Two strains recovered from mussels (Fl 28-2(T)) and sea water (W63(T)) were characterized as Arcobacter sp., but they could not be assigned to any known species using the molecular identification methods specific for this genus (16S rDNA-RFLP and m-PCR) and rpoB gene analysis. The 16S rRNA gene sequence similarity to the type strains of all Arcobacter species ranged from 92.2% to 96.7% with strain F128-2(T), and from 94.1% to 99.4% with strain W63(T), the most similar being A. bivalviorum (CECT 7835(T)) and A. defluvii (CECT 7697(T)), respectively. The phylogenetic analyses of 16S rRNA, and the concatenated sequences of gyrB, gyrA, rpoB, atpA and hsp60 genes confirmed that strains F128-2(T) and W63(T) belonged to two new lineages within the genus Arcobacter. Moreover, both strains showed differential phenotypic characteristics and MALDI-TOF mass spectra from all other Arcobacter species. Therefore, it has been demonstrated the existence of two new Arcobacter species and the proposed names are Arcobacter ebronensis (type strain F128-2(T) = CECT 8441(T) = LMG 27922(T)), and Arcobacter aquimarinus (type strain W63(T) = CECT 8442(T) = LMG 27923(T)). (C) 2014 Elsevier GmbH. All rights reserved.