Salamanders, Crawdads, and Giant Shellies are tied into the same mechanic: any given world will only have two of the three enemy types. As such, a world with both Crawdads and Giant Shellies will not have Salamanders. In Desktop version and Mobile version, this is taken into account by the Bestiary progression logic, and the missing enemy will register as unlocked when the other two exclusive creatures are unlocked.
Like their aforementioned analogs (Giant Shellies and Crawdads), Salamanders have multiple color variants that all share identical statistics.
The salamander is actually a real-world amphibian organism.
Despite Salamanders having different colors, the Salamander Banner is always the same color.
The Bestiary entry for the Salamanders: "An unusual amphibious bipedal lizard which inhabits the dark caverns. When threatened, it spews a highly corrosive acid everywhere."