e/First appearance datum

Information
has gloss	eng: First appearance datum is a term used by geologists and paleontologists to designate the first (oldest) appearance of a species in the geologic record. In other words, FADs represent the geologically oldest fossil of a particular species that has yet been discovered.
lexicalization	eng: First appearance datum
instance of	(noun) the earth science that studies fossil organisms and related remains paleontology, fossilology, palaeontology