Abstract
A single-celled green alga Coccomyxagreatwallensis Shunan Cao & Qiming Zhou, sp. nov., isolated from a specimen of Antarctic lichen Psoromahypnorum (Vahl) Gray, is described and illustrated based on a comprehensive investigation of morphology, ultrastructure, ecology and phylogeny. The cells of C.greatwallensis are ovoid to long ellipsoidal and measured 3-5 µm × 6-12 µm. The new species has distinct ITS rDNA and SSU rDNA sequences and differs from the phylogenetic closely related species C.antarctica, C.arvernensis and C.viridis in cell size, distribution and habitat.