Paleonews

Il blog dedicato ai Paleontologi !!!!

2009-07-06 – La masticazione degli Adrosauri (chewing of Adrosaurs)

Lo studio al microscopio elettronico delle tracce sui denti di alcuni Adrosauri ne rivelano la complessa tipologia di masticazione.

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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.”

 

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For interviews contact:
Dr Mark A. Purnell
Reader in Geology
Department of Geology
University of Leicester
University Road
Leicester LE1 7RH
UK
Tel +44 116 252 3645
Fax +44 116 252 3918
http://www.le.ac.uk/people/map2

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:
http://www.youtube.com/watch?v=NJUwQIXPCBE
http://www.youtube.com/watch?v=420UecB2YZQ

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: map2@le.ac.uk

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: c.gilby@nhm.ac.uk (not for publication)

6. Following images can be obtained from University of Leicester pressoffice@le.ac.uk

Captions follow:

     

  • 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 c.gilby@nhm.ac.uk 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:

Annunci

luglio 6, 2009 Posted by | - Adrosauri, - Ornitopodi, - R. Dinosauri, An. Vertebrates, Articolo sc. di riferimento, Italiano (riassunto), P - morfologia funzionale, Paleontology / Paleontologia, X - PNAS | , , , | Lascia un commento

2009-06-03 – Anoiapithecus brevirostris “Lluc”: new Hominid (nuovo ominide scoperto in Spagna)

In Italiano:

Lluc è il nome dell’ “Anoiapithecus” possibile nuovo antenato dell  – Soverato News – ‎2-giu-2009‎ – Non è detto però che l’ Anoiapithecus (nome scientifico attribuito sulla base del luogo di ritrovamento), benchè abbia un aspetto moderno sia un diretto

Firenze: un nuovo antenato per la famiglia Hominidae inToscana
 ECCO LLUC, NUOVO ANTENATO DELL’UOMO ANSA
Scoperto nuovo antenato dell’uomo ANSA
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New Hominid 12 Million Years Old Found In Spain, With ‘Modern’ Facial Features

ScienceDaily (June 2, 2009) — Researchers have discovered a fossilized face and jaw from a previously unknown hominoid primate genus in Spain dating to the Middle Miocene era, roughly 12 million years ago. Nicknamed “Lluc,” the male bears a strikingly “modern” facial appearance with a flat face, rather than a protruding one. The finding sheds important new light on the evolutionary development of hominids, including orangutans, chimpanzees, bonobos, gorillas and humans.

In a study appearing in the Proceedings of the National Academy of Sciences, Salvador Moyà-Solà, director of the Institut Català de Paleontologia (ICP) at the Universitat Autònoma de Barcelona, and colleagues present evidence for the new genus and species, dubbed Anoiapithecus brevirostris. The scientific name is derived from the region where the fossil was found (l’Anoia) and also from its “modern” facial morphology, characterized by a very short face.

 

Lluc reconstruction. (Credit: Image courtesy of Universitat Autònoma de Barcelona) Lluc reconstruction. (Credit: Image courtesy of Universitat Autònoma de Barcelona)

 The research team at the ICP also includes collaborator David M. Alba, predoctoral researcher Sergio Almécija, postdoctoral researcher Isaac Casanovas, researcher Meike Köhler, postdoctoral researcher Soledad De Esteban, collaborator Josep M. Robles, curator Jordi Galindo, and predoctoral researcher Josep Fortuny.

Their findings are based on a partial cranium that preserves most of the face and the associated mandible. The cranium was unearthed in 2004 in the fossil-rich area of Abocador de Can Mata (els Hostalets de Pierola, l’Anoia, Barcelona), where remains of other fossilized hominid species have been found. Preparing the fossil for study was a complicated process, due to the fragility of the remains. But once the material was available for analysis, the results were surprising: The specimen (IPS43000) combined a set of features that, until now, had never been found in the fossil record.

Anoiapithecus displays a very modern facial morphology, with a muzzle prognathism (i.e., protrusion of the jaw) so reduced that, within the family Hominidae, scientists can only find comparable values within the genus Homo, whereas the remaining great apes are notoriously more prognathic (i.e., having jaws that project forward markedly). The extraordinary resemblance does not indicate that Anoiapithecus has any relationship with Homo, the researchers note. However, the similarity might be a case of evolutionary convergence, where two species evolving separately share common features.

Lluc’s discovery may also hold an important clue to the geographical origin of the hominid family. Some scientists have suspected that a group of primitive hominoids known as kenyapithecines (recorded from the Middle Miocene of Africa and Eurasia) might have been the ancestral group that all hominids came from. The detailed morphological study of the cranial remains of Lluc showed that, together with the modern anatomical features of hominids (e.g., nasal aperture wide at the base, high zygomatic rood, deep palate), it displays a set of primitive features, such as thick dental enamel, teeth with globulous cusps, very robust mandible and very procumbent premaxilla. These features characterize a group of primitive hominoids from the African Middle Miocene, known as afropithecids.

Interestingly, in addition to having a mixture of hominid and primitive afropithecid features, Lluc displays other characteristics, such as a very anterior position of the zygomatic, a very strong mandibular torus and, especially, a very reduced maxillary sinus. These are features shared with kenyapithecines believed to have dispersed outside the African continent and colonized the Mediterranean region, by about 15 million years ago.

In other words, the researchers speculate, hominids might have originally radiated in Eurasia from kenyapithecine ancestors of African origin. Later on, the ancestors of African great apes and humans would have dispersed again into Africa — the so-called “into Africa” theory, which remains controversial. However, the authors do not completely rule out the possibility that pongines (orangutans and related forms) and hominines (African apes and humans) separately evolved in Eurasia and Africa, respectively, from different kenyapithecine ancestors.

The project at els Hostalets de Pierola is continuing and, the researchers anticipate, more fossil remains will be found in the future that will provide key information to test their hypotheses.


Journal reference:

  1. Salvador Moyà-Solà, David M. Alba, Sergio Almécija, Isaac Casanovas-Vilar, Meike Köhler, Soledad De Esteban-Trivigno, Josep M. Robles, Jordi Galindo, and Josep Fortuny. A unique Middle Miocene European hominoid and the origins of the great ape and human clade. Proceedings of the National Academy of Sciences, 2009; DOI: 10.1073/pnas.0811730106

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Other Links:

  • In English

Our earliest hominid ancestors may have been European

Thaindian.com – ‎1-giu-2009‎
According to a report in New Scientist, the fossil, named Anoiapithecus brevirostris by Salvador Moya-Sola of the Catalan Institute of Palaeontology in

Researchers from the Institut Catala de Paleontologia describe a

EurekAlert (press release) – ‎2-giu-2009‎ – The new hominid has been given the scientific name of Anoiapithecus brevirostris, in reference to the region where the town of els Hostalets is situated

Найденные останки Anoiapithecus brevirostris. Фото National

Lenta.ru – ‎9 ore fa‎
Они отмечают, что важность находки Anoiapithecus brevirostris безусловна, но вот выводы ученых могут быть ошибочны. В частности, специалисты говорят,
  • In GERMAN

Aus Europa nach Afrika und wieder zurück

wissenschaft.de – ‎19 ore fa‎ – Die Anoiapithecus brevirostris genannte Art hat sich vor rund zwölf Millionen Jahren in Europa entwickelt und wanderte von dort aus nach Afrika ein,

Unser spanisches Erbe sueddeutsche.de

 Knochenfund Stammt der Mensch aus Spanien? Bayerischer Rundfunk. Hominiden-Fossil Waren unsere frühesten Vorfahren Europäer? ZEIT ONLINE

All news in German

  • In SPANISH – ESPANOL

Investigadores catalães definem espécie Anoiapithecus brevirostris

Ciência Hoje – ‎44 minuti fa‎
Os cientistas baptizaram esta nova espécie de Anoiapithecus brevirostris (pois o fóssil foi encontrado em Anoia) eo ser de Lluc (aquele que ilumina).

Fóssil de Lluc ‘ilumina’ história dos hominídeos Diário de Notícias – Lisboa

giugno 3, 2009 Posted by | - Mammiferi, - Ominidi, - Primati, An. Vertebrates, Articolo sc. di riferimento, Cenozoic, Europa, Lang. - German, Lang. - Italiano, P - Paleoantropologia, P - Ritrovamenti fossili, Paleontology / Paleontologia, X - PNAS | Lascia un commento

2009-01-13 – Beipaosaurus, le prime piume non per il volo in Teropodi non aviani (Beipaosaurus, feathers for show)

Alcuni ricercatori cinesi hanno riconosciuto nelle piume apparteneti ad un Beipaosaurus (Dinosauria, Theropoda, Therizinosauridae) un morfotipo attualmente associato a piume utilizzate per “esibizionismo” (display) e non per il volo. Questa é la prima volta che viene riscontrata questa peculiarità in Teropodi non aviani.

Beipioaosaurus feathers

Beipioaosaurus feathers

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Earliest Feathers for Show, Not Flight

Jennifer Viegas, Discovery News

Jan. 12, 2009 — The world’s first feathers probably had nothing to do with flight or staying warm but were instead for showy display purposes, according to a new study that documents the most primitive known version of feathers, which were found on a Chinese dinosaur.

The dinosaur, Beipiaosaurus, sported the likely colorful feathers on its limbs, trunk, tail, head and neck, with the neck feathers resembling a lion’s mane.

Paleontologists now believe feathers evolved very early in archosaurs, the group that included dinosaurs, pterosaurs and relatives of crocodiles, in addition to today’s modern birds, crocodiles and alligators.

“Our analysis suggests that feathers might have a much longer history than previously thought,” lead author Xing Xu told Discovery News.

“The first feathers might have appeared in the fossil record in the Middle Triassic about 235 million years ago,” said Xu, a paleontologist at the Chinese Academy of Sciences in Beijing.

Xu and colleagues Xiaoting Zheng and Hailu You studied the remains of the Chinese dinosaur, which was excavated at the Early Cretaceous Yixian Formation of Jianchang, western Liaoning. They noticed two types of feathers on the specimen: short, thread-like structures, and longer, stiff, broader ones that represent the rudimentary feathers, according to the study.

Both types are described in a paper published in this week’s Proceedings of the National Academy of Sciences.

Similar structures have been found on Psittacosaurus, or “Parrot Lizard,” as well as some pterosaurs. The researchers therefore suspect the common ancestor of these creatures — along with Beipiaosaurus, which lived 125 million years ago — had the early feathers too.

Previously documented feathers on dinosaurs were described as having multiple filaments, or many fluff-creating strands. The feathers on the recently documented Chinese dinosaur, however, are believed to represent a much more primitive stage, since the feathers consist of just a single broad filament, but have a different structure than hair.

The morphology and distribution of these early feathers rule out use for flight and helping to keep the dinosaur warm, but instead suggest they were flashed during displays, perhaps for mating, identification and competition purposes.

“Most previous studies suggest that insulation might have been the primary function for the first feathers, but our discovery supports that display represents one of the earliest functions for feathers,” Xu said, adding that “flight function appears very late in feather evolution.”

The discovery negates the prior theory that feathers and flight co-evolved. It instead indicates pterosaurs, birds and other fliers recruited already existing feathers for flight.

Xu and her colleagues aren’t certain how feathers came into being in the first place, but they suspect that at some point, an animal’s skin developed epidermal tissue that gave rise to the thin, tubular protrusions. Members of the opposite sex must have liked what they saw in displays, since the trait stuck and flourished. An average bird today has over 20,000 feathers.

Cheng-Ming Chuong and his team from the Keck School of Medicine at the University of Southern California foreshadowed the recent discovery. Their studies on chickens predicted what these first, more basic, feathers would’ve looked like.

“Just like Rome, feathers are not made in one process,” Chuong said, hinting that a long and colorful history for feathers would likely emerge as more findings, such as the new discovery on Beipiaosaurus, come to light.

He added, “While Darwin’s theory has explained the ‘why’ of evolution, much of the ‘how’ remains to be learned. Evo-Devo (evolution of development) research promises a new level of understanding.”

The remains of the flashy, primitive-feathered Chinese dinosaur are now housed at the Shandong Tianyu Museum of Nature in China.

source: Dicovery channel news

other links:


BBC News

Downy dinosaur found in China was an early bird
Times Online – 15 ore fa
A dinosaur that would have been covered with feathers has been discovered in China, adding to evidence that supports the theory that birds evolved from ancient reptiles.
Dinosaur fossil reveals creature of a different feather Science News
Paleontologists Find Dinosaur Protofeather Wired News
ShortNews.com – LiveScience.com – Discovery Channel – BBC News
e altri 10 articoli simili »

IN GERMAN: faz.net

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A new feather type in a nonavian theropod and the early evolution of feathers (PNAS link)

Xing Xu, Xiaoting Zheng and Hailu You

 Abstract

All described feathers in nonavian theropods are composite structures formed by multiple filaments. They closely resemble relatively advanced stages predicted by developmental models of the origin of feathers, but not the earliest stage. Here, we report a feather type in two specimens of the basal therizinosaur Beipiaosaurus, in which each individual feather is represented by a single broad filament. This morphotype is congruent with the stage I morphology predicted by developmental models, and all major predicted morphotypes have now been documented in the fossil record. This congruence between the full range of paleontological and developmental data strongly supports the hypothesis that feathers evolved and initially diversified in nonavian theropods before the origin of birds and the evolution of flight.

gennaio 13, 2009 Posted by | - R. Dinosauri, 1 Cretaceo, Articolo sc. di riferimento, Asia, Bl - Top posts, Italiano (riassunto), Mesozoic, P - Evoluzione, P - morfologia funzionale, P - Paleoetologia, P - Preservazione eccezionale, Paleontology / Paleontologia, X - PNAS | , , , , , , , , , , , , | Lascia un commento

2008-11-25 – Uno straordinario esempio di organismi simbionti (Elysia chlorotica, Vaucheria litorea, symbionts)

più di ogni spiegazione guardatevi i video ….. incredibile !!!!!!

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 see free access videos from Supporting Information !!!!!

Horizontal gene transfer of the algal nuclear gene psbO to the photosynthetic sea slug Elysia chlorotica

Mary E. Rumpho, Jared M. Worful, Jungho Lee, Krishna Kannan, Mary S. Tyler, Debashish Bhattacharya, Ahmed Moustafa, and James R. Manhart

Abstract

The sea slug Elysia chlorotica acquires plastids by ingestion of its algal food source Vaucheria litorea. Organelles are sequestered in the mollusc’s digestive epithelium, where they photosynthesize for months in the absence of algal nucleocytoplasm. This is perplexing because plastid metabolism depends on the nuclear genome for >90% of the needed proteins. Two possible explanations for the persistence of photosynthesis in the sea slug are (i) the ability of V. litorea plastids to retain genetic autonomy and/or (ii) more likely, the mollusc provides the essential plastid proteins. Under the latter scenario, genes supporting photosynthesis have been acquired by the animal via horizontal gene transfer and the encoded proteins are retargeted to the plastid. We sequenced the plastid genome and confirmed that it lacks the full complement of genes required for photosynthesis. In support of the second scenario, we demonstrated that a nuclear gene of oxygenic photosynthesis, psbO, is expressed in the sea slug and has integrated into the germline. The source of psbO in the sea slug is V. litorea because this sequence is identical from the predator and prey genomes. Evidence that the transferred gene has integrated into sea slug nuclear DNA comes from the finding of a highly diverged psbO 3′ flanking sequence in the algal and mollusc nuclear homologues and gene absence from the mitochondrial genome of E. chlorotica. We demonstrate that foreign organelle retention generates metabolic novelty (“green animals”) and is explained by anastomosis of distinct branches of the tree of life driven by predation and horizontal gene transfer.

  • PNAS November 18, 2008 vol. 105 no. 46 17867-17871

novembre 25, 2008 Posted by | - Molluschi, Articolo sc. di riferimento, Attuale, Bio-Zoology / Bio-Zoologia, Bl - Top posts, Italiano (riassunto), Multimedia, P - Evoluzione, Video, X - PNAS | , , , , , , , | Lascia un commento

2008-11-20 – Germania: La più antica sepoltura multipla (oldest family tomb)

SCOPERTA LA PIU’ ANTICA TOMBA DI FAMIGLIA

2008-11-18 19:53

Sono stati vittime di una aggressionee chi li ha trovati li ha sepolti con molta cura: la mamma di fronte a un figlio e il papà di fronte all’altro rannicchiando i corpi e sistemandoli in modo che si guardassero l’un l’altro.

Sono i resti del più antico nucleo familiare mai scoperto finora. La famiglia, composta da una donna dall’età fra i 35 e i 50 anni, un uomo fra i 40 e 60, e due bambini di circa cinque e nove anni, è vissuta 4.600 anni fa, nei pressi del fiume Saal vicino ad Eulau, in Germania, insieme con altri nove individui sepolti nelle vicinanze.

A fare luce su età, parentela e luoghi dove sono cresciute queste persone è uno studio pubblicato sulla rivista dell’Accademia Americana delle Scienze, Pnas da un gruppo di ricerca coordinato dall’ Università tedesca Johannes Gutenberg- Mainz.

La ricerca ha ricostruito la tragedia dell’età della pietra con tecniche genetiche, isotopiche, antropologiche e archeologiche. I dati emersi evidenziano che tutti e 13 gli individui sepolti sono stati vittime di un’aggressione fatale perché mostrano segni di lesioni. In particolare, nella vertebra di una donna è stato trovato un proiettile di pietra e due adulti hanno il cranio fratturato.

Molte vittime, inoltre, hanno anche ferite da difesa alle ossa degli avambracci e delle mani. Secondo gli studiosi, queste persone avrebbero subito un raid da parte di un’altra comunità, e poi, sono state inumate con molta cura (insolita per il Neolitico) dagli individui superstiti dell’aggressione. Lo studio ha fatto anche luce su aspetti sociologici della comunità di appartenenza.

Misurando gli isotopi di stronzio presenti nel cibo intrappolato nei denti, gli scienziati hanno stabilito che le donne sepolte hanno vissuto l’infanzia in un luogo diverso da quello degli uomini e dei bambini.

“Questo dato – ha osservato uno degli autori, Alistair Pike, archeologo all’università di Bristol – è indice di esogamia, una regola per cui il coniuge deve essere scelto al di fuori del villaggio di appartenenza e di patrilocalità, un’usanza che impone ad una coppia di andare a vivere nei pressi della casa del padre del marito”. Tradizioni, conclude l’esperto, usate per evitare l’incrocio fra consanguinei e per intessere la rete di parentela con altre comunità.

fonte: ANSA

novembre 20, 2008 Posted by | - Italia, - Ominidi, - Primati, 1 Olocene, Archeology / Archeologia, Articolo sc. di riferimento, Lang. - Italiano, P - Paleoantropologia, Paleontology / Paleontologia, X - PNAS | , , , , , , | Lascia un commento

2008-11-03 – Biomineralizzazione: la bio-trasformazione di calcite amorfa in bio-struttura ordinata (biomineralization)

Grazie a un sincrotone (generatore di raggi x) applicato a un microscopio elettrinico un team di ricercatori ha osservato come in una larva di echinoderma (riccio di mare) si riesce a trasformare la calcite amorfa in una struttura cristallina ordinata. In futuro la comprensione di tali meccanismi potrebbe portare importanti implicazioni nella produzione di nano-materiali.

Sea urchin yields a key secret of biomineralization

MADISON — The teeth and bones of mammals, the protective shells of mollusks, and the needle-sharp spines of sea urchins and other marine creatures are made-from-scratch wonders of nature.

Used to crush food, for structural support and for defense, the materials of which shells, teeth and bones are composed are the strongest and most durable in the animal world, and scientists and engineers have long sought to mimic them.

Now, harnessing the process of biomineralization may be closer to reality as an international team of scientists has detailed a key and previously hidden mechanism to transform amorphous calcium carbonate into calcite, the stuff of seashells. The new insight promises to inform the development of new, superhard materials, microelectronics and micromechanical devices.

In a report today (Oct. 27) in the Proceedings of the National Academy of Sciences (PNAS), a group led by University of Wisconsin-Madison physicist Pupa Gilbert describes how the lowly sea urchin transforms calcium carbonate — the same material that forms “lime” deposits in pipes and boilers — into the crystals that make up the flint-hard shells and spines of marine animals. The mechanism, the authors write, could “well represent a common strategy in biomineralization….”

“If we can harness these mechanisms, it will be fantastically important for technology,” argues Gilbert, a UW-Madison professor of physics. “This is nature’s bottom-up nanofabrication. Maybe one day we will be able to use it to build microelectronic or micromechanical devices.”

Gilbert, who worked with colleagues from Israel’s Weizmann Institute of Science, the University of California at Berkeley and the Lawrence Berkeley National Laboratory, used a novel microscope that employs the soft-X-rays produced by synchrotron radiation to observe how the sea urchin builds its spicules, the sharp crystalline “bones” that constitute the animal’s endoskeleton at the larval stage.

Similar to teeth and bones, the sea urchin spicule is a biomineral, a composite of organic material and mineral components that the animal synthesizes from scratch, using the most readily available elements in sea water: calcium, oxygen and carbon. The fully formed spicule is composed of a single crystal with an unusual morphology. It has no facets and within 48 hours of fertilization assumes a shape that looks very much like the Mercedes-Benz logo.

These crystal shapes, as those of tooth enamel, eggshells or snails, are very different from the familiar faceted crystals grown through non-biological processes in nature. “To achieve such unusual — and presumably more functional — morphologies, the organisms deposit a disordered amorphous mineral phase first, and then let it slowly transform into a crystal, in which the atoms are neatly aligned into a lattice with a specific and regular orientation, while maintaining the unusual morphology,” Gilbert notes.

The question the Wisconsin physicist and her colleagues sought to answer was how this amorphous-to-crystalline transition occurs. The sea urchin larval spicule is a model system for biominerals, and the first one in which the amorphous calcium carbonate precursor was discovered in 1997 by the same Israeli group co-authoring the current PNAS paper. A similar amorphous-to-crystalline transition has since been observed in adult sea urchin spines, in mollusk shells, in zebra fish bones and in tooth enamel. The resulting biominerals are extraordinarily hard and fracture resistant, compared to the minerals of which they are made.

“The amorphous minerals are deposited and they are completely disordered,” Gilbert explains. “So the question we addressed is ‘how does crystallinity propagate through the amorphous mineral?'”

To answer it, Gilbert and her colleagues observed spicule development in 2- to 3-day-old sea urchin larvae. The sea urchin spicule is formed inside a clump of specialized cells and begins as the animal lays down a single crystal of calcite in the form of a rhombohedral seed, from which the rest of the spicule is formed. Starting from the crystalline center, three arms extend at 120 degrees from each other, as in the hood ornament of a Mercedes-Benz. The three radii are initially amorphous calcium carbonate, but slowly convert to calcite.

“We tried to find evidence of a massive crystal growth, with a well defined growth front, propagating from the central crystal through the amorphous material, but we never observed anything like that,” Gilbert says. “What we found, instead, is that 40-100 nanometer amorphous calcium carbonate particles aggregate into the final morphology. One starts converting to crystalline calcite, then another immediately adjacent converts as well, and another, and so on in a three-dimensional domino effect. The pattern of crystallinity, however, is far from straight. It resembles a random walk, or a fractal, like lightning in the sky or water percolating through a porous medium,” explains Gilbert.

The new work, according to Gilbert, brings science a key step closer to a thorough understanding of how biominerals form and transform. Knowing the step-by-step process may permit researchers to develop new crystal structures that can be used in applications ranging from new microelectronic devices to medical applications.

Public release date: 27-Oct-2008

Contact: Pupa Gilbert – pupa@physics.wisc.edu – 608-262-5829 – University of Wisconsin-Madison

source: http://www.eurekalert.org/pub_releases/2008-10/uow-suy102408.php

novembre 3, 2008 Posted by | Articolo sc. di riferimento, G - Biomineralizzazione, Italiano (riassunto), Paleontology / Paleontologia, X - PNAS | , , , | Lascia un commento

2008-10-22 – Proliferazione di organismi produttori di magnetite durante il “massimo termico del Paleocene-Eocene” (“Magnetic Death Star” fossil)

Studi geobiologici su microcristalli “giganti” di magnetite di origine biologica consentono nuove considerazioni sul “massimo termico del Paleocene-Eocene”.

Gli autori dello studio sostengono infatti che lo sviluppo di una spessa zona subossica con un elevata disponibilità di ferro bio-assilmilabile (prodottosi in seguito ai drammatici cambiamenti climatici e di pattern sedimentari dovuti a un forte riscaldamento globale) condusse alla diversificazione di organismi (anche eucarioti) produttori di magnetite.

N.B. vedi il filmato del cluster di cristalli ripreso al microscopio elettronico (Supporting Information)

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Geobiologists Discover Unique ‘Magnetic Death Star’ Fossil

 General Science / Archaeology & Fossils

Geobiologists Discover Unique 'Magnetic Death Star' Fossil

          (PhysOrg.com) — An international team of scientists has discovered microscopic, magnetic fossils resembling spears and spindles, unlike anything previously seen, among sediment layers deposited during an ancient global-warming event along the Atlantic coastal plain of the United States.

The researchers, led by geobiologists from the California Institute of Technology and McGill University, describe the findings in a paper published online this week in the Proceedings of the National Academy of Sciences (PNAS).
Fifty-five million years ago, Earth warmed by more than 9 degrees Fahrenheit after huge amounts of carbon entered the atmosphere over a period of just a few thousand years. Although this ancient global-warming episode, known as the Paleocene-Eocene Thermal Maximum (PETM), remains incompletely explained, it might offer analogies for possible global warming in the future.

Perhaps in response to the environmental stress of the PETM, many land mammals in North America became dwarfed. Almost half of the common sea bottom-dwelling microorganisms known as foraminifera became extinct in newly warmer waters that were incapable of carrying the levels of dissolved oxygen for which they were adapted.

“Imagine our surprise to discover not only a fossil bloom of bacteria that make iron-oxide magnets within their cells, but also an entirely unknown set of organisms that grew magnetic crystals to giant sizes,” said Caltech postdoctoral scholar Timothy Raub, who collected the samples from an International Ocean Drilling Program drill-core storehouse at Rutgers University in New Jersey.

A typical “giant” spearhead-shaped crystal is only about four microns long, which means that hundreds would fit on the period at the end of this sentence. However, the crystals found recently are eight times larger than the previous world record for the largest bacterial iron-oxide crystal.

According to Dirk Schumann, a geologist and electron microscopist at McGill University and lead author of the study, “It was easy to focus on the thousands of other bacterial fossils, but these single, unusual crystals kept appearing in the background. It soon became evident that they were everywhere.”

In addition to their unusually large sizes, the magnetic crystals occur in a surprising array of shapes. For example, the spearhead-like crystals have a six-sided “stalk” at one end, a bulbous middle, and a sharp, tapered tip at the other end. Once reaching a certain size, spearhead crystals grow longer but not wider, a directed growth pattern that is characteristic of most higher biological organisms.

The spearhead magnetic crystals compose a minor fraction of all of the iron-oxide crystals in the PETM clay layer. Most of the crystals have smaller sizes and special shapes, which indicate that they are fossils of magnetotactic bacteria. This group of microorganisms, long studied at Caltech by study coauthor Joseph Kirschvink, the Nico and Marilyn Van Wingen Professor of Geobiology, use magnets to orient themselves within Earth’s magnetic field, and proliferate in oxygen-poor water.

Spearheads are not, however, the rarest fossil type in the deposit. That honor belongs to a spherical cluster of spearheads informally dubbed the “Magnetic Death Star” by the researchers. The Magnetic Death Star may have preserved the crystals as they occurred in their original biological structure.

The researchers could not find a similar-shaped organism anywhere in the paleontological annals. They hypothesize that it may have been a single-celled eukaryote that evolved for the first time during the PETM and was outcompeted once the strange climate conditions of that time diminished. Alternatively, it may still exist today in a currently undiscovered location.

“The continental shelf of the mid-Atlantic states during the PETM must have been very iron-rich, much like the Amazon shelf today,” notes study coauthor Robert Kopp of Princeton University, who first started working on the project while a graduate student at Caltech. “These fossils may be telling a story of radical environmental transformation: imagine a river like the Amazon flowing at least occasionally where the Potomac is today.”

  Click here to enlarge image

The paper, “Gigantism in unique biogenic magnetite at the Paleocene-Eocene Thermal Maximum,” will appear in the early online issue of PNAS the week of October 20. The Caltech work was supported by the NASA Exobiology program.
Provided by California Institute of Technology

souurce: http://www.physorg.com/news143818456.html

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Original article:

Gigantism in unique biogenic magnetite at the Paleocene–Eocene Thermal Maximum

Dirk Schumann et al.

PNAS doi:10.1073/pnas.0803634105

 Abstract

We report the discovery of exceptionally large biogenic magnetite crystals in clay-rich sediments spanning the Paleocene–Eocene Thermal Maximum (PETM) in a borehole at Ancora, NJ. Aside from previously described abundant bacterial magnetofossils, electron microscopy reveals novel spearhead-like and spindle-like magnetite up to 4 μm long and hexaoctahedral prisms up to 1.4 μm long. Similar to magnetite produced by magnetotactic bacteria, these single-crystal particles exhibit chemical composition, lattice perfection, and oxygen isotopes consistent with an aquatic origin. Electron holography indicates single-domain magnetization despite their large crystal size. We suggest that the development of a thick suboxic zone with high iron bioavailability—a product of dramatic changes in weathering and sedimentation patterns driven by severe global warming—drove diversification of magnetite-forming organisms, likely including eukaryotes.

Abstract  –  Full Text (PDF)  –  Supporting Information

ottobre 22, 2008 Posted by | 6 Eocene, 7 Paleocene, G - Geobiology, Geology - Geologia, Multimedia, P - Extinctions, P - Paleoclimatologia, Paleontology / Paleontologia, X - PNAS | , , , , , , , | Lascia un commento

2008-10-22 – Bahamas: nuove considerazioni su paleo-faune oloceniche (Holocene, fossils)

Una ricerca pubblicata da David W. Steadman et al. su PNAS ha contribuito a far luce sulla storia e la preistoria delle faune delle Bahamas col ritrovamento di specie fossili datate 4200-1000 anni fa e strettamente imparentate con le faune attuali, e specie ora non più presenti sulle isole (probabilmente causa “competizione” con l’uomo).

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The Bahamas Yield Amazing Fossil Finds
By ScienceBlogs.com Greg Laden
Oct 22, 2008 – 12:56:24 AM

 

 

Bahamasextinct_Caracara_creightoni.jpg
Skull and mandible of the extinct Bahamas Caracara, Caracara creightoni, Sawmill Sink, Abaco, The Bahamas. Features that distinguish C. creightoni from the living C. cheriway include the larger, stouter mandible and rostrum as well as the larger nares. Photo: Scienceblogs/GregLaden

Scienceblogs.com – Plant and animal fossils recently discovered from an island in the Bahamas tell a story of habitat change and human involvement in local extinction.

These finds are reported in a paper by Steadman et al. in the Proceedings of the National Academy of Sciences.

Most people with an interest in natural history know about one or more regions that were at one time covered by “a great inland sea.” For instance, if you live in the American Midwest, you probably know that much of this region was covered by such a sea, evidenced by extensive limestone beds and other geological manifestations. As one learns more about these inland seas, one might get the impression that in the past there were a lot of inland seas! This is true, but it is easy to overlook the fact that there are many inland seas covering extensive regions today. One such expansive region is what we know of as the Gulf of Mexico, the Caribbean, and the area of the Bahamas. These are areas that consist largely of continent, not sea floor, but that are inundated by the sea during high water stands. Much of this region is exposed during Ica Age low water stands.

What this means is that “islands” such as the Bahamas are not the same kind of island as, say, the Galapagos or the Hawaiian Islands. The latter are volcanoes that arise from the sea floor, while the former are bits of continent that stick up above the high sea. So, as sea levels rise and fall in accordance with ice age cycles, this region shifts back and forth between islands of varying degrees of isolation to relatively large and contiguous blocks of continent. As this happens, we can presume that interesting biogeographical events take place.

There is not a large number of unique island species in the Bahamas, compared to Hawaii or the Galapagos, owing to this effect and their relative closeness to mainland even during high sea levels. However, there are some. But we also know that humans have been living on these islands for a long time, and one can ask the question, where there more island-adapted endemic species in the past that may have been wiped out by humans? Also, there are a number of missing species on these islands … animals that live on the mainland (like in Florida, Mexico, Guatemala, etc.) Did these animals (and plants, for that matter) live on these islands at one time? Did they disappear from these islands “on their own” (owing to an inability to maintain viable population sizes on the smaller islands) or were they also locally wiped out by humans?

 

 

© Copyright 2008 by thebahamasweekly.com –

These are complex questions and the answers will not be easily come by. This set of questions fits well into a decades long debate on the effects of human populations on local animal communities.

The paper by Steadman et al reports a remarkable set of finds that will go a long way to address these issues. They report on fossils recovered from a “blue hole” sinkhole on Great Abaco Island, in the Bahamas. The preservational environment for many of these remains is remarkably good. It has even been possible to radiocarbon date some of the remains. Most of the material dates to between 4,200 and 1,000 years ago.
Among the more remarkable finds are the following:

  • Two extinct species of tortoise.
  • An extant crocodile that no longer lives in The Bahamas (but is found in Cuba).
  • An extant hawk, Gundlach’s Hawk, no longer found in The Bahamas.

 

Human remains were also found.

A separate location that does not have dateable bones but that is believed by the researchers to be older is an owl roost. Owls fly around ingesting little critters, then regurgitate the bones (and fur, etc.) at habitually used roosting sites. This can produce very nice collections of microfauna, if there is a crack of crevasse or other spot in which the pellets can accumulate. This deposit included:

  • An extinct Bahamian flightless bird … a type of rail
  • The locally extinct Gundlach’s hawk
  • A flicker
  • A cave swallow
  • the Eastern Medowlark
  • Various mammals and rodents

Micro and macro remains of plants were also found and analyzed, providing the beginnings of a reconstruction of the overall ecology of the region at various points in time. The authors conclude:

[Both the plant and animal fossils from Sawmill Sink are beautifully preserved, greatly facilitating our upcoming morphological and systematic descriptions. These specimens also provide unparalleled opportunities to reconstruct ancient environments in the Bahamian Archipelago. Eventually we hope to be able to estimate long-term changes in such phenomena as fire regimes, plant communities, vertebrate turnover rates, body sizes of reptiles, terrestrial food webs including predator-prey relationships, and human impact on biotic communities. Such information is only beginning to be well documented in The Bahamas or on most other West Indian islands.]

David W. Steadman, Richard Franz, Gary S. Morgan, Nancy A. Albury, Brian Kakuk, Kenneth Broad, Shelley E. Franz, Keith Tinker, Michael P. Pateman, Terry A. Lott, David M. Jarzen, and David L. Dilcher (2007) Exceptionally well preserved late Quaternary plant and vertebrate fossils from a blue hole on Abaco, The Bahamas. PNAS Volume 104(50). Pp 19897-19902.

science blog article

 

 

Top of Page

source: http://www.thebahamasweekly.com/publish/for-your-information/The_Bahamas_Yield_Amazing_Fossil_Finds-004531.shtml

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original article:

Exceptionally well preserved late Quaternary plant and vertebrate fossils from a blue hole on Abaco, The Bahamas

David W. Steadman et al.

PNAS December 11, 2007 vol. 104 no. 50 19897-19902

Abstract Figures OnlyFull Text  Full Text (PDF)

Abstract

We report Quaternary vertebrate and plant fossils from Sawmill Sink, ablue hole” (a water-filled sinkhole) on Great Abaco Island, The Bahamas. The fossils are well preserved because of deposition in anoxic salt water. Vertebrate fossils from peat on the talus cone are radiocarbon-dated from ≈4,200 to 1,000 cal BP (Late Holocene). The peat produced skeletons of two extinct species (tortoise Chelonoidis undescribed sp. and Caracara Caracara creightoni) and two extant species no longer in The Bahamas (Cuban crocodile, Crocodylus rhombifer; and Cooper’s or Gundlach’s Hawk, Accipiter cooperii or Accipiter gundlachii). A different, inorganic bone deposit on a limestone ledge in Sawmill Sink is a Late Pleistocene owl roost that features lizards (one species), snakes (three species), birds (25 species), and bats (four species). The owl roost fauna includes Rallus undescribed sp. (extinct; the first Bahamian flightless rail) and four other locally extinct species of birds (Cooper’s/Gundlach’s Hawk, A. cooperii/gundlachii; flicker Colaptes sp.; Cave Swallow, Petrochelidon fulva; and Eastern Meadowlark, Sturnella magna) and mammals (Bahamian hutia, Geocapromys ingrahami; and a bat, Myotis sp.). The exquisitely preserved fossils from Sawmill Sink suggest a grassy pineland as the dominant plant community on Abaco in the Late Pleistocene, with a heavier component of coppice (tropical dry evergreen forest) in the Late Holocene. Important in its own right, this information also will help biologists and government planners to develop conservation programs in The Bahamas that consider long-term ecological and

ottobre 22, 2008 Posted by | 1 Olocene, America Central, Articolo sc. di riferimento, Italiano (riassunto), P - Ritrovamenti fossili, Paleontology / Paleontologia, X - PNAS | , , , , , | Lascia un commento