Image: Brachiosaur
William Sellers
The brachiosaur, shown in this computer reconstruction, was once thought to weigh 176,370 pounds. Now it's thought to have weighed 50,706 pounds.
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updated 6/5/2012 11:18:37 PM ET 2012-06-06T03:18:37

Dinosaurs were often hefty, but not as plump as previously thought.

A new study describes a new technique used to measure the weight and size of dinosaurs and other prehistoric animals. It could forever change museum exhibits, book illustrations, and other re-creations of these now-extinct species. The study appears in the latest issue of Biology Letters.

“This is a huge help for any sort of reconstruction,” lead author William Sellers told Discovery News. “We now have a number that suggests how much flesh to add to the bones and that should help people produce animals that are the right balance of too fat or too thin.”

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“This technique can also allow you to calculate the numbers you need for more sophisticated locomotor reconstructions, such as the running simulations we have produced in the past,” added Sellers, who is based at the University of Manchester’s Faculty of Life Sciences.

He and his team used lasers to measure the minimum amount of skin required to wrap around the skeletons of large modern animals that included reindeer, polar bears, giraffes and elephants. Doing this, the researchers noticed that the animals had almost exactly 21 percent more body mass than the minimum skeletal “skin and bone” wrap volume.

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The formula was then applied to a giant brachiosaur skeleton housed at Berlin’s Museum für Naturkunde. Previous estimates of this dinosaur’s weight have been as high as 176,370 pounds. This latest study, however, reduces the figure to just 50,706 pounds — impressively weighty, but not nearly as heavy.

“The 23-ton weight (50,706 pounds) is quite low, but I think it reflects the fact that all dinosaur weights are getting lower,” said Sellers, explaining that the estimated weight for this dino, along with other species, has been dropping since about the early 1960s.

He continued that the new estimate "reflects a better understanding of biology, and I think the early estimates were set in that big, fat and slow lizard mindset before the dinosaur renaissance. I think we will find that the lower estimates are much more appropriate for many dinosaurs."

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High-tech scanners, fast computers and other tools were simply not available back in the day when dinosaur weights were first estimated. Up until fairly recently, even experts resorted to some fairly homespun methods for attempting to calculate dinosaur heft.

"One very common method is to take an artist’s reconstruction sculpture of the animal and measure its volume by dipping it in water just like Archimedes," Sellers said. "That gives you the volumes, which you can multiply by the density to get its weight.”

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"The problem with this is the artist’s reconstruction," he said. "These are very time-consuming to do and probably rather inaccurate, so we thought we’d try a new method."

Aside from improved accuracy, the new method is minimally invasive and relatively quick. The primary limitation, for now, is that the specimen should consist of a complete skeleton that has been mounted.

"This is reasonably accurate because the bones fit together like a jigsaw puzzle," he said.

Heinrich Mallison of the Museum für Naturkunde told Discovery News that the new study describes “a brilliant approach: not trying to estimate soft tissues, but finding out how much a bone-only model underestimates the entire animal's mass.”

Mallison thinks it is “certainly a very good method for mammals, but I'd like to see tests with more details to find out if archosaurs (crocodiles and dinosaurs) have the same regressions, or differ.”

© 2012 Discovery Channel

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Explainer: The world's seven deadliest dinosaurs

  • Copyright 1985 Mark Hallett, "Awakening of Hunger"

    Yeah, it's cliche to say Tyrannosaurus rex was deadly. But the tyrant king was likely true to the billing. Its bone-crushing jaws could splinter prey like toothpicks, after all. And the beast was big, up to 40 feet long, 20 feet tall, and may have topped the scales at nearly 16,000 pounds.

    The king walked on two legs over a vast territory in western North America at the end of the Cretaceous, about 65 million years ago. Scientists wonder whether T. rex was more a lumbering scavenger or a quick and agile predator, but dead or alive, its meals were big, meaty and bloody.

    T. rex wasn't the only deadly dino, however. The globe was filled vicious killers. Click the arrows above to see more.

    — John Roach, msnbc.com contributor

  • Family diner

    Demetrios M. Vital

    Family meals for Majungasaurus crenatissimus were often bloody affairs of the grimmest sort: Kin were the main course. The evidence of its cannibalistic ways comes from telltale tooth marks on Majungasaurus bones that match up perfectly with the size and spacing of teeth in its jaws.

    The 20-foot-long dinosaur stalked the plains of Madagascar about 70 million years ago. At that time, the crime-scene investigators said, pickings were often slim. Their data indicate Majungasaurus fed on dried out "dino jerky" from its plant-eating compatriots as well as members of its own species. Cannibalism was likely just as common among dinosaurs as it is among living animals, but the evidence is rare.

  • Brow beater

    Todd Marshall

    Eocarcharia dinops' brow was swollen into a massive band of bone. The menacing head piece may have been used as a battering ram against rivals and to attract potential mates. Its blade-shape teeth were reserved for disabling live prey and severing their body parts.

    The 110-million-year-old beast and its snout-nosed, gut-and-carcass-scavenging relative Kryptops palaios were discovered in Africa's Sahara Desert. The approximately 7-foot-tall and 25-foot-long duo likely teamed up with a third carnivore and feasted on the long-necked plant-eater Nigersaurus.

  • Vicious rocker

    Parsons

    The toothy Masiakasaurus knopfleri likely speared prey with its forward projecting front teeth and then sliced and tore the captives into chewy chunks with its bladelike rears. This type of tooth arrangement is otherwise unknown in predatory dinosaurs.

    Scientists believe the German Shepherd sized beast feasted on fish, lizards, and other critters on the southern supercontinent Gondwana in the Late Cretaceous period, about 65 to 70 million years ago.

    The first part of this dinosaur's name means "vicious lizard" and the second part is derived from the Dire Straits singer and guitarist Mark Knopfler, whose music inspired the discoverers as they toiled on the African island nation of Madagascar.

  • Biggest carnivore?

    Prof. Rodolfo Coria / Ap

    At about 40 feet long and weighing an estimated 6 tons, Mapusaurus roseae was one of the biggest meat-eating dinosaurs to ever stalk the Earth. Bones of several individuals were discovered in one place, suggesting the giants may have hunted in packs that could have toppled perhaps the largest dinosaur that ever lived — a 100-foot-long plant eater called Argentinosaurus.

    Mapusaurus lived about 100 million years ago and was bigger than well known Tyrannosaurus rex and possibly larger than its older cousin, Gigantosaurus. Its teeth were narrow and blade like, made for slicing its prey. The bones were discovered in the Patagonia region of Argentina.

  • Going green

    MWS

    Falcarius utahensis is the living image of a vicious meat eater trying to go vegetarian. Scientists aren't sure if the bird-like relative of Velociraptor had fully kicked its taste for flesh, but its meat-cutting teeth had shrunk to leaf-cutting size and its gut had expanded sufficiently to ferment plants.

    Falcarius walked on two legs and stood about 4.5 feet tall. Head to tail, it was about 13 feet long and wielded sharp, curved, four-inch long claws — perhaps to grab a bite when it fell off the wagon? The dinosaur lived during the Early Cretaceous, about 125 million years ago, in what is today Utah.

  • Plant ripper

    utah.edu

    No plants were safe from Gryposaurus monumentensis, a big boned, duck-billed dinosaur that could have eaten any vegetation it stumbled across. Its massive skull packed more than 300 teeth for slicing up fibrous greens. Hundreds more replacement teeth rested in its jawbone for the call-up to action.

    The dinosaur lived in the Late Cretaceous, about 75 million years ago on the western side of a giant, shallow ocean that split North America at that time. The plant-munching beast may have reached 30 feet long as an adult and had a 3-foot-long head.

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