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Alright, a scene where Luke Skywalker activates his lightsaber while riding a rearing TaunTaun probable never happened, but you have to admit it looks cool - though I think you can get away with doing this in Star Wars Battlefront and Star Wars Battlefront II.
Now there are actually several subspecies of this repto - mammal distantly related to the Kybuck and indigenous to the planet Hoth. The specific subspecies used as both a pack animal and a scout-mount by the Rebel Alliance is the Giant TaunTaun.
Tauntauns are omnivorous and have - get this - scaly skin covered in fur, lack mammary glands, give birth to live young (Which they fed by regurgitating a milky substance), and are warm blooded. So they're part Frilled-Lizard, part Kangaroo - yes Marsupial are mammals.