TWEETS:
 It could have been a contender: Massive dinosaur drops a weight class.
 Just how big was Dreadnoughtus? Paleontologists make bones about new
estimates of this dino’s heft.
SUBTOPIC(s): Dinosaurs & Fossils (in Life)
---------------------------MAIN ART From SN
Caption: The gigantic dinosaur Dreadnoughtus schrani may not have weighed as much
as scientists first thought. A new analysis puts its weight at maybe just 22,000 kilograms
(24 tons).
Credit: Jennifer Hall
Filename/URL: https://www.sciencenews.org/article/new-analysis-cuts-massive-dino’sweight-half
Image source/permission to use:
----------------------------------------------Image #2: Filename/URL: https://www.sciencenews.org/article/new-analysis-cutsmassive-dino’s-weight-half
Caption: A 3-D model of Dreadnoughtus schrani helped researchers estimate the
dinosaur’s body volume (light blue, with volume of lungs and airway in black) and mass.
The new calculation suggests the dino was thinner (top) than first estimated (bottom).
Credit: K.T. BATES ET AL/BIOLOGY LETTERS 2015 (CC BY 4.0)
---------------------------HED: New analysis halves massive dino’s weight
DEK: Dreadnoughtus maybe wasn’t as hefty as first estimated
WEB SUMMARY: Now question about it, Dreadnoughtus schrani was enormous. But a
new estimate concludes this dino weighed just half as much as first thought.
By Meghan Rosen
One of the world’s heaviest dinosaurs just slimmed down — in a jiffy.
Scientists announced last year the discovery of Dreadnoughtus schrani. At the time, this
plant-eating dinosaur was estimated to have weighed about 59,000 kilograms (65 U.S.
tons). But a newer analysis now suggests Dreadnoughtus (Dred-NAW-tus) probably
weighed only about half that much. Details appeared online June 9 in Biology Letters.
The first estimate of this dino’s heft placed it among the largest land animals to have
ever lived. Instead, it may have been only a little bit bigger than a related dinosaur,
Apatosaurus. That is according to study coauthor Karl Bates. He is a biologist at the
University of Liverpool in England.
“It’s not the sort of game-changing, massive difference that it was built up to be,” Bates
says. Dreadnoughtus and Apatosaurus were both sauropods. Dinosaurs in this group
had long necks and tails. They walked on four legs. And they were enormous.
Kenneth Lacovara is a paleontologist at Drexel University, in Philadelphia, Pa. He and
his colleagues announced finding Dreadnoughtus last year. At that time, these experts
also shared their estimate of Dreadnoughtus’ mass. They arrived at their number using
measurements of the circumference of the longest bones in the dino’s hind legs and
forelegs.
Bates now says Lacovara’s team didn’t factor in the possibility for error. Bates and his
colleagues tried a different method. They used a computer program and measurements
from living animals. First, they estimated the volume of Dreadnoughtus. Next, the team
calculated the dino’s mass. They conclude that Dreadnoughtus might have weighed
between 22,000 and 38,000 kilograms (24 to 42 U.S. tons).
Lacovara isn’t convinced. The method used by Bates relies on a lot of guesswork, he
charges. Scientists don’t have a complete Dreadnoughtus skeleton. Only about half of
its bones had been found preserved as fossils.
An incomplete set of bones means the new study’s authors had to guess how chubby
Dreadnoughtus was. They also had to guess at the proportions of the dinosaur’s
skeleton. Even small changes in the animal’s length could lead to vast changes in its
overall body volume, Lacovara points out.
In contrast, all Lacovara’s team did was “walk up to two bones with a tape measure and
take a measurement. So there was zero opportunity for subjectivity,” Lacovara says.
“We’re never going to be able to put Dreadnoughtus on a scale,” he says. Still, he
argues that the method his team used to estimate the dinosaur’s mass, last year, has
been "the gold standard.”
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Power Words
(for more about Power Words, click here)
Apatosaurus A dinosaur whose name means deceptive lizard. It has a long neck and
thick, whip-like tail. Formerly known as a brontosaurus, it lived during the Jurassic
period, about 150 million years ago. In adulthood, this plant-eater would have weighed
some 36 metric tons and had an average length of perhaps 23 meters (75 feet). That
would have made it one of the largest animals to ever roam the Earth.
biology The study of living things. The scientists who study them are known as
biologists.
dinosaur A term that means terrible lizard. These ancient reptiles lived from about 250
million years ago to roughly 65 million years ago. All descended from egg-laying reptiles
known as archosaurs. Their descendants eventually split into two lines. They are
distinguished by their hips. The lizard-hipped line became saurichians, such as twofooted theropods like T. rex and the lumbering four-footed Apatosaurus (once known as
brontosaurus). A second line of so-called bird-hipped, or ornithischian dinosaurs, led to
a widely differing group of animals that included the stegosaurs and duckbilled
dinosaurs.
femur In humans, the large bone in the upper leg. It is commonly known as the
thighbone. In tetrapods (creatures with four limbs), it’s the large bone in the upper hind
limbs.
fossil Any preserved remains or traces of ancient life. There are many different types
of fossils: The bones and other body parts of dinosaurs are called “body fossils.” Things
like footprints are called “trace fossils.” Even specimens of dinosaur poop are fossils.
humerus
The long bone found in the upper arm or forearm of an animal.
mass A number that shows how much an object resists speeding up and slowing down
— basically a measure of how much matter that object is made from. For objects on
Earth, we know the mass as “weight.”
paleontology The branch of science concerned with ancient, fossilized animals and
plants. The scientists who study them are known as paleontologists.
sauropod A very large, four-legged, plant-eating dinosaur with a long neck and tail,
small head and massive limbs.
Further Readings
K. Baggaley. “There really was a Brontosaurus, study claims.” Science News for
Students. April 12, 2015.
S. Perkins. “Dinos: Some were ‘marathoners’.” Science News for Students. Dec. 12,
2014.
J. Raloff. “Biggest dino ever?” Science News for Students. Sept. 20, 2014.
S. Perkins. “Reviving dinosaurs.” Science News for Students. March 4, 2014.
Original Journal Source: K.T. Bates et al. Downsizing a giant: re-evaluating
Dreadnoughtus body mass. Biology Letters. Published online June 9, 2015. doi:
10.1098/rsbl.2015.0215.
Original Journal Source: K.J. Lacovara et al. A gigantic, exceptionally complete
Titanosaurian sauropod dinosaur from Southern Patagonia, Argentina. Scientific
Reports. Published online September 4, 2014. doi: 10.1038/srep06196.
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---------------------------KEYWORDS: Dreadnoughtus schrani, Apatosaurus, sauropods, dinosaurs, mass,
volume, fossils, plant-eaters, paleontology, skeletons,