The new species is "definitely big," said Kristina Curry Rogers, curator and head of the paleontology department at the Science Museum of Minnesota in St. Paul.
After reading the description of the back vertebra, she took out her tape measure and stretched it across her desk to better visualize the size.
"It's a huge sauropod," she said. "I'm not sure it's the biggest sauropod, but based on what we know about sauropods, it's probably one of the biggest sauropod bones ever found [from the size of the neck bones]."
According to Curry Rogers, who specializes in titanosaurs, size is always "a bit tricky" to gauge from the few fossils paleontologists have recovered from the group.
Other huge titanosaurs, including Argentinosaurus, are primarily known from limb bones, she says.
"When comparing vertebrae to limbs, you have to extrapolate, no matter what," she said. "But that's part of this science. You have to make this leap to imagine what they were like."
Puertasaurus significantly extends the time giant titanosaurs were known to roam the Earth, research leader Novas says.
"It was suggested that the heyday of these animals was around 90 to 100 million years ago and that the end of the Cretaceous was reserved for smaller sized titanosaurids," he said.
The Cretaceous period extended from 144 to 65 million years ago.
"Through the discovery of Puertasaurus, now we know that the giant titanosaurids survived in southern Patagonia up to the end of the Cretaceous."
Curry Rogers, of the Science Museum of Minnesota, says this finding adds weight to the notion that sauropods were an amazingly diverse and successful group.
"Here are dinosaurs that [contain both] giants and dwarfs, living on every continent," she said. "They are innovative and diverse at a time that is late in terms of the dinosaur calendar."
According to Novas, 70 million years ago southern Patagonia was periodically inundated with seawater from both the Atlantic and Pacific Oceans, since the Andes mountains hadn't yet formed.
Large fossilized logs were also found in the same beds (known as the Pari Aike formation) as Puertasaurus, indicating the region was once forested.
Other regional dinosaur contemporaries included small titanosaurs, an unnamed meat-eater, and the ornithischian (bird-hipped dinosaur) Telankauen santacrucensis. (Read about the Telankauen find: "Dinosaur Discovered in PatagoniaNamed 'Small Head'" [April 5, 2004].)
"Interestingly, bones of giant titanosaurs are very abundant in the Pari Aike beds, suggesting that these plant-eating animals were prosperous at the time of deposition of these beds," Novas said.
"It is not improbable that Puertasaurus moved in herds, a behavior that was also inferred for other sauropods."
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