Lava snake
From Tardis Wiki, the free Doctor Who reference
Lava snakes were a type of creature regularly battled by Church clerics in the 51st century. While Angelo found hunting down a Weeping Angel better than hunting lava snakes, Christian rebutted, "Actually, lava snakes weren't that bad." (TV: The Time of Angels)
The Shalka are also referred to as lava snakes and therefore could be related.
