Species of the red algal order Acrochaetiales mostly inhabit marine environments, with only two freshwater taxa Audouinella and Ottia . A new genus and species are described for freshwater red alga Pauciramus yunnanensis from Ailao Mountain, Yunnan, China. It is closely related to Ottia and a new order Ottiales was proposed for these genera. Pauciramus has unique combination of morphological characteristics including the following: plants caespitose and densely pulvinate, slender uniseriate filaments with well-developed rhizoids, rarely branched, cylindrical vegetative cell with a single, ribbon-shaped and parietal chloroplast, reproduction by tetrasporangia, and dense sporangial branchlet only at the upper portion of filaments. Phylogenetic analysis of sequence data from the plastid ribulose-1,5-bisphosphate carboxylase-oxygenase large-subunit ( rbc L), small subunit gene of the ribosomal cistron (SSU) and barcode region near the 5? end of the mitochondrial cytochrome oxidase subunit I (COI-5P) indicated that: the new taxon, P . yunnanensis , was in a well-supported clade with Ottia meiospora , and this clade was sister to order Palmariales and Acrochaetiales. To adhere to the principle of monophyly, a new freshwater order Ottiales including Ottia and Pauciramus is proposed. Despite the high sequence interspecific divergences and obvious morphological differences between genera Ottia and Pauciramus , seems impractical to establish a new family for a monospecific genus. Therefore, we temporarily classified Pauciramus into the family Ottiaceae, and made necessary revisions to the description to accommodate this genus.

Kunpeng FANG;Fangru NAN;Jia FENG;Junping Lü;Qi LIU;Xudong LIU;Shulian XIE

School of Life Science,Shanxi Key Laboratory for Research and Development of Regional Plants,Shanxi University,Taiyuan 030006,China

海洋湖沼学报（英文版）

[1]Kunpeng FANG;Fangru NAN;Jia FENG;Junping Lü;Qi LIU;Xudong LIU;Shulian XIE-.Pauciramus yunnanensis , gen. et sp. nov., a novel freshwater red alga from China with proposal of the Ottiales ord. nov. (Nemaliophycidae, Rhodophyta))[J].海洋湖沼学报（英文版）,2022(03):1245-1256

Pauciramus,Ottiales,Nemaliophycidae,Rhodophyta,Acrochaetiales,Audouinella,Ottia,caespitose,pulvinate,uniseriate,rhizoids,tetrasporangia,sporangial,branchlet,rbc,cistron,meiospora,Palmariales,monospecific,Ottiaceae

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