absolute min. cage size for 2 beardies??

[sapphire_moon]

My parents.........*rollseyes* they go by one book, and one book only. They have 2 beardies in a cage that is a little smaller than a 40 gall breeder. No heat gradiant, and not even a stick on thermometer.....
One is big, about adult size, the other one is a couple of in. smaller. Even though they are both the same age. The smaller one I noticed is kind of wrinkly....and when lieing flat on her belly is thin....the other one is fat and non wrinkly.....I said to mist them...my parents said "they don't need misting, the book said so." I wanted to slap her stupid. Although I think she already is. I know nothing about beardies so wrinklyness of the skin may be common. Or not. Please tell me what you think....