Circle of Transcendence

The Red Carnivorous Maw was presumably what its name suggests: a red-skinned carnivore.

In the Tenth Doctor's time stream, some time after the Bowie Base One incident and before he travelled to the Ood Sphere, he saved a planet from the Red Carnivorous Maw. The Doctor mentioned this adventure to Ood Sigma. (TV: The End of Time)