Some years ago while I was in my work area in the Division of Invertebrate Paleontology in the Natural History Building of the United States National Museum, Smithsonian Institution I was working with some fossil echinoids when a stranger came into my room. He intrduced himself as Louis Leakey and asked if he could visit with me for awhile. I offered him a chair and said I would be happy to visit with him.
I must say I was very startled to realize I was to have a one-on-one visit with this renowned anthropologist. After exchanging small talk for a few minutes I learned why Dr. Leakey had come to the Division of Invertibrate Paleontology instead of going to the Department of Anthropology. Dr. Leakey was not looking for someone to discuss fossil hominids, but rather to show a very unusual invertebrate fossil he found.
Reaching into his pocket and slowly withdrawing his closed fist he reached toward me and slowly opened his hand. I was amazed at the sight of a fossil rare indeed. It was a silicon dioxide perfect caterpillar without hair. A caterpillar is an animal composed of entirely soft parts. It is vary rare for such animals to be preserved as fossils especilly as three dimensional specimens. The Cambrian Burgess Shale contains soft body fossils but they are just a thin film on the rock.
I speculate this caterpillar must have been trapped in a mud deposit that turned to rock. As ground water slowly removed the organic material silicon dioxide gradually filled the cavity left by the caterpillar. After the erosion of the rock the caterpillar lay on the ground and Dr. Leakey found it. Even the little ambulatory appendages were visible on the abdominal surface.
Dr. Leakey and I sat for about an hour discussing fossils before he decided he had to leave.