>>149764883
Reposting but there's an entire scene where they show a computer analysis of how its blown off pieces continue to grow/multiply the cells, and there's a deleted scene (cut due to its grotesqueness) where they show the site in question where he was growing over rubble.
If you didn't watch the movie, just say so anon. In any case, Shin is more like a colony organism than a reptile.
https://www.youtube.com/watch?v=Gd_8ho66iCY