Urumaco

Urumaco is a town in Falcón State in northwestern Venezuela, about 400 kilometres west of Caracas, and its dry country holds the richest fossil ground in northern South America. The climate is arid, so vegetation hides little, and geologists prospecting for oil were the first to bring the fossils to science.

The whole district was wetland eight million years ago. Scientists think a great river system, the Paleo-Orinoco-Amazon, ran through the area carrying water from the interior of the continent northeast to the sea, and the brown shale and coal beds around the town are full of giants. "Urumaco was a place of giants eight million years ago," the palaeontologist Marcelo Sánchez-Villagra told the BBC, pointing to some of the largest crocodiles ever seen and undescribed fish three metres long.

The turtle came first. Harvard researchers found Stupendemys geographicus here in the 1970s, and it has been known to science since 1976. A Science Advances study led by Edwin Cadena described an 8-million-year-old shell from Venezuela nearly 2.4 metres long, the largest complete turtle shell known, from an animal estimated at 1,145 kilograms, almost 100 times its closest living relative, the Amazon river turtle. Males carried horn-like weapons at the front of the shell, probably for fighting one another, and one horn bears a long, deep scar. Large caimans bit into the shells. The first known lower jaws came from a 1994 dig at Urumaco.

Then came the rodent. Phoberomys pattersoni, named after Brian Patterson, a palaeontologist who worked in the region in the 1970s, was a 700-kilogram relative of the guinea pig about the size of a buffalo, roughly three metres long and just over a metre tall, with incisors about 20 centimetres from root to tip. Its remains, found in 2000 and nearly complete, were described in Science in 2003. It probably lived like a capybara, in and out of the water, and it was far too big to hide in a burrow from predators such as lion-sized marsupial cats.

Since 2000 the town has had its own museum, the Museo Paleontológico de Urumaco, whose palaeontologist Rodolfo Sánchez worked on the turtle study, and there is an archaeology and palaeontology park at La Cruz de Taratara near Coro.