Saturnyians
The Saturnyians first appeared in the Series 5 episode, The Vampires of Venice (Series 5 : Episode 6) as vampire like creatures from the planet Saturnyne. Their planet was consumed by one of the cracks in time, though one colony managed to escape through one of the cracks to another world, Earth. Here, they used perception filter technology to appear humanoid, though it gave them vampire like tendencies due to the human consciousness processing the danger they were in. Examples of this included fangs for teeth when they were posing a threat to a human. Rosanna Calvierri and her 10,000 male children made it to Venice in 1580 where she tried to ensure the continuation of her species by sealing the city of Venice from the outside world, and then taking young girls into her home under the pretence of offering them a good education. There, the girls’ blood was drained and replaced with Saturnynian blood to convert them into female Saturnyians.
Rosanna also plotted to sink Venice under a tidal wave of water, to provide her species a habitat to live in, for their true form (see picture below) is aquatic in nature. However, she was stopped from doing this by the Eleventh Doctor, who also stopped what she was doing at her ‘school’ and ending her races chance of survival. Rosanna committed suicide, and because her children did not have the ability to carry on their species without her, the species became extinct.
In the Series 5 finale, The Big Bang (Series 5 : Episode 13), the Doctor closed the cracks in time. This enabled Amy to remember her parents, so it could be assumed that someone, somewhere, was able to remember the Saturnyians and their planet was restored to the Universe.