The conifer Araucaria bladenensis and associated large pollen and ovulate cones from the Upper Cretaceous Ingersoll shale (Eutaw Formation) of Alabama

Abstract

Araucarian conifer remains from the Upper Cretaceous Ingersoll shale Konservat-Lagerstätte (Eutaw Formation) of Alabama include shoots of Araucaria bladenensis, an associated pollen cone, an ovulate cone, and an isolated bract-scale complex that were probably produced by the same plant species. Well-articulated A. bladenensis specimens with preserved cuticles reaffirm the original generic determination and show similarity to branches of the extant species A. bidwillii. The large pollen cone is remarkable as the earliest example comparable in size and pollen sac number to those of the largest extant Araucaria species. The co-occurrence of this cone with Upatoia barnardii in the Eutaw Formation also demonstrates that typical, small araucarian fossil pollen cones coexisted during the Late Cretaceous with modern appearing, large-coned species. The intact ovulate cone is large and ovoid but poorly preserved. An associated bract-scale complex displays lateral wings and a ligule. Comparisons with other fossil and extant araucarian conifers indicate affinity with section Bunya, making this the first North American record of the section. These fossils reaffirm that araucarian conifers were a significant component of the southeastern US Cretaceous flora, and provide a temporal and biogeographic context for the currently unexplained transition from small to large pollen cones in the family.