There's no real naming system, though they are categorized based on threat value via a grade system, higher numbers mean higher threat, so a Grade 1 would be those tunnel lurkers I mentioned a few pages back. The reason the lower numbers are weaker is because it's unclear just how strong they can get (Remember they kill for food, humans are not enough sustenance for the larger ones so they don't typically threaten settlements too frequently) so there needs to be wiggle room. And also that lower grades are more common, hearing Grade 1 wouldn't really peak any interests. Furthermore, if you want to add a monster just provide a link or description, what I listed was just a few as the variety are many. While they do technically have Species names there are so many it's quicker just to call them beast or monster because of just how many there are.