Bashforth Arden R, DiMichele William A
Department of Paleobiology, National Museum of Natural History Smithsonian Institution, Washington, DC 20560, USA.
Proc Natl Acad Sci U S A. 2012 Mar 27;109(13):4717-8. doi: 10.1073/pnas.1203261109. Epub 2012 Mar 15.