A Review and Evaluation of Homology Hypotheses in Echinoderm Paleobiology

The extraxial-axial theory (EAT) and universal elemental homology (UEH) are often portrayed as mutually exclusive hypotheses of homology within pentaradiate Echinodermata. The authors of this Element recommend these two hypotheses be used together to generate a better understanding of homology across Echinodermata.