Animals
caught within La Brea were killed, eaten, and their remaining soft parts
left to decay. The bones were often disarticulated, and spread about the
area. The remains would become buried by sediment and tar or asphaltic
material. Once covered, the bones were actually preserved rather than fossilized.
The tar actually penetrated the bone, and stopped it from decay. The bones
did not mineralize, but rather were preserved. 
