ends during starts during trunk somite trunk somite 1 fifth somite somite 1 XAO:0000406 Trunk somite that is initially the fifth somite, first forming around NF stage 19 and becoming more anteriorly positioned as the head somites degenerate. It is the most anterior somite by NF stage 45 and is adjacent to the otic vesicle. xenopus_anatomy NF stage 19 NF stage 47