Possesive Pronoun

[Jennifer Nevsky]

I know the possessive pronoun its is used as an adjective in sentences. In the possessie pronouns used as predicate pronouns, mine, ours, yours, his, hers, theirs, its does not appear and seems to have no function. Could you clarify this?

 

[5jj]

I ate my dinner, and the dog ate its.

Its just about possible, but rare. Sorry, I don't know why.