Tetraodontiformes is an order of highly derived ray finned-fish, also known as Plectognathi. Tetraodontiformes contain approximately 350 species, which are known for their brilliant amount of variety in structure, shape size, and way of life. They are located in mild and tropical marine waters worldwide, although some families are gone in the Eastern Pacific and the Atlantic, and a few species are found in the fresh waters of South America, Africa, and Southeast Asia. Tetraodontiformes are represented by ten families, which are mostly marine and settle in and around tropical coral reefs, but a handful of species are found in freshwater streams. They have no close relatives, and descend from a line coral-dwelling species that emerged around 40-million years ago. The families and their particular common habitats are as shown: Triancanthodidae (spike fishes), deep-water, absent in the Eastern Pacific, the most basal existing linage of tetraodontiformes. Balistidae (trigger fishes), and its sister group, Monacanthidae (filefishes), often related with coral or rocky reefs and surrounding sand and sea grass bed, with a few pelagic species: Aracanidae (box fishes), absent from the Atlantic and the Eastern Pacific) and its sister group Ostaciidae (trunk fishes), associated with coral and rocky reefs and surrounding shallow bottoms (some trunk fishes with pelagic young stages: one trunkfish species matures and spawns pelagically); Triodontidae (three-tooth puffers), a single existing species, in Indo-Western Pacific deep bottom waters; Molidae (ocean sunfishes), three well-known pelagic species in oceans worldwide, and perhaps one or two more localized regional taxa confirmed to southern oceans or Austral-Asia.
Photo Credit: http://en.wikipedia.org/wiki/Balistidae http://en.wikipedia.org/wiki/Diodontidae