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, tentacles of the Metroid Prime, a claw like that of a Zebesian and a translucent membrane with an inner nucleus reminiscent of most standard Metroid types. 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|