It is speculated that the new species formed 2.08 million years ago, when the Araguaia-Tocantins basin was cut off from the rest of the Amazon river system by huge rapids and waterfalls. It is possible that the shifting landscape isolated the dolphins from their fellows, because river dolphins are slow swimmers that rarely leap.
River dolphins are endangered and extremely rare, with three of the four known species listed by the IUCN’s as Vulnerable. Hrbek explains that the Araguaia river basin has been experiencing “significant anthropogenic pressure via agricultural and ranching activities, and the construction of hydroelectric dams” and that Inia araguaiaensis will most probably be classified as Vulnerable as well.
The discovery highlights the deficit in our knowledge of biodiversity and the potential impact of human actions on biodiversity.
Source: Hrbek T, da Silva VMF, Dutra N, Gravena W, Martin AR, et al. (2014) A New Species of River Dolphin from Brazil or: How Little Do We Know Our Biodiversity. PLoS ONE 9(1): e83623. doi:10.1371/journal.pone.0083623