This research is derived,in part,from the doctoral dissertation of the first author at the University of Maroua,Cameroon.The authors gratefully acknowledge the financial support provided by the Agence Universitaire de la Francophonie(AUF)through a scholarship grant.We extend our sincere appreciation to Florence Savignac for her invaluable assistance during laboratory analyses conducted at the ISTeP laboratory of Sorbonne Université,Paris,and to Martin Pickford,MNHN of Museum d'Histoire Naturelle de Paris,for improving the English.Authors gratefully acknowl-edge the editor-in-chef Dr.Zengqian Hou and anonymous reviewers for their suggestions,which have greatly improved the manuscript quality. （AUF）