Agro it and lead it to a cliff and shoot it from there you can't trap it to tame it. If the cliff didn't work have a quetzal ready with a cannon. And fly ahead of its head and fire at its head (must be hit in the head to tame) and once it is knocked out put a saddle on it to tame ( only last 16-20 hours so be ready to do something with it

More Titanosaur Taming & KO Tips