English: Myoanatomy of the head of Echinoderes spinifurca. Phalloidin staining and 3D reconstruction of the anterior region showing distinct muscle groups of the mouth cone, introvert and pharyngeal sheath. This specimen rotates on all three axes, beginning and ending with apical views. The introvert and mouth cone are fully extended. The pharynx is surrounded by a tulip-shaped muscular sheath (pale yellow) and is extended to reach the mouth cone (yellow). The oral styles and scalids (grayscale) do not have muscles. White lines on each side of the head correspond to the long terminal spines of this dorsoventrally curved specimen. Musculature is color-coded for the same specimen in Figure 2A-D of the manuscript.