Molidae is the family of the molas or ocean sunfishes, bizarre-looking 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 bony fish, with the ocean sunfish Mola mola recorded at up to 3.3 m (11 ft) in length.
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 are said to be able to produce sound by grinding their pharyngeal teeth, which are long and claw-like. Typical of a member of Tetraodontiformes, their teeth are fused into a beak-like structure, making it impossible for them to close their mouth.