When a group of Silurians evolved into Sea Devils, their Silurian crests became gill arches situated at the rear of the head through a process of exaptation. (PROSE: The Monster Vault [+]Loading...["The Monster Vault (novel)"])
The Sea Devils were distinguished by the gills on their heads. (TV: The Sea Devils [+]Loading...["The Sea Devils (TV story)"])
The gills were inherited by both the Warrior-class Sea Devils (COMIC: Clara Oswald and the School of Death [+]Loading...["Clara Oswald and the School of Death (comic story)"]) and the Pirate Sea Devils. (TV: Legend of the Sea Devils [+]Loading...["Legend of the Sea Devils (TV story)"]) The Sea Devil Warriors of Elite Group One were notably distinguished by both their silver skin and their lack of visible gills. (TV: Warriors of the Deep [+]Loading...["Warriors of the Deep (TV story)"])