Which features of ocean sunfishes distinguish them from other tetraodontiform fishes?

Ocean sunfishes, belonging to the family Molidae, are distinguished from other members of the order Tetraodontiformes by several unique anatomical and physiological features:

• Body Shape and Tail: Molas possess a distinctive, bullet-shaped appearance with a short, deep body that ends abruptly behind the tall dorsal and anal fins. Instead of a standard tail, they have a thick, rudderlike structure called a clavus, which develops as the fish grows due to the folding of the back fin into the body.1
• Dentition: They possess two tooth plates, with one in each jaw.2
• Skin: Their skin is leathery and relatively smooth, though it is often exceptionally thick.2
• Internal Anatomy: Unlike many other bony fishes, molas lack a swim bladder.2
• Size: While most tetraodontiforms are relatively small, molas are among the largest of all bony fishes, with some species reaching lengths of over 3 meters and weights exceeding 2,000 kg.21