[2] The crocodile flathead was first formally described as Platycephalus crocodilus in 1829 by the French zoologist Georges Cuvier,[3] the species was not described from a type specimen, it was based on an illustration and so is an iconotype.

[4] In 1925 David Starr Jordan and Carl Leavitt Hubbs proposed a new genus, Cocius, and named P. crocodilus as its type species.

[6] The crocodile flathead was considered to have a wide Indo-Pacific distribution but in 1996 Leslie W. Knapp described three new species and removed a fourth C. punctata from being a synonym of C. crocodilus.

[2] The crocodile flathead was considered to have a wide Indo-Pacific distribution but the revised species is restricted to the western Pacific Ocean in Japan, China and Taiwan.

The larvae and juveniles occasionally enter brackish waters in mangroves, particularly the lower reaches.