1. Department of Earth Sciences; University of Oxford; Oxford OX1 3AN UK
2. School of Geography, Earth and Environmental Sciences; University of Birmingham; Edgbaston Birmingham B15 2TT UK
3. Department of Earth Sciences; Natural History Museum; London SW7 5DB UK
4. Department of Vertebrate Zoology; National Museum of Natural History; Washington DC 20560 USA
5. Department of Ecology and Evolutionary Biology; Yale University; New Haven CT 06520 USA