Board Thread:Questions and Answers/@comment-17722079-20130927153503/@comment-4148041-20131119174824

People suspect sauropods in the past have had second "brains" (possibly just a big nerve knot) far down their spine, to cope with the stress of sending signals over such distances in their enormous bodies. I suspect that's what they were going for with the stem in Narga's tail.

I speculate it's to make sure that the tail can react as fast and accurate as the rest of Narga's body considering it's such a big part of its self-defense.