That’s hilarious, that the three sections of a bilateral body plan are two times brain and then the rest. I guess, it’s the lowest common denominator, though, as you can’t really section off a snail, for example.

Would be interesting whether the starfish larvae have tissue that’s genetically the trunk.
Wikipedia tells me that apparently the adult mouth forms on the left side of the larva body, the adult anus on the right side, so it’s certainly not as simple as just the trunk shortening until the head remains.

https://en.wikipedia.org/wiki/Brachiolaria

If the anus is on the top, they would wear a 5-legged pair of trousers on top. Nothing on the bottom.

Starfish equivalent of: