An unusual Miocene gastropod

                               height 77 mm, width 38 mm

Pereiraea gervaisi (Vézian, 1856) is an ususal gastropod. I acquired this specimen as an gift, but it was unidentified. I had to do some research in order to identify it, but I was pleased to discover that it is a rare, shallow-marine stromboid gastropod from Western Europe.

Genus Pereiraea is classified as within the small family Thersiteidae, which has only a few confirmed genera. This genus ranges in age from middle to late Miocene, and this specimen is of middle Miocene age (about 13 to 14 million years old). This age corresponds to the Langhian (Badenian) Stage of Europe. Pereiraea is found in Spain, Portugal, Italy, Algeria, and Solvenia. The specimen is from Sant Pau d'Ordal, Province of Barcelona, Spain.

Specimens of this species commonly are missing their their outer lip margin, and the specimen shown above is no exception. Researchers have surmised that this kind of breakage on P. gervaisi is the result of of predatory crab activity.

Pereiraea gervaisi lived in a dynamic shallow-marine environment in what is now referred to as the Central Paratethys Sea, a large inland sea. The Black Sea and the Caspian Sea are the present-day remnants of the Central Paratethys. During the middle and late Miocene, the Central Paratethys was subject to major episodes of lowering sea level, most likely following glacial activities. The sea-level drops restricted the open-marine connection to the adjacent Mediterranean Sea, and, as a result thick salt deposits (evaporites) formed in some of the deep Paratethys basins. In sum, it was a hazardous time for a gastropod like Pereiraea, which did not tolerate restricted-marine waters, to survive.

If you want to see more (and some very visually stunning) pictures of P. gervaisi, go to <www.stromboidea.de> and type in the genus and species names.