First fossil record of Staphylea L. (Staphyleaceae) from North America, and its biogeographic implications

The occurrences of Staphylea L. (Staphyleaceae) fossils have been abundantly documented from the Cenozoic of Eurasia, but none has been confirmed from North America to date. In this study, we describe Staphylea levisemia sp. nov. on the basis of seed remains from the latest Miocene to earliest Pliocene of northeastern Tennessee, southeastern USA. The seeds are characterized by a smoothly inflated body, a large hilar scar perforated by several vascular traces and bordered by a distinctive lip-like rim, a cuticle coating the seed coat interior, and seed coat section containing weakly developed tiny lumina. According to the paleogeographic distribution of the genus, it is hypothesized that Staphylea originated from western Eurasia no later than the late Oligocene, and arrived in eastern North America no later than the late Neogene, most possibly through the North Atlantic land bridges like many other seed plants.