a, b, H. carinatus, dorsal view of specimen ROM63983.1 from Stanley Glacier. a, The entire specimen photographed dry with polarized light. b, Detail of tissue associated with the operculum. c, Dorsal view of specimen KUMIP366447 from the Spence Shale, photographed wet with polarized light. d, Larva of the extant brachiopod Glottidia, with retracted lophophore. This image was from figure 1b of ref. 31. Scale bars, 2 mm (a–c) and 0.2 mm (d). Abbreviations: bw, body wall; c, conical shell; cl, clavicle; cp, cardinal process; ct, connective tissue; es, embryonic shell; g, gut; lh, left helen; ls, larval shell; ms, muscle scar; mt, medial tentacle; o, operculum; pd, pedicle; rh, right helen; t, tentacle.