Palaeontologists in Argentina have found a tooth belonging to a titanosaur, a group of long-necked plant-eating dinosaurs which are thought to have grown up to 35 metres long and weighed 100 tonnes.
Titanosaur fossils are widespread, they have been discovered in Antarctica and a single tail bone was found in New Zealand by famous fossil hunter Joan Wiffen.
The tooth the scientists have now found is 32% bigger than any discovered before.
They say this either means titanosaurs grew even bigger than previously thought, or they have found the remains of a new type of titanosaur with very large teeth compared to its body size.
The findings have been published in the journal Cretaceous Research.
