A Gram-stain-negative, rod-shaped and orange-pigmented bacterial strain designated 10MBP4-2-1T was isolated from the sediment on the surface of a plastic straw collected from oyster-farming areas in Quanzhou Bay, PR China. Catalase activity and oxidase activity were positive. Flexirubin-type pigment was absent. The 16S rRNA gene of strain 10MBP4-2-1T showed highest sequence similarity to Portibacter lacus YM8-076T of 98.3 %. Phylogenetic analysis based on 16S rRNA gene sequences and 120 conserved concatenated proteins indicated that strain 10MBP4-2-1T was affiliated to the genus Portibacter and formed a monophyletic clade with P. lacus YM8-076T. The digital DNA–DNA hybridization, average nucleotide identity and average amino acid identity values between strain 10MBP4-2-1T and P. lacus YM8-076T were estimated to be 17.7, 70.4 and 70.3 %, respectively. The respiratory quinone was menaquinone 7. The major fatty acid composition was iso-C15 : 0, iso-C17 : 0 3-OH and summed feature 3 (C16 : 1  ω7c and/or C16 : 1  ω6c). The draft genome size was 5 191 941 bp with DNA G+C content of 39.2 %. Based on phylogenetic analyses and whole genomic comparisons, strain 10MBP4-2-1T represents a novel species, for which the name Portibacter marinus sp. nov. is proposed. The type strain is 10MBP4-2-1T (=MCCC 1K07073T=KCTC 92101T). Additionally, phylogeny and whole genomic comparison of the family Lewinellaceae placed Lewinella cohaerens and the remaining Lewinella (currently comprising 11 species) in two clearly distinguishable clades recognized at the genus level. Thus, a novel genus named Neolewinella gen. nov. is proposed to accommodate the 11 species. Our study provides a taxonomic framework for the family Lewinellaceae based on genomic data.