It has been suggested that bilateral symmetry may have evolved before the split between Cnidaria and Bilateria , and that the radially symmetrical cnidarians have secondarily evolved radial symmetry , meaning the bilaterality in cnidarian species like N. vectensis have a primary origin .
Newer research strongly indicates that bilateral symmetry evolved before the split between Cnidaria and Bilateria : the radially symmetrical cnidarians have evolved radial symmetry secondarily .