The big-headed Pantanal swamp turtle, Acanthochelys macrocephala (Family Chelidae), is a medium-sized aquatic turtle (carapace length to 295 mm), endemic to the Pantanal and Chaco ecoregions of Brazil, Bolivia, and northern Paraguay. It has a limited distribution in the upper Río Paraguai drainage and is apparently restricted to the swampy lowlands of the Pantanal and the arid plains of the northern Chaco. The species inhabits marshes, wetland areas, shallow bays and brackish lagoons (salinas),

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... as well as opportunistically utilizing ephemeral waterbodies, including roadside drainage ditches and farm irrigation reservoirs and artificial ponds in pasturelands (tajamares). Population levels appear relatively robust at present and the species is not uncommon, but ongoing patterns of habitat loss in the Chaco, combined with climate change leading to increased aridity and threat to ephemeral water resources potentially threaten the species, and it is currently categorized as Near Threatened on the IUCN Red List. distribution. -Brazil, Bolivia, Paraguay. Distributed in the upper Río Paraguai drainage, in the Pantanal ecoregion encompassing parts of Mato Grosso and Mato Grosso do Sul in Brazil, eastern Bolivia, and northern Paraguay, and in the Chaco ecoregion of southern Bolivia and northern and central Paraguay. synonyMy. -Platemys macrocephala Rhodin, Mittermeier, and McMorris 1984, Acanthochelys macrocephala, Phrynops chacoensis Fritz and Pauler 1992, Acanthochelys chacoensis, Mesoclemmys chacoensis. subspecies. -None currently recognized. stAtus. -IUCN 2009 Red List: Near Threatened (LR/nt) (assessed 1996, needs updating); CITES: Not Listed. Taxonomy. -This species was described as Platemys macrocephala by Rhodin, Mittermeier, and McMorris (1984a) based on specimens from the Pantanal region of Brazil and Bolivia. The type locality is Caiçara, Rio Paraguai, Mato Grosso, Brazil (16˚03'S, 57˚43'W) and the holotype (Naturhistorisches Museum Wien 1293) was collected by Johann Natterer in 1826. The holotype was first identified as a Platemys radiolata by Siebenrock (1904), who cred-Figure 1. Acanthochelys macrocephala, adult female from nr. Filadelfia, Chaco, Paraguay. Photo by Thomas and Sabine Vinke.