In Northern Patagonia, paleontologists have unearthed an ancient lagoon ecosystem surrounded by sand dunes and palm trees where prehistoric creatures thrived. Excavations of 78 million year-old rocks, from a quarry just outside General Roca city in Argentina, yielded a treasure trove of 432 fossils belonging to over a hundred animal groups.

The majority of the fossils belonged to turtles, but other residents were fish, crocodile relatives, slugs—including the first fossil record of the Neocyclotidae, a family of tropical land snails, and the first record of Leptinaria, a genus of small tropical air-breathing land snails—and dinosaurs.

The most important find among them all: a new titanosaur called Chadititan calvoi.

Though researchers have known the Anacleto rock formation where the fossils were discovered for decades, there had never been a finding with such diversity in a single place in Northern Patagonia, says coauthor Diego Pol, a paleontologist at the Museo Argentino de Ciencias Naturales Bernardino Rivadavia in Buenos Aires and a National Geographic Explorer. Today, the team of Argentinian and Uruguayan researchers published their findings on the new titanosaur and the site in Revista del Museo Argentino de Ciencias Naturales.

“The fossil fauna there is diverse, and our understanding of Southern Hemisphere ecosystems from near the end of the Age of Dinosaurs is still very incomplete,” says paleontologist Matthew Lamanna of the Carnegie Museum of Natural History in Pittsburgh who was not involved in the research.

The site is so rich because it was probably an oasis amid harsh environments in the Argentinian Patagonia in the late Cretaceous period. At the time, temperatures were about five to 10 degrees Celsius higher than today, and biodiversity hotspots would concentrate in higher latitudes, as tropical regions were too hot for most species. “This is a very particular environment, with deposits of sand dunes interspersed with small lakes—and just like we see today in arid places, water concentrates biodiversity,” Pol says.

Of the more than 400 fossil records found, about 20 belong to Chadititan calvoi. “Chadi”, or “salt” in the Mapudungun language spoken by Mapuche groups refers to the excavation site, located at the margins of a salt flat, the Salitral Moreno lowlands.The full genus name translates to "Titan of the Salt.” The species calvoi is a tribute to the late Argentinian paleontologist Jorge Calvo, who described several titanosaurs and coined the clade Rinconsauria, to which the new species belongs.

Titanosaurs are known for their exceptional proportions, ranging from cow-sized one metric ton animals to whale-sized beasts of about 60 metric tons, says Lamanna.While the largest titanosaurs reached over 100 feet in length, the new species is around 22 feet or seven meters long—about the same length as a minibus or RV. “Chadititan is on the small side as titanosaurs go, though it still would’ve been big compared to most of today’s animals,” he adds.

Some of the fossilized C. calvoi bones share characteristics with other late Cretaceous herbivore or plant-eating dinos found in the region such as the Overosaurus and the Muyelensaurus. But other features set the new species apart. “For example, it has a lateral bulge in its femur, its neural spine is projected backwards, and its humerus is really thin and broad,” Pol explains.

To Lamanna, the finding is interesting because it suggests that the titanosaur subgroup to which C. calvoi belongs, the rinconsaurians, “may have had unusual body proportions, potentially being more giraffe-like in build than most other sauropods,” he says.

Though titanosaurs roamed all over the globe, it was in South America that they were most diverse and abundant—and the subcontinent’s most important herbivores. “In any terrestrial ecosystem, herbivores have a key role as they are the intermediaries between plants and all the other links of the food chain,” Pol explains. Researchers don’t know for certain which large dinosaurs were predators to titanosaurs, “but they, especially the young ones, were probably prey to other species,” Pol says.

When an asteroid brought about the end of the dinosaurs about 66 million years ago, titanosaurs were the last long-necked herbivores alive. Studying the new species and others could help paleontologists understand how biodiversity changed as the world approached the end of the dinosaur reign. “Titanosaurs include among their ranks some of the very last non-bird dinosaur species on the planet,” Lamanna says.

Herbivore dinosaurs in the Southern Hemisphere seem to contradict other trends leading up to the Chicxulub asteroid impact in the Gulf of Mexico. Pol notes that some studies suggest there was a crisis in biodiversity just prior to the mass extinction event, especially among herbivores. “This is something of our particular interest because we want to put this thesis to test, as we’re not convinced it is true—especially in South America, where herbivore diversity seems to have been pretty high,” he adds.