Fig. 1

Morphology of the head and tentacles of Owenia borealis (SEM). A The head viewed from the top. B Tentacle. C Ventral pharyngeal organ. D Forked tip of tentacle. E Ciliated oral and non-ciliated aboral sides of tentacle. F A portion of the oral side of tentacle. Abbreviations: as – aboral side; cf. – collar fold; ci – cilia; dp – dorsal part of pharyngeal organ; m – mouth; mi – microvilli; og – oral groove; os – oral side; sb – setae bundle; t – tentacle; vll – ventrolateral lip; vp – ventral part of pharyngeal organ; vpo – ventral pharyngeal organ