1. Palaeoecosystems Group; Department of Earth Sciences; Durham University; Durham DH1 3LE UK
2. Biodiversity Institute & Department of Ecology and Evolutionary Biology; University of Kansas; Lawrence KS 66045 USA
3. Department of Palaeobiology; Swedish Museum of Natural History; PO Box 50007 SE-104 05 Stockholm Sweden
4. Department of Earth Sciences; Palaeobiology; Uppsala University; Villavägen 16 SE - 752 36 Uppsala Sweden