A Relict

1. (formal) Something that, or someone who, survives or remains or is left over after the loss of others; a relic.

• (archaic) The surviving member of a married couple after one or the other has died; a widow or widower.
• (biology, ecology) A species, organism, or ecosystem which has survived from a previous age: one which was once widespread but which is now found only in a few areas.
• (geology) A structure or other feature which has survived from a previous age.
• (linguistics) A survival of an archaic word, language or other form.