Vicious imaginary beasts, 2 meter high (about 6 feet) and 5 meters long (not including the tail) fire-breathing turtles, with a long spiked dragon tail which they uses to whip and pierce their victims with. Another one of their evolutionary gifts are very powerful triangular jaws, that end with a point, with which great pressure could be applied on a single point of something unfortunate enough to be caught in between them.
Dracoturtles existed up to the middle ages, secluded in caves, usually near volcanos, everflowing rivers of lava, or other hot places. When knights came to slay them, they used their immensely powerful jaws like a can opener, to open the armour of the knight.
At winter when there were less knights,
they had to resort to kidnapping princesses so valiant knights would come and rescue them.
With the passing of the middle ages and the introduction of gunpowder to the world, they were extinct, together with their more deadly brothers - the dragons.
Turtles, however, were not considered dangerous by the humans and so were not slain... But they are... and one day... expect the turtles to exact revenge upon the foolish humans who killed their brothers.
The imaginary beasts are used in no book, in no movie, by no person... but they should.
Also see: Shlomo the Camel
Examples of not-so-famous Dracoturtles: Randolf the Mighty, Squary the Square-jawed...