What is "gracilidris"

Gracilidris is a genus of dolichoderine ants with nocturnal behaviour; thought to have gone extinct 15-20 million years ago, they have been found in Paraguay, Brazil, and Argentina and were described in 2006.

The single existing fossil in Dominican amber makes the genus a Lazarus taxon. The only known extant species, Gracilidris pombero, nests in small colonies in the soil. These ants have been described only very recently and little is known about them.