Kenneth Lacovara with the right tibia of dreadnoughtus schrani Kenneth Lacovara Photograph: Kenneth Lacovara, The spectacular remains of one of the largest beasts ever to walk the planet have been unearthed by fossil hunters in southern Patagonia.The unique haul of bones includes a metre-wide neck vertebra, a thigh bone that stands as tall as a man, and ribs the size of planks, representing the most complete skeleton of a colossal plant-eating titanosaur recovered anywhere in the world.
The new species was so enormous that researchers named it Dreadnoughtus schrani after the dreadnought battleships of the early 20th century on the grounds that it would fear nothing that crossed its path.
From measurements of the bones, scientists worked out that Dreadnoughtus weighed nearly 60 tonnes and reached 26 metres from snout to tail, making it the largest land animal for which an accurate body mass can be calculated.
The colossal dreadnoughts lived around 77m years ago in a temperate forest at the southern tip of South America. Its bodyweight equates to as many as a dozen African elephants or more than seven of the Tyrannosaurs rex species, according to Kenneth Lacorvara, a paleontologist at Drexel University in Philadelphia. Details of the find are published in the journal, Scientific Reports.
Another giant prehistoric animal, Argentinosaurus, was probably of comparable size but its dimensions are known only from a clutch of backbone vertebrae, a shinbone and a handful of other bone fragments. The diplodocus, which lived 80m years earlier than dreadnoughtus, weighed in at a comparatively measly 16 tonnes.
Lacorvara caught a first glimpse of the remains during a field trip to the stunning but barren scrubland of southern Patagonia in 2005. What appeared to be a small collection of bones soon became an extensive haul of more than 100 bone fragments, exquisitely well preserved when the animal apparently drowned in quicksand.
Though staggering in its dimensions, close inspection of the bones revealed that the animal was not fully grown when it died. “That was a real shock to us,” Lacorvara told the Guardian. “When you look at the bones of dreadnoughtus, it’s clear this individual was still growing fast. There are no indications of a cessation of growth.”
It took Lacorvara’s team, working with Argentinian experts, four successive years to excavate the entire skeleton which amounts to more than 45% of the animal’s bones. Only a single tooth and a small fragment of the dinosaur’s jaw were found from the head. The loss of much of the skull is common in fossils of giant plant-eaters, because the skull bones are relatively small and light to enable the dinosaur to lift its head. During the excavation the team unearthed the remnants of a second, smaller titanosaur.
The site lies around 62 miles (100km) off the power grid and four hours’ drive from the nearest town. “I’ve spent a total of about a year living in my tent next to this dinosaur. We live very simply down there. We eat crackers for breakfast, a can of tuna and a piece of cheese for lunch, and every night we have a piece of meat on a stick,” Lacorvara said. “Every couple of weeks we make a foray into town for food and showers.”
In the late Cretaceous period, the site was a mixed forest of conifers and broad-leafed trees cut through by meandering waterways. The rivers were prone to flooding, and the sudden surge of water would have turned surrounding flood plains into sinking sand. The dreadnoughtus was apparently in the wrong place at the wrong time. “Shortly after these individuals died, or as they died, they were buried quickly and deeply in what was essentially quicksand. That led to the high number of bones and the exquisite preservation,” Lacorvara said.
One vertebra from dreadnoughtus has what looks like a bite mark on it, the sign of a scavenger taking a nibble on the dinosaur corpse before it was completely entombed. Several teeth from meat-eating predators that match the bite marks were found at the scene.
The dinosaur had three large claws on each of its back feet, a muscular 10m-long tail and an even longer neck. The tail may have been used as a club to protect itself. “They were absolutely able to defend themselves. If dreadnoughtus so much as leaned on a predator it would kill it. A big, bold dreadnoughtus with a territory to guard must have been a really fearsome creature that you don’t want to be anywhere near,” Lacorvara said.
The researchers are now using the remains to learn more about how the animal moved. By taking laser scans of the bones they have printed out 3D-scale models of the dinosaur and turned them into robots by adding motors to move their limbs.
Other work with Mary Schweitzer at North Carolina State University aims to recover ancient cells and soft tissue from the animal to understand its biological makeup.
Neural spines to the left, chevrons to the right: bones of the dreadnoughtus schrani unearthed in southern Patagonia, Argentina. Photograph: Kenneth Lacovara
“Dreadnoughtus gives us our first good look at the anatomy of these gigantic sauropod dinosaurs, that were previously known from rather incomplete material,” said Paul Barrett, a paleontologist at the Natural History Museum in London.
“This new information will help to shed new light on the relationships among these giants and the number of times true gigantism evolved. Ultimately, it may also be able to help us understand the upper size limits to life on land, in terms of the physical constraints imposed by bone and muscle strength, blood pressure and feeding requirements.”