Giant Dinosaurs Unearthed in Argentina

The bones of seven huge dinosaurs that each weighed more than a dozen elephants and had femurs bigger than a human adult have been discovered in Argentina.

The bones of seven huge dinosaurs that each weighed more than a dozen elephants and had femurs bigger than a human adult have been discovered in Argentina, scientists announced.

The plant-eating beasts plodded across South America 95 million years ago, during the Mesozoic Era, and they may represent a new species. The creatures may even be the biggest dinosaurs known, outshining their long-tailed, long-necked titanosaur cousins like Argentinosaurus, said the paleontologists who excavated the bones.

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Using jackhammers, shovels and even bulldozers, researchers of the Museum of Paleontology Egidio Feruglio in Argentina's Patagonia region removed the fossils from a site in the center of Chubut province, about 160 miles (260 kilometers) from the city of Trelew. A farm worker first discovered dinosaur bones there in 2011. So far, scientists have found more than 200 fossils at the site, including leg bones, vertebrae, teeth and tail bones. [See Photos of the Dino Discovery]

The amazing state of preservation of the bones is rare. The animals, all adults, appear to have died around the same time. The researchers speculate that they they succumbed to dehydration or got stuck in the mud while gathering around small pools of water to drink. In this deadly graveyard, the reptiles may have become food for scavengers like carnivorous dinosaurs in the Tyrannotitan genus.

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Based on the fossils of the newfound herbivore sauropod, which has yet to receive a name, scientists think it would have stretched 131 feet (40 meters) in length and weighed 80 tons (73 tonnes).

"It's like two semi trucks, one after another, and the equivalent of more than 14 African elephants' weight together," researcher José Luis Carballido, of Museum of Paleontology Egidio Feruglio in Argentina's Patagonia region, said in a statement.

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The sauropod's femur next to researcher Pablo Puerta.

As paleontologists increasingly unearth evidence of feathers in prehistoric fossils, our conceptions of what dinosaurs looked like when they roamed the earth has gradually evolved.

Instead of the reptilian appearance we all recognize from childhood toys and films like Jurassic Park, many dinosaurs in fact more closely resembled birds, kind of like this recently discovered little guy, Eosinopteryx brevipenna, a flightless theropod dinosaur that roamed China during the Middle/Late Jurassic period.

Archaeopteryx, also known as Urvogel, the German word for "original bird" or "first bird," was first discovered in 1860 and later fossils of this species presented some of the earliest evidence of flight in these prehistoric animals.

An intermediate creature that was not quite dinosaur but not exactly a bird either when it lived 150 million years ago, Archaeopteryx had teeth, a long tail, and wings capable of flight with claws at the end for grabbing prey.

A century after the discovery of Archaeopteryx, paleobiologists increasingly found anatomical connections between birds and dinosaurs. In the 1970s, artists began to portray dinosaurs with feathers based on accumulating evidence.

Megapnosaurus, shown here, was another species with whom researchers began early to identify with feathers. A lightweight animal that could reach up to 10 feet in length and roamed Jurassic Zimbabwe, Megapnosaurus, also known as Syntarsus, traveled in packs and preyed on small reptiles and fish.

Many of the fossils unearthed that provided evidence of feathers had deteriotated over the eons they remained buried. It wasn't until 2010 that researchers identified color pigments in feathers from dinosaurs and early birds.

Sinosauropteryx, illustrated here, was a theropod dinosaur that had "simple bristles -- precursors of feathers -- in alternate orange and white rings down its tail," according to a description of the study's findings.

Given that so many feathered dinosaurs were in fact flightless, the purpose of the feathers has been a subject of debate. Some dinosaurs may have evolved feathers for social signaling; others had plumage to provide insulation.

In the cases of some dinosaurs, such as the two oviraptors, herbivores related to T. rex that lived during the Cretaceous period, researchers believe the feathers were used for mating displays, similar to modern-day peacocks and turkeys.

You might be fooled into thinking the animals in this illustration are something between a murder of crows and a band of blue jays. In fact they are Microraptors that lives more than 130 million years ago.

These four-winged, plumed dinosaurs were no larger than modern-day pigeons and sported iridescent tail feathers.

Researchers believe the shimmering plumage was likely used in mating and other social interactions.

Like the diversity among birds today, not all feathered dinosaurs were lightweight, agile animals. A massive tyrannosaur that lived in China until about 65 million years ago, Yutyrannus huali, meaning "beautiful feathered tyrant," grew up to 30 feet long and could weigh more than 3,000 pounds.

This titanic tyrannosaur, as it was described, significantly increases the size range for feathered dinosaurs.

In a stunning find published in the journal Science in 2011, paleontologists uncovered dinosaur feather preserved in amber that dated back some 79 million years ago.

This discovery provided scientists a new window into the evolution of feathers in terms of structure in the evolutionary timeline from dinosaurs to birds. Even shades of color remained well preserved in the amber.