Middle Triassic Nautilida from the Besano Formation of Monte San Giorgio, Switzerland

Abstract

Abstract For the first time, nautilids from the Besano Formation (Anisian/Ladinian boundary) are documented. The extremely rare material was collected from two different outcrops at Monte San Giorgio (Southern Alps, Ticino, Switzerland). This material is represented by only five specimens described here. The three best specimens belong to the taxa Enoploceras rieberi sp. nov., Germanonautilus aff. ellipticus and Syringonautilus sp. indet., documenting the presence of the families Tainoceratidae and Syringonautilidae in the middle Besano Formation. Another nautilid specimen is described in open nomenclature, representing an additional taxon. The new species Enoploceras rieberi n. sp. is currently the only occurrence of the genus Enoploceras in the Middle Triassic. Nautilida are poorly known from the Middle Triassic Tethyan region, mostly from sediments deposited in pelagic environments. This is the first record of these nautilids from an usually anoxic depositional paleoenvironment of an intra-platform basin, where the sediments of the Besano Formation were laid down.

Keywords

• Nautilida
• Middle Triassic
• Besano Formation
• Southern Alps
• Switzerland