Related
The "Dragon" family consists not only of Dragons, but of anything even vaguely reptilian or lizard-like. It's the true Dragons you should worry about, though.
Effective Weapons
Members
The "Dragon" family consists not only of dragons, but of anything even vaguely reptilian or lizard-like. This is good, since at the time you get the Wyrmkiller, the last thing you'll want to see is a real Dragon. In practical terms, the Dragon family affiliation is rarely relevant. The Wyrmkiller is useful for killing snakes and Lizards early in the game, and that's about it.
Members
Effective Weapons
Excalibur, Holy Lance
The Dragon family includes turtles for some reason, but every member has one thing in common: they're all dangerous. You won't find a weapon that's effective against them until the end of the game, but both the Holy Lance and the Excalibur are worth keeping around to exploit this weakness (at least until you get the Masamune).