PASSIONFLOWER-LIKE SEEDS (PASSIFLOROIDESPERMA) FROM THE PLIOCENE GRAY FOSSIL SITE OF EASTERN NORTH AMERICA AND THEIR BIOGEOGRAPHIC IMPLICATIONS

Gray Fossil Site (GFS), Tennessee, U.S.A., is the only Pliocene plant macrofossil site currently known from the Appalachian region of the eastern United States. Genera described from fruit and seed material in the GFS macroflora to date include trees, shrubs, and vines, i.e., Carya (hickory), Sinomenium (moonseed), Staphylea (bladdernut), and Vitis (grapes). Based on the presence of these taxa, the flora has been interpreted as having strong biogeographic connections to fossil and modern floras of the Laurasian landmasses. Recently, however, seeds referable to the passionflower family (Passifloraceae) were identified from GFS. The GFS seeds have a slightly asymmetrical obovate shape, short chalazal extension (apical appendage), and palisade seed coat structure consistent with Passifloraceae subfamily Passifloroideae. The GFS seeds are thus referable to Passifloroidesperma C. Martínez 2017, a genus encompassing all fossil seeds of the Passifloroideae-type. The shape and ornamentation of the GFS seeds are similar to those the modern New World species Passiflora incarnata (maypop, eastern North America) and Passiflora edulis (purple granadilla, South America). Today, Passifloroideae are widespread, but most diverse in the American and African tropics. Few other occurrences of seeds of Passifloroideae are known in the fossil record, with other reports being from the Paleogene of Colombia and Cenozoic of Europe. Thus, the occurrence of Passifloroidesperma at GFS is significant because it adds to the limited fossil record of Passifloroideae and provides evidence of a tropical biogeographic element in the GFS macroflora.