Wikipedia
Isocrania
Isocrania is an extinct genus of brachiopods found during the Upper Cretaceous. Early representatives were attached to the underground, but later species are presumed to be free living at an increasingly earlier age. This was probably an adaptation to the increasing very thick and fine sedimentation during the latest Cretaceous.
ignabergensis lateral.jpg|Isocrania egnabergensis, lateral view ignabergensis internal.jpg|internal