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Comment by mishac | Hacker News Reader

Weirdly, echinoderms are considered part of the Bilateria clade.

Apparently they're bilateral as juveniles and only become radially symmetric as adults (https://en.wikipedia.org/wiki/Bilateria)

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Yep. If you look carefully at a most starfish, you can see that they are bilaterally symmetric. For example, when there are five legs, if you mentally halve the animal along a leg, only one of the five legs results in both sides matching.

That still undermines the articles thesis and that an odd leg can't be bilateral.

I have one head and four appendages (two for each side, but only one head bilateral down the middle). I don't see why they couldn't have a leg, bilateral down the middle ( like a head?)

Or a tail

Anyone know if there is "handedness" in tails, particularly in monkeys where they use their tails while climbing. Do individuals always curl their tails clockwise or anticlockwise around a branch?

Well, technically you have a tail too. I suppose a better description would be a spine, stunted in one end (tailbone), extended at the top (head), with two set of limb pairs (arms, legs).

Well said and excellent point.

Whoa, it does actually look like a little biped flubber: http://science-at-home.org/wp-content/uploads/2009/12/starfi...

Hence the "almost all".

Well, if I were a starfish, I would take issue with that dismissive phrase. They are members of a large, and, I assume, proud phylum.

"Echinodermata [is the] second-largest grouping of deuterostomes (a superphylum), after the chordates...Echinoderms are also the largest phylum that has no freshwater or terrestrial (land-based) representatives."

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

Well, that's exactly what proves the point that you could evolve three legged animals from bilaterally symmetric ones.

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