Chimera

From Palaeos.org

In paleontology, a chimera is a fossil "organism" that actually consists of a mixture of the remains of several different organisms.

In genetics, a chimera is an individual (animal, plant, or other multicellular organism) made up of different populations of cells deriving from different zygotes, which can arise from fusion of embryos, or, with human intervention, transplantation.

Neither is to be confused with Chimaera, a genus of cartilaginous fish. The word "chimaera" is also used as a common name for this and related (chimaerid) cartilaginous fishes.