Fig. 2

Gnathobase-like structures of A. symbrachiata preserved with the frontal appendages. a-b, YKLP 13314 and its interpretative drawing, showing a pair of GLSs and an isolated one, note the triangular sclerite (P-element) in the lower right corner. c, e, close-up of GLSs (boxed in a), arrows in e indicating two poorly preserved distal spines of a paired GLS. d, f, YKLP 13313a and its interpretative drawing, showing a pair of GLSs with a long stem, hollow arrows indicating possible inter-podomere membrane, solid arrow in d indicating the rising position of the endite. g, detail of the paired GLSs (boxed in d). See Methods for abbreviations. Scale bars: a, b, d, f, 5 mm; c, e, g, 2 mm