Fig. 5

Richtersius coronifer s.s. (Richters, 1903) from the Billefjorden population, buccal apparatus seen under SEM. a. Dorsal view of the entire buccal apparatus. b Buccal crown, lateral view. c Buccal crown, dorsal view d Buccal crown, ventral view. e Placoids, dorsal view. f Placoids ventral view. Filled arrows indicate cuticular hook on T-shaped apophysis, empty arrow indicates dorsal triangular apophysis, filled indented arrowhead indicates bulbous apophysis on the begging of the ventral lamina, empty indented arrowhead indicates ventral triangular apophysis, filled arrowheads indicate constrictions of macroplacoids, empty arrowhead indicates dorsal spikes, asterisk indicates a bilobed apophysis in the pharynx. Scale bars in μm