Litseoxylon gen. nov. (Lauraceae): The most ancient fossil angiosperm wood with helical thickenings from southeastern Asia

New genus and species Litseoxylon nanningensis gen. et sp. nov. is described on the basis of well-preserved mummified fossil wood from the upper Oligocene Yongning Formation of the Nanning Basin, Guangxi, South China. Litseoxylon gen. nov. is convincingly placed into the Litsea complex, the core group of the tribe Laureae of the Lauraceae family, and has a remarkable similarity to the alliance of extant genera Litsea, Lindera, Actinodaphne and Neolitsea. The new genus represents the first lauraceous fossil wood of the Litsea complex. Litseoxylon nanningensis is the most ancient known fossil angiosperm wood with helical thickenings reported from southeastern Asia. This species provides important evidence for the southward spread of taxa having helical thickenings from northeastern Asia, presumably triggered by abrupt global cooling near the Eocene-Oligocene boundary.