Strain 2CBEGH3T, which is an obligately anaerobic, non-pigmented, non-spore-forming, non-motile, Gram-stain-positive coccobacillus, was isolated from a faecal sample of a healthy Japanese man. The 16S rRNA gene sequence analysis showed that strain 2CBEGH3T represented a member of the family Atopobiaceae and formed a monophyletic cluster with Olsenella uli DSM 7084T (93.6 % sequence similarity), Olsenella umbonata strain lac31T (93.0 %), Olsenella profusa JCM 14553T (92.7 %) and Olsenella scatoligenes strain SK9K4T (92.7 %) as closest neighbours and Atopobium species. The hsp60 gene sequence analysis supported the phylogenetic relationships based on the 16S rRNA gene sequences, with sequence similarity values of 82.1-84.7 % to the four species described above. A unique three-base (one amino acid residue) insertion was found in the alignment regions of the hsp60 gene sequence of strain 2CBEGH3T. The major end products from d-glucose were d- and l-lactic acids produced at the ratio of 75 : 25, while four species of the genus Olsenella produced d- and l-lactic acids at ratios of 94-98 : 2-6. The isolate formed characteristic crater-like colonies on Eggerth-Gagnon agar plates. The major cellular fatty acids were C18 : 1�s9c, C18 : 1�s9c dimethyl acetal (DMA) and C16 : 0 DMA. The G+C content of the genomic DNA was 68.4 mol%. On the basis of these data, strain 2CBEGH3T represents a novel species in a novel genus of the family Atopobiaceae, for which the name Parolsenella catena gen. nov., sp. nov. is proposed. The type strain of P. catena is 2CBEGH3T (=JCM 31932T=DSM 105194T).