LAURACEOUS FLOWERS FROM THE POTOMAC GROUP (MIDCRETACEOUS) OF EASTERN NORTH-AMERICA

Fossil inflorescences and flowers of Mauldinia mirabilis gen. et sp. nov. are described from the early Cenomanian Elk Neck beds of northeastern Maryland, U.S.A., and are assigned to the family Lauraceae. Specimens are exceptionally well preserved and provide the earliest evidence of trimerous floral organization and endosperm in angiosperms. Inflorescences are compound and consist of elongated axes bearing distinctive, spirally arranged lateral, bilobed cladode-like units. Each lateral unit typically bears five sessile bisexual flowers on the adaxial surface. Flowers have a perianth of three small outer and three larger inner tepals, and an androecium of nine fertile stamens in three whorls. In addition, there is an inner fourth whorl of three dorsiventrally flattened staminode-like structures, and each of the three fertile inner stamens has an associated pair of staminode-like appendages with clavate-sagittate heads. Anthers dehisce by two valves that are hinged distally. The gynoecium consists of a superior, unilocular carpel with a single anatropous, pendent ovule. Floral organization in M. mirabilis is the same as that of many extant Lauraceae, and the unique inflorescence structure can also be interpreted in terms of inflorescence patterns in extant taxa. Mauldinia mirabilis is the first unequivocal documentation of Lauraceae from the Cretaceous and provides further evidence for considerable diversity among magnoliid dicotyledons at an early phase in angiosperm diversification.