Elongate, moderately robust; distinctive flat head with sucking disc of 16-22 plates, reaches to about end of pectoral fin; lower jaw projecting; gill rakers 28-37, 26-28 lower rakers; dorsal rays 21-27; anal rays 20-24; pectoral rays 25-32; tail fin slightly concave to straight; pelvics broadly joined to belly.
Uniformly dark greyish brown.
Size: grows to 86 cm.
Habitat: commonly attached to sharks, sometimes in gill chamber, but also on large fishes, rays, and turtles.
Depth: 0-200 m?
Circumtropical; throughout the tropical eastern Pacific except for the upper Gulf of California.