Big enough. Really. Trust me
The takes-a-bit-to-get-used-to thing in that series is that only the cool characters (e.g. Shiron, Ranshiin, Dandy ( <3 ) ) are really cool and mrawr-y drawn, while all others, especially all humans, are drawn in a really crappy schoolbook manga style with all the totally overdeone expressions and proportions and visual emotion effects and that.
It is OK once you see it as the really important characters being emphasized that way, opposed to the funny and weird and ugly humans.
But yes, Shiron and Ranshiin are both Dinosaucer size plus some, said two-tailed (sadly) but otherwise really cool anthro croc is 'bout a foot over your average human. (whose size is a little hard to guess, as in addition to most humans appreaing being caricatures instead of having anything near proportions the series seems to play in New York, but at the same time New York seems to be in Japan.
)