Gill anatomy of Vetulicola rectangulata from Yunnan, China. (A,B) Latero-obliquely compressed specimens ELEL-EJ081561A and ELEL-EJ080255A with internal gill openings. (C,D) Interpretative line drawings of (A) and (B), respectively. (E,F) Details of right gill slits 1 to 4 and left gill slits 1 to 3 in (A) and (B), respectively; internal openings (arrowheads; notably right gill 2 in (E)) are surrounded by a zone of striations and folds. (G) Schematic reconstruction of Vetulicola gill system (viewed from the interior) with plates and lappets flanking the lateral groove removed for clarity, showing two adjacent gill slits with anteriorly positioned apertures. Abbreviations: Cz, concentric zone; Dm, dorsal midline; Fp, fin-like process; Go, gill opening; Lp, left plate; LG1-4, left gill slits 1 to 4; LLg, left lateral groove; M, mouth; Po, gill pouch; RLg, right lateral groove; Rp, right plate; RG1-5, right gills 1 to 5; T, tail; Tr, gill trough. Scale bars: 1 cm in (A) to (D); 5 mm in (E) and (F).