This section provides an overview of a newly proposed classification of arm postures for crinoids both living and extinct (Messing et al., in review) for the online, revised volume of the Treatise on Invertebrate Paleontology. The order of posture types in the video follows the submitted article, which includes many still images in color and black and white, as well as line drawings. The videos were gathered from a variety of sources and are mostly from deep water. Some of the crinoids featured have only recently been observed in the wild and photographed for the first time. Brief descriptions of each posture type, taxa, depth, location, and source follow for each clip.