2008-09-23 – Scoperto il più piccolo dinosauro del Nord America (Albertonykus borealis, alvarezsaur, Early Maastrichtian, Canada )
America’s Smallest Dinosaur Uncovered
ScienceDaily (Sep. 23, 2008) — An unusual breed of dinosaur that was the size of a chicken, ran on two legs and scoured the ancient forest floor for termites is the smallest dinosaur species found in North America, according to a University of Calgary researcher who analyzed bones found during the excavation of an ancient bone bed near Red Deer, Alberta.
“These are bizarre animals. They have long and slender legs, stumpy arms with huge claws and tweezer-like jaws. They look like an animal created by Dr. Seuss,” said Nick Longrich, a paleontology research associate in the Department of Biological Sciences. “This appears to be the smallest dinosaur yet discovered in North America.”
Called Albertonykus borealis, the slender bird-like creature is a new member of the family Alvarezsauridae and is one of only a few such fossils found outside of South America and Asia. In a paper published in the current issue of the journal Cretaceous Research, Longrich and University of Alberta paleontologist Philip Currie describe the specimen and explain how it it likely specialized in consuming termites by using its small but powerful forelimbs to tear into logs.
“Proportionately, the forelimbs are shorter than in a Tyrannosaurus but they are powerfully-built, so they seem to have served a purpose,” Longrich said. “They are built for digging but too short to burrow, so we think they may have been used to rip open log in search of insects.”
Longrich studied 70 million-year-old bones that were collected on a dig led by Currie at Dry Island Buffalo Jump Provincial Park in 2002 where the remains of more than 20 Albertosaurus sarcophagus individuals were found. Albertosaurs are a type of tyrannosaur. The bones were placed in storage at the Royal Tyrrell Museum and Longrich came across them while trying to compare Albertosaurus claws to another dinosaur species.
“This is the oldest and most complete dinosaur of its kind known from North America and it provides evidence that these dinosaurs migrated to Asia through North America,” he said.
Longrich, who specializes in studying dinosaur-era ancestors of birds, completed his PhD at the University of Calgary under the supervision of zoology professor Anthony Russell. In September 2006 Longrich argued that that earliest known ancestor of birds, a feathered creature called Archaeopteryx, likely flew with wings on all four limbs after examining fossils originally collected in Germany in 1861.
“You can really find amazing things if you just keep looking at fossils we already have sitting in museum collections,” he said. “The number of dinosaur discoveries is actually accelerating because we just keep digging up more material to work with.”
Canada, scoperto dinosauro grande come un pollo
mercoledì, 24 settembre 2008 11.13
CALGARY (Reuters) – Un ricercatore canadese ha scoperto quello che si pensa essere il più piccolo dinosauro del Nord America, grande come un pollo e che si nutriva insolitamente di insetti.
Chiamato Albertonykus borealis, la strana creatura — che risale a 70 milioni di anni fa — aveva le caratteristiche degli uccelli, comprese le zampe magre, il becco a tenaglia e gli arti superiori tozzi e con grossi artigli.
Le sue ossa sono state trovate vicino al Red Deer, ad Alberta — zona ricca di fossili — nel 2002.
Il dinosauro fa parte della famiglia Alvarezsauridae, i cui fossili finora erano stati trovati solo in America del sud e Mongolia, ha spiegato Nick Longrich, paleontologo dell’Università di Calgary.
La scoperta prova che i dinosauri migrarono in Asia dalla parte meridionale dell’emisfero occidentale, spiega Longrich, la cui ricerca sull’Albertonykus è stata pubblicata sulla rivista Cretaceous Research.
“La maggior parte dei dinosauri che conosciamo — come i tirannosauri, carnivori giganti o i triceratopi, grossi erbivori — erano grandi. Questo è molto piccolo (alto circa 70 cm) e pensiamo che fosse un insettivoro”.
- Longrich et al. Albertonykus borealis, a new alvarezsaur (Dinosauria: Theropoda) from the Early Maastrichtian of Alberta, Canada: implications for the systematics and ecology of the Alvarezsauridae. Cretaceous Research, August 2008; DOI: 10.1016/j.cretres.2008.07.005
A new alvarezsaur, Albertonykus borealis, is described from the Lower Maastrichtian of the Horseshoe Canyon Formation, Alberta, Canada. Forelimb and hindlimb elements from at least two individuals were recovered from the Albertosaurus bonebed at Dry Island Provincial Park, along with pedal phalanges from nearby localities. Phylogenetic analysis shows that Albertonykus is the sister taxon of the Asian clade Mononykinae, consistent with the hypothesis that the alvarezsaurs originated in South America, and then dispersed to Asia via North America. The discovery of Albertonykus provides important insights into the biology of the Alvarezsauridae. As in other alvarezsaurs, the forelimbs of Albertonykus are specialized for digging, but they are too short to permit burrowing; they were most likely used to dig into insect nests. Potential prey items are evaluated in light of the fossil record of social insects. Ants were a minor part of the ecosystem during the Cretaceous, and mound-building termites do not appear until the Eocene. This leaves the possibility that Albertonykus preyed on wood-nesting termites. We tested this hypothesis by examining silicified wood from the Horseshoe Canyon Formation. It was found that this wood frequently contains borings, which resemble the galleries of dampwood termites (Termopsidae).
Keywords: Alvarezsauridae; Horseshoe Canyon Formation; Edmontonian; Maastrichtian; Isoptera; Alberta
Link 1 (Blog: Theropoda)
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