These are an unnamed extraterrestrial species which crash landed on Earth through meteorite-esque cocoons.
These aliens are quadrupedal, having long legs (all four legs are the same length), armed with bear-like claws, rows upon rows of sharp fangs, having no eyes, nostrils, or ears to speak of, and communicate through sonar, shrieks, screams, snarls, and growls. They are also a sexually dimorphic species, the females being dog-sized and almost completely hairless, while the males being gorilla-sized and having a very thick coat of hair, so black in colour it dosen't reflect any light at all. The males are also seen to have bioluminescent "glowing" fangs.
It is theorized in the film, that these aliens are invaders floating through space, looking for a planet to "infest", and when they do find a planet, the female excretes a musk-like fluid so the males are able to track her and then reproduce, populating their new home.
- Attack the Block (2011)