TESTING HOMOLOGY BY CONGRUENCE - THE PECTORAL GIRDLE OF TURTLES

The recent analysis of the homologies of the elements in the highly de rived pectoral girdle of turtles is used as an example to clarify how character congruence tests conjectures of homology in cladistic analys is. Character congruence does not test alternative conjectures of simi larity i.e. alternative character definitions and/or descriptions. It will only test the proposition that an observed relationship of simila rity is homologous or not, and hence indicate whether this observed re lationship of similarity may be parsimoniously explained by common anc estry, or must rather be treated as homoplasy. To test alternative hyp otheses of homology, or alternative conjectures of similarity, the dat a matrix must be constructed such as to allow the evaluation of these alternatives on the basis of parsimony.