Definitions of, evolutionary trends within, and classification of early brevaxonate pollen

摘要: Abstract The vast majority of brevaxonate pollen morphotypes were produced by plants which have long been extinct. As a result, satisfactory answers to number questions pertaining their evolution, morphology, and classification yet be proposed. Among the more vexing problems associated with Brevaxones, are considered in this article, are: (1) time first appearance; (2) clear concise definition early (i.e., middle Late Cretaceous) Brevaxones groups; (3) evolutionary trends within as revealed TEM SEM studies. In addition, new is proposed for Normapolles group respect Postnormapolles, three-fold morphologic subdivision presented.