Araguaian river dolphin

Skull and lower jaw of the holotype. Length of the ruler 10 cm.

Inia araguaiaensis is occurring in the northeastern Brazil Flussdelfinart, which was described as new in January 2014. It is the first river dolphin newly described since 1918, the year of description of between 2004 and 2006 probably extinct Chinese river dolphin ( Lipotes vexillifer ). The previously known distribution area of Inia araguaiaensis includes the upper and middle Rio Araguaia and some coming from the Brazilian state of Goiás tributaries. Perhaps the species occurs also in the Rio Tocantins and possibly in the entire catchment area of Rio Araguaia and Tocantins above the Tucuruí reservoir.

Features

Compared with its nearest relative, the Amazon river dolphin ( Inia geoffrensis ) and Inia boliviensis, Inia araguaiaensis has a wider skull (measured at the parietal bone ), a wider upper jaw and lower teeth per jaw half ( 24-28, 25-29 geoffrensis at I and 31-35 in I. boliviensis ). The front 19 to 21 pairs of teeth in both jaws are tapered, the rear 6-8 ( molars ) have a pointed apex that extends from the crown to the lip side, and an indentation on the tongue side.

System

Inia araguaiaensis is the sister species of the Amazon river dolphin ( Inia geoffrensis ) and has been separated from during the Gelasian about 2 million years ago when the current area of Rio Araguaia and Tocantins was cut from the Amazon basin. The sister group of the clade from Inia araguaiaensis and Inia Inia boliviensis is geoffrensis. I. boliviensis was isolated prior to about 2.9 million years ago by the Teotonio rapids in the upper Rio Madeira region.