In Super Metroid, the space pirates are humanoid, crab-like creatures with large claws and varying colors to designate their ranks. However, in Metroid Prime, they're distinctly more reptilian, with weapons attached to their arms (a blaster and sword). In Prime 2, their design changes again, more insect like with claws again, and a similar story happens in Prime 3, where they take on a more reptile/mammal appearance again.
The typical Space Pirate from Super Metroid: 
A Space Pirate from Metroid Prime: 
Lastly, from Prime 3: Corruption: 
Based on the brief look we got from the Metroid Prime 4 trailer, the Space Pirates seem to be based off the design from Prime 3.
Is there any reason in canon that the Space Pirates look so different from game to game? Prime 3 outright states Samus visits their home world, yet that design is vastly different from the rest of the series. My initial assumption was that the term Space Pirate was a catch-all term for a faction, but that would imply species diversity within their ranks which they do not seem to have.

