Micro CT surface rendered (A) and 2D section (B–G) images of the basal part of arm (7–13th arm segments) of Asteronyx loveni (NSMT E-5638). A basal lateral view. Section planes of figures B–G are shown by dotted tetragons B vertical longitudinal section, adradial side of the arm C, D horizontal longitudinal section, aboral view C is set on more aboral side than D horizontal longitudinal section, oral view E–G transverse vertical sections from basal (E) to distal (G) arm, basal view. Vertebrae, lateral arm plates, arm spines and muscles are colored red, blue, yellow and purple, respectively. Red and blue arrow heads (B–G) indicate radial nerve canals and radial water canals, respectively. Arrows indicate the orientations (ab, aboral; ba, basal; dis, distal; or, oral). Abbreviations: E, epidermis; EO, external ossicle.