1. CNRS, Univ. Lille, UMR 8198 - Evo-Eco-Paleo, F-59000 Lille, France
2. Department of Geology, Ghent University, Campus Sterre, Krijgslaan 281-S8, B-9000 Ghent, Belgium
3. British Geological Survey, Keyworth, Nottingham NG12 5GG, UK
4. Van Mildert College and Institute of Advanced Study, Durham University, Cosin's Hall, Durham DH1 3RL, UK