Sporophytes and gametophytes of Polytrichaceae from the Campanian (late Cretaceous) of Georgia, USA

A new genus and species (Eopolytrichum antiquum) of the moss family Polytrichaceae are described for fossil sporophyte capsules and associated gametophytes from the early Campanian (Late Cretaceous) Buffalo Creek Member of the Gaillard Formation in central Georgia, U.S.A. The capsules show diagnostic features of the Polytrichaceae but differ from those of all extant genera. The capsules are terete in cross section, somewhat dorsiventrally flattened, and have a swollen, asymmetrical apophysis and mammillose exothecium. Stomatal complexes, each surrounded by a ring of subsidiary cells, are confined to the apophysis. The operculum is tall and dome shaped, but the calyptra and beak of the operculum are not preserved. The remains of a peristomial membrane are present around the rim of the capsule after the operculum has dehisced, but peristome teeth are absent, and the epiphragm is retained in the operculum. Spores are alete, spherical, and echinulate. Associated sterile and fertile gametophytes have leaves with adaxial, presumed photosynthetic, lamellae on the blade surface in addition to other anatomical structures comparable to extant Polytrichaceae. Inadequacies in the moss fossil record have led to contrasting interpretations as to the age of the origin of mosses and the extent of evolutionary change in the group since the Paleozoic. These fossils, which represent the first unequivocal polytrichaceous sporophytes known from the fossil record, along with other fossil mosses from this early Campanian locality, provide the first definitive evidence of modern families of mosses in the Cretaceous and demonstrate that mosses were already diverse by approximately 80 million years before present.