Symphurus is a genus of fish in the family Cynoglossidae found in the Atlantic, Indian and Pacific Ocean. Most species mainly occur in relatively shallow water, including estuaries. Some species are also found in deeper water, including S. thermophilus that lives at hydrothermal vents (the only flatfish known from this habitat). These species are distinguished by merged dorsal, caudal and anal fins, the absence of a lateral line and pectoral fins, and the presence of only one pelvic fin. They are sinistral flatfishes, meaning that as adults, their crania are asymmetrical, with both eyes on the left side. The largest species grows to about 32 cm (1 ft) long.