The Pentamians were a sentient race native to the planet Pentam V. They only needed to eat and sleep one day out of four, and did not understand the human need for intermittent short breaks. (TOS short story: "Ambition")
By the late 24th century, the Pentamians had made contact with the Federation, and a Pentamian Starfleet admiral named Nyllis was commanding officer of Starbase 120. A group of them, along with members of other races, were trapped on Pacifica during the Borg Invasion of 2381, but were able to leave when the crisis was over. (TNG novel: Losing the Peace)
- While it is unclear what they physically look like, Nyllis was described as being short and compactly built.