Living fossil

The coelacanth and the dawn redwood are living fossils.

Source: wiktionary

[I]n fresh water we find some of the most anomalous forms now known in the world, as the Ornithorhynchus and Lepidosiren, which, like fossils, connect to a certain extent orders now widely separated in the natural scale. These anomalous forms may almost be called living fossils; they have endured to the present day, from having inhabited a confined area, and from having thus been exposed to less severe competition.

Source: wiktionary

The Gingko, whose single existing species was aptly termed a living fossil by [Charles] Darwin and which survived to modern times only in eastern Asia and is now a prized ornamental tree in all temperate countries, has an ancestral history that goes back to remote geologic time.

Source: wiktionary

It features in textbooks as well, a prime example of a "living fossil", a reminder of past glories now hanging on in a last-ditch action against final extinction. But is nautilus really an anachronism?

Source: wiktionary