Three-dimensional reconstruction of myoanatomy in Echinoderes horni . (A-C) Single specimen with the introvert fully everted. (D-F) Single specimen with the introvert fully retracted. Anterior to the top in all images. Notable musculature: (A) lateroventral view: outer oral style muscles, neck circular muscle, segmented trunk muscles; (B) lateroventral, with introvert in apical view: mouth cone circular muscles, introvert retractors; (C) lateral view: diagonal muscles, dorsal muscles, dorsoventral muscles; (D) lateroventral view: ventral muscles, lateral continuous fibers, terminal spine muscles; (E) apical-ventral view showing introvert and mouth cone within the trunk: neck circular muscle, introvert circular muscle; (F) ventral view: introvert circular muscle retractors, ventral muscles, pharynx retractors, terminal spine muscles, tergal extension muscles, hindgut dilators. Abbreviations: i, introvert; n, neck; t, trunk. Scale bar, 30 μm.