Trawl and market surveys of East China Sea fishes conducted between 1998 and 2001 disclosed seven specimens of Thamnaconus that could not be unequivocally allocated to any of the seven Thamnaconus species reported from the western Pacific Ocean. Because of their outward resemblance to both T. hypargyreus and T modestus, the seven specimens, together with T. hypargyreus and T. modestus specimens taken in the East China Sea, were subjected to a detailed comparative morphological examination to investigate the possibility of the former being hybrids. These specimens displayed either a mosaic-like distribution of both T. hypargyreus and T modestus features or features intermediate between the latter. They were clearly distinguishable from the other western Pacific Thamnaconus species. Accordingly, together with the trawl survey showing an overlap between the distributions of T. hypargyreus, T. modestus and the seven specimens, it is very likely that the seven unidentifiable specimens were T. hypargyreus/T. modestus hybrids.
