ACKNOWLEDGEMENTS

We deeply thank A.M. Rocha Torrallardona and M.P. Melgarejo Damián for their technical support. Mr. G. Alvarez Reyes prepared some of the specimens illustrated here. A. Altamira prepared the photographic material. G. Carbot Chanona, A.S. Nuñez Vera, and D. Vázquez Bautista collaborated on the field work. For the loan of the IHNFG and FCMP 00/497 specimens we thank M.A. Coutiño José (IHNFG) and P. García Barrera ( FCMP 00/497). E.D.O. was supported by FOMIX (fondos mixtos CONACyT-Gobierno del Estado de Chiapas, project CHIS-2005-C03-020) and IHNE (project "prospección de localidades fosilíferas y Rescate del patrimonio paleontológico de Chiapas"). J.A.O was supported by the Programa de Apoyo a Proyectos de Investigación e Innovación Tecnológica, UNAM (Project IN225008). A.B.P. thanks Programa de Mejoramiento al Profesorado (PROMEP/103.5/08/802).