Seldarria

Seldarria is a black dragon located near the volcano's peak in The Charred Vale, Stonetalon Mountains. She is currently being protected by circling Black Drakes. Like Onyxia, she is a brood mother bearing many young Black Dragon Whelps. A part of her children has been transformed in hound food by Houndmaster Jonathan and a number of her eggs has been destroyed.

Speculation
Given that Obsidia was said to be one of the last breeding black dragons, it is likely that Seldarria has been killed, or that she is one of the other remaining, or simply that the Red dragonflight doesn't know of her. As there is no quest to kill her, it is unknown what her status is after the annihilation of the black dragons.