XVI International Botanical Congess

Relationships of the zosterophylls and lycopsids were evaluated on a data set of 40 taxa and 22 characters. Searches were run on PAUP and results were summarized using semi-strict consensus. Adams consensus identified problematic taxa. Initial analyses were performed over 18 OTUs. Analyses with additional OTUs retained many the initial relationships, but basal relationships of several zosterophylls and other primitive taxa were unresolved. Two monophyletic taxa were identified: one with axillary tubercles and the other with spiny emergences. Lycopsids were part of the spiny taxon, making the zosterophylls paraphyletic. Character distributions mapped onto the phylogeny support evolution of microphylls via transformation of spiny zosterophyll emergences (enation theory). Other microphyll evolution hypotheses were not supported.