Mirrorite

Mirrorite were large, flat, savage predators. They were capable of flight, and had shiny reflective backs and savage teeth around a gaping mouth located on their underbelly.

They stalked their prey by lying low and creeping up when the prey has become weak enough not to be able to fight back. Mirrorites evolved to split into two halves, each a little weaker than the whole. Each was capable of independent movement and hunting.

It was unknown how a Mirrorite came to be found in the Australian outback in 1943, but the creature was captured and returned home by the Eleventh Doctor and Amy Pond. (DWAM: Seeing Things)