The Selakar were a race of telepathic humanoids that lived half a million years prior to the 24th century. They had enslaved the Siri until their involvement in the Great Psionic War broke their thrall over them. The only survivors lived aboard the Axis Hub Station in the Axis of Time.
At least one of the individuals encountered by Starfleet and the Federation Department of Temporal Investigations in 2381 was just over two meters tall with large silvery blue eyes, a bald head, and chocolate-brown skin covered in diamond-shaped patches of forest green and gold. (DTI novel: Watching the Clock)