Polysternon

Polysternon is a genus of turtles in the extinct family Bothremydidae. It was described by Portis in 1882, and contains the species "P. provinciale" (originally placed in the genus "Pleurosternon"), which existed during the Cretaceous of what is now France; "P. atlanticum", which existed during the Cretaceous at Laño in what is now Spain, and a new species, "P. isonae", from the Late Maastrichtian of Spain.
The species epithet of "P. isonae" refers to the municipality Isona i Conca Dellà in Catalonia, where the type specimen was discovered in the Tremp Formation.
Distribution.
Fossils of "Polysternon" have been found in: