LUPIA, RICHARD. Sam Noble Oklahoma Museum of Natural History and School of Geology and Geophysics, University of Oklahoma, 2401 Chautauqua Avenue, Norman, OK 73072. - Megaspore and fern mesofossil floras from the Aptian-Santonian (Cretaceous) of the Atlantic and Gulf Coastal Plains.
Numerous mesofossil floras, deposited approximately 80-115 million
years ago (Ma), containing charcoalified and lignitized flower,
fruits, seeds and leaves, have been found along the Atlantic and Gulf
Coastal Plains of the United States. Although angiosperms from these
localities have been intensively studied, other plant remains have not
been examined in as much detail. The megaspore floras and fern
mesofossils that have been recovered from three localities are
described. Cumulatively, at least ten genera and thirteen species of
megaspores are recognized from Northeast Plaza (Aptian, 115Ma,
Maryland), Mauldin Mountain (Cenomanian, 99Ma, Maryland) and Upatoi
Creek (Santonian, 84Ma, Georgia) localities. Megaspores identified so
far have affinities either to heterosporous
lycophytes—Bohemisporites, Erlansonisporites,
Minerisporites, Paxillitriletes, and three additional
"genera"—or to heterosporous ferns—Arcellites,
Ariadnaesporites, and Molaspora. On the basis of
recently described sporocarp remains, Molaspora is a dispersed
megaspore belonging to the extant genus Regnellidium
(Marsileaceae). At both sites in Maryland, lycopsid megaspores are
more diverse and abundant than fern megaspores. At Upatoi Creek,
lycopsid megaspores are more diverse, but approximately equivalent in
abundance to fern megaspores. Fern mesofossils—pinnules with and
without sporangia, and rachis fragments—are present at all sites. At
Mauldin Mountain, isolated pinnules enclosing sporangial clusters are
among the most common fossils. At Mauldin Mountain and Upatoi Creek,
fertile pinnules assignable to Onychiopsis, a fern with
affinities to Dicksoniaceae and previously known only from sediments
of Cenomanian age and older, have been identified.
Key words: Cretaceous, megaspores, palynology, petridophytes