Wolfspider
Explorer
Indeed they did. Well to be more accurate they are a species of Monotreme (Monotreme - Wikipedia, the free encyclopedia)
They are an egg laying mammal species that nurses their young. The article does a very good job of making it all sound good, but what it basically comes down to is Dragons are not lizards. They may look like Lizards but they're not. So if Dragons aren't lizards there's no reason to assume Dragonborn are lizards either. After all a whale looks like a big fish but it isn't.
So why don't dragons as portrayed in the D&D4e art have boobies?