what ‘is’ the beast titan?

not sure how to phrase it but: i understand it as it’s ability is that it the user becomes a titan that is an amalgamation of an existing animal the user somehow has a connection to and a titan. if that is the case then why can falco’s titan fly as the jaw titan? there weren’t any beast titans ever that had some kind of association with a bird? does the intro imply they can become dinosaurs even if they no longer exist (or is this simply an artistic decision to depict the passage of time)? does the user not even have to have seen the animal? this titan always stood out as kind of weird to me, because other titans can throw things so techincally zeke’s ‘ability’ is that he can speak in titan form and look like a monkey? or is the ability to control pure titans also built into this titan? and if that is the case, the why does it need to look like a monkey to do those things?