Because dude like bro

i thought they were descendants of

cats

its also a completely different world from earth with different animals so theyre probably completely unrelated to earth life in any way

But they have a kangaroo/wallaby type build.
My theory on why they're called slugcats is probably because when threatened they make a caterwauling noise, and their ears resemble those little things ontop of a slugs head

they dont have pouches or anything tho and theyre tiny

canonically theyre biologically engineered lifeforms anyways like the leviathans and miros birds

Mf they're atleast 3 feet tall maybe so they're probably wallabys idk

They're probably some form of marsupial maybe

originally in development they were called "bear creatures" so idk