The ultrastructure of in situ araucarian pollen from the male cone Callialastrobus sousai, Lower Cretaceous of Catefica, Lusitanian Basin, western Portugal

Abstract

Pollen morphology and ultrastructure are described for fossil pollen of the Araucariacites and Callialasporites types extracted from a Callialastrobus sousai pollen cone previously reported from the Lower Cretaceous Almargem Formation near the village of Catefica, in the Estremadura region, western Portugal. Pollen grains were studied with transmitted light and scanning and transmission electron microscopy. The pollen grains are medium-sized, being smaller and with a thicker exine in the Callialasporites type. Both pollen types appear inaperturate, although both polar regions are represented by a thinner exine. The exine sculpture (granulate/microechinate) and ultrastructure (granular sexine and lamellate/homogeneous endexine) are generally the same in Araucariacites- and Callialasporites-type grains. Saccus-like structures in the Callialasporites-type pollen are formed by loosely arranged endexine lamellae, while Araucariacites-type pollen is asaccate. The exine structure of the Araucariacites- and Callialasporites-type grains also agrees well with that of known araucariaceous pollen.