Researchers from the Federal University of Amazonas in Manaus, Brazil have announced the discovery of a new species of Amazon river dolphin, which themselves are already rare as it is. The discovery, the first of its kind in nearly 100 years, suggests the dolphins are so rare that researchers have asked that they immediately be given endangered species protection. The name currently on the table for the new river dolphin species is Araguaian boto.

The new river dolphin species makes it just the fifth of its kind. Four of the five, including this new species of river dolphin, live in freshwater rivers, while the La Plata Dolphin survives in saltwater estuaries. All five species inhabit areas of either Asia or South America. According to the researchers, true river dolphins are among the rarest and most endangered vertebrates on Earth.

When the team first observed Araguaian boto, they didn’t realize they’d happened upon a new species of river dolphin until closer examination. They then realized that these botos were both genetically and morphologically different from other known river dolphin species.

“We looked at the mitochondrial DNA which is essentially looking at the lineages, and there is no sharing of lineages,” the study’s lead author Tomas Hrbek said, according to the BBC.

Most river dolphins grow to an average size of around eight feet long, and come in several colors including white, yellow and even pink. This new species of river dolphin is a little smaller than most and sports a different number of teeth, but otherwise their differences are mostly genetic.

“The groups that we see, the haplotypes, are much more closely related to each other than they are to groups elsewhere. For this to happen, the groups must have been isolated from each other for a long time,” Hrbek said.

The International Union for the Conservation of Nature (IUCN) Red List classifies three of the four previously known river dolphin species as “near threatened.” Due to the low genetic diversity among the specimen samples and a relatively low population, coupled with human activity in their natural environment, the researchers urge the IUCN to grant the new species of river dolphin “vulnerable” status, at a minimum.

Baiji, a former species of river dolphin, was declared “functionally extinct” on December 13, 2006. It was the first record of an aquatic mammalian extinction in 50 years.