Dreadnoughtus, a 130,000-Pound Dinosaur That Wasn‘t Done Growing
PHILADELPHIA â€” Eighty-five feet long, 30 feet tall, 130,000 pounds and still growing when it died, this dinosaur is among the largest land animals that ever lived â€” so big its discoverers are calling it the Dreadnoughtus.
Its skeleton, unearthed in the Patagonia region of Argentina, is the first of this species and most complete ever found in the group of gargantuan dinosaurs known as titanosaurs, scientists reported on Thursday. An international team led by Kenneth J. Lacovara, a paleontologist at Drexel University in Philadelphia, describe the fossil in the journal Scientific Reports.
â€œWhat we can say with certainty is this is the biggest land animal that we can actually put a number on,â€ Dr. Lacovara said.
Even what remains of the bones is huge. â€œWe‘ve got 16 tons of bone in my lab right now,â€ Dr. Lacovara said.
The better known Brachiosaurus dinosaur weighed only 75,000 pounds; an empty Boeing 737-900 weighs about 93,700 pounds. A male African elephant, the largest land animal today, weighs a minuscule 15,000 pounds by comparison. (Blue whales dwarf all land animals, past and present, growing to 300,000 pounds.)
Most titanosaurs are known from only a few bones. The vertebrae along the backbone of Argentinosaurus, a titanosaur that some claim to be the biggest of dinosaurs, are larger than those of Dreadnoughtus, but crucial bones needed to accurately estimate its mass have not yet been found.
With Dreadnoughtus, the researchers have more than 200 bones, representing 45 percent of the skeleton and 70 percent of the bones behind the head. That includes the left thighbone, more than six feet tall, and an upper armbone, which allowed a precise calculation of the weight of 130,000 pounds, or 65 tons.
â€œIt‘s a pretty good one,â€ Patrick O‘Connor, a professor of anatomy at Ohio University who was not involved with the new research. â€œMost often they‘re not anywhere this complete.â€
And this Dreadnoughtus appears to have been an adolescent. From the microscopic bone structure, the researchers argue that it had yet not reached its full-grown size when it died, sometime from 84 million to 66 million years ago.
â€œI think they put together a solid argument,â€ Dr. O‘Connor said of that conclusion. â€œI think it will engage a lively debate.â€
The skeleton currently fills most of Dr. Lacovara‘s laboratory at Drexel. The vertebrae bones of the 30-foot tail stretch along a table along one wall, then turn the corner to continue along the next wall. The bones near the muscle that wagged the tail are notably heftier than those in other titanosaurs. â€œIt seems to be muscled even more than you might expect,â€ Dr. Lacovara said.
â€œOver here, we have a single vertebra from the neck of this guy,â€ he said, pointing to a three-foot-long bone on the floor that he said was from halfway up the neck of Dreadnoughtus. â€œIt gives you an idea just how big this animal was.â€
He then picked up what looked like a fossilized piece of rope. â€œWe actually have what we believe are neck tendons, preserved,â€ he said. â€œYou can imagine a dinosaur as big as a house with a 30-foot neck is going to need a lot of tension in that neck. This is probably howit could hold its neck up and even be in a relaxed position.â€
Many of the bones, like the ribs, are hollow. In modern animals, the mass roughly correlates with the internal body temperature. â€œIf you put 65 tons on that graph, it would be a temperature way above the temperature that would cook meat,â€ Dr. Lacovara said.
Kenneth J. Lacovara, a paleontologist at Drexel University in Philadelphia with a more than six-foot-tall thigh bone. Credit Jessica Kourkounis for The New York Times
The hollows most likely contained air sacs that connected the respiratory system and allowed titanosaurs to essentially fan themselves on the inside, he said.
The researchers found a single cylindrical tooth about an inch long. Dreadnoughtus would have had rows of these teeth, like prongs on a garden rake, allowing them to strip ferns and other vegetation and swallow them without chewing.
â€œThe stomach is larger than a draft horse,â€ Dr. Lacovara said, â€œso they can leave this stuff laying in their stomach for who knows how long, maybe months, probably.â€
Dr. Lacovara discovered the fossil in 2005, along with a smaller Dreadnoughtus. It took the team of scientsts, team, which included Matthew C. Lamanna of the Carnegie Museum of Natural History in Pittsburgh and Lucio M. Ibiricu of the of the Centro Nacional PatagÃ³nico in Argentina, four years to excavate the skeletons, which were shipped to Philadelphia by container ship, then several more to prepare and study the fossils.
The researchers performed laser scans of all of the bones and published 3-D models of each, freely available. That will allow other paleontologists to study the fossil from afar and print three-dimensional replicas of the bones.
â€œThis will literally obviate the need for scientists, in some cases, to fly across the world to visit the skeleton,â€ Dr. Lacovara said. â€œMan, if we had this for all of the dinosaurs that existed, our lives would be so much better.â€
A student of Dr. Lacovara‘s is currently working with a Drexel engineer using sophisticated medical models to understand how Dreadnoughtus moved. â€œWe‘re applying that technology to this dinosaur,â€ Dr. Lacovara said, â€œbecause we can see all of the muscle attachments.â€
The scientists are also looking at thin slices of bone to better understand how the dinosaur grew, and even looking to reverse the fossilization to extract soft tissues.
The fossil, which is on loan to Dr. Lacovara to conduct the research, is expected to return to Argentina next year.
Its full name is Dreadnoughtus schrani â€” for the Dreadnought, the almost impervious World War I-era battleship, and Adam Schran, a technology entrepreneur who helped finance the research.
â€œProbably a pretty surly beast,â€ Dr. Lacovara said. â€œI wouldn‘t want to get anywhere near this guy. If he leaned against you, you‘re dead.â€