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.
Old Fish Makes New Splash: Coelacanth Find Rewrites History of the Ancient Fish
ScienceDaily (May 2, 2012) — Coelacanths, an ancient group of fishes that were once thought to exist only in fossils, made headlines in 1938 when one of their modern relatives was pulled alive from the ocean. Now coelacanths are making another splash — and University of Alberta researchers are responsible for the discovery.
Lead U of A researcher Andrew Wendruff identified coelacanth fossils that he says are so dramatically different from previous finds, they shatter the theory that coelacanth evolution was stagnant in that their body shape and lifestyle changed little since the origin of the group.
Wendruff says his one-metre-long, fork-tailed coelacanth was one of an “offshoot” lineage that lived 240 million years ago. It falls between the earliest coelacanth fossils dating back 410 million years and the latest fossils dated about 75 million years ago, near the end of the age of dinosaurs.
“Our coelacanth had a forked tail, indicating it was a fast-moving, aggressive predator, which is very different from the shape and movement of all other coelacanths in the fossil record,” said Wendruff.
The researchers say all other ancient coelacanth fossils, and even the modern living coelacanths, have very different bodies.
The first modern coelacanth, or “living fossil,” was captured 74 years ago off the coast of South Africa. Since then, others have been caught in southern oceans near the Comoros Islands, Tanzania and Indonesia.
The fork-tailed fossils described by the U of A team were found in the Rocky Mountains near Tumbler Ridge, British Columbia. Wilson says the eastern range of the Rockies 240 million years ago was a very different place from what it is today. “The area was underwater, lying off the western coast of the supercontinent Pangaea.”
Wendruff’s research co-author, U of A professor emeritus Mark Wilson, describes typical coelacanths as having chunky bodies, fins of varying size and broad, flexible tails. “These fish were slow-moving and probably lay in wait for their prey,” said Wilson.
Wendruff’s coelacanth is so different from all others that it’s been given its own name, Rebellatrix, which means “rebel coelacanth.” The researchers say Rebellatrix came along after the end-Permian mass extinction 250 million years ago, an event so lethal it wiped out 90 per cent of marine life.
Rebellatrix filled a previously occupied predator niche, but it didn’t fare well.
“Rebellatrix was likely a spectacular failure in the evolution of cruising predation,” said Wendruff. “Clearly, some other fish groups with forked tails must have outperformed this coelacanth, as it does not appear later in the fossil record.” Wilson notes that one group of fishes that may have outperformed Rebellatrix were sharks, fossils of which were found in the same rocks.
The research by Wendruff and Wilson was published May 2 as the cover article in the Journal of Vertebrate Paleontology.
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.”
Egg-Laying Beginning of the End for Dinosaurs
ScienceDaily (Apr. 17, 2012) — Their reproductive strategy spelled the beginning of the end: The fact that dinosaurs laid eggs put them at a considerable disadvantage compared to viviparous mammals. Together with colleagues from the Zoological Society of London, Daryl Codron and Marcus Clauss from the University of Zurich investigated and published why and how this ultimately led to the extinction of the dinosaurs in the journal Biology Letters.
The dinosaur’s egg and the tiny dino baby
Weighing in at four tons, the mother animal was 2,500 times heavier than its newly hatched dinosaur baby. By way of comparison, a mother elephant, which is just as heavy, only weighs 22 times as much as its new-born calf. In other words, neonates are already big in large mammal species. The staggering difference in size between newly hatched dinosaurs and their parents was down to the fact that there are limits to the size eggs can become: After all, larger eggs require a thicker shell and as the embryo also needs to be supplied with oxygen through this shell, eventually neither the shell nor the egg can grow any more. Consequently, newly hatched dinosaur babies cannot be larger in the same way as in larger species of mammal.
Many species occupy one niche each; one species occupies many niches
In addition, new-born mammals occupy the same ecological niche as their parents: As they are fed with milk directly by the mother, they do not take any niche away from smaller species. With large dinosaurs, however, it was an entirely different story: They did not only occupy the adults’ one niche during their lifetime, but also had many of their own to pass through — from niches for animals with a body size of a few kilos and those for ten, 100 and 1,000-kilo animals to those that were occupied by the fully grown forms of over 30,000 kilograms.
Daryl Codron explains what this means for biodiversity: “The consensus among researchers is that animals of particular body sizes occupy particular niches. In the case of the dinosaurs, this would mean that a single species occupied the majority of the ecological niches while mammals occupied these through numerous species of different sizes.” Accordingly, the research results reveal that dinosaurs of a small and medium body size were represented with far fewer individual species than was the case in mammals — because their niches were occupied by the young of larger species.
“An overview of the body sizes of all dinosaur species — including those of birds, which are also dinosaurs after all — reveals that few species existed with adults weighing between two and sixty kilograms,” specifies Codron. And Marcus Clauss sums up the consequences of this demonstrated by the researchers using computer simulations: “Firstly, this absence of small and medium-sized species was due to the competition among the dinosaurs; in mammals, there was no such gap. Secondly, in the presence of large dinosaurs and the ubiquitous competition from their young, mammals did not develop large species themselves.” The third insight that the computer simulation illustrates concerns small dinosaurs: They were in competition both among their own ranks and with small mammals. And this increased pressure brought the small dinosaurs either to the brink of extinction or forced them to conquer new niches. The latter enabled them to guarantee their survival up to the present day, as Codron concludes, since “back then, they had to take to the air as birds.”
Catastrophe: Small dinosaurs take to the air and large ones die out
The dinosaurs’ supremacy as the largest land animals remained intact for 150 million years. The mass extinction at the Cretaceous-Tertiary boundary, however, spelled trouble as the species gap in the medium size range turned out to be disastrous for them. According to the current level of knowledge, all the larger animals with a body weight from approximately ten to 25 kilos died out. Mammals had many species below this threshold, from which larger species were able to develop after the calamity and occupy the empty niches again. The dinosaurs, however, lacked the species that would have been able to reoccupy the vacant niches. That was their undoing.
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.”
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.
Mystery Human Fossils Put Spotlight On China
ScienceDaily (Mar. 14, 2012) — Fossils from two caves in south-west China have revealed a previously unknown Stone Age people and give a rare glimpse of a recent stage of human evolution with startling implications for the early peopling of Asia.
The fossils are of a people with a highly unusual mix of archaic and modern anatomical features and are the youngest of their kind ever found in mainland East Asia.
Dated to just 14,500 to 11,500 years old, these people would have shared the landscape with modern-looking people at a time when China’s earliest farming cultures were beginning, says an international team of scientists led by Associate Professor Darren Curnoe, of the University of New South Wales, and Professor Ji Xueping of the Yunnan Institute of Cultural Relics and Archeology.
Details of the discovery are published in the journal PLoS ONE. The team has been cautious about classifying the fossils because of their unusual mosaic of features.
“These new fossils might be of a previously unknown species, one that survived until the very end of the Ice Age around 11,000 years ago,” says Professor Curnoe.
“Alternatively, they might represent a very early and previously unknown migration of modern humans out of Africa, a population who may not have contributed genetically to living people.”
The remains of at least three individuals were found by Chinese archaeologists at Maludong (or Red Deer Cave), near the city of Mengzi in Yunnan Province during 1989. They remained unstudied until research began in 2008, involving scientists from six Chinese and five Australian institutions.
A Chinese geologist found a fourth partial skeleton in 1979 in a cave near the village of Longlin, in neighbouring Guangxi Zhuang Autonomous Region. It stayed encased in a block of rock until 2009 when the international team removed and reconstructed the fossils.
The skulls and teeth from Maludong and Longlin are very similar to each other and show an unusual mixture of archaic and modern anatomical features, as well as some previously unseen characters.
While Asia today contains more than half of the world’s population, scientists still know little about how modern humans evolved there after our ancestors settled Eurasia some 70,000 years ago, notes Professor Curnoe.
The scientists are calling them the “Red-deer Cave people” because they hunted extinct red deer and cooked them in the cave at Maludong.
The Asian landmass is vast and scientific attention on human origins has focussed largely on Europe and Africa: research efforts have been hampered by a lack of fossils in Asia and a poor understanding of the age of those already found.
Until now, no fossils younger than 100,000 years old have been found in mainland East Asia resembling any species other than our own (Homo sapiens). This indicated the region had been empty of our evolutionary cousins when the first modern humans appeared. The new discovery suggests this might not have been the case after all and throws the spotlight once more on Asia.
“Because of the geographical diversity caused by the Qinghai-Tibet plateau, south-west China is well known as a biodiversity hotspot and for its great cultural diversity. That diversity extends well back in time” says Professor Ji.
In the last decade, Asia has produced the 17,000-year-old and highly enigmatic Indonesian Homo floresiensis (“The Hobbit”) and evidence for modern human interbreeding with the ancient Denisovans from Siberia.
“The discovery of the red-deer people opens the next chapter in the human evolutionary story — the Asian chapter — and it’s a story that’s just beginning to be told,” says Professor Curnoe.
Two New Species of Horned Dinosaur Named
ScienceDaily (Mar. 12, 2012) — Two new horned dinosaurs have been named based on fossils collected from Alberta, Canada. The new species, Unescopceratops koppelhusae and Gryphoceratops morrisoni, are from the Leptoceratopsidae family of horned dinosaurs. The herbivores lived during the Late Cretaceous period between 75 to 83 million years ago. The specimens are described in research published in the Jan. 24, 2012, online issue of the journal Cretaceous Research.
“These dinosaurs fill important gaps in the evolutionary history of small-bodied horned dinosaurs that lack the large horns and frills of relatives like Triceratops from North America,” said Michael Ryan, Ph.D., curator of vertebrate paleontology at The Cleveland Museum of Natural History, lead author on the research. “Although horned dinosaurs originated in Asia, our analysis suggests that leptoceratopsids radiated to North America and diversified here, since the new species, Gryphoceratops, is the earliest record of the group on this continent.”
Unescoceratops koppelhusae lived approximately 75 million years ago. It measured about one to two meters (6.5 feet) in length and weighed less than 91 kilograms (200 pounds). It had a short frill extending from behind its head but did not have ornamentation on its skull. It had a parrot-like beak. Its teeth were lower and rounder than those of any other leptoceratopsid. In addition, its hatchet-shaped jaw had a distinct portion of bone that projected below the jaw like a small chin.
The lower left jaw fragment of Unescoceratops was discovered in 1995 in Dinosaur Provincial Park, a United Nations Educational, Scientific and Cultural Organization (UNESCO) World Heritage Site by Philip Currie, Ph.D., now of the University of Alberta. Originally described in 1998 by Ryan and Currie, the dinosaur was referred to as Leptoceratops. Subsequent research by Ryan and David Evans, Ph.D., of the Royal Ontario Museum in Toronto, Canada, determined the specimen was a new genus and species. The genus is named to honor the UNESCO World Heritage Site designation for the locality where the specimen was found and from the Greek “ceratops,” which means “horned face.” The species is named for Eva Koppelhus, Ph.D., a palynologist at the University of Alberta and wife of Currie.
Gryphoceratops morrisoni lived about 83 million years ago. It had a shorter and deeper jaw shape than any other leptoceratopsid. Researchers believe the individual was a full-grown adult. Based on unique characteristics of the jaw and its size, the researchers believe that Gryphoceratops was an adult that did not exceed one-half meter in length. This means it is the smallest adult-sized horned dinosaur in North America and one of the smallest adult-sized plant-eating dinosaurs known.
Lower right jaw fragments of Gryphoceratops were discovered in southern Alberta in 1950 by Levi Sternberg while he worked for the Royal Ontario Museum. The genus is named for “Gryphon,” a mythological Greek figure with the body of a lion and the head of an eagle, which is a reference to the animal’s beaked face. The species name honors Ian Morrison, a Royal Ontario Museum technician, who discovered how the bones fit together.
Second author Evans, associate curator of vertebrate palaeontology at the Royal Ontario Museum and assistant professor at the University of Toronto, said, “Small-bodied dinosaurs are typically poorly represented in the fossil record, which is why fragmentary remains like these new leptoceratopsids can make a big contribution to our understanding of dinosaur ecology and evolution.”
Contributing authors are Philip Currie, Ph.D., of the University of Alberta; Caleb Brown of the University of Toronto; and Don Brinkman, Ph.D., of the Royal Tyrrell Museum of Palaeontology.