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2009-03-18 – Hesperonychus Elizabethae: un nuovo mini-dinosauro carnivoro (mini meat-eating dinosaur)

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Scoperto fossile di dinosauro nano 

Viveva nell’America del nord 75 milioni di anni fa

(ANSA)- ROMA, 17 MAR – Dei mini-dinosauri carnivori vivevano nell’America del nord, 75 milioni di anni fa. Lo conferma un fossile scoperto da paleontologi canadesi. Il fossile, scoperto da Nick Longrich e Philip Currie delle universita’ di Calgary e Alberta, viveva nell’odierno Canada. Era piu’ piccolo di un gatto e correva su due zampe fornite di artigli. Probabilmente cacciava insetti e piccoli mammiferi. Resti fossili di questo dinosauro furono gia’ trovati circa 25 anni fa.

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Alberta researchers discover mini meat-eating

dinosaur

It had razor sharp claws and its teeth may have been the terror of Alberta 75 million years ago — among animals smaller than a squirrel, that is.
University of Calgary researcher Nicholas Longrich sits with a model of tiny dinosaur, which likely weighed less than two kilograms. (University of Calgary)

University of Calgary researcher Nicholas Longrich sits with a model of tiny dinosaur, which likely weighed less than two kilograms. (University of Calgary)

The kitten-sized predator identified by paleontologists at the University of Calgary and the University of Alberta is the smallest carnivorous dinosaur ever found in North America. The next smallest meat-eating dinosaur ever found on the continent was about the size of a wolf.

“Until we found this animal, basically we had no evidence for any small carnivores being present in North America,” said University of Calgary researcher Nicholas Longrich, in a video released by the university on Monday.

Longrich and the University of Alberta’s Philip Currie have written an article describing the velociraptor-like dinosaur, published Monday in the Proceedings of the National Academy of Science.

The tiny, bird-like predator ran on two legs and was about half the size of a housecat, weighing less than two kilograms, and standing about as tall as an average wastebasket. It likely hunted near the ground in marshes and forests for insects, small mammals, amphibians and “maybe even baby dinosaurs,” Longrich said.

The researchers have given the dinosaur the scientific name Hesperonychus Elizabethae.

Hesperonychus means “western claw” and Elizabethae is a tribute to the late Elizabeth (Betsy) Nicholls, the well-known Alberta paleontologist and former curator at the Royal Tyrrell Museum in Drumheller who originally unearthed the bones.

Found 20 km from Dinosaur Provincial Park

Nicholls found the fossilized claws and a well-preserved pelvis in 1982 at the Dinosaur Park Formation, about 20 kilometres east of Dinosaur Provincial Park, or about 140 kilometres east of Calgary. Longrich said he was going through the collections at the University of Alberta when he stumbled across the bones less than two years ago.

Previously, paleontologists believed they belonged to a juvenile dinosaur of some sort.

Longrich noticed that one of the bones looked like the hip bones of some velociraptor-like dinosaurs excavated in China. Those Chinese dinosaurs were a little less than a metre long.

On closer examination, Longrich noticed that the pelvic bones had fused together — something that happens after the animal stops growing, indicating that it was an adult.

Because quite a number of bones were found, the researchers suggest that Hesperonychus was an important part of the ecosystem in the late Cretaceous period, as small predators such as cats and foxes are an important part of the ecosystem today.

The results also show for the first time that tiny velociraptor-like dinosaurs lived not just in China, but also in North America, and that such dinosaurs continued to roam the Earth about 45 million years longer than previous records suggested.

2009-03-16-hesperonychus-elizabethae-02

source: cbc.ca

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Researchers ID North America’s smallest dinosaur

Reuters – ‎13 ore fa‎
By Scott Haggett CALGARY, Alberta (Reuters) – Canadian researchers said on Monday they have discovered North America’s smallest known dinosaur, a pint-sized
Telegraph.co.uk

 

AFP

Miniature carnivore dinosaurs roamed North America

AFP – ‎18 minuti fa‎
WASHINGTON (AFP) – Meat-eating dinosaurs the size of a small chicken roamed areas of North America 75 million years ago, according to research by Canadian

marzo 18, 2009 - Posted by | - R. Dinosauri, - Teropodi, 1 Cretaceo, America Northern, An. Vertebrates, Bl - Top posts, Blogs, Lang. - Italiano, Mesozoic, P - Ritrovamenti fossili, Paleontology / Paleontologia, Theropoda | , , , , , , ,

3 commenti »

  1. Well, what about the teeth? Denticles, serration? curvature? pfpuech@yahoo.fr

    Commento di Pierre-François Puech | marzo 25, 2009

  2. I’ve not read all the PNAS Article. I’ll investigate and I’ll reply to you.
    Thanks for the question !!

    Commento di Giuseppe Buono | marzo 26, 2009

  3. http://www.larousse.fr/encyclopedie/article/_DINOSAURE_DU_SUD_DE_LA_FRANCE/ Pierre-Francois PUECH
    La diversité des dinosaures traduit une grande faculté d’adaptation qui s’exprime dans la diversité dentaire. Le profil et la section des dents carnassières est celui d’un cône aplati qui ne laisse pas supposer une découpe de la viande comme le ferait le croisement serré des lames de ciseaux, c’est pourquoi nous présentons ici l’aspect d’usures vu au microscope électronique qui indiquent diverses possibilités comme celle de la pénétration de la série de pointes du sécateur à os de poulet.
    La répartition spécifique des stries microscopiques des dents de la collection P. et A. Méchin (Aix en Provence) illustre leur action:
    -l’extrémité active de la dent en baguette de l’herbivore Titanosaure est arrondie par l’usure et couverte de stries suivant l’axe de la dent alors que le reste des surfaces en est pratiquement exempte;
    -la forme “en feuille” dotée de longues cannelures de l’herbivore Rhabdodon présente un bord libre en “V” couvert de multiples stries parallèles entre elles qui se poursuivent un court temps sur la face externe. L’aspect est identique à celui observé sur les dents de cerfs (Puech et al. 1981);
    -la pointe de la dent conique de Tarascosaure est érodée comme le sont les multiples petits dômes des “denticules” des deux arêtes crénelées (antérieure et postérieure). De nombreux dômes sont fracturés, si bien que l’on suppose que leur fonction a été de pénétrer les matières saisies et que les plus dures (comme l’os) ont été serrées très fortement pour être brisées;
    -la petite dent pointue de Variraptor n’est crénelée que sur l’arête postérieure. Cette dentelure est faite d’une suite de plots profilés “en quille”. Les stries sont localisées sur la pointe principale de la dent et sur les plots de la dentelure, elles sont toutes orientées suivant le grand axe de la dent. L’action essentielle de la dent pointue du carnivore a donc été de pénétrer axialement dans les aliments, la série de petites pointes latérales ayant pour fonction de relayer la découpe au fur et à mesure de l’enfoncement.
    Les données mettent en évidence différents états microscopiques des surfaces qui résultent de la pénétration des dents au cours de leur action pour mordre, retenir, percer, taillader les aliments. Chaque dent de dinosaure a montré une spécialisation en fonction du choix alimentaire. Le végétarien, comme le carnivore, agrippe les aliments mais il ajoute une action transversale d’écrasement nécessaire pour déstructurer les végétaux. La recherche d’un lien entre l’usure dentaire et la forme de la dent n’est qu’une première étape de connaissance qui, après de nouvelles découvertes de fossiles, va s’étendre à l’étude de populations dans la recherche de choix alimentaires suivant l’âge ou les saisons. Il sera alors possible de vérifier l’hypothèse émise de migrations saisonnières des dinosaures à duvet et à plumes, comparables à celles de leurs descendants les oiseaux (Mitch Leslie 2007).

    Commento di Pierre-François Puech | maggio 18, 2009


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