Placental Hoshijiro (エナ星白 Ena Hoshijiro) refers to the Hoshijiro grown from Gauna Placenta, first encountered when Nagate recovered a Gauna "pilot" from Gauna 491. Snipped from the Gauna before the True Body was destroyed, this Placenta sample replicated the human anatomy of Hoshijiro perfectly.
Biologically, the Gauna replicated Hoshijiro's human anatomy perfectly, down to bone structure and internal organs. This Placenta sample is covered in a placental pilot suit, and mutters semi-intelligible phrases at times, including "Tani..kaze ... kun." It appears to have some of Hoshijiro's memories from before she was killed by the Gauna.
Cut off from her Gauna (and severed before the True Body was pierced by a Kabizashi), Placental Hoshijiro was recovered by Nagate and brought to the ET Research Center for analysis. Initially focusing on the Kabizashi vault, she began to turn her focus to Nagate, especially when he visited her several times at the OSL Lab.
Covered in a thin suit of placenta, she remained at the lab until needed by Kunato (recently possessed by Ochiai) in order to give birth to a new Chimera, after the first Chimera was harvested for artificial Kabi. From her placental womb came Tsumugi Shiraui, the second Chimera.
It is unknown whether or not she is still alive following this.
[Editor's note: Possible personality/memory transfer into Tsumugi? The gauna she spawned from was one of the "Crimson Hawk Moths," and along with the shape of the distended placental womb being taken into consideration, the editor is put in mind of a caterpillar cocooning and re-emerging as something else via metamorphosis]