Holtz were tough, horned thermophilic organisms found within Lower Norfair, near Ridley's Lair on the planet Zebes. Their mannerisms closely resemble those of a Geruta or Reo; they will hover in one spot (in terms of a Geruta they actually hang in place) before swooping down upon an unsuspecting victim, then flying back upwards again.
Holtz are notorious for their powerful armor plating, a possible indication that they are not in fact a natural entity. Instead, it is possible that they have been genetically or cybernetically altered by the Space Pirates, who took over the planet some time after Samus Aran's departure. Hunters should note that the easiest way to dispatch a Holtz is with Ice Beam technology, as it either supercools their armor to the point of shattering or lowers their body temperature to a level at which they cannot survive.
Despite the destruction of their homeworld, some found their way aboard the Biologic Space Laboratory Research Station orbiting above SR388. However, it is unknown if they were brought here by scientists to study or by Space Pirates to invade. Either way, all those aboard the station were consumed by the X Parasites that infested the area. Due to the possibility of them being Space Pirate bio-weapons, they are considered extinct in the wild instead of entirely extinct.