Fossil
From Memory Alpha, the free Star Trek reference
A fossil is the mineralized or otherwise preserved remains or traces of animals, plants, and other organisms. Paleontology and micropaleontology are academic disciplines which depend on the study of fossils.
Fossils of indigenous insects have been found on Mars. (TNG: "The Last Outpost", "Datalore")
Lt. Commander Data recorded significant fossil remains around the area of a predatory vine on the planet Surata IV in the year 2365. (TNG: "Shades of Gray")
In 2369, a microscopic cellular fossil, designated LB10445, was found in a cavern on Earth along with Data's severed head. (TNG: "Time's Arrow")
In 2373, Commander Chakotay stated that the USS Voyager's fossil records proved that the Voth civilization was from the planet Earth. (VOY: "Distant Origin")
In 2376, an away team on the Delta Flyer found fossilized metallic lifeforms in a rock inside a graviton ellipse. The rock was billions of years older than the Earth. (VOY: "One Small Step")
[edit] Derogatory usage
Someone can be called a "fossil" figuratively (often as an insult) if said person is extremely old or the views they hold are seen as archaic. Chief Miles O'Brien inferred that Doctor Julian Bashir considered him a "fossil" when he suggested that O'Brien prefered "Old Style" racquetball rules. (DS9: "Rivals")
