Opabinia, an invertebrate with a proboscis.

505 million years ago, in the middle of the Cambrian, part of what are now the mountains of western Canada lay under the sea, near a vertical submarine cliff. From time to time, a mudslide covered the seabed. Living things that were unfortunate enough to be there died from lack of oxygen and were buried. Thus arose the geological formation of the Burgess Shales, where, in 1966, British paleontologist Harry Blackmore Whittington discovered a new, well-preserved specimen of Opabinia, an animal so strange that at the first public presentation of Whittington’s analysis, the audience erupted in laughter. With a total length of about four inches, its main feature is the flexible, hollow proboscis that projects downward from the bottom of the head.