Extended Data Figure 3: H. carinatus from Stanley Glacier (specimen ROM 59943.1).

a, b, Photographs of part and counterpart of the specimen. a, Part, photographed dry with polarized light. b, Counterpart, photographed wet with polarized light. c, Operculum (composite image of part and counterpart) showing extended tentacles, photographed dry with polarized light. Scale bars, 2 mm. Abbreviations: cl, clavicle; cp, cardinal process; ct, connective tissue; g, gut; ms, muscle scar; pl, pharynx lumen; t, tentacle; vo, visceral organ.