Lo studio al microscopio elettronico delle tracce sui denti di alcuni Adrosauri ne rivelano la complessa tipologia di masticazione.
Dino tooth sheds new light on ancient riddle
Scientists discover major group of dinosaurs had unique way of eating unlike anything alive today
|| IMAGE: These are teeth from the lower jaw of a hadrosaur, Edmontosaurus, showing its multiple rows of leaf-shaped teeth. The worn, chewing surface of the teeth is towards the top.Click here for more information.
Microscopic analysis of scratches on dinosaur teeth has helped scientists unravel an ancient riddle of what a major group of dinosaurs ate- and exactly how they did it!
Now for the first time, a study led by the University of Leicester, has found evidence that the duck-billed dinosaurs- the Hadrosaurs- in fact had a unique way of eating, unlike any living creature today.
Working with researchers from the Natural History Museum, the study uses a new approach to analyse the feeding mechanisms of dinosaurs and understand their place in the ecosystems of tens of millions of years ago. The results are published today in the Proceedings of the National Academy of Sciences.
Palaeontologist Mark Purnell of the University of Leicester Department of Geology, who led the research, said: “For millions of years, until their extinction at the end of the Cretaceous, duck-billed dinosaurs – or hadrosaurs – were the World’s dominant herbivores. They must have been able to break down their food somehow, but without the complex jaw joint of mammals they would not have been able to chew in the same way, and it is difficult to work out how they ate. It is also unclear what they ate: they might have been grazers, cropping vegetation close to the ground – like today’s cows and sheep – or browsers, eating leaves and twigs – more like deer or giraffes. Not knowing the answers to these questions makes it difficult to understand Late Cretaceous ecosystems and how they were affected during the major extinction event 65 million years ago.
|| IMAGE: These are teeth from the upper jaw of a hadrosaur, Edmontosaurus. The specimen was molded and coated with gold for examination using a Scanning Electron Microscope to give high power…Click here for more information.
“Our study uses a new approach based on analysis of the microscopic scratches that formed on hadrosaur’s teeth as they fed, tens of millions of years ago. The scratches have been preserved intact since the animals died. They can tell us precisely how hadrosaur jaws moved, and the kind of food these huge herbivores ate, but nobody has tried to analyse them before.”
The researchers say that the scratches reveal that the movements of hadrosaur teeth were complex and involved up and down, sideways and front to back motion. According to Paul Barrett palaeontologist at the Natural History Museum “this shows that hadrosaurs did chew, but in a completely different way to anything alive today. Rather than a flexible lower jaw joint, they had a hinge between the upper jaws and the rest of the skull. As they bit down on their food the upper jaws were forced outwards, flexing along this hinge so that the tooth surfaces slid sideways across each other, grinding and shredding food in the process”.
The scratch patterns provide confirmation of a theory of hadrosaur chewing first proposed 25 years ago, and provides new insights into their ecology, say the researchers.
The research also sheds light on what the dinosaurs ate. Vince Williams of the University of Leicester said: “Although the first grasses had evolved by the Late Cretaceous they were not common and it is most unlikely that grasses formed a major component of hadrosaur diets. We can tell from the scratches that the hadrosaur’s food either contained small particles of grit, normal for vegetation cropped close to the ground, or, like grass, contained microscopic granules of silica. We know that horsetails were a common plant at the time and have this characteristic; they may well have been an important food for hadrosaurs”.
|| IMAGE: This is a highly magnified Scanning Electron Microscope view of the surface of one of the hadrosaur teeth, showing the scratches created about 67 million years ago by tooth movements…Click here for more information.
One of the big surprises of this study is that so much information about such large animals can be gleaned from such a tiny patch of tooth. “By looking at the pattern of scratches in an area that is only about as wide as a couple of human hairs we can work out how and what these huge herbivores were eating” notes Williams. “And because we can analyse single teeth, rather than whole skeletons, the technique has the potential to tell us a lot more about dinosaur feeding and the ecosystems in which they lived.”
For interviews contact:
Dr Mark A. Purnell
Reader in Geology
Department of Geology
University of Leicester
Leicester LE1 7RH
Tel +44 116 252 3645
Fax +44 116 252 3918
1. The erroneous idea that all dinosaurs could chew is so widely accepted that the memorable ‘Chewits’ advertising campaigns of the 1980s were based on the idea. Note that the dinosaur shown in the adverts is not a hadrosaur:
2. The paper “Quantitative analysis of dental microwear in hadrosaurid dinosaurs, and the implications for hypotheses of jaw mechanics and feeding” by Vincent S. Williams, Paul M. Barrett and Mark A. Purnell is published in the Proceedings of the National Academy of Sciences (online Early Edition).
3. Vince Williams and Mark Purnell are at the University of Leicester, UK; Paul Barrett is at the Natural History Museum, London, UK. A pdf of the paper is available from Mark Purnell: email@example.com
4. Winner of Visit London’s 2008 Kids Love London Best Family Fun Award, the Natural History Museum is also a world-leading science research centre. Through its collections and scientific expertise, the Museum is helping to conserve the extraordinary richness and diversity of the natural world with groundbreaking projects in 68 countries
5. To arrange an interview with Paul Barrett please contact: Claire Gilby, Senior Press Officer, Natural History Museum, Tel: 020 7942 5106 Email: firstname.lastname@example.org (not for publication)
6. Following images can be obtained from University of Leicester email@example.com
- Teeth from the lower jaw of a hadrosaur, Edmontosaurus, showing its multiple rows of leaf-shaped teeth. The worn, chewing surface of the teeth is towards the top. Credit: Vince Williams, University of Leicester.
- Teeth from the upper jaw of a hadrosaur, Edmontosaurus. The specimen was moulded and coated with gold for examination using a Scanning Electron Microscope to give high power magnification of the microscopic scratches. Credit: Vince Williams, University of Leicester.
- Highly magnified Scanning Electron Microscope view of the surface of one of the hadrosaur teeth, showing the scratches created about 67 million years ago by tooth movements and feeding. The small black boxes show the areas, each less than half a millimetre wide, in which scratches were analysed. Credit: Vince Williams, University of Leicester.
- Artists reconstruction of a hadrosaur eating; analysis of tooth wear indicates grazing low growing silica rich plants, like horsetails, was more likely than browsing on bushes. Contact firstname.lastname@example.org for image.
Hadrosaur fact file
This study is based on Edmontosaurus: Lived USA and Canada 65-68 million years ago; Length up to 13 m, weight up to 3 tonnes; One of the most abundant dinosaurs of its time; Known from many complete skeletons, including several mummies with skin impressions and gut contents preserved.
Notes for editors:
per informazioni in italiano vedi:
BLOG THEROPODA – Limusaurus inextricabilis Xu et al. (2009) – Prima Parte: Un Ceratosauria senza denti dal Giurassico Superiore della Cina!
New dinosaur gives bird wing clue
The Limusaurus fossil sits among small crocodile fossils
A new dinosaur unearthed in western China has shed light on the evolution from dinosaur hands to the wing bones in today’s birds.
The fossil, from about 160 million years ago, has been named Limusaurus inextricabilis.
The find contributes to a debate over how an ancestral hand with five digits evolved to one with three in birds.
The work, published in Nature, suggests that the middle three digits, rather than the “thumb” and first two, remain.
Theropods – the group of dinosaurs ancestral to modern birds and which include the fearsome Tyrannosaurus rex – are known for having hands and feet with just three digits.
It has been a matter of debate how the three-fingered hand developed from its five-fingered ancestor. Each digit among the five was composed of a specific number of bones, or phalanges.
Palaeontologists have long argued that it is the first (corresponding to the thumb), second, and third fingers from that ancestral hand that survived through to modern birds, on grounds that the three fingers in later animals exhibit the correct number of phalanges.
However, developmental biologists have shown that bird embryos show growth of all five digits, but it is the first and fifth that later stop growing and are reabsorbed.
The remaining three bones fuse and form a vestigial “hand” hidden in the middle of a bird’s wing.
James Clark of George Washington University in Washington DC and Xing Xu from the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing hit an palaeontologist’s gold mine in the Junggar Basin of northwestern China.
Previous digs have unearthed the oldest known fossil belonging to the tyrannosaur group and the oldest horned dinosaur among several others.
The dinosaurs had beaks and may have had feathers
This time, the ancient mire has yielded a primitive ceratosaur, a theropod that often had horns or crests, many of whom had knobbly fingers without claws.
“It’s a really weird animal – it’s got no teeth, had a beak and a very long neck, and very wimpy forelimbs,” Professor Clark told BBC News.
“Then when we looked closely at the hand, we noticed it was relevant to a very big question in palaeontology.”
The fossil has a first finger which is barely present, made up of just one small bone near the wrist. The fifth finger is gone altogether.
It is a fossil that appears to offer a snapshot of evolution, proving that the more modern three-fingered hand is made up of the middle digits of the ancestral hand, with the outer two being shed.
The third finger is made up of the four phalange bones that the second should have, and it is presumed that the second would lose one bone to become like the first finger that was missing in the fossil.
This process of shifting patterns of gene expression from one limb or digit to another is known as an “identity shift”, and was again caught in the act – making the conflicting theories of bird hand origin suddenly align.
“This is amazing – it’s the first time we’ve seen this thing actually starting to disappear,” Jack Conrad, a palaeontologist at the American Museum of Natural History, told BBC News.
“There’s been this fundamental rift – there was no way to make peace between the good data we were seeing from the developmental biologists and the palaeontological evidence that showed with every fossil we found we were seeing [fingers] one, two and three.”
FOXNews – 17/giu/2009
Uno studio di un iologo evoluzionista australiano pubblicato Biology letter supporta la teoria dei Sauropodi aspiravolvere. Secondo tale studio i sauropodi non potevano sollevare la testa (la pressione sanguigna da sopportare per inviare sangue al cerevello), tuttavia la loro stazza gli permetteva comunque di arrivare a raccogliere foglie da rami inaccessibili ad altri erbivori mentre il lungo collo gli permetteva di sostare in luogo e di agire appunto come un aspirapolvere agendo tutto intorno
Sauropod dinos kept a level head
Long-necked sauropod dinosaurs would had to have used far too much energy to hold their neck upright and browse tall trees, says an Australian evolutionary biologist.
Dr Roger Seymour of the University of Adelaide reports his findings in the Royal Society journal Biology Letters.
Sauropods were about as heavy as a whale and had necks nearly five times the length of a giraffe’s.
The animals have generally been reconstructed with upright necks and it was assumed they grazed on tall trees.
But Seymour has calculated that to do this the dinosaurs would have needed to use 50% of the energy they consumed just to support their long necks.
“I think most people would agree that if you spent half of your energy pumping the blood around the body it would be an enormous cost,” says Seymour, who studies blood pressure in animals.
Seymour says the longer an animal’s neck, the higher the blood pressure it requires to pump blood to the brain.
“The giraffe’s blood pressure is twice that of other mammals,” he says.
While a human has a blood pressure of around 100 millimetres of mercury, a giraffe has a blood pressure of 200, says Seymour.
He says a sauropod with an upright 9-metre neck would have had to have a blood pressure of 700.
“That is exceptionally high,” says Seymour.
Seymour says to produce such a high pressure, the sauropod would need a heart with a 2-tonne left ventricle, which would be a challenge to fit in the animal.
And his most recent research has calculated that 50% of the energy it consumed would be used just to circulate the sauropod’s blood.
“Even though they may have had access to a larger amount of food, it would have cost more than the gain, basically,” says Seymour.
He says a giraffe with a 2-metre neck uses around 20% of its energy to circulate blood and humans use about 10%.
The ‘vacuum cleaner principle’
Previously, it was thought that sauropods must have been semi-aquatic or amphibious to support their enormous bulk.
When palaeontologists decided the animals were terrestrial, they assumed the neck was used like a giraffe’s, says Seymour.
But, he says, the sauropod’s enormous size meant the animal would have had many options for feeding even without having to lift their long neck vertically.
“Even without raising the head, these animals could browse higher than a giraffe,” says Seymour.
Seymour says feeding with a horizontal neck meant the animal could keep the bulk of its body in one place while using its long neck to graze in numerous places.
“It’s the vacuum cleaner principle,” he says.
Telegraph.co.uk – 1-apr-2009
Long-necked dinosaurs kept their heads down and did not raise them to the trees to graze, according to a new study. By Kate Devlin, Medical Correspondent …
L’acidificazione degli oceani dovuta al crescente aumento di CO2 nell’atmosfera, ha comportato una riduzione del 35% nello spessore della conchiglia nel foraminifero Globigerina bulloides dal periodo pre-industiale ad oggi.
Ciò oltre ad alterare l’equilibrio della vita marina è una brutta notizia anche per noi esseri umani in quanto una riduzione di spessore nelle conchiglie significa una maggior quantità di CO2 che non viene fissato dagli organismi nelle loro conchiglie e che quindi rimane ad intossicare l’aria che respiriamo.
Proof on the Half Shell: A More Acid Ocean Corrodes Sea Life
Ocean acidification is taking a toll on tiny shell-building animals
By David Biello
SHELL GAME: Foramnifera, like Globigerina bulloides pictured here, are having a harder time building big shells in a more caustic Southern Ocean. COURTESY OF ANDREW MOY
The shells of tiny ocean animals known as foraminifera—specifically Globigerina bulloides—are shrinking as a result of the slowly acidifying waters of the Southern Ocean near Antarctica. The reason behind the rising acidity: Higher carbon dioxide (CO2) levels in the atmosphere, making these shells more proof that climate change is making life tougher for the seas’ shell-builders.
Marine scientist Andrew Moy at the Antarctic Climate & Ecosystems Cooperative Research Center (ACE) in Hobart, Tasmania, and his Australian colleagues report in Nature Geoscience this week that they made this finding after comparing G. bulloides shells in ocean cores collected along the South Tasman Rise in 1995 with samples from traps collected between 1997 and 2004. The cores provide records that stretch back 50,000 years.
“We knew there were changes in carbonate chemistry of the surface ocean associated with the large-scale glacial-interglacial cycles in CO2 [levels], and that these past changes were of similar magnitude to the anthropogenic changes we are seeing now,” says study co-author William Howard, a marine geologist at ACE. “The Southern [Ocean] works well [to study this issue] as it is a region where anthropogenic CO2 uptake, and thus acidification, has progressed more than in other regions. Other variables, such as temperature, have changed, but not as much.”
The researchers found that modern G. bulloides could not build shells as large as the ones their ancestors formed as recently as century ago. In fact, modern shells were 35 percent smaller than in the relatively recent past—an average of 17.4 micrograms compared with 26.8 micrograms before industrialization. (One microgram is one millionth of a gram; there are 28.3 grams in an ounce.)
“We don’t yet know what impact this will have on the organisms’ health or survival,” Howard says, but one thing seems clear: the tiny animals won’t be storing as much CO2 in their shells in the form of carbonate. “If the shell-making is reduced, the storage of carbon in the ocean might be, as well.”
That’s bad news for the climate, because the ocean is responsible for absorbing at least one quarter of the CO2 that humans load into the air through fossil fuel burning and other activities—and it is the action of foraminifera and other tiny shell-building animals, along with plants like algae that lock it away safely for millennia.
It will be harder to get such a clear sign in a shell from other ocean regions—as variables like temperature and the amount of minerals available can significantly change the chemistry of a given ocean region. As Howard noted, the Southern Ocean has absorbed lots of manmade CO2 while temperatures and nutrients have not changed as much, making it more ideal for studying ocean acidification than other areas. Scientists examining foraminifera in the Arabian Sea, however, have found similar results, and Howard speculates the situation may be similar in the North Atlantic region, because it also absorbs a significant chunk of manmade CO2.
Howard says that CO2 emissions must be cut or captured and stored permanently in some fashion to halt this gradual acidification of the world’s oceans. In the meantime, he adds, it’s likely that many of the other shell-building oceanic animals are suffering similar fates as G. bulloides.
ABC Science Online – 12 ore fa
“The ocean is currently taking up somewhere in the neighbourhood of a third of our fossil fuel emissions,” says Howard, a palaeo-climatologist.
Reduced calcification in modern Southern Ocean planktonic foraminifera
Andrew D. Moy, William R. Howard, Stephen G. Bray & Thomas W. Trull
Abstract: Anthropogenic carbon dioxide has been accumulating in the oceans, lowering both the concentration of carbonate ions and the pH (ref. 1), resulting in the acidification of sea water. Previous laboratory experiments have shown that decreased carbonate ion concentrations cause many marine calcareous organisms to show reduced calcification rates2, 3, 4, 5. If these results are widely applicable to ocean settings, ocean acidification could lead to ecosystem shifts. Planktonic foraminifera are single-celled calcite-secreting organisms that represent between 25 and 50% of the total open-ocean marine carbonate flux6 and influence the transport of organic carbon to the ocean interior7. Here we compare the shell weights of the modern foraminifer Globigerina bulloides collected from sediment traps in the Southern Ocean with the weights of shells preserved in the underlying Holocene-aged sediments. We find that modern shell weights are 30–35% lower than those from the sediments, consistent with reduced calcification today induced by ocean acidification. We also find a link between higher atmospheric carbon dioxide and low shell weights in a 50,000-year-long record obtained from a Southern Ocean marine sediment core. It is unclear whether reduced calcification will affect the survival of this and other species, but a decline in the abundance of foraminifera caused by acidification could affect both marine ecosystems and the oceanic uptake of atmospheric carbon dioxide.
Correspondence to: William R. Howard1 e-mail: Will.Howard@utas.edu.au
Link: nature.com – supplementary information
Nature Geoscience – Published online: 8 March 2009 | doi:10.1038/ngeo460
Completata la scansione tridimensionale di Lucy, i risultati saranno utilizzati per provare a risolvere alcuni quesiti riguardanti la morfologia funzionale (postura, movimenti, possibilità di salire sugli alberi ….)
Famous fossil Lucy scanned at the University of Texas at Austin
Data offers new insights into ancient human ancestor
AUSTIN, Texas—Researchers at The University of Texas at Austin, in collaboration with the Ethiopian government, have completed the first high-resolution CT scan of the world’s most famous fossil, Lucy, an ancient human ancestor who lived 3.2 million years ago.
Lucy is in the United States as part of a world premiere exhibit organized by the Houston Museum of Natural Science.
John Kappelman, professor of anthropology in the College of Liberal Arts, led the scientific team that conducted the scan of Lucy, whose remains include about 40 percent of her skeleton, making her the oldest and most complete skeleton of any adult, erect-walking human fossil.
“By examining the internal architecture of Lucy’s bones, we can study how her skeleton supported her movement and posture, and compare that to modern humans and apes,” Kappelman said. “Because Lucy is so complete, she is one of the few fossils that permit us to compare how she used her arms versus how she used her legs. These new data will allow us to examine the theory that she climbed about in the trees, as well as walked on two legs when she was on the ground.”
Although Lucy is small (about one meter tall), her contribution to science has been large. She represents a distinct species of human ancestor, known as Australopithecus afarensis, or “southern ape of Afar,” in reference to where the bones were found.
Prior to the 1974 discovery of Lucy, some theories of evolution suggested human-like intelligence evolved before upright posture (bipedalism). But the existence of ancient bipeds like Lucy refutes this theory because their brain is not significantly larger than that of a modern chimpanzee.
The Ethiopian government entrusted Lucy to Kappelman and Richard Ketcham, associate professor of geological sciences in the Jackson School of Geosciences and director of the university’s High-Resolution X-ray Computed Tomography Facility, one of the world’s premier labs for this work.
Scientists at the facility have scanned thousands of delicate fossils and biological specimens, including irreplaceable items such as the brain case of Archaeopteryx (one of the oldest and most primitive birds known). Because CT allows scientists to see inside fossils without doing any harm, it has become one of the most powerful tools for studying precious, one-of-a-kind specimens.
“We have more experience scanning natural history objects and dealing with the issues that can arise in scanning natural material than any other lab in the world,” Ketcham said. “The equipment is constantly updated and we’ve created a large, specialized toolkit to process the scan data and to extract the maximum amount of information from it. There’s no other place the Ethiopian government could have sent Lucy to get better imagery or to acquire it more safely.”
For 10 days the university team worked around the clock to scan all 80 pieces of Lucy’s skeleton. The scientists created custom-built foam mounts to safely hold the specimens in the scanner. And each piece was carefully examined before and after scanning to ensure that no damage occurred during the project.
The successful completion of Lucy’s scan means that the specimen is now safely archived in digital format, another of the reasons behind the scanning.
“These scans will ensure that future generations are familiar with Lucy,” said Jara Mariam, director general of Ethiopia’s Authority for Research and Conservation of Cultural Heritage, “and will know of Ethiopia’s central contribution to the study of human evolution. A virtual Lucy will be able to visit every classroom on the planet.”
“In some ways, scanning Lucy was the easy part,” Ketcham said. For the next several months, the research team, consisting of scientists from all around the country, will be reviewing and processing the data and generating images to analyze Lucy’s skeleton and begin to answer important questions ranging from whether she climbed among the tree branches to how she chewed.
This ancient hominin, whom Ethiopians call “Dinkenesh” (“You are beautiful”), is the feature attraction in the exhibit, “Lucy’s Legacy: The Hidden Treasures of Ethiopia,” which is touring the United States. More than a quarter million people viewed the fossil at Houston Museum of Natural Science during 2007 and 2008. After the brief layover in Austin for the scan, Lucy moved to the Pacific Science Center in Seattle where she is on exhibit through March.
Kappelman said the university’s scanning project represents a model for future collaborations between public educational programs and scientific research.
“There is an understandable tension between museum curators, who like to display fossils, and scientists who want to conduct research on the specimens,” Kappelman said. “Our project demonstrates these goals are not mutually exclusive—but mutually beneficial. The museum exhibit that features Lucy offers a once in a lifetime opportunity to introduce millions of people to the actual evidence for human evolution, and seeing the real fossil is so much more meaningful than viewing a plastic replica.”
“Having Lucy here also means that scientists can conduct research that asks new questions about the fossil and this knowledge feeds back into the ongoing exhibit and continues to educate,” Kappelman said. “Lucy may be old, but she still has lots of new secrets to tell.”
In addition to Kappelman and Ketcham, the scientific team includes: Robert Fajardo at Harvard Medical School; Brian G. Richmond at George Washington University; Christopher Ruff at Johns Hopkins University School of Medicine; and Robert S. Scott at Rutgers, The State University of New Jersey.
Contacts: Christian Clarke Casarez, director of international public affairs, 512-232-6241 or email@example.com
J.B. Bird, communications coordinator, Jackson School of Geosciences, 512-232-9623, firstname.lastname@example.org
Contact: Christian Clarke Casarez – email@example.com – 512-232-6241
University of Texas at Austin
Scoperto negli scisti devoniani di Bundenbach, Germania (Hunsrück Slate) un nuovo artropode chiamato Schinderhannes bartelsi. I ricercatori ritengono che le sue espansioni frontali rappresentano le “strutture progenitrici” delle omologhe chele di scorpioni e limuli attuali
Origin of claws seen in 390-million-year-old fossil
February 5th, 2009 in General Science / Archaeology & Fossils
A missing link in the evolution of the front claw of living scorpions and horseshoe crabs was identified with the discovery of a 390 million-year-old fossil by researchers at Yale and the University of Bonn, Germany.
This is a photograph of Schinderhannes bartelsi. Credit: Steinmann Institute/University of Bonn
Reconstruction of Schinderhannes bartelsi. Credit: Elke Groening
The specimen, named Schinderhannes bartelsi, was found fossilized in slate from a quarry near Bundenbach in Germany, a site that yields spectacularly durable pyrite-preserved fossils — findings collectively known as the Hunsrück Slate. The Hunsrück Slate has previously produced some of the most valuable clues to understanding the evolution of arthropods – including early shrimp-like forms, a scorpion and sea spiders as well as the ancient arthropods trilobites.
“With a head like the giant Cambrian aquatic predator Anomalocaris and a body like a modern arthropod, the specimen is the only known example of this unusual creature,” said Derek Briggs, director of Yale’s Peabody Museum of Natural History and an author of the paper appearing in the journal Science.
Scientists have puzzled over the origins of the paired grasping appendages found on the heads of scorpions and horseshoe crabs. The researchers suggest that Schinderhannes gives a hint. Their appendages may be an equivalent to those found in the ancient predatory ancestor, Anomalocaris — even though creatures with those head structures were thought to have become extinct by the middle of the Cambrian Period, 100 million years before Schinderhannes lived.
The fossil’s head section has large bulbous eyes, a circular mouth opening and a pair of segmented, opposable appendages with spines projecting inward along their length. The trunk section is made up of 12 segments, each with small appendages, and a long tail spine. Between the head and trunk, there is a pair of large triangular wing-like limbs — that likely propelled the creature like a swimming penguin, according to Briggs. Unlike its ancestors from the Cambrian period, which reached three feet in length, Schinderhannes is only about 4 inches long.
This finding caps almost 20 years of study by Briggs on the Hunsrück Slate. “Sadly, the quarry from which this fabulous material comes has closed for economic reasons, so the only additional specimens that are going to appear now are items that are already in collectors’ hands and that may not have been fully prepared or realized for what they are,” said Briggs.
Source: Yale University
Science 6 February 2009: Vol. 323. no. 5915, pp. 771 – 773 – DOI: 10.1126/science.1166586
A Great-Appendage Arthropod with a Radial Mouth from the Lower Devonian Hunsrück Slate, Germany
Gabriele Kühl, Derek E. G. Briggs, Jes Rust
Great-appendage arthropods, characterized by a highly modified anterior limb, were previously unknown after the Middle Cambrian. One fossil from the Lower Devonian Hunsrück Slate, Germany, extends the stratigraphic range of these arthropods by about 100 million years. Schinderhannes bartelsi shows an unusual combination of anomalocaridid and euarthropod characters, including a highly specialized swimming appendage. A cladistic analysis indicates that the new taxon is basal to crown-group euarthropods and that the great-appendage arthropods are paraphyletic. This new fossil shows that features of the anomalocaridids, including the multisegmented raptorial appendage and circular plated mouth, persisted long after the initial radiation of the euarthropods.
Abstract » Full Text » PDF » Supporting Online Material » (Supporting Online Material: free access with photos)
Antichissime impronte rinvenute nel precambriano dell’arabia Saudita sono state riconosciute come impronte di spugne. La scoperta ha ovviamente importantissime implicazioni di carattere ia tassonomico che soprattutto paleobiologico ed evoluzionistico
Ancient sponges leave their mark
By Jonathan Amos
Science reporter, BBC News
The rocks date to a time of dramatic gaciation on Earth
Traces of animal life have been found in rocks dating back 635 million years.
The evidence takes the form of chemical markers that are highly distinctive of sponges when they die and their bodies break down in rock-forming sediments.
The discovery in Oman pushes back the earliest accepted date for animal life on Earth by tens of millions of years.
Scientists tell Nature magazine that the creatures’ existence will help them understand better what the planet looked like all that time ago.
“The fact that we can detect these signals shows that sponges were ecologically important on the seafloor at that time,” said lead author Gordon Love, from the University of California, Riverside.
“We’re not saying we captured the first animal; we’re saying they’re an early animal phylum and we’re capturing them when their biomass was significant.”
Researchers can usually determine the presence of ancient life in rock strata by looking for the fossilised remains of skeletons or the hardened record of the creatures’ movements, such as their footprints or crawl marks.
Sponges are among the simplest multi-celled organisms
But for organisms deep in geological history that were extremely small and soft bodied, scientists have had to develop novel techniques to uncover their existence.
One of these newer methods involves detecting breakdown products from the lipid molecules which act as important structural components in the cell membranes of animals.
Over time, these will transform to leave a molecule known as cholestrane; and for sponges, this exclusively takes the form known as 24-isopropylcholestane.
Dr Love’s team found high concentrations of this biomarker in rocks located at the south-eastern edge of the Arabian peninsula.
They were laid down in what would have been a shallow marine environment at least 635 million years ago.
“Even though there must have been sufficient oxygen in the water to maintain the metabolism of these primitive animals, I think their size would have been restricted by oxygen being nowhere near modern values,” the UC Riverside researcher said.
“We’re probably talking about small colonies of sponges with body dimensions of a few millimetres at most. They’d have been filtering organic detritus in the water column.”
The discovery is fascinating because it pre-dates the end of the Marinoan glaciation, a deep freeze in Earth history that some argue shrouded the entire planet in ice.
Scientists often refer to the term “snowball Earth” to describe conditions at this time.
So to find animal life apparently thriving during this glaciation seems remarkable, commented Jochen Brochs, from the Australian National University, Canberra.
“If there really was a snowball Earth, how did those sponges survive? The full snowball Earth hypothesis would predict that the oceans were frozen over by 2km, even at the equator,” he told BBC News.
“Only at hot springs could any organism survive but it is questionable that you would have sponges in a hot spring. I haven’t made my mind up about snowball Earth but perhaps these sponges are telling us something about this glaciation.”
Dr Love’s view is that the presence of these animals puts limits on the scale of the ice coverage.
“I believe there were areas of what we might call refugia – areas of open ocean where biology could go on. And in this case, it could be evidence that we had some sort of evolutionary stimulation of new grades of organisms as well.”
In un nuovo articolo scientifico free access su PLOS descritte evidenze di combattimento per i Triceratopi
January 28, 2009 in Archaeology & Paleontology
Horning In on Triceratops
In a study published in the journal PLoS ONE, researchers conjecture that the three horns of Triceratops were often used for fighting–because museum specimens show much more scarring than in the horns of a related species. Cynthia Graber reports
Triceratops, as the name suggests, were huge dinosaurs adorned with three horns on their heads. Scientists now say those horns may have been a sort of battle bludgeon. Andrew Farke is a curator at the Raymond M. Alf Museum of Paleontology in California. He became curious about that headgear. Farke and colleagues wanted to investigate whether Triceratops fought each other with their horns. Which posed a problem: obviously, we can’t go back in time to watch the animals interact. So the researchers resorted to some techniques out of a Cretaceous CSI.
They examined more than 400 museums specimens of Triceratops and another closely related one-horned dinosaur called Centrosaurus. They scanned the skulls for injuries around where Triceratops might have locked horns and wrestled. Their assumption was that if the horns were just for display, both species would show few scars.
But the Triceratops had 10 times more skull injuries than their Centrosaurus cousins. The most likely explanation is that they probably jabbed each other in the head while fighting. The researchers published their findings in the journal Public Library of Science ONE. They also caution that the horns could have served more than one purpose—perhaps fighting and flaunting.
Triceratops benutzte Hörner als Waffen
Spiegel Online – 2 ore fa
Auch die These, die Dinosaurier hätten damit Fressfeinde wie den Tyrannosaurus rex abgewehrt, ist verbreitet – ebenso wie die Annahme, Triceratops habe die Hörner im Kampf gegen Artgenossen benutzt und mit dem Nackenschild gegnerische Stöße abgewehrt. …
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Dal Cretaceo di Liaoning (Cina) l’ennesimo ritrovamento spettacolare: un piccolo pterosauro caratterizzato da un’ampiezza alare di soli 25 centimetri circa e da un becco appuntito e privo di denti.
Pterosaur Fossil With 10 Inch Wingspan Discovered
With a wingspan of only 10 inches, this weird fossil is one of the world’s smallest species of flying Pterosaurs.
It was recently discovered in the western part of China’s Liaoning Province, which is believed to have been a forested area during the early Cretaceous Period some 120 million years ago.
This pterosaur was equivalent to the size of a modern blackbird.
“The fossil is very well preserved and it has long sharp bill. It was toothless and its skull was just over 4cm (more than 1-inch) long.” said Wang Xiaolin of the Chinese Academy of Sciences.
Despite its small stature and wingspan, this small toothless reptile may well be the ancestor of gigantic Pterodactyls whose wing tips stretched 20-feet from wingtip to wingtip. This new species has been christened Nemicolopterus crypticus, meaning “hidden flying forest dweller”.
The slight shiver that might be crawling up your back is a reminder that in its own way that this fossil is a connection to all living things, humans included.
Un ritrovamento di una ricca fauna a dinosauri nel cretaceo terminale della Russia (Area sub-artica) sembra sconfessare il modello di estinzione lenta dei dinosauri.
——————————————————————————————————————————————-Published online 19 January 2009 | Nature | doi:10.1038/news.2009.40
Dinosaur fossils suggest speedy extinction
Arctic find challenges the idea that the massive reptiles declined slowly.
Fossils uncovered recently in the Arctic support the idea that dinosaurs died off rapidly — perhaps as the result of a massive meteor hitting Earth. The finding contravenes the idea that dinosaurs were already declining by this time.
Geological evidence indicates that an impact occurred near the Yucatán Peninsula at the end of the Cretaceous 66 million years ago. But whether the event created an all-out apocalypse that wiped out the dinosaurs is still a matter of debate. Despite many species dying out, many others survived, including mammals and the small feathered dinosaurs that were the ancestors of today’s birds.
Some palaeontologists suggest that non-avian dinosaurs were in decline before the impact — perhaps as a result of major volcanic events or global cooling.
Now, reporting in Naturwissenschaften1, Pascal Godefroit at the Royal Belgian Institute of Natural Sciences and his colleagues describe fossils found in northeastern Russia that suggest dinosaurs were not in decline at all. Although dinosaur fossils have already been found in the Arctic, the new find is unique because of its age: Godefroit and his team have dated the beds at between 68 million and 65 million years old — just before the time of the extinction.
“We found that there is no indication that the biodiversity of dinosaurs decreased just before the [extinction] event,” says Godefroit. The team found that herbivorous, duck-billed hadrosaurs and velociraptor-like bipedal theropods seem to be as common as they were in other parts of the planet at the time. Along with this discovery is the presence of the first dinosaur eggshells found in polar regions, hinting that the dinosaurs were residents rather than migrants.
Bang or whimper?
That such healthy polar populations existed just before the extinction would seem to strike a blow against the theory that the animals were already declining. But palaeontologists are cautious.
“The presence of these dinosaurs is certainly concordant with the idea of a sudden extinction, but not incontrovertible evidence for it,” says Tom Rich of Museum Victoria in Melbourne, Australia.
Robert Spicer of the Open University’s Earth sciences department in Milton Keynes, UK, suggests that when the dinosaurs died out, the site may have lain along the edge of the Arctic Circle rather than deep within it.
“The weak link here is the palaeoposition of the site,” he says. “With that said, such diversity even at this latitude suggests that dinosaurs were far more robust than we give them credit for. It makes me ask very serious questions about what could make animals that were resilient enough to live under these conditions suddenly go extinct.”
Attributing the extinction to any one cause is risky, adds Bill Clemens of the University of California, Berkeley. Work by David Wake, also at the University of California, Berkeley, and Vance Vredenburg of San Francisco State University2, suggests that the decline of modern amphibians involved a variety of factors ranging from the introduction of predators to disease and habitat loss, Clemens says.
“Ask what is endangering modern amphibians, the answer varies according to species,” he adds. “I think the same was probably true with the dinosaurs.”
- Naturwissenschaften advance online publication doi:10.1007/s00114-008-0499-0 (2009).
- Proc. Natl. Acad. Sci. USA 105, 11466-11473 (2008).