Fossil seeds of Passiflora L.: An Oligocene record of a new species and a Pleistocene record of a modern species from the Gulf of Mexico Coastal Plain

Abstract

We describe two small, compressed seeds from the Gulf of Mexico Coastal Plain that display a reticulate-foveolate seed coat pattern as species of Passiflora subgenus Passiflora. One was obtained from the basal layer of the Catahoula Formation in Wayne County, Mississippi, and is late Oligocene in age (25–23.8 Ma), supported by planktonic foraminferal and nannofossil zones. The other is from a Pleistocene river terrace (luminescent dating of 85–82 ka) on the banks of the Mobile River in Alabama. The Oligocene seed is tridentate (consisting of a central apical appendage and well-displayed lateral protrusions to the sides of this appendage), symmetrical, and has a palisade seed coat structure with ruminate endosperm. Its characters allow tentative placement within supersection Laurifolia and series Tiliifolia. Extensive comparisons with seeds of extant species of Passiflora subgenus Passiflora serve as the basis for recognizing it as a new species, Passiflora axsmithii sp. nov. The Pleistocene seed is obovate, slightly asymmetrical, has a small crown around the base of the apical appendage, and insubstantial lateral projections. As the Pleistocene seed is geologically young and fits the description of seeds produced by the native extant species Passiflora incarnata (supersection Passiflora, series Passiflora), we consider it very likely to be a representative of that species. The Oligocene seed is the earliest reliable record, thus far, of genus Passiflora. The Pleistocene seed is likely the earliest record, to date, of the extant species P. incarnata.