The best-known valid species of Tanystropheus is T. longobardicus, which comes from the Besano Formation (also known as the Grenzbitumenzone), an Anisian-Ladinian formation exposed at Monte San Giorgio on the Italy-Switzerland border. The first T. longobardicus specimens were described in 1930s, and Monte San Giorgio continues to produce new specimens up to the present day. In 2005, Dr. Silvio Renesto described a T. longobardicus specimen from Switzerland which preserved the impressions of skin and other soft tissue. Five new specimens of T. longobardicus were described by Stefania Nosotti in 2007, allowing for a more comprehensive view of the anatomy of the species.