2009-04-23 – Puijila darwini: Anello mancante nell`evoluzione dei Pinnipedi (missing link in pinniped evolution)

recommended links:

http://nature.ca/puijila/index_e.cfm (Official home page)

http://www.eurekalert.org/pub_releases/2009-04/cmon-feo042009.php (good scientific description of the discovery)

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 Fossil of a walking seal found

Remains of a previously unknown mammal could represent a missing link in pinniped evolution

By Solmaz Barazesh

Web edition : Wednesday, April 22nd, 2009 

Researchers discovered remains of a previously unknown pinniped in the Canadian Arctic. (Inset shows bones that were found.) The fossilized skeleton was about 65 percent complete. (Illustration fills in the missing pieces.)

A fossilized skeleton of what researchers are calling a walking seal has been uncovered in the Canadian Arctic. The remains of this previously unknown mammal could shed light on the evolution of pinnipeds, the group that includes seals, sea lions and walruses, researchers report in the April 23 Nature.

The animal, named Puijila darwini, had a long tail and an otterlike body with webbed feet and legs like a terrestrial animal, the researchers report. But P. darwini also had a pinniped-like skull.

“We realized there was no way this was an otter,” says study coauthor Natalia Rybczynski of the Canadian Museum of Nature in Ottawa. The walking seal probably lived about 20 million years ago and was adept at moving both on land and in water, the team reports. 

 

Researchers describe Puijila darwini (illustration shown) as a walking seal, with the legs of a terrestrial animal, a seal-like skull and webbed feet.

 Scientists had theorized that pinnipeds evolved from land-dwelling ancestors but had little fossil evidence to support that claim. The new finding could be the missing link in pinniped evolution, the researchers report.

“This is a fantastic discovery,” comments evolutionary biologist Annalisa Berta of San Diego State University.

The finding may also indicate that the Arctic was a geographic center for pinniped evolution, the researchers speculate.

But, Berta notes, other early pinnipeds have been discovered in the North Pacific and Eurasia. “We can’t yet conclude the Arctic was the area of origin for pinnipeds,” Berta says.

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Jakarta Post

Otter-like fossil reveals early seal evolution

The Associated Press – ‎22-apr-2009‎

One expert called it “a fantastic discovery” that fills a crucial gap in the fossil record. The 23 million-year-old creature was not a direct ancestor of …

Walking Seal Called Missing Link in Evolution FOXNews

Otter-Like Fossil Is a Missing Link in Seal Evolution Discover Magazine

Science Now  – Times Online  – CTV.ca  – Science News

tutte le notizie (193) »

2009-03-09 – L’inquinamento “corrode” la vita marina (Acid Ocean, thinner shells)

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.

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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.

source: http://www.sciam.com/article.cfm?id=more-acid-ocean-corrodes-sea-life

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Shells ‘thinning due to fossil fuels’

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.

Carbon dioxide threatens marine life ABC Online

Rising ocean acidity cutting shell weights – study Reuters

Scientific American  – Sydney Morning Herald  – LiveScience.com

tutte le notizie (49) »

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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 rates^{2, 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

2009-03-03 – L’origine del sesso (sex origin) 2: Multimedia

Multimedia and scientific article from Nature:

The mother fish

Ancient fish fossils shed light on the origins of sex.

• Research paper: Long et al.
• + supplementary informations
• + figures
• News & Views article
• Video
• Podcast: search for 26 February 2009

see also previous post: 2009-02-28 – L’origine del sesso (sex origin)

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Scientific publication, Info and Abstract:

Devonian arthrodire embryos and the origin of internal fertilization in vertebrates

John A. Long, Kate Trinajstic & Zerina Johanson

Nature 457, 1124-1127 (26 February 2009) | doi:10.1038/nature07732;

 

Evidence of reproductive biology is extremely rare in the fossil record. Recently the first known embryos were discovered within the Placodermi¹, an extinct class of armoured fish, indicating a viviparous mode of reproduction in a vertebrate group outside the crown-group Gnathostomata (Chondrichthyes and Osteichthyes). These embryos were found in ptyctodontids, a small group of placoderms phylogenetically basal to the largest group, the Arthrodira^{2, 3}. Here we report the discovery of embryos in the Arthrodira inside specimens of Incisoscutum ritchiei from the Upper Devonian Gogo Formation of Western Australia⁴ (approximately 380 million years ago), providing the first evidence, to our knowledge, for reproduction using internal fertilization in this diverse group. We show that Incisoscutum and some phyllolepid arthrodires possessed pelvic girdles with long basipterygia that articulated distally with an additional cartilaginous element or series, as in chondrichthyans, indicating that the pelvic fin was used in copulation. As homology between similar pelvic girdle skeletal structures in ptyctodontids, arthrodires and chondrichthyans is difficult to reconcile in the light of current phylogenies of lower gnathostomes^{2, 3, 5}, we explain these similarities as being most likely due to convergence (homoplasy). These new finds confirm that reproduction by internal fertilization and viviparity was much more widespread in the earliest gnathostomes than had been previously appreciated.

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 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 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

2009-01-20 – Nuovo fossile fornisce informazioni sull’evoluzione dei pesci (Fossil, fishes evolution)

Il reperto fossile (Siluriano, Herefordshire, UK) di un pesce acanthode presenta una morfologia della mandibola e del cranio che suggerice che gli Acanthodi fossero un gruppo eterogeneo, e che Squali e Placodermi siano evoluti da essi.

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Fossil illuminates jaw evolution

By Tanya Syed BBC News The 415-million-year-old-fossil was excavated from Herefordshire, UK A fossil fish is shedding light on the evolution of jawed vertebrates. It is one of the earliest known jawed fish in the fossil record, a scientist from Uppsala University, Sweden, reports in the journal Nature. The specimen is the first example of a well-preserved braincase of a group of extinct fish called acanthodians from the Paleozoic era. The fossil fish was unearthed in Herefordshire, UK, in the 1940s and is an estimated 415 million years old. The study was led by Martin Brazeau from Uppsala University in Sweden. “Because of their superficially shark-like and bony fish-like appearance, acanthodians have played an important role in trying to elucidate the origins of modern jawed vertebrates,” he told BBC News. Different proportions The fossil’s dimensions differ from typical Acanthodes fossils in two important ways, Dr Brazeau explains. The front of the preserved head is short while the back end is long. “This is really what braincases of early sharks and armoured fish looked like,” he says. “When we look at early bony fishes, the back end of the braincase is very short and the front end is long – which is what Acanthodes were like.” “This figures in nicely with the emerging idea that acanthodians don’t form a group of fishes that are all closely related to each other. Some of these fossils are primitive sharks while others are primitive bony fishes.” The study also suggests that some acanthodians are ancestors to all modern jawed vertebrates. This is really what braincases of early sharks and armoured fish looked like. Dr. Martin Brazeau, Uppsala University, Sweden “We’ve already got scores of known acanthodians, but braincases are known in only one of these, belonging to the Acanthodes genus. “Fitting them into the picture of early jawed vertebrate evolution has been extremely difficult because of the lack of data.” “Previously, we’ve had to operate on an assumption that the braincase of the Acanthodes fossil was stereotypical for all the other acanthodians.”

 source: http://news.bbc.co.uk/2/hi/science/nature/7830479.stm

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The braincase and jaws of a Devonian ‘acanthodian’ and modern gnathostome origins – p305

Martin D. Brazeau

doi:10.1038/nature07436

First paragraph | Full Text | PDF (1,741K) | Supplementary information

See also: Editor’s summary

2008-10-23 – Epidexipteryx hui: le piume per “esibizionismo” e non per volare (2)

Dopo quasi un mese dal lancio mediatico della scoperta di Epidexipteryx hui se ne torna a parlare, così aggiorniamo le notizie.

Epidexipteryx hui è un dinsoauro teropode il cui reperto fossile presenta resti di piumaggio in particolare anche su una coda dall’aspetto assai bizzarro.

L’età del reperto, l’appartenenza al gruppo dei teropodi (lo stesso dela maggior parte dei dinosauri piumati, e quello dal quale si evolveranno poi gli uccelli), e il fatto che il piumaggio dell’esemplare sembra non avere attinenza con la capacità di volare, fanno ritenere gli studiosi che il piumaggio possa essere nato con una funizone di “visual communication” (l’esempio attuale più classico è quello della coda dei pavoni).

Epidexipterix hui, from Nature

A mio modesto parere, non essendo uno specialista di dinosauri, sebbene è chiaro che le piume della coda avevano un significato “visuale”, ciò non esclude che il piumaggio in genere possa essere un carattere evolutivo legato inizialmente alla “regolazione termica”.

precedente post: Epidexipteryx hui : le piume per “esibizionismo” e non per volare

Epidexipteryx - Images courtesy Qui Ji & Xing Lida

P:S: the informal name given to this dinosaur is “Hushiyaolong” after the name of “Hu Yaoming”, a young deceased Chinese paleomammalogist. The fossil specimen will be exhibited at the Paleozoological Museum of China starting October 25 (link).

The fossil specimen of Epidexipteryx hui ("Hushiyaolong") (Xinhua photo)

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see for comments of Dr Angela Milner, associate keeper of palaeontology at the Natural History Museum, London:

New feathered dinosaur looks like déjà vu for birds, but not a …
DigitalJournal.com – 2008-10-27  – It’sa dinosaur with display feathers, but no flight feathers. It dates from Middle to Late Jurassic, and it would have been for enthusiasts only as a pet.

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Other links (updated on 2008-10-23 11:02 Italy):

New feathered dinosaur discovered BBC News – 7 ore fa By James Morgan The fossil of a “bizarre” feathered dinosaur from the era before birds evolved has been discovered in China. …

Bird-Like Dinosaur Sported Bizarre Tail Feathers FOXNews – 9 ore fa By Jeanna Bryner Epidexipteryx is the oldest theropod (two-legged meat-eating dinosaur) known to possess display feathers. Epidexipteryx is the oldest …

Tiny dinosaur ‘the peacock of its day’ Scotsman – 9 ore fa A PIGEON-SIZED feathered dinosaur with impressive tail plumage may have been the peacock of its day, scientists have discovered. …

Early dinosaur’s feathers were for show, not flight CBC.ca – 13 ore fa Epidexipteryx, a new feathered maniraptoran dinosaur from the Jurassic period of China, is a primitive, flightless member of the avialan group. …

First Dinosaur Feathers for Show, Not Flight? National Geographic – 13 ore fa One of the oldest known dinosaur relatives of birds had “bizarre” anatomy, including long, ribbon-like tail feathers that suggest plumage may have first …

Dinosaur feather mating discovery The Press Association – 14 ore fa A pigeon-sized feathered dinosaur with impressive tail plumage may have been the peacock of its day, scientists have discovered. …

Weird dino rewrites the book on birds AFP – 14 ore fa PARIS (AFP) — A tiny, egg-robbing dinosaur that lived more than 150 million years ago could help explain a key phase in the evolution of birds, …

Fancy Feathers Predated Flight in Dinosaur-Bird Hybrid Wired News – 15 ore fa By Alexis Madrigal October 22, 2008 | 12:16:03 PMCategories: Dinosaurs A part-bird, part-dinosaur described in the journal Nature this week didn’t have …

China finds fossils of small feathered dinosaur Reuters UK – 15 ore fa HONG KONG (Reuters) – Archaeologists in China have discovered fossils of a pigeon-sized feathered dinosaur which they believe to be an ancestor of birds. …

Shake a tail feather: Scientists reveal the pigeon-sized dinosaur … Daily Mail – 14 ore fa By Daily Mail Reporter Is it a bird? Is it a dino-saur? The answer to both questions is yes. This bizarre pigeon-sized creature, which roamed the planet …

Shake a tale feather: Scientists reveal the pigeon-sized dinosaur … Daily Mail – 14 ore fa By Daily Mail Reporter A strange pigeon-sized dinosaur that roamed the planet more than 150 million years ago was the oldest known relative of birds, …

Shake Your Jurassic Tail Feather Discover Magazine – 14 ore fa In recent years, dinosaurs have gotten awfully cute. They’re no longer Victorian lumps of saggy muscle. A lot of them are not even frightening. …

New bizarre feathered dinosaur discovered in China Science Centric – 15 ore fa by Stanislav P. Abadjiev | 22 October 2008 17:00 GMT — A new stage in the early history of birds is published in the most recent issue of the journal Nature …

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Other links, in german:

Chinesischer Saurier hatte bereits Federn, flog aber noch nicht WELT ONLINE – 5 ore fa Oktober 2008, 02:43 Uhr Peking – Chinesische Forscher haben in der Inneren Mongolei das Skelett einer bisher unbekannten Dinosaurier-Art ausgegraben. Das Skelett stamme von einem halbwüchsigen Tier, es handle sich dabei um den ältesten federtragenden, … Kurioser Vogelsaurier aus der Jurazeit Frankfurter Allgemeine Zeitung Das Geheimnis der gefiederten Echsen derStandard.at WELT ONLINE e altri 66 articoli simili » Wissenschaft aktuell Nachrichtendienst Hui: Schicke Schwanzfedern zierten neu entdeckte Übergangsform … Wissenschaft aktuell Nachrichtendienst – 16 minuti fa Das Fossil eines frühen Vogelverwandten macht das Wissen rund um den Übergang zwischen Sauriern und Vögeln noch komplexer: Fliegen konnte Epidexipteryx hui zwar vermutlich nicht, aber er hatte bereits ein schmückendes Federkleid. …

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Original scientific article:

A bizarre Jurassic maniraptoran from China with elongate ribbon-like feathers

Fucheng Zhang¹, Zhonghe Zhou¹, Xing Xu¹, Xiaolin Wang¹ & Corwin Sullivan¹

1. Laboratory of Evolutionary Systematics of Vertebrates, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, PO Box 643, Beijing 100044, China

Correspondence to: Fucheng Zhang¹ Correspondence and requests for materials should be addressed to F.Z. (Email: zhangfucheng@ivpp.ac.cn).

Nature 455, 1105-1108 (23 October 2008) | doi:10.1038/nature07447; Received 14 June 2008; Accepted 19 September 2008

 

Abstract:

Recent coelurosaurian discoveries have greatly enriched our knowledge of the transition from dinosaurs to birds, but all reported taxa close to this transition are from relatively well known coelurosaurian groups^{1, 2, 3}. Here we report a new basal avialan, Epidexipteryx hui gen. et sp. nov., from the Middle to Late Jurassic of Inner Mongolia, China. This new species is characterized by an unexpected combination of characters seen in several different theropod groups, particularly the Oviraptorosauria. Phylogenetic analysis shows it to be the sister taxon to Epidendrosaurus ^{4, 5}, forming a new clade at the base of Avialae⁶. Epidexipteryx also possesses two pairs of elongate ribbon-like tail feathers, and its limbs lack contour feathers for flight. This finding shows that a member of the avialan lineage experimented with integumentary ornamentation as early as the Middle to Late Jurassic, and provides further evidence relating to this aspect of the transition from non-avian theropods to birds.

 

Epidexipteryx hui : le piume per “esibizionismo” e non per volare

vedi pure aggiornamento: 2008-10-23 – Epidexipteryx hui: le piume per “esibizionismo” e non per volare (2)

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First Dinosaur Feathers for Show, Not Flight?

Charles Q. Choi
for National Geographic News

September 29, 2008

The oldest known dinosaur relative of birds had “bizarre” anatomy, including long, ribbon-like tail feathers that suggest plumage may have first evolved for show rather than for flight, scientists say.

Farmers unearthed a fossil of the new dino species, dubbed Epidexipteryx hui, from the hills of Inner Mongolia in late 2007.
The remains date back 152 million to 168 million years ago, making the newfound creature slightly older than Archaeopteryx, the most primitive known bird.

(Related: “Earliest Bird Had Feet Like Dinosaur, Fossil Shows” [December 1, 2005].)

Like other avialans—birds and their closest dinosaur relatives—Epidexipteryx is a theropod, a group of two-legged animals that includes Tyrannosaurus rex.

A fossil of Epidexipteryx hui found in Mongolia shows long, ribbon-like tail feathers in addition to a body covered with shorter plumage.

Researchers think the pigeon-size Epidexipteryx might have used its plumes as flashy ornaments, since it was mostly covered in short feathers that lack the structure necessary for flight.

“For example, [the feathers] could potentially have played a role in displays intended to attract a mate, scare off a rival, or send a warning signal to other individuals of the same species,” said study co-author Fucheng Zhang, a paleontologist at the Chinese Academy of Sciences in Beijing.

“This is very exciting indeed, since it gives us a window into a stage of avialan history just preceding the appearance of the classic ‘first bird,'” Zhang said.

“It shows that the use of feathers for visual communication—as opposed to other functions such as insulation and flight—was a very early development.”

“Bizarre” Anatomy

Epidexipteryx lived in the mid- to late Jurassic period in a lush, well-vegetated area that was rich in salamanders and other possible prey.

The dinosaur had claws similar to those of ground-foraging birds, such as ostriches and turkeys, and its front teeth were large and protruding.

 

“One can certainly imagine [the teeth] being used to snatch at small prey, such as lizards, small mammals, or even insects,” Zhang said.

Strangely, Epidexipteryx’s anatomy seems to be a hodgepodge of features taken from a variety of animals.

For instance, its front limb bones and short, bony tail resemble those of living birds. But its short, high skull and large front teeth look like those of small theropods called oviraptors.

“It’s not uncommon for features present in one group to appear independently in another,” Zhang said of the newfound dino’s “bizarre” anatomy.

“It’s also typical for different parts of the body to evolve at different rates, so that some bits end up looking very specialized whereas others remain primitive.”

(See pictures of other “bizarre” dinosaurs.)

Zhang and his colleagues reported their findings last week in Nature Precedings, an online pre-publication service run by the journal Nature.

Evolution Experiments?

Luis Chiappe is a paleontologist with the Natural History Museum of Los Angeles County and a former National Geographic Society grantee. (National Geographic News is part of the National Geographic Society.)

He said that the mosaic of features suggests “there was a lot of evolutionary experimentation around the origin of birds, with many different kinds of lineages reaching different levels of ‘birdness.'”

But Chiappe, who was not involved in the new study, is skeptical of the idea that feathers originated as ornaments.

“Feathers could have served an aerodynamic function of some sort whether you fly or not. You could flap feathered wings and run faster,” he said.

“Still, these ornamental feathers are a really interesting new piece of evidence into why feathers first originated.”

SOURCES AND RELATED WEB SITES

• Chinese Academy of Sciences
• Nature Precedings
• Natural History Museum of Los Angeles County

http://news.nationalgeographic.com/news/2008/09/080929-bizarre-dinosaur.html
 

 free access article: http://precedings.nature.com/documents/2326/version/1

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  vedi approfondimento sul blog “Theropoda“

I pesci fossili di Bolca forniscono nuovi esempi di asimmetria [Amphistium, Heteronectes, Pleuronectiformes]

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I pesci fossili di Bolca forniscono nuovi esempi di asimmetria[vedi numero di Settembre 2008 di “Le Scienze”]

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Links:

http://www.telegraph.co.uk/earth/main.jhtml?view=DETAILS&grid=&xml=/earth/2008/07/09/sciflat109.xml

Video from Youtube:

http://www.youtube.com/watch?v=qSYl4aMe0BE

Links from Nature.com 

1.	The evolutionary origin of flatfish asymmetry Matt Friedman SUMMARY: All adult flatfishes (Pleuronectiformes), including the gastronomically familiar plaice, sole, turbot and halibut, have highly asymmetrical skulls, with both eyes placed on one side of the head. CONTEXT: …Naturhistorisches Museum, Vienna (NHMW). Total length is 142 mm; standard length is 111 mm. Horizon and locality. Bolca, possibly Monte Postale locality, northern Italy. Lower Eocene (Ypresian; SBZ11). Diagnosis. Stem pleuronectiform… Nature 454, 209 – 212 (10 Jul 2008), doi: 10.1038/nature07108, Letter Abstract | Full Text | PDF | Rights and permissions | Save this link
2.	The eyes have it Daniel Cressey SUMMARY: Fossilized flatfish settle evolutionary conundrum. CONTEXT: …I first noticed the fossil, it was sitting unidentified in a drawer of indeterminate fossil fish pieces from Monte Bolca [in Italy],” he says. “And believe me, it didn t look like much at the time it was an incomplete specimen… Nature News (09 Jul 2008), doi: 10.1038/news.2008.946, News Full Text | Save this link
3.	Palaeontology: Squint of the fossil flatfish Philippe Janvier SUMMARY: Evolutionary biologists have floundered when trying to explain how the asymmetrical head of flatfishes came about. ‘Gradually’ is the answer arising from exquisite studies of 45-million-year-old CONTEXT: …(which has been known for a long time). The specimens all come from the exceptional fossil-fish locality of Bolca, Italy, and were once regarded as possible flatfish relatives on the basis of their postcranial skeleton. However, this… Nature 454, 169 – 170 (09 Jul 2008), doi: 10.1038/454169a, News and Views Full Text | PDF | Rights and permissions | Save this link

2008-09-22 – Pesce fossile con dita (Panderichthys, 1) (Abstract from Nature)

Letter

Nature advance online publication 21 September 2008 | doi:10.1038/nature07339; Received 12 June 2008; Accepted 14 August 2008; Published online 21 September 2008

 

The pectoral fin of Panderichthys and the origin of digits

Catherine A. Boisvert¹, Elga Mark-Kurik² & Per E. Ahlberg¹

1. Subdepartment of Evolutionary Organismal Biology, Department of Physiology and Developmental Biology, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18A, 752 36 Uppsala, Sweden
2. Institute of Geology at Tallinn University of Technology, Ehitajate tee 5, 19086 Tallinn, Estonia

Correspondence to: Catherine A. Boisvert¹ Correspondence and requests for materials should be addressed to C.A.B. (Email: catherine.boisvert@ebc.uu.se).

 

One of the identifying characteristics of tetrapods (limbed vertebrates) is the presence of fingers and toes. Whereas the proximal part of the tetrapod limb skeleton can easily be homologized with the paired fin skeletons of sarcopterygian (lobe-finned) fish, there has been much debate about the origin of digits. Early hypotheses¹ interpreted digits as derivatives of fin radials, but during the 1990s the idea gained acceptance that digits are evolutionary novelties without direct equivalents in fish fin skeletons. This was partly based on developmental genetic data², but also substantially on the pectoral fin skeleton of the elpistostegid (transitional fish/tetrapod) Panderichthys, which appeared to lack distal digit-like radials³. Here we present a CT scan study of an undisturbed pectoral fin of Panderichthys demonstrating that the plate-like ‘ulnare’ of previous reconstructions is an artefact and that distal radials are in fact present. This distal portion is more tetrapod-like than that found in Tiktaalik ⁴ and, in combination with new data about fin development in basal actinopterygians⁵, sharks⁶ and lungfish⁷, makes a strong case for fingers not being a novelty of tetrapods but derived from pre-existing distal radials present in all sarcopterygian fish.

http://www.nature.com/nature/journal/vaop/ncurrent/abs/nature07339.html

NB – SUPPLEMENTARY INFORMATIONS (with video and pictures)

http://www.nature.com/nature/journal/vaop/ncurrent/suppinfo/nature07339.html