There's a bug in Ark Mobile(Ultimate mobile edition one. Not the old one.) where if you tame a Carcha, you don't get the dossier(if you're on Evolved, you should get the Carcha dossier if you tame one). If you want to get the dossier, just tame another one with the opposite gender(if you have a Male, get a Female and vice versa) and Breed them. You should get the dossier when Imprinting/Claiming the Baby.