Fossil Astropanax Seem. (Araliaceae) from the early Miocene (21.73 Mya) Mush Valley plant assemblages of Ethiopia

Astropanax is a monophyletic genus found in the Africa–Madagascar–Seychelles region whose evolutionary and biogeographic history, and that of related Araliaceae genera, are poorly known. In this paper, we report the presence of Astropanax leaves and pollen in Ethiopia 21.73 million years ago from the Mush Valley locality, which preserves leaf material with cuticles, fruits, seeds, woods, and less common biota including insects. Astropanax was part of a moist tropical forest community surrounding a volcanic crater lake and dominated by a single legume taxon (Englerodendron mulugetanum). Forty-nine leaf morphotypes have been documented at Mush and, along with Astropanax, identified taxa all have living relatives mainly confined to west, central, and east African forests. The plant genera found together at Mush include groups limited today to both lowlands (e.g. the swamp palm, Sclerosperma), and uplands (e.g. Hagenia). Astropanax species are most often found today in the uplands. Subsequent to the early Miocene, some genera present at Mush may have diverged into lineages that comprise the highland and lowland forest species known today. Araliaceae fossils are known from Paleogene localities primarily across the northern continents; the occurrence of Astropanax in the early Miocene of Ethiopia appears to represent the earliest definitive occurrence of Araliaceae on the African continent.