1. Department of Palaeobiology; Swedish Museum of Natural History; Box 50007 SE-104 05 Stockholm Sweden
2. Oak Spring Garden Foundation; 1176 Loughborough Lane Upperville VA 20184 USA
3. School of Forestry and Environmental Studies; Yale University; New Haven CT 06511 USA
4. Department of Geoscience; University of Aarhus; Høegh-Guldbergs Gade 2 DK-8000 Aarhus C Denmark