Why aren't echinoderms considered more closely related to other radially symmetrical animals like the cnidarians?

1 Answer
jza
Nov 7, 2017

Because they are triploblastic ( Triblastica ).

Explanation:

Their body is composed of endoderm, mesoderm and ectoderm. While Cnidaria are Diblastica, so they are composed only from two layers: endoderm and ectoderm.

In addition larvae of Echinoderms are bilaterally symmetrical and they become nearly-radial only as adults.

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