This is the harness worn by Sigourney Weaver as the chestburster breaks out. It is all cable operated and these gather down through a waist strap and would have attached to levels off camera.
No skin remains and the smaller appendages and head area are missing from the puppet. It is fixed to the harness and has no tail so I think there may have been a second used for full chestburster body shots.
The cables were cut but remain long. There are two blood tubes and lots of fake blood staining to the waist strap.
