Nanaloricus sp. Comparative diagram of the 3D rendered muscular system at different stages of body retraction. The outer contour of the specimens is represented by the white lines, while the arrows indicate the transition from fully extended to retracted body. Anterior faces upwards in all aspects. A: Specimen with fully extended introvert. The prominent pharyngeal bulb musculature is located anteriorly to the abdominal transverse muscle I. The dorsal and ventral retractors span the head region, which is characterized by the presence of a net-like muscular structure. B: Specimen with slightly retracted introvert. The pharyngeal bulb musculature is located between abdominal transverse muscle I and II. Note that the net-like thin muscles in the head are arranged as a thick, ring-like structure. C: Specimen with introvert retracted. The neck circular muscle merges the net-like thin muscles in the head. The pharyngeal bulb musculature is located posteriorly in the abdomen, between abdominal transverse muscle II and V. Color code: abdominal transverse muscle I, red; abdominal transverse muscles II-V, light blue; buccal tube retractors and mouth cone retractors, white; dorsal longitudinal retractor muscle, dark blue; introvert anterior ring muscle, dark red; introvert posterior ring muscle, brown; neck circular muscle, purple; net-like thin muscles, dark yellow; pharyngeal bulb musculature, yellow; short posterior longitudinal muscles, green; posteriormost short curved muscles, light purple; thin longitudinal muscles, dark green; ventral longitudinal retractor muscle, orange. Abbreviations: cs, clavoscalid; lo, lorica; mc, mouth cone; ss, spinoscalid.