A newly unearthed "supermassive" dinosaur, Dreadnoughtus schrani, is the largest known land animal for which mass can be accurately calculated, concludes a new study.
The dinosaur, whose scientific name means "fear nothing" and is nicknamed "Dread," is described in the latest issue of Scientific Reports. Dread measured 85 feet long and weighed about 65 tons, according to the study, which also reports that the dinosaur's skeleton is the most complete ever found for its type.
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Lead author Kenneth Lacovara said that Dread "weighed as much as a dozen African elephants or more than seven T. rex." Not surprisingly, this dinosaur had no known predators. If its sheer massiveness did not scare away hungry others, its "weaponized tail" would have.
"No doubt Dread would use its amazingly muscled tail to fend off attack," Lacovara, an associate professor in Drexel University's College of Arts and Sciences, told Discovery News. "If an animal made it under its tail, three large claws would be waiting for them on each back foot."
He added, "I can't imagine that it was a good idea to attack a full-grown, healthy Dreadnoughtus."
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The otherwise peaceful herbivore likely spent its days fulfilling what Lacovara calls "a life-long obsession with eating."
"Every day is about taking in enough calories to nourish this house-sized body," he explained. "I imagine their day consists largely of standing in one place. You have this 37-foot-long neck balanced by a 30-foot-long tail in the back. Without moving your legs, you have access to a giant feeding envelope of trees and fern leaves."
Once the forest section had been cleared, Dread would probably then take a few steps to the left or right and start feasting all over again.
Lacovara suspects that Dread had a stomach the size of a horse. Food would remain there for long periods, churning in stomach acids that efficiently extracted nutrients.
The dinosaur, represented by two specimens, was unearthed in southern Patagonia. Dread lived approximately 77 million years ago in a temperate forest at the southern tip of South America.
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Based on sedimentary deposits at the site, the two dinosaurs were buried quickly after a river flooded and broke through its natural levee, which would have turned the ground into something like quicksand. The dinosaurs' rapid and deep burial, Lacovara said, accounts for the extraordinary level of fossil completeness.
"Its misfortune was our luck," he added.
Dread was a titanosaur, meaning a type of four-legged, plant-eating dinosaur from the Middle Jurassic to Late Cretaceous periods.
"Titanosaurs are a remarkable group of dinosaurs, with species ranging from the weight of a cow to the weight of a sperm whale or more," said paleontologist Matthew Lamanna, a curator at the Carnegie Museum of Natural History.
"But the biggest titanosaurs," Lamanna continued, "have remained a mystery because, in almost all cases, their fossils are very incomplete."
Another titanosaur, Argentinosaurus, could knock Dread off its top size spot in the dinosaur record books if more complete specimens for it are found.
As Lacovara said, "I think it is very likely that Argentinosaurus is the most massive dinosaur yet known, however, I don't think we can make a reliable estimation of its mass."
He and his team continue to analyze Dread, which they made into a virtual skeleton mount that is now available for anyone to download from the paper's open-access online supplement. Since a single bone for the dinosaur can weigh hundreds of pounds, the digital model makes life a lot easier for the paleontologists.