Sporophytes and gametophytes of Dicranaceae from the Santonian (Late Cretaceous) of Georgia, USA.

A new species (Campylopodium allonense) of the moss family Dicranaceae is described for fossil sporophyte capsules and associated gametophytes from the late Santonian (Late Cretaceous) Buffalo Creek Member of the Gaillard Formation in central Georgia, USA. The sporophyte capsules are most comparable to those of the living genus Campylopodium. Sporangia are curved, cylindrical, and strumose, with an obliquely rostrate operculum, cucullate calyptra, and compound annulus. The peristome is haplolepidous with 16 dicranoid, apically bifid teeth that are vertically striate on the outer surface and asymmetrically trabeculate on the inner surface. Spores are spherical, alete, and finely rugose, and thus differ from the finely papillose spores of extant Campylopodium. Associated fossil gametophytes are consistent with the morphology of extant Campylopodium and have leaves with a broad sheathing base and a narrow blade. Spores identical to those in the sporangium occur on the leaf surfaces of one of the gametophyte specimens, providing circumstantial evidence that both sporophyte and gametophyte belong to the same species. Inadequacies of the moss fossil record have led to contrasting interpretations of the timing of evolutionary change in this lineage since the Paleozoic. Campylopodium allonense unequivocally provides the earliest evidence of Dicranaceae in the fossil record. This material, along with other fossil mosses from this late Santonian locality, indicates the presence of modern families of mosses in the Cretaceous. In a phylogenetic context, these fossils from two different subclasses imply that mosses were already diverse by the Late Cretaceous.