C.A. Repenning, whom we honor in this volume, was in the beginning stages of his study of fossil fragments from Units G and I at Hueyatlaco (unifacial tools) at the time of his death, and was excited about what he was finding. We would like to think he would be pleased with this summary and the stratigraphic evidence presented here, and with his part in the work. "Rep" shared much of his knowledge with us, encouraged us, and gave us friendly advice. He is fondly remembered.
The authors would especially like to thank M. Payn for his support of field work at Hueyatlaco from 1997 to the present and for financial support of several new dating attempts, and for sharing the results with us. His 2006 award-winning documentary video, Valsequillo, an Archaeological Enigma resulted from his insistence that any new work at the Hueyatlaco site and in the laboratory be recorded on film.
The authors wish to acknowledge editors L.H.Taylor, C.J. Bell, and L.L. Jacobs for kindly allowing us to submit our manuscript and for their patience. Also, our deepest thanks to C. Malde, HEM's widow, who supplied much-needed critical information.