Jennifer Viegas, Discovery News

July 14, 2009 — A multi-institutional team of scientists this week reports the discovery of a giant new dinosaur in Utah, Nothronychus graffami, which stood 13 feet tall and had nine-inch-long hand claws that looked like scythes.

SLIDE SHOW: Therizinosaur: A Dino With Nine-Inch Nails

 

Its skeleton, described in the current issue of Proceedings of the Royal Society B, represents the most complete remains ever excavated of a therizinosaur, meaning “reaper lizard.” It is one of only three such dinosaurs ever found in North America.

Lead author Lindsay Zanno told Discovery News that therizinosaurs, including the new Utah species, “are unusual in that they have small heads with a keratinous beak at the front of the mouth — the same material as the beak of modern birds — and small leaf-shaped teeth.”

“Their bellies are proportionally enormous, supporting large guts,” added Zanno, who is a researcher in the Department of Geology at The Field Museum. “They have greatly enlarged claws on their hands, short legs and tails, and four-toed feet.”

Therizinosaurs are theropod predatory dinosaurs, a group that includes the legendary Tyrannosaurus rex. The newly discovered 92.5-million-year-old Utah dinosaur was no lightweight either. As Zanno said, “You wouldn’t want to run into this guy in a dark alley.” But its teeth, beak, gut and other anatomical characteristics suggest it was an omnivore that mostly feasted on plants.

Co-author David Gillette, curator of paleontology at the Museum of Northern Arizona, told Discovery News the formidable-looking claws on Nothronychus graffami probably weren’t used to kill other large animals, but instead might have tackled “digging into termite mounds, mucking on the bottom of a lake or pond like a goose or moose, and raking leaves into its mouth from a mangrove forest like a ground sloth.”

To better understand the dietary evolution of theropods, the researchers studied information on 75 other species within this group. They determined therizinosaurs experienced an early evolutionary split from the Maniraptora, which includes modern birds and their closest extinct relatives. One such relative was Velociraptor, a carnivore that probably kicked prey to death with its large hind foot claws.

The new Utah dinosaur therefore suggests that “iconic predators like Velociraptor, one of the dinosaurian villains in the movie Jurassic Park — may have evolved from less fearsome plant-eating ancestors,” according to the scientists.

Since the very meat-loving Velociraptor emerged some 20 million years after plant-chomping Nothronychus graffami, it’s now thought that some dinosaurs might have first been carnivores that evolved into omnivores or herbivores, which re-evolved back into meat-eaters.

Paleontologists aren’t sure why some dinosaur lineages may have see-sawed back and forth with their diets.

“Our current thoughts are that in gaining the ability to eat more than just meat, maniraptorans may have been able to invade new niches in the ecosystem that were unavailable to them before,” Zanno said. “In other words, they may have been able to find a new way of living in the ecosystem and new resources to exploit that gave them an advantage and allowed them to diversify into new forms.”

Aside from what it reveals about dinosaur diets, the new Utah species is significant because of where it was found: in marine sediments that would have been between 60 and 100 miles away from the closest shoreline. The ancient sea is now part of a desert. Merle Graffam, a member of the excavation team, found the dinosaur while searching for sea-dwelling animals. The dinosaur was named after him.

“A big mystery is how this animal — either alive or as a carcass — could get so far out to sea without being torn apart by predators and scavengers,” Gillette said. “This ecosystem had at least five species of plesiosaurs and many sharks and predatory, scavenging fish.”

He added, “Maybe (the dinosaur) was stranded at sea and struggled for a few days before drowning and sinking to the bottom.”

Paul Heinrich, a research associate at the Louisiana Geological Survey, offers another explanation. He thinks such complete dinosaur skeletons recovered in seaways may have rafted out to open water on “floating islands” after storms.

The recovered Utah dinosaur’s remains are now on public display at the Museum of Northern Arizona. The exhibit, Therizinosaur: Mystery of the Sickle-Claw Dinosaur, will close in September before moving to the Arizona Museum of Natural History in Mesa.

http://dsc.discovery.com/news/2009/07/14/sickle-claw-dinosaur.html

World’s Oldest Dinosaur Burrow Discovered In Australia

Posted on: Friday, 10 July 2009, 16:20 CDT | Related Video

Paleontologists have discovered the world’s oldest dinosaur burrows in Australia.  The 106-million-year-old burrows are the first to be found outside of North America, and were much closer to the South Pole when they were created.

In total, three separate burrows have been discovered, the largest of which was about 6ft. long.  Each burrow had a similar design and was just large enough to contain the body of a small dinosaur.

The discovery supports the theory that dinosaurs living in harsh, cold climates burrowed underground to survive.

The only other known dinosaur burrow was discovered in 2005 in Montana, and contained the bones of an adult and two young dinosaurs of a small new species called Oryctodromeus cubicularis. Two years after its discovery, scientists dated the burrow from 95 million years ago.   

The older burrows in Australia were found by one of the researchers who made the original Montana discovery.

“Like many discoveries in paleontology, it happened by a combination of serendipity and previous knowledge,” said Anthony Martin of Emory University in Atlanta.

“In May 2006, I hiked into the field site with a group of graduate students with the intention of looking for dinosaur tracks. We did indeed find a few dinosaur tracks that day, but while there I also noted a few intriguing structures,” he told BBC News.

Martin returned to the site, known as Knowledge Creek about 150 miles from Melbourne, to study the structures in July 2007 and again in May of 2009.

He was astonished at what he found.

“I was scanning the outcrop for trace fossils, and was very surprised to see the same type of structure I had seen in Cretaceous rocks of Montana the previous year,” said Martin.

That original structure was the burrow of O. cubicularis.

“So to walk up to the outcrop and see such a strikingly similar structure, in rocks only slightly older, but in another hemisphere, was rather eerie,” Martin said.

Within the rock, which is part of the Otway group of rocks that have produced a large diversity of vertebrate fossils, Martin discovered three separate burrows less than 10 feet apart, two of which formed a semi-helix twisting down into the rock.

The largest and best-preserved burrow turns twice before ending in a larger chamber. Dubbed tunnel A, it is more than 6 feet in length. Martin calculates that an animal weighing around 22 pounds would have created each burrow. Twisting burrows can help keep predators at bay and provide a steady temperature and humidity environment.

Alligators, aardwolves, coyotes, gopher tortoises and striped hyenas are among the modern animals that make such burrows.

Although Martin isn’t sure which species of dinosaur made the burrows, he noted how similar their designs are to the burrow created by O. cubicularis.

A number of small ornithopod dinosaurs, which stood upright on their hind legs and were about the size of a large iguana, were believed to have lived in the area during the same time in the Cretaceous period.

Martin has ruled out a number of other sources that could have created the burrows.

The fact dinosaurs created them makes sense, he said.

Australian researchers first proposed two decades ago that some dinosaurs might have created burrows to survive harsh climates they couldn’t escape from by migrating.

“It gives us yet another example of how dinosaurs evolved certain adaptive behaviors in accordance with their ecosystems,” Martin said.

“Polar dinosaurs in particular must have possessed special adaptations to deal with polar winters, and one of their behavioral options was burrowing. It provides an alternative explanation for how small dinosaurs might have overwintered in polar environments.”

Martin hopes that paleontologists will be on the look out for dinosaur burrows, and for dinosaurs that are physically adapted to burrowing into soil.

The findings were published in the journal Cretaceous Research.

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Image 1: Drawing by James Hays, Fernbank Museum

Image 2: Following his Montana discovery of the first trace fossil of a dinosaur burrow, Emory University paleontologist Anthony Martin has found evidence of older, polar dinosaur burrows in Victoria, Australia.

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On the Net:

• Emory Blog
• Cretaceous Research – Abstract

Source: redOrbit Staff & Wire Reports

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Scoperti i più grandi denti di dinosauro: misurano 9,83 cm

Misurano 9,83 centimetri di lunghezza  i più grandi denti di un dinosauro carnivoro mai scoperti. Sono  stati rinvenuti in Spagna, nella Arzobispo Formation, da un  gruppo di ricercatori della Teruel-Din¢polis Joint Palaeontology  Foundation e appartenevano a un dinosauro della famiglia degli  Allosauroidi, che comprendeva grandi esemplari che misuravano  fra i sei e i 15 metri.
I dinosauri, spiegano i ricercatori, durante la loro vita  perdevano i denti «da latte» e ne mettevano di nuovi: quello  descritto sulla rivista Estudios Geol¢gicos, sembra un dente  permanente e non da latte perchè non mostra alcun segno di  riassorbimento sulla superficie. Secondo i paleontologi, la  presenza di un grande dinosauro del gruppo Allosauroidea  completa le testimonianze fossili di dinosauri già scoperti  nella medesima formazione in Spagna. In passato, infatti, sono  emersi numerosi fossili (da denti a parti di arti) di dinosauri  vegetariani, come i sauropodi, gli stegosauridi e gli  ornitopodi.

Fonte: Gazzetta di Parma