Abstractions

摘要

Knowledge about the earliest stages of vertebrate evolution draws heavily on information from 500-million-year-old fossils of early chordates - an animal group thatrnincludes vertebrates and their closest relatives. Lacking bones, teeth or shells, these ancient soft-bodied animals left behind a sparse record, and there are few well-preserved examples. This has made it hard to interpret their anatomy and evolutionary significance. Now, Mark Purnell and his colleagues at the University of Leicester, UK, have learned more about the way such organisms decay and how this may affect their proper placement in the evolutionary tree (see page 797).