 In 2009 Balthasar and Butterfield found in western Canada two specimens from about 505 million years ago of a new fossil, "Lingulosacculus nuda", which had two shells like those of brachiopods but not mineralized.In the authors' opinion, the U-shaped gut extended beyond the hinge line and outside the smaller shell.This would have precluded the attachment of muscles to close and open the shells, and the 50% of the animal's length beyond the hinge line would have needed longitudinal muscles and also a cuticle for protection.