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2009-02-07 – Tra i fossili più antichi: Spugne (precambrian fossil sponges)

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

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Ancient sponges leave their mark

By Jonathan Amos
Science reporter, BBC News

Rocks in Oman
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.”

Tiny creatures

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
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.”

Icy planet

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.”

Jonathan.Amos-INTERNET@bbc.co.uk

 

http://news.bbc.co.uk/2/hi/science/nature/7871099.stm

febbraio 7, 2009 Posted by | An. Invertebrates, Articolo sc. di riferimento, Asia, Bl - Top posts, Italiano (riassunto), P - Preservazione eccezionale, P - Ritrovamenti fossili, Paleontology / Paleontologia, Precambriano, X - Nature | , , , , , , , | Lascia un commento

2008-11-26 – Tracce attuali di un Protista (Gromia sphaerica) mettono in discussione l’origine di quelle fossili

La scoperta di tracce lasciate da un piccolo organismo sul fondo dell’Oceano mette in dubbio l’origine di trace analoghe risalenti al Precambriano. Infatti molte tracce analoghe erano state attribuite ad organismi vermiformi (e quindi evolutivamente molto più complessi) mentre ora tale scoperta fa nascere nuovi interrogativi sull’interpretazione delle tracce fossili del precambriano e sulla diversificazione iniziale dei Bilateralia (wiki link: ENG, GER, ITA).

Tale scoperta ha inoltre spinto gli autori della ricerca a far partire il progetto “deep-sea palaeontology”, ossia la costruzione di una databas di trcce attuali da confrontare poi con quelle fossili

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‘Grape’ is key to fossil puzzle

 

It moves slowly across the ocean floor
The protist is similar to a grape in size and shape

A single-celled ball about the size of a grape may provide an explanation for one of the mysteries of fossil history.

Writing in Current Biology, researchers say the creature leaves tracks on the seabed which mirror fossilised tracks left up to 1.8 billion years ago.

Many palaeontologists believe only multi-celled organisms could have made these tracks.

This has been difficult to confirm as no multi-cellular fossils of such an age have ever been found.

Covered in mud

The discovery was made by marine biologists monitoring the sea bed in the Bahamas. They noticed a great deal of tracks made by grape-shaped creatures called protists. Dr Mikhail “Misha” Matz from the University of Texas at Austin, US, led the research.

“We were looking for pretty animals that have eyes, are coloured, or glow in the dark; instead, the most interesting find was the organism that was blind, brainless, and completely covered in mud,” he said.

The researchers say the 3cm-wide, single-celled protists propel themselves using tiny protruding legs called pseudopodia. A number of openings all over the body act as mouths and outlets for waste.

The protists move very slowly, taking weeks or even months to make a track of a few centimetres. As the sea bed currents where they were observed are very slight, their tracks are not washed away.

Worm casts

The protist tracks look very similar to fossil tracks found in the pre-Cambrian era more than 500 million years ago.

Perhaps the most famous are the “worm casts” found in the Stirling Ranges in Western Australia. In 2002, these were dated to at least 1.2 billion years old.

The Stirling formation fossil is at least 1.2 billion years old
The worm casts may not have been made by worms after all

This dating presented a problem for palaeontologists; they assumed multi-cellular organisms with bilateral symmetry, where two halves of their bodies are approximate mirror images of each other, had to be responsible for such tracks, but there is no fossil evidence for the existence of such creatures until several million years later.

Fossil experts believe bilateral symmetry is what gave the organism the ability to make the tracks, with the impressions being produced when the organism moved its weight from one side to another.

Dr Matz believes protists provide an explanation of how the tracks could have been made without the need for organisms with bilateral symmetry.

“We used to think that it takes bilateral symmetry to move in one direction across the seafloor and thereby leave a track,” he explains.

“You had to have a belly and a backside and a front and back end. Now, we show that protists can leave traces of comparable complexity and with a very similar profile.”

Cambrian explosion

Bilateral symmetry appeared in the Cambrian era about about 542 million years ago, early creatures quickly diversified into all of the major animal groups of today. Quite how or why this rapid diversification, known as the Cambrian explosion, occurred is still one of the biggest questions in animal evolution.

Very few fossils exist of organisms that could be the pre-Cambrian ancestors of bilateral animals, and even those are highly controversial. Fossil traces, such as these tracks are the most accepted evidence of the existence of these proto-animals.

We now have to rethink the fossil record
Dr Mikhail ‘Misha’ Matz,University of Texas at Austin

Dr Matz says all tracks which predate the rapid evolution of life seen in the Cambrian explosion – could come from protists.

“Pretty much anything within the Precambrian fossil record can in principle be attributed to large protozoans, from the earliest traces and fossils of the Stirling formation,” he says.

The researchers say forms described as “globular or bulbous collapsible bodies” which were found fossilised together with the Stirling formation’s worm trails are probably the remains of creatures very similar to the protists they found at the bottom of the sea.

The protist is about the size of a grape
The tracks resemble those found in prehistoric times

Genetic analysis shows this moving protist from the Bahamas is broadly the same as a stationary type found in the Arabian sea.

The researchers are now beginning a project which they call “deep-sea palaeontology” to create a catalogue of tracks produced by a variety of present-day underwater animals for comparison with the fossil record.

Dr Matz says the giant protists’ bubble-like structure is probably one of the planet’s oldest body designs, and may have existed for 1.8 billion years.

“Our guys may be the ultimate living fossils of the macroscopic world,” he says.

Friday, 21 November 2008

source: http://news.bbc.co.uk/2/hi/science/nature/7739703.stm

Deep-sea protists may explain trace fossil evidence attributed to ancient animals

Public release date: 20-Nov-2008
[ Print Article | E-mail Article | Close Window ]

Contact: Cathleen Genova
cgenova@cell.com
617-397-2802
Cell Press

A new discovery challenges one of the strongest arguments in favor of the idea that animals with bilateral symmetry—those that, like us, have two halves that are roughly mirror images of each other—existed before their obvious appearance in the fossil record during the early Cambrian, some 542 million years ago. In the November 25th issue of Current Biology, a Cell Press publication, researchers report the first evidence that trace fossils interpreted by some as the tracks of ancient bilaterians could have instead been made by giant deep-sea protists, like those that can still be found at the seafloor to this day.

Protists are a diverse group of predominantly microscopic organisms. They are commonly single-celled with a single nucleus, but they may attain larger size by having many nuclei or forming colonies of identical, unspecialized cells. In the new study, the team describes macroscopic groove-like traces produced by living giant protists, known as Gromia sphaerica, which look something like a grape in terms of shape and size. Those grooves bear a remarkable resemblance to the trace fossils from the Precambrian, including ones as much as 1.8 billion years old.

“Our paper gives the precedent of a protozoan that is motile, produces macroscopic traces, and has a large hydrostatically supported body,” said Mikhail Matz of the University of Texas at Austin. “With these possibilities demonstrated, pretty much anything within the Precambrian fossil record can in principle be attributed to large protozoans, from the earliest traces and fossils of the Stirling formation that are 1.8 billion years old to the weird Ediacaran biota with which the Precambrian culminated.”

This new “protozoan option” takes the edge off the most compelling evidence of primitive bilaterians in the Precambrian that is so important for what has been called the “ancient school,” he says. That line of thinking holds that the apparently explosive diversification of multicellular body plans during the Cambrian is an artifact of the fossil record; it suggests that bilaterians actually existed long before the Cambrian and evolved gradually over time. Others think instead that the Cambrian explosion really happened the way it appears that it did and that evolutionary mechanisms must therefore be sought to explain the rapid diversification.

“Previously one could say, ‘There were traces, therefore there must have been bilaterians,’ whereas now it is ‘There were traces, therefore there may have been bilaterians,’ which is, obviously, not nearly as strong a statement,” Matz said.

He calls the findings a “classic case of scientific serendipity.” They stumbled upon the giant protists while working on a project exploring the interaction between light and life in the ocean. “We were looking for pretty animals that have eyes, are colored, or glow in the dark,” Matz said. “Instead, the most interesting find was the organism that was blind, brainless, and completely covered in mud.”

Almost nothing is known about G. sphaerica, he added. His team is now deep sequencing the genes expressed in this giant protist and a few related protozoans to get a better idea about their evolutionary relationships to one another. They also plan to initiate a project on “deep-sea paleontology” to create a catalogue of traces produced by a variety of present-day animals. “There is surprisingly little data on this, so paleontologists have to resort to speculations a lot when interpreting fossil traces,” Matz said.

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 The researchers include Mikhail V. Matz, University of Texas at Austin, Austin, TX; Tamara M. Frank, Harbor Branch Oceanographic Institute at Florida Atlantic University, Fort Pierce, FL; N. Justin Marshall, The University of Queensland, Brisbane, Queensland, Australia; Edith A. Widder, Ocean Research and Conservation Association, Fort Pierce, FL; and Sonke Johnsen, Duke University, Durham, NC, USA.

source: http://www.eurekalert.org/pub_releases/2008-11/cp-dpm111308.php

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scientific article:

Giant Deep-Sea Protist Produces Bilaterian-like Traces

Mikhail V. Matz, Tamara M. Frank, N. Justin Marshall, Edith A. Widder, Sönke Johnsen
Current Biology – 20 November 2008
Summary | Full Text | PDF (846 kb)

Abstract:

One of the strongest paleontological arguments in favor of the origin of bilaterally symmetrical animals (Bilateria) prior to their obvious and explosive appearance in the fossil record in the early Cambrian, 542 million years ago, is the occurrence of trace fossils shaped like elongated sinuous grooves or furrows in the Precambrian. Being restricted to the seafloor surface, these traces are relatively rare and of limited diversity, and they do not show any evidence of the use of hard appendages. They are commonly attributed to the activity of the early nonskeletonized bilaterians or, alternatively, large cnidarians such as sea anemones or sea pens. Here we describe macroscopic groove-like traces produced by a living giant protist and show that these traces bear a remarkable resemblance to the Precambrian trace fossils, including those as old as 1.8 billion years. This is the first evidence that organisms other than multicellular animals can produce such traces, and it prompts re-evaluation of the significance of Precambrian trace fossils as evidence of the early diversification of Bilateria. Our observations also render indirect support to the highly controversial interpretation of the enigmatic Ediacaran biota of the late Precambrian as giant protists.

novembre 26, 2008 Posted by | America Central, Articolo sc. di riferimento, Attuale, Italiano (riassunto), P - Evoluzione, P - Impronte, P - Ritrovamenti fossili, Paleontology / Paleontologia, Precambriano | , , , , , , , , , , , , | Lascia un commento

2008-11-09 – Utah, USA: Nessuna “pista da ballo” per i dinosauri (no “dinosaur dance floor”)

Un sopralluogo di altri ricercatori (i paleontologi Brent Breithaupt, Alan Titus e Andrew Milner, e il geologo Rody Cox) afferma che le persunte impronte di dinosauri recentemente descritte (in Vermilion Cliffs National Monumen) non sono altro che forme di erosione. Intanto gli autori dello studio Marjorie Chan and Winston Seiler, sembrano convincersi delle critiche; e in particolare Marjorie Chan si difende affermando che se le tracce sono effettivamente forme di erosione sono diverse da quelle che si ritrovano all’interno della stessa formzione rocciosa.

precedente post: 2008-10-20 – USA: nuovo ritrovamento di impronte di dinosauri, la “sala da ballo”! (dinosaur tracks,”dinosaur dance floor”)

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Paleontologists Doubt ‘Dinosaur Dance Floor’

Potholes or Tracks? Both Sides Team for Follow-up Study

Media Contacts

Nov. 7, 2008 – A group of paleontologists visited the northern Arizona wilderness site nicknamed a “dinosaur dance floor” and concluded there were no dinosaur tracks there, only a dense collection of unusual potholes eroded in the sandstone.

So the scientist who leads the University of Utah’s geology department says she will team up with the skeptics for a follow-up study.

“Science is an evolving process where we seek the truth,” says Marjorie Chan, professor and chair of geology and geophysics, and co-author of a recent study that concluded the pockmarked, three-quarter-acre site in Vermilion Cliffs National Monument was a 190-million-year-old dinosaur “trample surface”.

“We went through the proper scientific process of careful study, comparisons with other published works and peer review” of the study by independent scientists, Chan adds. “We gave the project considerable critical thought and came up with a different interpretation than the paleontologists, but we are open to dialogue and look forward to collaborating to resolve the controversy.”

On Oct. 30 – more than a week after the Utah study was publicized worldwide – four scientists hiked to the remote wilderness-area site: paleontologist Brent Breithaupt, director and curator of the University of Wyoming’s Geological Museum; U.S. Bureau of Land Management paleontologist Alan Titus and geologist Rody Cox; and paleontologist Andrew Milner of the St. George (Utah) Dinosaur Discovery Site at Johnson Farm.

They saw dinosaur tracks en route, but none in the pockmarked “dance floor.”

“There simply are no tracks or real track-like features at this site,” Breithaupt says. “We will be investigating the formation of these features in the upcoming study. Science works best when scientists work together.”

Chan and Winston Seiler, who conducted the research as part of his master’s thesis, say they are not retracting their study, which was published in the October issue of Palaios, an international paleontology journal. But they acknowledge there are strong arguments for the features being potholes rather than dinosaur tracks. The original study cited the possibility that the features were potholes and outlined arguments against it.

Chan says if the features are potholes, they are extremely unusual compared with typical potholes on the Colorado Plateau – and their formation still needs to be explained fully. She will work with Breithaupt and the others to examine the site in greater detail.

“A reinterpretation could emerge, but those conclusions have not yet been written as a scientific paper and need to be submitted to a journal for publication after peer review by other scientists,” she says.

Nevertheless, the University of Utah geologists feel obligated to inform the public of the difference of opinion because of wide publicity about the “dinosaur dance floor.”

“The public interest has been tremendous, and fortunately there are many other fantastic, accessible, documented dinosaur track sites than can be visited in the area,” Breithaput says.

Seiler spent considerable time at the unusual site. He acknowledges that the dinosaur track interpretation is controversial, further study is warranted, and if the paleontologists turn out to be correct, “that’s part of science.”

Chan adds: “This is how science works, and we’ll have to see how it shakes out in the end.”

The original Oct. 20 “dinosaur dance floor” news release and high-resolution photos are at: http://www.unews.utah.edu/p/?r=042508-1

source:

http://unews.utah.edu/p/?r=110708-1

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previous post: 2008-10-20 – USA: nuovo ritrovamento di impronte di dinosauri, la “sala da ballo”! (dinosaur tracks,”dinosaur dance floor”)

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Other links:


PhysOrg.com

Paleontologists Doubt ‘Dinosaur Dance Floor’
Science Daily (press release) – 7 nov 2008
7, 2008) – A group of paleontologists visited the northern Arizona wilderness site nicknamed a “dinosaur dance floor” and concluded there were no dinosaur tracks there, only a dense collection of unusual potholes eroded in the sandstone.
Dinosaur experts bust up prehistoric party theory The Associated Press
Dancing with the dino stars: Dispute boils Salt Lake Tribune
Newspost Online – United Press International – LocalNews8.com – Salt Lake Tribune
e altri 110 articoli simili »

novembre 9, 2008 Posted by | - R. Dinosauri, 2 Jurassic / Giurassico, America Northern, Italiano (riassunto), P - Impronte, P - Ritrovamenti fossili, Paleontology / Paleontologia | , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , | Lascia un commento

2008-10-20 – USA: nuovo ritrovamento di impronte di dinosauri, la “sala da ballo”! (dinosaur tracks,”dinosaur dance floor”)

Pubblicato sul numeo di Ottobre della rivista Palaios, dai ricercatori dell’università dello Utah Winston M. Seiler e Marjorie A. Chan, uno studio preliminare su un nuovo sito contenente tracce di dinosauri.

L’area è situata al confine tra Arizona e Utah e gli strati contenenti le tracce appartengono alla Navajo Sandstone Formation e risalgono a 190 milioni di anni fa (Giurassico inferiore).

Le tracce sia di piedi che di code presentano un’elevata densità di frequenza, sono state attribuite ad almeno tre ichnogeneri cf. Eubrontes, cf. Anchisauripus, cf. Grallator, e curiosamente fino ad ora erano state ritenute forme di erosione superficiale.

Il rinvenimento di tali impronte è significativo anche perche le aree della Navajo Sandstone Formation erano ritenute un unico immenso deserto, ma il fatto che vi fossero animali con elevate necessità fa ritenere invece dovevano essere presenti anche aree on risorse sufficienti al loro fabbisogno.

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Public release date: 20-Oct-2008
Contact: Lee Siegel
leesiegel@ucomm.utah.edu
801-581-8993
University of Utah

‘A dinosaur dance floor’

Numerous tracks at Jurassic oasis on Arizona-Utah border



Geologist Winston Seiler with some of the dinosaur tracks he identified for his thesis as a University of Utah master’s degree student. The impressions once were thought to be potholes…
Click here for more information.


SALT LAKE CITY – University of Utah geologists identified an amazing concentration of dinosaur footprints that they call “a dinosaur dance floor,” located in a wilderness on the Arizona-Utah border where there was a sandy desert oasis 190 million years ago.

The three-quarter-acre site – which includes rare dinosaur tail-drag marks – provides more evidence there were wet intervals during the Early Jurassic Period, when the U.S. Southwest was covered with a field of sand dunes larger than the Sahara Desert.

Located within the Vermilion Cliffs National Monument, the “trample surface” (or “trampled surface”) has more than 1,000 and perhaps thousands of dinosaur tracks, averaging a dozen per square yard in places. The tracks once were thought to be potholes formed by erosion. The site is so dense with dinosaur tracks that it reminds geologists of a popular arcade game in which participants dance on illuminated, moving footprints.

“Get out there and try stepping in their footsteps, and you feel like you are playing the game ‘Dance Dance Revolution’ that teenagers dance on,” says Marjorie Chan, professor and chair of geology and geophysics at the University of Utah. “This kind of reminded me of that – a dinosaur dance floor – because there are so many tracks and a variety of different tracks.”

“There must have been more than one kind of dinosaur there,” she adds. “It was a place that attracted a crowd, kind of like a dance floor.”

A study identifying the dinosaur track site was published in the October issue of the international paleontology journal Palaios. Chan is senior author of the study, which was conducted for a master’s degree thesis by former graduate student Winston Seiler, who now works at Chevron Inc., in Bakersfield, Calif.



University of Utah geologist Winston Seiler walks among hundreds of dinosaur footprints in a “trample surface ” that likely was a watering hole amid desert sand dunes during the Jurassic Period…
Click here for more information.


Seiler says the range of track shapes and sizes reveals at least four dinosaur species gathered at the watering hole, with the animals ranging from adults to youngsters.

“The different size tracks [1 inch to 20 inches long] may tell us that we are seeing mothers walking around with babies,” he says.

The site – a 6-mile roundtrip hike from the nearest road – is in Arizona in the Coyote Buttes North area of the Paria Canyon-Vermilion Cliffs Wilderness, which is part of the U.S. Bureau of Land Management’s (BLM) Vermilion Cliffs National Monument. The track site – about halfway between Kanab, Utah, and Page, Ariz. – is near a popular wind-sculpted sandstone attraction known as the Wave.

A Dense Collection of Dinosaur Footprints – and a Few Tail Drags
 
 Chan says the new study is the first scientific publication to identify the impressions as dinosaur footprints on a trample surface.

As part of the study, Seiler marked off 10 random plots, each of 4 square meters, or roughly 2 yards by 2 yards. He counted 473 tracks within those plots – an average of 12 per square meter. He conservatively estimates the 3,000-square-meter site (about 0.75 acres) has more than 1,000 tracks, but he and Chan believe there perhaps are thousands.

Numerous dinosaur track sites have been found in the western United States, including more than 60 in Navajo Sandstone, where actual dinosaur bones are rare.

“Unlike other trackways that may have several to dozens of footprint impressions, this particular surface has more than 1,000,” Seiler and Chan wrote. And they say the density of tracks is much greater than it is at even larger track sites, such as the one at Coral Pink Sand Dunes State Park in Utah.

The dinosaur tracks and tail marks near the Wave were preserved in the vast Navajo Sandstone Formation. But unlike the dunes that make up much of the Navajo Sandstone, the tracks are within what was a wet, low watering hole between the dunes.

“We’re looking at an area much like the Sahara Desert with blowing sand dunes,” Seiler says. “Areas between these sand dunes could have had ponds – oases.”

The 2.4-inch-wide tail-drag marks – which are up to 24 feet long – are a special discovery because there are fewer than a dozen dinosaur tail-drag sites worldwide, Seiler says. Four tail drags were within the 10 plots he surveyed, and there are others nearby.

“Dinosaurs usually weren’t walking around with their tails dragging,” he says.



This Eubrontes dinosaur footprint — including three toes and a heel — measures roughly 16 inches long. Dinosaur footprints are named by their shape because the species and genus of…
Click here for more information.


Potholes – or Prints from Four Kinds of Dinosaurs?
 
 Chan first visited the site of the dinosaur tracks in 2005 with a BLM ranger who was puzzled by them. Chan initially called them potholes, which are erosion features common in desert sandstone, “but I knew that wasn’t the whole story because of the high concentration and because they weren’t anywhere else nearby but along that one surface.”

Seiler first saw the site in 2006. “At first glance, they look like weathering pits – a field of odd potholes,” he says. “But within about five minutes of wandering around, I realized these were dinosaur footprints.”

One anonymous reviewer of the Palaios study still believes the holes are erosion features. The study argues the impressions are from dinosaurs because:

     

  • They are the correct size for tracks made by big animals, and are limited to a single rock bed.  
  • Four different kinds of footprint shapes are seen repeatedly in 14 percent of the impressions, and they include obvious claw, toe and heel marks. The other impressions “are clearly similar.”  
  • One-third of the prints are surrounded by small ridges or mounds. Such features would be expected when animals stepped in wet sand.  
  • The tracks “are rarely flat and are typically oriented at an angle into the sediment … and indicate a clear direction of travel” to the west-southwest. Seiler says the direction the dinosaurs walked “either was dictated by the large dunes that bounded this wet area, or it could be communal behavior, like walking together as a pack.”  
  • About one-eighth of the tracks show “overprinting,” in which a dinosaur stepped in the footprint of another or even in its own prints. 

“While these impressions may be mistaken for potholes caused by weathering, close examination reveals many footprint features,” Seiler says.

Dinosaur footprints are named by their shape because the animals that made them haven’t been identified. Four kinds of footprints were found on the trample surface:

     

  • Eubrontes footprints measure 10 inches to 16 inches long and have three toes and a heel. Eubrontes tracks are believed to have been made by upright-walking dinosaurs 16 to 20 feet long, or smaller than Tyrannosaurus rex.  
  • Grallator tracks are about 4 inches to 7 inches long, are three-toed and were left by small dinosaurs only a few feet tall.  
  • Sauropodomorph dinosaur tracks, which are more circular than the other types, were left by creatures that walked on four legs and were the largest dinosaurs at the site. Their tracks range from 6 inches to 11 inches long. Seiler says the tail-drag marks are associated with these circular footprints, so they likely were made by sauropods.  
  • Anchisauripus tracks measure 7 inches to 10 inches long and were made by dinosaurs that ranged from 6 feet to 13 feet in length. 
An Oasis for Dinosaurs in a Vast Desert of Dunes
 
 When the footprints were made 190 million years ago, “the continents were arranged so this area was in the tropics” and was part of the supercontinent named Pangaea, says Seiler. “It was a desert, like the Sahara but much larger than the Sahara is today,” covering much of Utah, Wyoming, Colorado, New Mexico, Arizona and Nevada.

“Some studies indicate winds probably were much stronger than normal because all the continents were together,” says Chan. “That’s why you had monster dunes.”

“To support large dinosaurs, there probably wasn’t just one watering hole for them to go to, but many,” Seiler says. “They wandered between a network of watering holes for food and water.”

In that sense, the trample surface is not “just a wet pond,” but “it’s possibly a record of global climate change” – a shift from drier to wetter conditions, Chan says.

She says the traditional view is that the Navajo Sandstone represents “a vast, dry uninhabitable desert. But now we are seeing there are a lot of variations, and there were periods when dinosaurs were living there.”

Seiler envisions the dinosaurs were “happy to be at this place, having wandered up and down many a sand dune, exhausted from the heat and the blowing sand, relieved and happy to come to a place where there was water.”

The trample surface “helps paint a picture of what it was like to live back then,” he says. “Tracks tell us what the dinosaurs were doing, what their behavior was, what life was like for them, what they did on a day-to-day basis.”

After the dinosaurs left their prints, the trample surface was covered by shifting dunes, which eventually became Navajo Sandstone. Then, the rock slowly eroded away, exposing the tracks. The tracks eventually will erode too, Seiler says.

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 Seven additional images relevant to this press release are available:

Dinosaur Footprints and Tail-drag Marks
Grallator Dinosaur Track
Sauropodomorph Dinosaur Track
Dinosaur Trackway
Extent of the ‘Dinosaur Dance Floor’
Dinosaur Dance Floor Locator Map
Geologist Winston Seiler

Note: Access to Area is Limited, Permits Required

The dinosaur trample surface and a nearby feature known as the Wave are in the Coyote Buttes North Special Permit Area of the Paria Canyon-Vermilion Cliffs Wilderness Area. A permit and $7 per person fee are required to enter the area.

There is now a four-month wait for the 10 permits issued daily by phone or online. For permits by phone, call the U.S. Bureau of Land Management in St. George, Utah, at (435) 688-3246. For information and permits online, go to http://www.blm.gov/az/st/en/arolrsmain.html , and then click on “Coyote Buttes.” (If Coyote Buttes page doesn’t open, follow instructions to enable TLS security.)

An additional 10 permits are issued daily – one day in advance of the hike – during a 9 a.m. walk-in lottery March 15-Nov. 14 at the Paria Contact Station, and Nov. 15-March 14 at the BLM’s Kanab (Utah) Field Office.

News media interested in accessing the area should contact Linda Price, Vermilion Cliffs National Monument manager, at (435) 688-3241.

University of Utah Public Relations
201 Presidents Circle, Room 308
Salt Lake City, Utah 84112-9017
(801) 581-6773 fax: (801) 585-3350
www.unews.utah.edu

source: http://www.eurekalert.org/pub_releases/2008-10/uou-dd101708.php

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In German:

Dancefloor für Dinos
Spiegel Online – 1 ora fa
Hunderte Fußabdrücke von Sauriern glauben Paläontologen im Westen der USA gefunden zu haben. Die Spuren liegen so dicht beieinander, dass die Forscher den
190 Millionen Jahre alt: Forscher entdecken Dinosaurier-Treffpunkt
Hannoversche Allgemeine (Abonnement) – 1 ora fa
Auf einen 190 Millionen Jahre alten Versammlungsplatz von Dinosauriern sind US-Forscher gestoßen. Bisher haben die Wissenschaftler mehr als 1000 Spuren
Dinosaurier-“Tanzboden” entdeckt
scinexx | Das Wissensmagazin mit Science-News aus – 5 ore fa
Eine erstaunliche Konzentration von Dinosaurierfußspuren haben Geologen an der Grenze zwischen Arizona und Utah entdeckt. Vor rund 190 Millionen Jahren eine

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Other links: (update on 2008-10-21 11:27 Italy)


CBS News

Geologists discover `dinosaur dance floor’
The Associated Press – 1 ora fa
SALT LAKE CITY (AP) – Geologists say they have discovered prehistoric animal tracks so densely packed on a 3/4-acre site that they’re calling it a “dinosaur dance floor.” The site along the Arizona-Utah state line offers a rich new set of clues about
U. geologists discover dinosaur stomping ground Salt Lake Tribune
Dinosaur Dance Floor’ FOXNews
Discovery Channel – Science Daily (press release) – Discover Magazine
e altri 215 articoli simili »

Rock records dino ‘dance floor’
BBC News – 17 ore fa
Scientists have identified an amazing collection of dinosaur footprints on the Arizona-Utah border in the US. There are so many prints – more than 1000
Geologists discover ‘dinosaur dancefloor’ in remote American
Daily Mail – 39 minuti fa
By Claire Bates Scientists have likened the wealth of tracks and tail-drag marks on the three-quarter acre site to a crowded ‘dinosaur dance floor.

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Other links in Italiano: (update on 2008-10-21 18:05 Italy)


La Repubblica
DINOSAURI: TROVATA NELLO UTAH UNA ”PISTA DA BALLO” PREISTORICA
ASCA – Agenzia Stampa Quotidiana Nazionale – 22 minuti fa
(ASCA) – Roma, 21 ott – Un gruppo di geologi dell’Utah ha scoperto un’area a densissima concentrazione di impronte di 190 milioni di anni fa lasciate sulle
“Sembra una pista da ballo” La Repubblica
e altri 2 articoli simili »
MONDO GIURASSICO,CRESTE DINOSAURI SERVIVANO A COMUNICARE
La Repubblica – 17 ott 2008
I dinosauri utilizzavano le lunghe creste ossee sulla testa per produrre suoni musicali con cui comunicavano tra di loro: e’ la nuova teoria degli

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Original Article:

PALAIOS

Volume 23, Issue 10 (October 2008), pag 700

A Wet Interdune Dinosaur Trampled Surface in the Jurassic Navajo Sandstone, Coyote Buttes, Arizona: Rare Preservation of Multiple Track Types and Tail Traces

Winston M. Seiler and Marjorie A. Chan

ottobre 20, 2008 Posted by | - R. Dinosauri, 2 Jurassic / Giurassico, America Northern, Articolo sc. di riferimento, Italiano (riassunto), Lang. - German, Lang. - Italiano, P - Impronte, P - Ritrovamenti fossili, Paleontology / Paleontologia | , , , , , , , , , , , , , , , , , , , , , , , , , , , , | 1 commento

2008-10-14: Kansas,Usa: Scoperte le più antiche tracce fossili di un insetto volatore (Fossil Impression,Flying Insect)

Due studiosi della Tufts University (Kansas,Usa), Richard J. Knecht e Jake Benner, hanno persentato la scoperta del ritrovamento delle più antiche tracce fossili di un insetto volatore rinvenute a North Attleboro.

insect-impression-may-the-the-oldest-ever-found

insect-impression-may-the-the-oldest-ever-found

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Researchers Discover Oldest Fossil Impression of a Flying Insect

Description

Tufts University student and a faculty lecturer uncover what they believe is the world’s oldest known full-body impression of a primitive flying insect, a 300 million-year-old specimen from the Carboniferous Period. Surprise discovery made in a most unlikely place – behind a suburban strip mall.

While paleontologists may scour remote, exotic places in search of prehistoric specimens, Tufts researchers have found what they believe to be the world’s oldest whole-body fossil impression of a flying insect in a wooded field behind a strip mall in North Attleboro, Mass.

During a recent exploration as part of his senior project, Richard J. Knecht, a Tufts geology major, and Jake Benner, a paleontologist and senior lecturer in the Geology Department, set out to hunt for fossils at a location they learned of while reading a master’s thesis that had been written in 1929. With chisels and hammers, the team reached the shale and sandstone outcropping described in the paper. There they delicately picked away pieces of rock before reaching a section that yielded fossils. Just below the surface, they uncovered a fossilized impression of a flying insect.

Not just any fossil

It was not just any fossil. Knecht says it is the world’s oldest known full-body impression of a primitive flying insect, a 300 million-year-old specimen from the Carboniferous Period. It is a rare find in the specialized world of ichnology, which is the study of fossilized animal tracks, impressions and trails to investigate behavior. Knecht says a preserved full-body impression of a flying insect from this or any previous period has never been discovered.

The fossil, Benner says, “captures a moment in time over 300 million years ago when a flying insect just happened to land on a damp, muddy surface leaving almost a perfect impression of its body behind.”

Knecht and Benner presented the fossil at the Second International Congress on Ichnology, in Krakow, Poland last month. The pair will present other trace fossils from the site, including tracks of amphibians and precursors to reptiles, at the Annual Meeting of the Geological Society of America meeting in Houston later this month.

Paleontologists use fossilized remains of insect bodies to study anatomy and develop hypotheses about evolutionary processes. Typically the only evidence available for this type of work is remains of insect wings. Bodies of primitive flying insects are rarely preserved and therefore little is known about them. The North Attleboro fossil will provide researchers with evidence of how it moved once it landed on a surface, as well as its stance, position of its legs and details about its abdomen and thorax.

The impression is about three inches long and is imprinted on the flat side of a rock. The impression does not contain direct evidence of the insect having wings but Knecht and Benner say evidence suggests that it was a winged insect. According to Benner, the insect’s anatomy and body plan are consistent with those of primitive flying insects. He also points out that “there are no walking tracks leading up to the body impression, indicating that it came from above.”

Michael S. Engel, a leading entomologist at the University of Kansas, is working with Knecht and Benner to study the insect. He says that a preliminary inspection of the anatomy indicates that it may be related to the common mayfly. “We can tell from the imprint that it has a very squat position when it lands,” Engel says. “Its legs are sprawled and its belly is pressed down. The only group that does that today is the mayfly.”

Identifying the insect will also help the researchers to gain knowledge about the ecosystem of that period and what type of animals lived in it. The specimen may also advance understanding of insect flight and evolution from smaller, non-flying scurrying animals.

“Once we pin down what type of insect it is we can begin to think about the conditions, the climate and life that must have existed in the environment to support its life,” says Knecht. “One focus is the insect itself. Another is the broader big picture of the world it lived in.”

A moment 300 million years ago

The insect lived in the Pennsylvanian Era – the second half of the Carboniferous Period – and dates back to about 310 million years. Nearby sites of similar age exist in the Canadian Maritimes, Pennsylvania and the southeastern United States. There are no other active explorations of Pennsylvanian rock formation in New England.

Knecht learned of the site while conducting research on sedimentary rocks in the region for his senior thesis. He found an obscure reference to it in an unpublished master’s thesis on amphibian trackways that was originally written by a Brown University student in 1929. The paper was published a year later in the Geological Society of America Bulletin.

Knecht, 30, is a senior at Tufts who enrolled through Tufts’ Resumed Education for Adult Learners program (REAL), following coursework at the University of Massachusetts-Boston. He is a native of Chatham, Mass. At Tufts he has received four grants and fellowship money to support his work from the Paleontological Society, the Geological Society of America and Tufts University.

 

Tufts University, located on three Massachusetts campuses in Boston, Medford/Somerville, and Grafton, and in Talloires, France, is recognized among the premier research universities in the United States. Tufts enjoys a global reputation for academic excellence and for the preparation of students as leaders in a wide range of professions. A growing number of innovative teaching and research initiatives span all Tufts campuses, and collaboration among the faculty and students in the undergraduate, graduate and professional programs across the university’s schools is widely encouraged.

source: http://www.newswise.com/articles/view/545296/

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other links: (updated 2008-10-16 10:18 Italy)

http://www.thesunchronicle.com/articles/2008/10/15/news/3799255.txt

Mall-sprawl site yields a treasure from eons past
Boston Globe – 1 ora fa
Tufts geology senior Richard J. Knecht with his North Attleborough fossil discoveries, including the 310 million-year-old footprints of what is believed to
World’s oldest fossil of flying insect discovered in North
Boston Globe – 12 ore fa
By Colin Nickerson, Globe Correspondent Scientific sleuthing by a Tufts University geology team in a rock formation behind a strip mall in North
Oldest Full-Body Insect Fossil Found
FOXNews – 18 ore fa
Scientists have uncovered what they are calling the oldest full-body impression of a flying insect, possibly an ancient mayfly. “[The fossil] captures a
Tufts research: oldest flying insect fossil found
WTEN – 11 ore fa
AP – October 15, 2008 4:44 PM ET NORTH ATTLEBOROUGH, Mass. (AP) – Tufts University researchers have uncovered what they believe is the oldest fossil of a
World’s oldest flying insect fossil found
United Press International – 12 ore fa
BOSTON, Oct. 15 (UPI) — A US student and his teacher say they’ve found the world’s oldest known fossil impression of a flying insect.
300 Million-Year-Old Fossil Found In N. Attleboro
WBZ – 16 ore fa
NORTH ATTLEBORO (WBZ) ― Geologists in North Attleboro estimate that a recently discovered fossil is 300 million years old. Geologists found the fossil
Here’s the buzz about fossil in NA
Attleboro Sun Chronicle – 15 ott 2008
BY AMY DeMELIA SUN CHRONICLE STAFF Geologists are buzzing about a fossil found in North Attleboro that researchers say may be the oldest whole-body
Researchers Discover Oldest Fossil Impression of a Flying Insect
Scientific Frontline – 14 ott 2008
While paleontologists may scour remote, exotic places in search of prehistoric specimens, Tufts researchers have found what they believe to be the world’s

ottobre 14, 2008 Posted by | - Insetti, America Northern, Lang. - Italiano, P - Ritrovamenti fossili, Paleontology / Paleontologia, Paleozoico | , , , , , , , , , , | Lascia un commento

2008-10-11 – Nuove tracce in Cina: I primi umani lasciarono l’Africa 1,8 milioni di anni fa (China, early humans)

Early humans left Africa 1.8 million years ago, suggests ancient fossil trail

October 10th, 2008 – 4:40 pm ICT by ANI

Washington, Oct 10 (ANI): Using advanced dating techniques, scientists have determined that a trail of stone tools and fossil bones found in China, suggests that early humans left Africa 1.8 million years ago.
Over a million years ago, a band of early humans left their stone tools and two front teeth near a stream in southwest China.
For decades, the precise age of the fossils has remained a mystery, leaving open a central question in paleontology that how quickly did our human ancestors reach China after leaving Africa?
Now, thanks to advanced dating techniques, scientists may finally have the answer.
Chinese paleontologists discovered the two incisors in 1965 and the relatively simple stone tools in 1973 in the Yuanmou Basin.
The teeth came from a hominin, the group that includes humans and our exclusive ancestors, and might be from the species Homo erectus, a direct ancestor of humans that may have been the first human to spread beyond Africa about 1.8 million years ago.
Lacking solid dates, researchers thought until a decade ago that the earliest humans didn”t reach Asia until 1 million years ago.
But a series of dates for fossils from one site in Java, Indonesia, in particular, have recently shown that Homo erectus was there 1.66 million years ago and possibly earlier.
This changed the old textbook view that human ancestors spread around the globe only after they had big brains and more advanced stone hand axes, which appear in Africa about 1.6 million years ago.
Now, a team of Chinese and American researchers has redated the Yuanmou Basin site using a paleomagnetic technique that relies on rock samples to determine the direction of Earth’’s magnetic field when the rocks were formed.
Although the original hillside where the fossils were found has been excavated, the discoverers recorded the layer of sediment where they uncovered the teeth and tools.
The new team traced that sediment layer – or time horizon – throughout the basin, collecting 318 rock samples from it.
The researchers reported that the fossils came from a layer of rock just above a magnetic landmark known as the Olduvai-Matuyama reversal boundary, which is at least 1.77 million years old.
This makes the fossil site slightly younger, about 1.7 million years old.
This age estimate represents “the oldest definite fossil and archaeological evidence of early hominins in China and mainland East Asia,” according to co-author Rick Potts, a paleoanthropologist at the Smithsonian Institution in Washington, D.C.
Taken together, these dates from at least three fossil sites are convincing many researchers that early humans were moving rapidly across Asia 1.77 million to 1.66 million years ago. (ANI)

source: http://www.thaindian.com/newsportal/india-news/early-humans-left-africa-18-million-years-ago-suggests-ancient-fossil-trail_100105649.html

ottobre 11, 2008 Posted by | 1 Olocene b, Asia, P - Paleoantropologia, P - Ritrovamenti fossili, Paleontology / Paleontologia | , , , , , , , , , | Lascia un commento