There are currently three recognized species in this genus:[1]
H. leptorhynchus is known from the Chao Phraya and Mekong River drainages in Indochina.[2] H. typus inhabits rivers of Sumatra and southeast Borneo.[3] H. waandersii is known from medium- to large-sized rivers of Sumatra and Peninsular Malaysia.[2]
H. leptorhynchus grows to about 47.2 centimetres (18.6 in) SL.[4] H. typus reaches a length of about 37.7 cm (14.8 in) TL.[3] H. waandersii has a maximum recorded length of about 70.0 cm (27.6 in) TL.[5]
The stomachs of the specimens of H. waandersii are more or less filled with mollusks, usually bivalves.[5] H. waandersii enters flooded forests.[5] H. waandersii migrates upstream when water levels begin to rise at the beginning of the flood season and moves downstream as water clears at the end of the flood season.[5]
Unlike H. waandersii, H. leptorhynchus stays in permanent river channels and does not move into flooded forests. However, it also migrates upstream and downstream with changes in the water level.[2] H. leptorhynchus feeds primarily on bivalves.[2]
