Experiment 7526 was an unsuccessful attempt at converting a Space Pirate into an Elite Pirate. Its remains can be seen inside a tall, indestructible Xenome Containment Unit in the Research Lab Aether room of the Phendrana Drifts, in Metroid Prime.
Interestingly, it resembles a Zebesian moreso than any other Pirate on Tallon IV.
"This tank holds the remains of experiment 7526. Conversion of Elite Pirate unsuccessful."
E3 2001 concept art of Prime depicted a creature that shared superficial similarities with several other creatures, such as the coloration and head of the Parasite Queen, the asymmetry and tentacles of the two forms of Metroid Prime, and a claw like that of a Zebesian. This creature highly resembles experiment 7526. An anonymous developer from Retro Studios later revealed that this creature was a scrapped enemy, a mutated Space Pirate that was a failure in the Pirate Phazon experiments. It was then repurposed as background fodder. 
|Characters||EPG-8644 and EPG-8656 • EPG-8701 and EPG-8702 • Experiment 7526 • Omega Pirate • Phazon Elite|
|Technology||Chameleon Manta • Energy-siphon system • Omega Pirate Absorption System • Plasma Artillery Cannon • Plasma Incendiary Launcher • Repulsion Shield • Wave Quake Generator • Wrist Bayonet • Cryosleep Tank|
|Unused Bosses and Species|
|Metroid: Zero Mission||Crocomire • Ridley-2|
|Metroid Prime||Fireflea • Kraid • IceBoss • Ripper • Skree • Maggot • Kihunter • Sova • Chomper Fish • Experiment 7526 • Tallon Chameleon • Carnivorous Plant • Phazon Blastcap • Phazon Burrower • Zebesian|
|Metroid Prime 2: Echoes|| Dark Pirate Aerotrooper • Dark Shriekbat • Dark Sporb • Dark Triclops • Infant Shriekbats • Kenobite • Phlogus • Triclops • Zoomer • Sova • Icemite|
Metroid 1.5: Mad AI • Humetroid • Thrash-hunters • Shock beast
|Metroid Prime 3: Corruption||Advanced Pirate Militia • Advanced Shield Militia • Assault Pirate Militia • Assault Shield Militia • Big Metroid • Crocomire • Endocoon • Mantha • Phase Sprite • Phazite Armored Trooper • Phazon Tentacle • Reptilicus-G • Salamander|
|Super Metroid||Bang • Reflec • Stoke|
|Metroid: Other M||Zebesian|
|Metroid Fusion||Geega • "Hive" • Kago spawn • Skree • Toxic Gas|
|3DS Metroid game||Boss Creature|