Abelisaurs are usually even fingerless, their arms are basically just meat socks. That's the thing when people state Tyrannosaurs have useless arms, they actually -kept- their fingers and claws, and the arms themselves are strong too.. Abelisaurs however..

I just wonder why on earth Carnotaurus evolved those tiny arms :o
after all its bottom jaw was pretty weak, so biting power wasn't the strongest.