Carapace broad, flat, much wider posteriorly than anteriorly. Brown, olive, or black above. Head commonly with yellow, orange, or red markings. Plastron yellow, grey or brown. Large females have very wide and flattened shells, sometimes with a shallow groove along the midline, and usually extensive areas of black on the plastron.
Males are smaller than females.
Juveniles have a head with large, lemon-yellow spots and yellow spots encircling black dots on the dorsal. Head spots darken and disappear with age. Strong keel on carapace. Northern South America in jungle rivers and Orinoco and Amazon river drainages. Begin nesting 2 to 3 weeks after the onset of basking, often at night.