A new species of South American side-necked turtle is described from the state of Piauí, Brazil. It is related to the Amazonian species of the genus Mesoclemmys s.l. (new acceptation) and is apparently a biogeographically relictual population of a species formerly living under a more humid climate in northeastern Brazil.
Chelonii; Chelidae; systematics; taxonomy; phylogeny; Mesoclemmys perplexa; new species; Piauí; Brazil
