Gracilidris is a genus of dolichoderine

Dolichoderinae

Dolichoderinae is a subfamily of ants, which includes species such as the Argentine ant , the erratic ant, the odorous house ant, and the cone ant. This subfamily is distinguished by having a single petiole and a slit-like orifice, rather than the round acidopore encircled by hairs that typifies...

 ants with nocturnal behaviour; thought to have gone extinct 15-20 million years ago, they have been found in Paraguay

Paraguay

Paraguay , officially the Republic of Paraguay , is a landlocked country in South America. It is bordered by Argentina to the south and southwest, Brazil to the east and northeast, and Bolivia to the northwest. Paraguay lies on both banks of the Paraguay River, which runs through the center of the...

, Brazil

Brazil

Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...

, and Argentina

Argentina

Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...

 and were described in 2006.
The single existing fossil in Dominican amber makes the genus a Lazarus taxon

Lazarus taxon

In paleontology, a Lazarus taxon is a taxon that disappears from one or more periods of the fossil record, only to appear again later. The term refers to the account in the Gospel of John, in which Jesus raised Lazarus from the dead...

.
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.