1. Instituto de Geociencias (CSIC-UCM); c/José Antonio Novais 2 28040 Madrid Spain
2. Department of Earth Sciences; University College London; Gower Street London WC1E 6BT UK
3. GeoBiosphere Science Centre; Department of Geology; Lund University; Sölvegatan 12 SE-223 62 Lund Sweden
4. Área de Paleontología; Facultad de Ciencias; Universidad de Extremadura; 06006 Badajoz Spain