The tropical lowland rainforest is a paradise for Lejeuneaceae. Borneo is located in the heart of the biodiversity hotspots of Philippines, Sundaland and Wallacea. During an expedition to explore liverwort diversity of Sabah, Borneo we found an undescribed ocellate taxon in the lowland ultramafic rainforests. Our phylogenetic analyses based on the nuclear ribosomal ITS region and two chloroplast regions (rbcL, trnL-trnF) suggest that this unknown species belongs to the subtribe Lepidolejeuneinae of Lejeuneaceae. On the basis of the combined molecular phylogenetic and morphological data, here we propose a new genus, Thiersianthus, to accommodate this new species. Capillolejeunea known only from the East African Islands and Kymatolejeunea endemic to New Zealand were included in molecular analysis for the first time.