Friday, January 24, 2014

[Cetology • 2014] Inia araguaiaensis | Araguaian Boto or Araguaian River Dolphin | Boto-do-Araguaia • A New Species of River Dolphin from the Araguaia-Tocantins basin of Brazil or: How Little Do We Know Our Biodiversity

Araguaian Boto | Boto-do-Araguaia
Inia araguaiaensis Hrbek, Farias, Dutra & da Silva 2014

True river dolphins are some of the rarest and most endangered of all vertebrates. They comprise relict evolutionary lineages of high taxonomic distinctness and conservation value, but are afforded little protection. We report the discovery of a new species of a river dolphin from the Araguaia River basin of Brazil, the first such discovery in nearly 100 years. The species is diagnosable by a series of molecular and morphological characters and diverged from its Amazonian sister taxon 2.08 million years ago. The estimated time of divergence corresponds to the separation of the Araguaia-Tocantins basin from the Amazon basin. This discovery highlights the immensity of the deficit in our knowledge of Neotropical biodiversity, as well as vulnerability of biodiversity to anthropogenic actions in an increasingly threatened landscape. We anticipate that this study will provide an impetus for the taxonomic and conservation reanalysis of other taxa shared between the Araguaia and Amazon aquatic ecosystems, as well as stimulate historical biogeographical analyses of the two basins.

Cranium (a) and mandible (b) of the holotype of Inia araguaiaensis, a South American river dolphin species described in 2014. A 10 cm ruler is shown.
                        doi: 10.1371/journal.pone.0083623.g001


Cetacea Brisson, 1762.
Odontoceti Flower, 1867.
Iniidae Gray, 1846.
Inia d’Orbigny, 1834.

Inia araguaiaensis sp. nov.
Hrbek, Farias, Dutra & da Silva 2014

Etymology: The specific name refers to the geographic area where the new species is currently known to occur.

Suggested common name: We propose the common names “Boto-do-Araguaia” and “Araguaian boto” for this species. Boto is the common regional and international name of species of Inia, and Araguaia refers to the geographic distribution of this species.

Figure 1. Distribution map of all known species and subspecies of Inia.
show more Black outline denotes the limit of the Amazon basin. Question marks denote uncertainty as to which species occurs in the Tocantins River downstream of the Tucuruí dam which potentially delimits the distributions of I. geoffrensis and I. araguaiaensis sp. nov. Bars on the Madeira River represent a series of rapids that delimit the distribution of I. geoffrensis and I. boliviensis. The single bar on the northern limit of the Amazon basin represents the Casiquiare canal which connects the Amazon and Orinoco basins, and is thought to delimit the I. g. humboldtiana subspecies from I. g. geoffrensis.

Inia araguaiaensis - Rio Araguaia
by Cristiane Moraes

“Boto-do-Araguaia” and “Araguaian Boto” 
photo: Nicole Dutra /

Hrbek, Tomas; Da Silva, Vera Maria Ferreira; Dutra, Nicole; Gravena, Waleska; Martin, Anthony R.; Farias, Izeni Pires. 2014. A New Species of River Dolphin from Brazil or: How Little Do We Know Our Biodiversity. In Turvey, Samuel T. PLoS ONE 9: e83623.