The pyra­mid-shaped, wood­ed moun­tain of Monte San Gior­gio beside Lake Lugano is regard­ed as the best fos­sil record of marine life from the Tri­as­sic Peri­od (245–230 mil­lion years ago). The sequence records life in a trop­i­cal lagoon envi­ron­ment, shel­tered and par­tial­ly sep­a­rat­ed from the open sea by an off­shore reef. Diverse marine life flour­ished with­in this lagoon, includ­ing rep­tiles, fish, bivalves, ammonites, echin­o­derms and crus­taceans. Because the lagoon was near land, the remains also include land-based fos­sils of rep­tiles, insects and plants, result­ing in an extreme­ly rich source of fos­sils.