Chelonian has multiple, interrelated meanings:
Chelonia, the order uniting all turtles Genus of sea turtle of which the green sea turtle is the only extant member The Chelonians, an alien race of humanoid tortoises that appear in the science fiction TV series Doctor Who Chelonian Conservation and Biology, International Journal of Turtle and Tortoise Research Chelonia, a fictional religious cult in the 2018 video game Red Dead Redemption 2
See also Cheloniology, the study of turtles.