CCSS: 6.RP.A.1

TEKS: 6.4C

Turtles in Trouble

Ryan M. Bolton/ (Big-Headed Turtle); ZSSD/Minden Pictures (Pig-Nosed Turtle); DreamOfShadows/Wikipedia Commons (Giant Softshell); Chris Van Wyk/Zoological Society of London (Mary River Turtle); Schellhorn/ullstein bild via Getty Images (Snake-Necked Turtle)

Sporting a green mohawk of algae, the Mary River turtle stands out from the crowd. But this cool turtle lives life on the EDGE—the Evolutionarily Distinct and Globally Endangered species list. The list tracks animals that aren’t closely related to any other living creatures. An animal’s EDGE rank is based on “how unique it is evolutionarily and how likely we are to lose it,” says Rikki Gumbs. He’s an evolutionary biologist at Imperial College London.

Turtles often score particularly high on the EDGE list because they live so long. The species are very distinct because they began evolving millions of years ago. “If these species go extinct,” Gumbs warns, “we lose that whole branch of millions of years of evolution.”