Largest freshwater turtle ever

The largest freshwater chelonian ever was Stupendemys geographicus, a prehistoric species of freshwater side-necked turtle that lived approximately 13 million to 7 million years ago, during the Miocene period. It grew up to 4 metres (13 feet) long and weighed 1.25 tonnes (1.4 US tons). The only chelonian bigger than this species was the massive prehistoric marine turtle Archelon ischyros, which is estimated to have weighed more than 2.2 tonnes (2.4 US tons). S. geographicus inhabited lakes and rivers in what is today Colombia and Venezuela in northern South America.

Fossilized male specimens of S. geographicus can be readily distinguished from females by a pair of distinctive front-facing horns on both sides of their shell, very close to their neck. Scientists believe that these horns may have been used as weapons, like lances, for fighting other males over territory or mates, because deep scars have been detected in their fossils.

There was also a slightly smaller and more slender second species of Stupendemys, named S. souzai, which lived in what is today northern Brazil.