Exceptional carbonate deposits of the Dalby Limestone developed during the Upper Ordovician (KukruseStage to Idavare substage) in the area of Tvären and Lockne (Sweden) as a result of two nearly coeval bolide impacts into the marine environment. The deposits are characterized by thicknesses numerous times greater
than common for the unit and with a wider range of facies. The type area for the Dalby Limestone in the Siljan District, Dalarna, (Sweden) is used together with the Kårgärde section in Siljan for comparison of gastropod diversity and distribution together with the Lockne and Tvären successions. A fauna of 12 species, comprising about 200 specimens, of paragastropods, tergomyans and gastropods is described presenting a higher diversity than previously documented from the limestone. Species recognized from Tvären include Bucania erratica Frisk & Ebbestad, 2007, Holopea? sp., Eotomaria cf. E. notabilis (Eichwald, 1840), Lophospira cf. L. subulata (Koken in Koken & Perner 1925), and Pleurorima? sp. These have been found in erratics originated from the shallower rim facies in the Tvären crater. The fauna from Lockne includes Sinuites cf. S. corpulentus Koken in Koken & Perner, 1925, Deaechospira cf. D. elliptica (Hisinger, 1831), and Ectomaria sp. In Dalarna (Fjäcka and Kårgärde) Mimospira tenuistriata Wängberg-Eriksson, 1979 has previously been recorded (Wängberg-Eriksson, 1979). Besides this species, an in situ specimen of Eccyliopterus regularis Remelé, 1888 and museum
collections of Laeogyra reinwaldti (Öpik, 1930), Sarkanella epelys Frisk & Ebbestad, 2007 and Deaechospira elliptica (Hisinger, 1831) are recognised from the type locality, Kårgärde, and Furudal. Significant biostratigraphical and biogeographical results from this study are 1) the presence of Mimospira, Laeogyra, Sarkanella epelys indicates a strong faunal connection with Bohemia, Czech Republic. 2) Sarkanella is reported from outside Bohemia for the first time. 3) Bucania erratica n. sp. represents one of the earliest records of the genus in Baltoscandia. A single case of shell repair from failed predation is recorded in this species. 4) Synonyms for Eccyliopterus princeps Remelé and E. regularis Remelé are proposed. 5) The significance of Laeogyra, Eccyliopterus, and Deaechospira for regional correlation within the Upper Ordovician of Baltoscandia is confirmed.
2007. 89- p.