Fossil
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. A form of fossilization was petrification.

Fossils of indigenous insects have been found on Mars. ()

Lieutenant Commander Data recorded significant fossil remains around the area of a predatory vine on the planet Surata IV in the year 2365. According to Data, true fossilization required several millennia. ()

In 2369, a microscopic cellular fossil, designated LB10445, was found in a cavern on Earth along with Data's severed head. ()

In 2371, what appeared to be a fossil of an ammonite-like creature was displayed in Ishka's home on Ferenginar. ()

In 2373, the  featured a fossilized ammonite. ()

That same year, Commander Chakotay stated that the 's fossil records proved that the Voth civilization was from the planet Earth. ()

In 2376, an away team on the  found fossilized metallic lifeforms in a rock inside a graviton ellipse. The rock was billions of years older than the Earth. ()

By 2380, Captain Carol Freeman had an ammonite fossil among the items in her ready room on the . ()

Derogatory usage 
Someone could be called a "fossil" figuratively (often as an insult) if said person was extremely old or the views they held were seen as archaic. Chief Miles O'Brien inferred that Doctor Julian Bashir considered him a "fossil" when he suggested that O'Brien preferred "old style" racquetball rules. ()  

In approximately 3074, The Doctor's backup copy, the EMH backup module, referred to himself as "some sort of fossil" when he learned that roughly 700 years had passed and he didn't know what happened to Voyager or its crew.  assured him that he wasn't a fossil but rather a living witness to history. ()

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de:Fossil
Geology
Insults