Non-canon warning: This article or section contains information that may not be considered an official part of the Metroid series in the overall storyline by Nintendo.
Concept Art Gallery from Metroid Prime 2: Echoes.
The Humetroid is a creature created in Metroid 1.5, an early draft of Metroid Prime 2: Echoes. Concept art of it survived into the final game's Concept Gallery. It is the second Metroid/human hybrid in the series after Samus Aran in her Fusion Suit and is followed by Dark Samus.
Metroid 1.5[]
A Humetroid
"•Humetroid: Standing roughly 6 feet tall the Humetroid is a half metroid / half human entity that excels in stealth, sabotage, scouting, and long distance kills. It has a detachable metroid in its chest that can be dispersed in order to attack enemies from a distance and scout an area. Once the metroid is released, the Humetroid body cloaks and the player will have control of the metroid. Because of they[sic] symbiotic nature between the Metroid and the Humetroid body, if one is killed, the other will perish.
•Because of its ability to absorb energy from other players and creatures, the Humetroid can also temporally[sic] gain an opponents[sic] ability"
Non-canon warning: Non-canonical information ends here.