A new lineage of fresh‐ and brackish‐water mussels (Bivalvia, Mytilidae) from Southeast Asia

Three species of mussels collected from fresh- and low salinity (10 psu or lower) brackish-water environments in southern Thailand, Singapore, northern Borneo south Sulawesi formed a new, well-supported distinct mytilid clade based on molecular phylogeny. All are small (< 30 mm) with either radially ribbed smooth shells. Internally, the upper edges ascending lamellae outer inner demibranchs are, respectively, fused to mantle lobes visceral mass. A new genus Parabrachidontes is proposed accommodate three species. Of genus, one described as (Parabrachidontes amnicus sp. n.), other two poorly known (P. leucostictus P. cochinensis) re-described. The closely related Mytella, Perna Arcuatula. Together, they clade, most members which have ctenidial attached and/or These genera clearly phylogenetically clades containing brackish- fresh-water ctenidia free mantle: comprising Limnoperna Sinomytilus (together constituting Limnoperninae), Xenostrobus Vignadula (forming Xenostrobinae). We therefore suggest existence at least lineages mytilids living rivers estuaries East Asia Australasia.