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 color it doesn't reflect any light at all. The males are also seen to have bioluminescent "glowing" fangs - which were initially mistaken for eyes.
It is theorized in the film, that these aliens are invaders floating through space on solar winds, looking for a planet to "infest", and when they do find a planet which is suitable, the female excretes a musk-like fluid so the males are able to track her and then reproduce after landing on the planet, populating their new home.
- Attack the Block (2011)