Acknowledgements

Thanks go to the authors and librarians who responded to requests for reprints and information, especially Martin Pickford, Sorbonne Universités, who answered numerous queries. Tribute must also be paid to various indispensable online archives, particularly the Biodiversity Heritage Library (www.biodiversitylibrary.org) and Gallica (http://gallica.bnf.fr). The University of Edinburgh provided access to JSTOR through its Alumni Access Program. Richard G. Klein, Stanford University, kindly reviewed an early draft and drew my attention to several important references. Andries van Aarde, AOSIS, made excellent suggestions for improving the text. Open Access publication was made possible through grants from the University of the Witwatersrand Centre of Excellence for Palaeosciences and the Palaeontological Scientific Trust (PAST), both in Johannesburg.