As stated many times on the forum, brachiopods differ from bivalves regarding symmetry. Brachiopods have sagittal symmetry (side to side), just like humans, birds, reptiles etc. Bivalves have coronal symmetry (front to back). It seems that coronal symmetry is an outlier in biology, and I'm having trouble coming up with many examples in the animal kingdom.
Is coronal symmetry a different branch in the evolutionary chain than sagittal symmetry? I guess the question could also apply to radial symmetry or asymmetry.
Put another way, is symmetry something very basic within evolutionary chains, or do chains develop with mixed symmetry?