LATE CAMBRIAN PHOSPHATOCOPIDS FROM SOUTHERN SWEDEN

The world famous upper Cambrian Alum Shales at Andrarum, Scania, southern Sweden, have been intensely investigated since the late 19th century. The succession consists of alum shale, limestone beds, and concretions (”stinkstones”), and is richly fossiliferous. Most geological studies in Andrarum have been focused on trilobites and the geochemistry of the strata. A largely neglected group of fossils is the phosphatocopids. Their world-wide distribution coupled with short ranging taxa suggests a great biostratigraphical potential and we have initiated a study on these bivalved arthropods from Andrarum. The bulk of the material was collected in the SE part of the ”Great Quarry” whereas the rest is from the NW part. The phosphatocopids occur almost exclusively in limestones and have been recovered from several stratigraphical levels in the lower part of the upper Cambrian. The collection includes nearly 140 well-preserved, complete valves (including external moulds) and more than 400 fragmentary specimens. Members of the genus Cyclotron (predominantly C. ventrocurvatum, C. lapworthi, and C. angelini) are most common, but one specimen of Veldotron bratteforsa and several specimens tentatively assigned to Vestrogothia steffenschneideri and Trapezilites minimus, have also been identified. Phosphatocopids are abundant at certain stratigraphical levels and, along with trilobites, dominate the late Cambrian fauna in the Andrarum successions. Phosphatocopids and trilobites rarely co-occur, and when they do one of these fossil groups is strongly subordinate. Obviously phosphatocopids differed from trilobites in their mode of life, feeding habits, and/or environmental preference. This makes phosphatocopids a potentially important biostratigraphical tool in strata lacking trilobites and may add to the knowledge of the depositional environment in which alum shales were formed.