Abstract: Fossil Lagerst¨atten are deposits containing abundant and/or exceptionally preserved fossils, often including soft-bodied tissue. Of these, Konservat-Lagerst¨atten are especially important because they provide not only a much more complete record of the diversity and paleoecology of ancient communities, but also more detailed information on the taxonomy and anatomy of the biota compared to the normal shelly fossil record. However, Konservat-Lagerst¨atten are rare because they require exceptional physical and chemical depositional conditions. Environmental conditions during the Cambrian may have been more favorable for the preservation of soft-bodied organisms than later in the Paleozoic, and such Lagerst¨atten provide evidence of biodiversity changes during the Cambrian explosion. Although the Ordovician Radiation or Great Ordovician Biodiversification Event (GOBE) has been well documented, this is based mainly on the shelly fossil record because soft-bodied organisms are poorly represented during the 45 million years of the Ordovician. Only three Lagerst¨atten, Beecher's Trilobite Bed in upper New York State, the Soom Shale in South Africa, and the recently recognized biota in Manitoba, Canada, approach the extent of soft-tissue preservation in Cambrian deposits. All the three Lagerst¨atten are of Late Ordovicianage. 　The Winneshiek fauna was discovered recently near Decorah, northeast Iowa, USA (Fig. 1). It is preserved in a new stratigraphic unit which consists of greenish-brown to dark-gray sandy laminated shale with abundant organic carbon and pyrite (Fig.2). The new fauna contains both invertebrate and vertebrate fossils; current recovery includes eurypterids and other chelicerates,phyllocarid crustaceans, ostracods, linguloid brachiopods, mollusks, isolated conodont elements and bedding plane assemblages,skeletal elements of jawless fish, various indeterminate fossil forms, and bromalites and other trace fossils (Fig. 3). Most of these fossils are extraordinarily preserved, some with soft tissues or body impressions, establishing the status of this deposit as a Konservat-Lagerst¨atte, the only significant example of Middle Ordovician (Whiterockian) age. .........