A long-lived humanoid species, outwardly identical to humans, whose members have quietly lived among people on Earth for thousands of years.
The Lanthanites are a humanoid species who look human but live for many thousands of years. Members of the species have lived on Earth through much of recorded history, blending in with the human population and keeping their true nature to themselves, which makes them living witnesses to centuries of events.
The best known Lanthanite is Pelia, who joins the crew of the USS Enterprise as chief engineer in the second season of Strange New Worlds. Pelia is cheerfully eccentric and a keen collector of antiques, many of which she acquired at the time they were new. She is a veteran Starfleet engineer who had taught at Starfleet Academy before joining the ship, and her long life gives her a perspective on Earth history that her younger shipmates find by turns useful, amusing and unsettling.
Pelia's presence turned the Lanthanites into an established part of the franchise. Writers use the species for humour, letting a single character casually recall distant eras, and for stories that look at human history from the outside through the eyes of someone who lived it.