A new araucarian pollen cone with in situ Cyclusphaera Elsik from the Aptian of Patagonia, Argentina.

Abstract: A new araucarian pollen cone Alkastrobus peltatus gen. et sp. nov. is described from the Anfiteatro de Ticó Formation (Baqueró Group) of Aptian age in Santa Cruz province, Argentina. The pollen cones are mostly compressions and their microsporangia contain the well-known Cyclusphaera Elsik pollen. The morphology, anatomy and ultrastructure of the pollen cones along with the pollen grains were examined under light, scanning and transmission electron microscopy. An affinity with the Araucariaceae is established on the basis of microsporophyll anatomy and morphology, and comparison of Cyclusphaera with other araucarian pollen grains. In Patagonia during the Cretaceous Period, plants producing Araucariacites, Balmeiopsis and Cyclusphaera pollen lived together. All three types of pollen are found inside microsporangia. Araucariacites, the only type that has survived to the present day, is found in the extant genera Araucaria and Agathis. The new genus confirms the broad diversity that Araucariaceae attained during the Early Cretaceous within western Gondwana. [Copyright &y& Elsevier]