Fig. 7

Morphology of the gnathobase-like structures of A. symbrachiata. a, YKLP 13317, showing three isolated GLSs preserved in a row. b, interpretative drawing of the top GLS (morph-A, see main text) in a. c, close-up of the mouth region of YKLP 13889. d, close-up of the morph-A GLS of YKLP 13889 (boxed in c). e-f, close-up of the morph-B GLSs of YKLP 13889 (boxed in c), hollow arrows showing the sharp meeting point of the inner and distal edges, note that distal spines are set within sockets as indicated by the linear swollen region (solid arrows). g-j, close-up of distal spines showing cone-in-cone pattern, g-i, from YKLP 13313, boxed in a; j, from YKLP 13889, boxed in e. See Methods for abbreviations. Scale bars: a-c, 1 cm; d-f, 2 mm; g-j, 1 mm