Early Eocene Ripogonum (Liliales: Ripogonaceae) leaf macrofossils from southern Australia

Abstract

We present evidence that fossil leaves from an early Eocene estuarine mudstone deposit at Lowana Road in western Tasmania include the oldest records of the extant monocot genus, Ripogonum (Ripogonaceae). These fossils are similar to the extant eastern Australian and Papua New Guinean R. album R.Br. and New Zealand R. scandens J.R. et G.Forst., and are described as a new species, R. tasmanicum Conran, R.J.Carp. & G.J.Jord. The venation, cuticular and other leaf features of this fossil are included in a morphology-based phylogenetic analysis for the genus, and character evolution is discussed in relation to the ecology of the extant species and the palaeoenvironments of known Ripogonaceae fossil sites. The fossil (albeit on leaf characters) was placed close to the base of a black-fruited, Australian endemic Ripogonum clade. This suggests that the family have a long and conservative evolutionary history in association with moist forests, with the fossil locality showing palaeoclimate similar to the environments that most Ripogonum species still occupy today.