Molidae is the family of the molas or ocean sunfishes, unique fish whose bodies come to an end just behind the dorsal and anal fins, giving them a “half-a-fish” appearance. They are also the largest of the ray-finned bony fishes, with the ocean sunfish Mola mola recorded at up to 3.3 metres (11 ft) in length and 2 tonnes (2.2 short tons) in weight.
They have the fewest vertebrae of any fish, only 16 in Mola mola. They have fairly rough skin. Also, they completely lack all caudal bones, and most of their skeleton is made of cartilage. There are no bony plates in the skin; it is, however, thick and dense like cartilage. They also lack a swim bladder. The meat contains the same toxin as in pufferfish and porcupine fish, but not in the same amounts.
Molids mostly swim by using their anal and dorsal fins, the pectoral fins are probably just stabilizers. To steer, they squirt a strong jet of water out of their mouth or gills. They can also make minor adjustments in the orientation of the anal fin or the dorsal fin so as to control the amount of force it produces and the angle at which the force is produced. In this respect, they use their fins much like a bird uses its wings.
Molids are said to be able to produce sound by grinding their pharyngeal teeth, which are long and claw-like. Typical of a member ofTetraodontiformes, their teeth are fused into a beak-like structure, making it impossible for them to close their mouth. Despite this, they feed mainly on soft-bodied animals, such as jellyfish and salps, although they will also take small fish or crustaceans.
(From Wikipedia, July 5th, 2010)
Body an elongate oval (depth 25-48% of SL), strongly compressed; mouth small, funnel like, a vertical slit when closed, opens at the front, is a beak (without a central suture) composed of teeth fused to the jaws; gill openings small, on side just before pectorals; pectorals long, pointed; no pelvics; 17-19 rays; anal 18-19 rays; pectoral 13 rays; no tail base; dorsal and anal fins long and high, symmetrical, used for locomotion, at rear of body, their rear rays joined to tail fin immediately behind them that is reduced to a vertically elongate, short, blunt rudder, with oblique profile, no rear pointed extension; skin smooth, covered with small, hard, hexagonal plates.
Dark grey to dark blue above, silvery on sides and belly; head and lower belly with thin undulating black-edged white bars; white spots and vertical streaks on body between dorsal and anal fins.
(From EOL via Shorefishes of the Tropical Eastern Pacific Online Information System, July 4th, 2010)