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- n. Plural form of ecdysozoan.
Sorry, no etymologies found.
If a major protostome group, the lophotrochozoa (which includes the snails) use nodal to set up left and right, that implies that the ecdysozoans are the odd group - they secondarily lost nodal function.
The ecdysozoans, animals like insects and crustaceans and nematodes, which do show asymmetries, don't use nodal for that function.