Distribution
The twist-necked turtle inhabits a large area throughout northern and central South America, from the southern Orinoco drainage in Venezuela to the Amazon basin in Brazil. However, Platemys platycephala, does not inhabit large rivers but instead prefers shallow creeks and forest floors.
Ernst (1983) surveyed the extensive geographical range of the twist-necked turtle and determined the presence of a dark subspecies in the western range of Platemys platycephala. The author uses the "Quaternary forest refuge theory" to explain the existence of this subspecies. The theory is based on significant climatic changes occurring in and around the equator during the Quaternary period. During these climatic changes of glaciation the northern rainforests of South America received less rainfall and deteriorated then subsequently expanded during interglaciation. This change caused allopatric speciation to occur among many species and gave rise to a new subspecies- Platemys platycephala melanonota.
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