Baiji

The Baiji Dolphin [1] Also called the White Dolphin, was a mob that could have been added into the game, had the pandas not won the vote. It's confirmed that it's a Baiji Dolphin since the polls were exclusive to China. It’s also theorized that the Baiji Dolphin/White Dolphin would have the same abilities as the dolphin

The white dolphin is unlikely to be added, as sadly, the baiji dolphin has been listed as possibly extinct in real life[2], but some other river dolphins are possibilities.

Modded Version

Baiji do not spawn naturally. They can be revived if the player brushes up a baiji bone from suspicious sand. When the bone is found, it can be placed in a DNA extractor, which can form it's spawn egg. Bringing the Baiji back to life will give you the achievement "Welcome back, Baiji" a reference to how recently the animal went extinct.

A Baiji