On calcareous microfossils from the Campanian-Maastrichtian boundary stratotype at Tercis (southwestern France); gilianelles, a new group of problematica.

Enigmatic calcareous microfossils are present in the stratotype section at Tercis, Landes, France (Campanian-Maastrichtian boundary). Thirty to thirty-five forms have been pictured and 1 to 100 specimens have been picked for each of them. The single-chambered tests show a small aperture. They present an axial symmetry, which is altered when radial equatorial expansions are added to the 75 to 200 p,m-large bodies of discoidal, spheroidal, cupuliform, conical or barrel-like shapes. These peculiar characters are those of the gilianelles, a group of uncertain status created here. In addition to their palaeontological interest, these microfossils display a short time distribution and might have a stratigraphical interest. Gilianella stellata n. gn. n. sp. is described as a type form and illustrated.