Matamata: Chelus fimbriatus, by William H. Espenshade III, an article about these turtles. They occur in northern South America, including both the Orinoco River and Amazon River basins.
Matamata Turtles: Chelus fimbriatus biology and captive requirements, by David T. Kirkpatrick.
Scientific Expeditions to Patagonia Organized by University of Connecticut: Groundbreaking ecological research at Torres del Paine National Park, Magallanes, Chile. Details about past and future expeditions.