Seven: Four From Five or One?

[Kuruharan]

Could a dragon have killed an entire Dwarven community and, having received a mortal wound, died in the process, therefore leaving no witnesses?

Possibly, but somebody would have eventually figured out that something had happened. The dwarven reliance on trade for food would mean it would be likely their neighbors would know they were there, and the area was rather populated.

And what about the petty dwarves?

They were long dead.

[alatar]

Originally Posted by Kuruharan

Possibly, but somebody would have eventually figured out that something had happened. The dwarven reliance on trade for food would mean it would be likely their neighbors would know they were there, and the area was rather populated.

So it would be safe to say that, as we have no information about the Dragon attacks, stupendous battles, Dwarven Camlosts and other artifacts of missing Rings, that it simply just wasn't written and so glossed over.

They were long dead.

Think that you meant 'they were short dead'.

[alatar]

Appendix B, The Tale of Years, of The Return of the King, gives us a hint regarding when the Dragons may have consumed the four Rings of Power.

The Third Age: Year 2570 - About this time Dragons reappear in the far north and begin to afflict the Dwarves.

and

Year 2589 - Dáin I is slain by a Dragon.

At this time Sauron's already in Dol Guldur, Sméagol-Gollum is in hiding with the One Ring in the Misties, Brego's built the Golden Hall, Elrond's widowed (no, she didn't die, but he has the remote all to himself), Thrór and his Ring return to Erebor and his brother, Grór heads off to the Iron hills (and whats does he have in his pocketses?).

So, to me, with the fall of Dáin, we know the fate of one. Three to go...