This is based on the pelvic fin(s) of fish. Pelvic spines create a webbed or spined section along the belly of your dragon. They do not need to extend the entirety of the dragon’s body. You may create betta-like fins and even sails using this modifier. You may choose to have these spines movable by your dragon, similar to the sailfish’s namesake. Optionally, you may add webbing to the spines, or have up to two rows of spines running symmetrically along the belly. They will always be close to the belly and never on the sides of your dragons.
Examples:
Charged Pelvic Fins:
This allows you to create two lines of fins, running symmetrically down the body. They should still be positioned very close to the belly.