CHLORANTHUS-LIKE STAMENS FROM THE UPPER CRETACEOUS OF NEW JERSEY

Fossil angiospermous stamens with in situ pollen from the Turonian (ca. 90 million years before present, Late Cretaceous) of New Jersey are described and assigned to the Chloranthaceae. The fossil stamens, which are three-parted and bear two bisporangiate thecae on the central lobe and one bisporangiate theca on each lateral lobe, are indistinguishable from stamens of several extant species of Chloranthus. The pollen is spheroidal, 13–18 μm in diameter, with a reticulate exine and apparently elongate/elliptical apertures. The pollen is similar to that in extant Chloranthus in grain size, shape, exine sculpture, and aperture structure. Like pollen of some extant species of Chloranthus, aperture number in the fossil pollen appears to be variable. Because fossil pistillate chloranthoid reproductive structures have not been found at this locality it is unknown whether the fossil stamens described here were borne on the side of the ovary, as in extant Chloranthus, or in another arrangement. The three-parted stamen of Chloranthus is unique in angiosperms and there has been considerable debate concerning the origin and evolutionary significance of the structure. Uncertainty as to whether the three-parted stamen represents a synapomorphy for the genus or a retained plesiomorphy in angiosperms is the primary reason why these fossil stamens are not assigned to the extant genus Chloranthus.