Patagonia was once the home of the largest land animals that ever lived, humungous creatures longer than a blue whale and much heavier than even the giant sauropods of other continents. Immense as the ones we have named and studied are, a specimen currently under excavation appears to be bigger yet. As yet, the palaeontologists extracting it are not sure whether they’ve found a new species, or simply an oversized member of one we already know about.
The existing record holder for the most massive animal to walk (or at least plod) the Earth is the 63-ton Patagotitan mayorum. However, investigations of South America's Cretaceous rocks are still in their infancy, compared to the Northern Hemisphere, where discoveries date back to the “bone wars” of the 19th century. The first P. mayorum were only dug up in 2014 and scientifically described in 2017, so it's not a total shock to find something even bigger.
In the mid-Neuquén river valley, dinosaur hunters have found 24 intact tail vertebrae from what is clearly a member of the titanosaur clade, along with parts of the pelvic and pectoral girdles. “The remains continue under the rock, so we will continue with their rescue in future campaigns,” Dr Alejandro Otero of the National Scientific and Technical Research Council told Agencia CTyS.
Under normal circumstances, palaeontologists finding a bunch of bones would wait to piece together all the specimen they could before publishing a scientific paper. It’s often decades between a specimen being found and scientific publication.
The rules are a little different for a world record, and Otero is the first author of a paper in Cretaceous Research describing what has been found so far.
"Regarding size, very accurate estimates of body mass could not be made, because we do not yet have long bones such as the humerus or femur, which are the bones traditionally used to make these estimates," Otero said in a statement. “But, having made some comparisons with Patagotitan mayorum…for example with vertebrae and other elements of the waists, it gives us that the bones of this animal are between 10 and 20 percent bigger.” That would likely make it more than 40 meters (130 feet) long and as tall as an 8-story building.
The find was made in 2012 when members of a team from a variety of Argentinian institutions went for a walk to relax while extracting another specimen, showing just how easy it is to find something astonishing in this under-explored part of the world. Even then, it was obvious the specimen was large, but it took the slow process of removing the surrounding rock without damaging the bones to reveal the scope of the discovery.
Besides its size, the specimen has excited the authors because, so far, it is much more intact than the typical titanosaur fossil, which often has to be reconstructed from a handful of scattered bones.
The rocks in which the titanosaur tail was encased are around 98 million years old; having been laid down on what was then a river flood plain. Teeth and coprolites (fossilized dung) from carnivorous dinosaurs that probably fed on it have been found around the specimen. It is considered unlikely even the mightiest predator could have brought down a beast such as this, so these accompanying fossils are thought to be from scavengers that happened upon one of the biggest meals of all time.