The Besano Formation is a geological formation in the southern Alps of northwestern Italy and southern Switzerland. This formation, a thin but fossiliferous succession of dolomite and black shale, is famous for its preservation of Middle Triassic (Anisian–Ladinian) marine life including fish and aquatic reptiles. It is exposed on Monte San Giorgio and is among the formations responsible for the area being designated as a UNESCO World Heritage Site. In Switzerland, it is also known as the Grenzbitumenzone. The Anisian-Ladinian boundary lies in the upper part of the Besano Formation.
Image: Tanystropheus NT small
Image: Besanosaurus DB15
Image: Cymbospondylus buchseri skeleton 01
Image: Cyamodus hildegardis
In the geologic timescale, the Anisian is the lower stage or earliest age of the Middle Triassic series or epoch and lasted from 247.2 million years ago until 242 million years ago. The Anisian Age succeeds the Olenekian Age and precedes the Ladinian Age.
The Muschelkalk in Europe is mainly Anisian aged