The form of large swimming animals is fairly consistent across distantly related groups. As example, all aquatic mammals, save the quadrupedal semiaquatic forms, have adapted for a fish-like shape with a vertically-moving tail and two flippers on their chest
Mammals, clearly, have only 4 limbs, of which all four are on the torso. Hence, I must ask if this form would be the ideal for a similar fish-shaped animal which possesses a pair of cephalofoils somewhat similar to a hammerhead shark
Specifically, the animal has a fish-shaped body with a dorsal fin and a fluked tail like a dolphin. It ancestrally has 6 fully moveable limbs, one pair on the head, one pair at the front of the chest, and one pair between the torso and tail. Which of these limbs should be retained or lost to reach a hydrodynamic ideal for swimming within this ancestral limb configuration?