 Size and morphology of the first calcified stage are highly variable between (but not within) trilobite taxa, suggesting some trilobites passed through more growth within the egg than others.Early developmental stages prior to calcification of the exoskeleton are a possibility (suggested for fallotaspids), but so is calcification and hatching coinciding.The earliest post-embryonic trilobite growth stage known with certainty are the "protaspid" stages (anamorphic phase).