Published online: 23 May 2007; | doi:10.1038/news070521-6 / http://www.nature.com/news/2007/070521/full/070521-6.html

Bald dino casts doubt on feather theory

Fossil calls into question the purpose of the first feathers.

Katharine Sanderson

Sinosauropteryx may not have been a feathery dinosaur after all. Proc. R. Soc. Lond. B

Feathery dinosaurs might not have been as common as experts thought, according to researchers who analysed a fossil of a creature previously thought to have feathers, and found instead that it was bald.

The discovery calls into question the theory that the first feathers evolved not for flight but for insulation, and that they made their first appearance in relatively early dinosaur lineages that later evolved into modern birds. If these dinosaurs didn't have feathers, or feather-like structures, then feathers may have evolved at a later time, and been used for flight right from the start.

The fossil represents a dinosaur called Sinosauropteryx, which lived in the Early Cretaceous period roughly 140 million years ago. The specimen, found in Liaoning Province, China, has distinctive patterns seen in its skin. Previous studies of other related dinosaurs with similar markings have led experts to conclude that these dinosaurs were covered with downy 'protofeathers'.

But Theagarten Lingham-Soliar from the University of KwaZulu-Natal in Durban, South Africa, and his colleagues now say otherwise. Instead, they argue that these structures are degraded remains of collagen fibres, the main connective tissue in animals.

Decomposing theory

Lingham-Soliar and his colleagues produced high-resolution microscopic images of the fossil that, he says, show that these structures represent degraded soft tissue. The regular pattern of the fibres suggests that Sinosauropteryx had a frill of skin along its neck, back and tail. And the random orientation of some of the fibres, previously attributed to protofeathers, are more likely to indicate breakages in the regular pattern of collagen fibres as the dinosaur decomposed.

The researchers also say that the absence of herringbone-shaped patterns - which would be seen if feathers were present - puts another nail in the coffin for the protofeather suggestion. They publish their findings in Proceedings of the Royal Society B¹.

If Sinosauropteryx was indeed featherless, then it may be that feathers arrived on the evolutionary scene later than palaeontologists had thought.

But the discovery does not mean that Sinosauropteryx and its kin were not the forefathers of birds. "There's no need to panic," says David Unwin, a dinosaur expert at the University of Leicester, UK. "This doesn't in any way challenge the idea that dinosaurs had feathers and that dinosaurs gave rise to birds." The real argument now is when in evolutionary history feathers started to emerge. "Things may be more complex than we thought," he says.

And even if Sinosauropteryx was featherless, it is still possible to argue that feathers evolved for something other than flight. "There are many other dinosaurs between the microraptor [a bird-like dinosaur thought to glide, but not fly] and Sinosauropteryx with feathers that are not ostensibly flight feathers," says Unwin. This result simply throws into doubt the first step in feather evolution.

Unwin is happy to believe that this single specimen is probably featherless and has a fibrous structure, although he suggests this doesn't have to be collagen but could also be muscle fibre or elastin. Unwin wants to see an analysis of a much greater number of specimens, using a wider range of analytical techniques, before he is convinced either way about Sinosauropteryx and its feathers, or lack of them. "It's almost dangerous to only look at one or two specimens," he says.

References

1. Lingham-Soliar T., et al. Proc. R. Soc. Lond. B, doi:10.1098/rspb.2007.0352 (2007).

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Un dinosaure chauve étonne les chercheurs

Par Jean-Luc Goudet - Futura-Sciences

Figurant parmi les ancêtres des oiseaux, ce dinosaure n'avait pas de plumes. Est-ce si surprenant ? Oui ! Car les paléontologues qui le paraient d'un joli plumage doivent revoir maintenant leur copie sur l'histoire de la plume...

http://www.futura-sciences.com/fr/sinformer/actualites/news/t/paleontologie/d/un-dinosaure-chauve-etonne-les-chercheurs_11920/  

On connaît le "crachat de coucou", cet amas mousseux qui cache sa larve, lui passe souvent inaperçu. Ce petit insecte sauteur connu sous le nom impropre de "Cicadelle écumeuse" ne fait plus partie de la famille des Cicadelles (Cicadellidae) mais de celle des Cercopes (Cercopidae). 

http://demons-et-merveilles.club.fr/galeries/homopteres/pages/cicadelle.html

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 Homoptères, Ordre d'insectes piqueurs-suceurs caractérisés par des ailes antérieures entièrement cornées et par le fait assimilables aux élytres des coléoptères...L'insecte adulte est de petite taille, de l'ordre du centimètre, et il est doté d'un rostre qui lui permet de perforer les végétaux pour se nourrir de leur sève. La larve se sustente à l'identique et vit au sein d'un amas spumeux communément appelé "crachat de coucou". Pour faire simple disons que les excréments de la larve sont à la fois liquides et visqueux , et que la larve en question y pulse de l'air pour former ce "crachat" où elle va se développer jusqu'au stade adulte. Etant très fragile, elle y trouve une relative protection contre les prédateurs mais surtout l'hydratation permanente qui lui est nécessaire, les bulles d'air assurant par ailleurs une régulation thermique tout aussi indispensable et efficace. Par référence à la bionique (étude de processus biologiques en vue de leur transposition à des fins industrielles), on pourrait dire que la frêle cicadelle a découvert bien avant l'homme le principe et les propriétés isolantes des mousses alvéolaires...Nota: quand elles sont dérangées les Cicadelles, et les espèces des familles voisines, ont la faculté de sauter avec une grande vivacité, et à bonne distance http://perso.orange.fr/insectes.net/cicadelle/cica2.html

Les hominidés (ensemble du rameau humain) sont considérés comme le groupe frère des panidés (les Chimpanzés) avec lesquels ils partagent un ancêtre commun.
Toumaï possède une association de caractères anatomiques de la face, des canines et du basi-crâne qui indiquent clairement son appartenance au rameau humain et le séparent des Gorilles et des Chimpanzés.
Son âge voisin de 7Ma et l'ensemble de ses caractères anatomiques, indiquent qu'il est proche du dernier ancêtre commun aux Chimpanzés et aux humains. Il montre que cette dernière dichotomie est sûrement plus ancienne (au moins 7 Ma) que prévu par certaines phylogénies moléculaires.
Pour le moment tous ces éléments font de Toumaï le plus ancien hominidé connu et, permettent de le considérer comme l'ancêtre de tous les hominidés ultérieurs, c'est à dire : l'ancêtre du rameau humain.
Par ses canines coniques il est moins dérivé que Ardipithecus (4.4 - 5.8 Ma), dont il peut être considéré comme l'ancêtre.
Compte tenu du caractère très fragmentaire du matériel actuellement publié pour Orrorin (6Ma) les comparaisons sont difficiles. Toutefois par sa canine supérieure très semblable à celle d'un Chimpanzé femelle, Orrorin s'éloigne complètement du nouvel hominidé tchadien.  

http://www.cnrs.fr/cw/fr/pres/compress/Toumai/lienparen.html 

George peut être fier de sa célébrité. Mais cela ne le mènera pas très loin. Car George est une tortue géante des Galapagos, une des espèces les plus caractéristiques de l'archipel. Mais aussi une des plus rares. En fait, George est le seul représentant encore existant de Geochelone abingdoni nigra, et donc au bord de l'extinction. http://www.futura-sciences.com/fr/sinformer/actualites/news/t/zoologie/d/galapagos-il-faut-sauver-la-tortue-geante-george_11738/

Published online: 2 May 2007; | doi:10.1038/news070430-5 / http://www.nature.com/news/2007/070430/full/070430-5.html

Human ancestors went underground for dinner

Like mole rats, hominins may have had a diet rich in bulbs and tubers.

Michael Hopkin

Paranthropus robustus was perhaps smart enough to dig for food. MAURICIO ANTON/ SCIENCE PHOTO LIBRARY

Palaeontologists have turned to an unlikely source in a bid to uncover the dietary habits of some of humanity's oldest ancestors. They have studied the teeth of mole rats found in South Africa to bolster the theory that prehistoric hominins may have eaten underground bulbs and tubers, rather than meat or grass.

African mole rats, which live underground and eat starchy plant organs such as bulbs, have similar chemical signatures in their teeth to those of two ancient hominin species found at the same site, the new research shows. This suggests that they may have had similar diets.

The discovery helps to solve a paradox surrounding the diets of Australopithecus africanus and Paranthropus robustus, which lived in southern Africa around 2.5 million and 1.5 million years ago, respectively. When the chemical signatures of their teeth were recently analysed, the results suggested that these hominins ate grassy plants, or the remains of animals that had eaten such plants. But their flat, wide teeth, while good for crushing hard objects, would have been useless at tearing through these tough foods.

A group led by Justin Yeakel of the University of California, Santa Cruz, reasoned that one solution to this problem would be if hominins chewed on the starchy bulbs and tubers from those same grassy plants, rather than tearing up the upper green portions. That would explain both the chemical signature and the design of their teeth.

"Hominins had teeth like ours, which were designed to eat something really, really hard, like small seeds - not tough grasses or raw meat," says Yeakel's colleague Nathaniel Dominy.

Chew on this

The chemical signature in teeth comes about because different foods have a distinctive mixture of carbon isotopes, which shows up in the teeth of animals that eat those foods. Grassy plants, for example, give a particular isotopic signature.

The researchers looked for this signature in the teeth of present-day mole rats (Cryptomys) and in fossilized mole-rat remains from almost 2 million years ago. As they report in Proceedings of the Royal Society B¹, the range of isotopes seen in these species overlaps with that found in A. africanus and P. robustus.

"This study certainly adds to the body of evidence that the diet of early hominins included bulbs, corms and possibly tubers," says Dominy. These categories include modern-day foods such as the shallot, taro and yam, respectively.

Although one might expect creatures that live underground to feed primarily on underground plant material, how did early humans develop the habit? "Our early ancestors had the advantage of a relatively large brain to help recognize specific plants and to make simple tools for extracting them from the ground," Dominy says.

References : Yeakel J. D., Bennett N. C., Koch P. L. & Dominy N. J. Proc. R. Soc. B, doi:10.1098/rspb.2007.0330 (2007).