subfossil
Geological term for remains that are not fully fossilized, often from the late Quaternary.
この半化石は約1万年前のものだ。
This subfossil is about 10,000 years old.
Compound of 半 (half) and 化石 (fossil), literally 'half-fossil'. The exact historical derivation is uncertain, but the term is a modern scientific coinage.