: Dragons were rational and could speak (all the dragons Tolkien describes in detail were highly prolix). None of the beasts is recorded as acting in a rational manner or speaking - they were beasts not "Rational incarnates."

: Tolkien is not shy of calling a dragon a dragon. Indeed he has a number of more detailed descriptive names for them, cold-drakes and fire-drakes for example. Tolkien never describes the beasts as dragons.

As a complete side point about dragons, I've come to the belief that part of the reason the peoples of the east and south are in the service of Mordor is because of the presence (past and/or present) of dragons in those areas of the world. As for evidence, #1 is that many dragons probably would have fled far away from the havens of the elves after the War of Wrath; #2 that dragons were responsible for devouring 4 (or 3?) of the 7 dwarf rings, but there were only 1 or 2 (maybe three) dwarf clans in the nw of ME; #3 the standard of the Southrons is a black dragon; and #4 the resistance of the southrons and easterlings was not as successful (for some unknown or unmentioned reason) as the westrons'.

As for your original point, yes. I agree the the beasts are not dragons. Though I guess I might argue that there is a possibility that they are a leftover brood of the creatures that perhaps Morgoth bred into dragons. That is at least possible, though maybe not probable.

Cheers.

Dave C-Q