A new species of Antarctoxylon is described from the Coniacian Hidden Lake Formation of James Ross Island as A. mixai Sakala, sp. nov. This angiosperm fossil wood shows a unique combination of features in having indistinct growth ring boundaries, scalariform perforation plates with about 30 bars and rays both narrow (1-6-seriate) and very wide (up to 18-seriate).
Its systematic affinities and exact living relative at the specific, generic or even familial level cannot be specified. Along with Weinmannioxylon nordenskjoeldii from James Ross Island and the angiosperm woods from the Williams Point on Livingston Island, this record provides further evidence of the earliest record of arboreal angiosperms in Antarctica.