Lazarus taxon
In 1974 Batten pointed out that the Lower Triassic record lacked genera and species which had been present in the Permian, but which reappeared 20 million years later in the Middle Triassic. Jablonski later coined the term 'Lazarus taxon' for species and genera which disappear from the fossil record, only to reappear later when conditions return to normal.