The fine structure and morphology of Cyclusphaera pollen collected from the early Cretaceous of Argentina is described. The diporate grains possess an exine structure that combines features of both angiosperms and gymnosperms, and raises questions as to the validity of using certain pollen characters in the identification of major taxonomic groups through time.
Bibliographical noteFunding Information:
ACKNOWLEDGEMENTS A portion of this study wz1s completed while Archan- gelsky sewed as a Distinguished Visiting University Pro- fessor at The Ohio State University. This study bras sup- ported in part by funds from the National Science Foun- dation (BSR-8313786; BSR-8402813) and CONICET of Argentina.