It may have been the intent back then but the newer films changed that.
As for the fossilized comment Dallas makes, he is incorrect because I think something can only be fossilized is if its beneath the earth. Its more like dessicated or something. Which doesn't actually take that long to happen.
But then he is just a blue collar captain of an old rig of a ship. A giant alien corpse is out of his expertise and he was just making a laymen's observation.