The giant South American turtle is the largest river turtle in South America. It has a broad, domed and streamlined carapace for active swimming in moderate river currents. The colour may be influenced by the algae that is attached to it, but is usually olive green to brown in colour.
It nests during the low water season, laying from 75 to 125 leathery eggs per clutch. This species is mainly herbivorous, feeding on aquatic vegetation and plant matter that falls into the water. However, it is also known to be somewhat opportunistic, feeding on small, slow-moving prey and carrion.
Mutual cleaning behaviour between individuals of this species has been observed. One turtle will position itself at right angles to a second turtle and use its jaws to pull algae from its shell. The turtles will then switch position.