Wessex Formation

The Wessex Formation is an English fossil site and geological formation that dates back to the Barremian stage of the Early Cretaceous. It is part of the Wealden Group and underlies the younger Vectis Formation.

Invertebrates
Invertebrates are commonly preserved in the Wessex Formation. Freshwater bivalves can be found including unionoids such as Margaritifera, Nippononaia, and Unio. These bivalves are helpful in reconstructing what the freshwater paleoenvironment may have been like during the formation's deposition. Specimens of Viviparus, a genus of freshwater snail, have also been found. Cretamygale chasei, a species of  Mygalomorph spider, has been described from a specimen found in amber. It is believed to be the oldest known Nemesiid and the second oldest Mygalomorph.