‘big dig’ at Tule Springs, revealing the site to be rich with Ice Age fossils.
“Tule Springs likely had the highest density of large animals in the area during the Late Pleistocene, and the marshy environment was very good for preserving at least some of the bones and teeth of animals that died there,” said Rowland.
“In the 50 years since the ‘big dig,’ the scientists have confirmed that humans interacted with Ice Age animals. We now have a new list of questions about life and death in the Pleistocene, and a new tool kit of research techniques to help us get the answers.”
The identity of the find was confirmed by Xiaoming Wang of the Los Angeles County Museum of Natural History, an expert on extinct species of the dog family. Bonde has been surveying the Tule Springs area since 2007, and he and a group of UNLV undergraduate studentss are prospecting for more fossils.
The center of the original ‘big dig’ is on the same parcel of land where Bonde discovered the wolf fossil.
The dire wolf bone, in addition to other bones collected by UNLV researchers, are cataloged, studied, and stored at UNLV.
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.
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.
T. Rex’s Killer Smile Revealed
ScienceDaily (Mar. 18, 2012) — One of the most prominent features of life-size models of Tyrannosaurus rex is its fearsome array of flesh-ripping, bone-crushing teeth.
Until recently, most researchers who studied the carnivore’s smile only noted the varying sizes of its teeth. But University of Alberta paleontologist Miriam Reichel discovered that beyond the obvious size difference in each tooth family in T. rex’s gaping jaw, there is considerable variation in the serrated edges of the teeth.
“The varying edges, or keels, not only enabled T. rex’s very strong teeth to cut through flesh and bone,” says Reichel, “the placement and angle of the teeth also directed food into its mouth.”
Reichel analyzed the teeth of the entire tyrannosaurid family of meat-eating dinosaurs and found T. rex had the greatest variation in tooth morphology or structure. The dental specialization was a great benefit for a dinosaur whose preoccupation was ripping other dinosaurs apart.
Reichel’s research shows that the T. rex’s front teeth gripped and pulled, while the teeth along the side of the jaw punctured and tore flesh. The teeth at the back of the mouth did double duty: not only could they slice and dice chunks of prey, they forced food to the back of the throat.
Reichel says her findings add strength to the classification of tyrannosaurids as heterodont animals, which are animals with teeth adapted for different functions depending on their position in the mouth.
One surprising aspect of T. rex teeth, common to all tyrannosaurid’s, is that they weren’t sharp and dagger-like. “They were fairly dull and wide, almost like bananas,” said Reichel. “If the teeth were flat, knife-like and sharp, they could have snapped if the prey struggled violently when T. rex’s jaws first clamped down.”
Reichel’s research was published in The Canadian Journal of Earth Science.