Diversity, palaeoecology and systematics of a marine fossil assemblage from the Late Triassic Cassian Formation at Settsass Scharte, N Italy

摘要: A marine fossil assemblage from the Late Triassic (Early Carnian) Cassian Formation is reported. It was retrieved by bulk sampling, including wet sieving and quantitative picking, surface collection. The collection consists of c. 460 specimens (foraminiferans not included) representing 54 species. In terms abundance species richness, it strongly dominated molluscs, especially gastropods. 97 % individuals are molluscs. most abundant gastropods Goniospira armata, Schartia carinata Helenostylina convexa, followed scaphopod Plagioglypta undulata bivalve Palaeonucula strigilata. Disarticulated echinoderm ossicles (mostly echinoids, crinoids, few holothurians) comprise almost all rest assemblage. studied shows moderate diversity, similar to those previously reported assemblages or associations basinal settings. However, differs considerably in taxonomic composition described Formation. small a result their primary these ancient living communities sampling method (sieving at 0.5 mm), because previous were obtained performing collections, which easily overlooked. fauna interpreted as an autochthonous soft bottom that lived low epifaunal shallow infaunal habitats. Detritivory, deposit feeding microcarnivory represent main types. Most fully motile but slow, either (scaphopods, nuculids, gastropod Domerionina) (most other gastropods, echinoids). present underlines pronounced heterogeneity biota. grade lithification diagenetic alteration facilitates investigation This minimizes possible preservation biases, so reflects alpha diversity this community unusually high degree. following taxa new: convexa n. sp., gen. Schartiinae subfam.; Cassianastraea Bandel non Volz replaced with Bandelastraea nom. nov.