New genus of fossil Fagaceae from the Santonian (Late Cretaceous) of central Georgia, U.S.A.

A new genus and species (Antiquacupula sulcata) is established for fossil staminate flowers, bisexual flowers, fruits, and cupules from the late Santonian (Late Cretaceous) Buffalo Creek Member of the Gaillard Formation in central Georgia, U.S.A. Together with Protofagacea, recently described from the same locality, these remains constitute the earliest fossil evidence of the Fagaceae sensu lato. Staminate flowers of the new genus are pedicellate, with six free tepals in two cycles of three, 12 free stamens, and a vestigial gynoecium with three styles. Bisexual flowers are epigynous and actinomorphic, with six free tepals in two whorls, 12 free stamens, and a syncarpous gynoecium with three styles. The ovary is trilocular, with two anatropous, apically pendulous ovules per locule. The styles are partially connate below, with trichomes around and between the style bases. Fruits are triangular in cross section, with nearly equal sides, and contain a single seed. Cupules comprising multiple series of bracts contain at least six fruits. The staminate and bisexual flowers both have slender, thin-walled nectary lobes between the filament bases and distinctive, multicellular glandular structures on the surface of the gynoecium. Pollen grains found in the anthers and on the surface of the flowers and fruits are small and tricolporate, with a finely perforate tectum. Comparison of these fossils to extant and fossil taxa clearly indicates a relationship to extant Fagaceae sensu lato, based on the presence of the cupule and flower and fruit morphology. The discovery of Antiquacupula, in addition to Protofagacea, indicates an early divergence of at least two lineages within the Fagaceae, both with cupules, by the Santonian. In addition, Antiquacupula shares several characters with extant rosids and hamamelids and may be a key taxon for clarifying the relationships among these groups as well as within the Fagaceae.