the position of the modern mountain would have been an island or shallow environment during the Jurassic. Its Jurassic sediments are now eroded away to reveal older Triassic and Permian rocks. Conversely, Monte Generoso, immediately to the east of Monte San Giorgio, is composed mostly of Jurassic basinal sediments. Outcrops of Jurassic sediments are also seen close to the Po Plain, at the south edge of Monte San Giorgio (in a broad sense). The productive "marble" quarries found south of Monte San Giorgio actually mined non-metamorphosed limestone, rather than true marble. These limestone units were formed at the same general time as the Moltrasio Limestone. Ecological heritage The fauna and flora of Monte San Giorgio are diverse, with some species found nowhere else in Switzerland. The prevailing ecosystems are mixed broadleaf forests and meadows influenced by the mountain's sub-Mediterranean climate. Monte San Giorgio is one of the southernmost areas of Switzerland, with mild winters, high humidity, and many hours of sunshine. Due to the variation in underlying geology, both acidic and alkaline soils are developed, supporting different vegetation communities. The rhyolite-based northern slope is mostly covered by Castanea sativa (sweet chestnut), Quercus petraea (sessile oak), and Fraxinus excelsior (European ash). The dolomite-based southern slope is more diverse in its plant life and soil quality, with common plants including Carpinus betulus (common hornbeam), Ostrya carpinifolia (European hop-hornbeam), Tilia (linden), Asperula taurina, Quercus pubescens (pubescent oak), and Fraxinus ornus (manna ash). The driest and most alkaline soils of Monte San Giorgio are home to the Ticino dry meadows, a unique biome with over 100 plant and species, 38 of which are rare or endangered within Switzerland. Carex humilis (dwarf sedge) and Molinia caerulea arundinacea (tall moor grass) are the most common grasses, while Monte San Giorgio supports the few Swiss populations of wildflowers such as Adenophora liliifolia, Gladiolus imbricatus, Iris graminea, Lotus herbaceus, and Danthonia alpina. 102 species of vertebrates are found on Monte San Giorgio, 37 of which are endangered in Switzerland. The mountain is the only Swiss stronghold for Microtus savii (Savi's pine vole), and hosts breeding sites for amphibians such as Bufo bufo (common toad), Rana temporaria (common frog), Rana dalmatina (agile frog), Hyla intermedia (Italian tree frog), and other species. Invertebrates are even more diverse, including some species which are very rare in Switzerland, such as Pyrgus armoricanus (Oberthur's grizzled skipper), Euchorthippus declivus (Jersey grasshopper), and Pholidoptera littoralis