moellendorffii, ARP homologs are present and YABBY homologs are absent, it has been postulated that YABBY genes are unique to seed plants. We generated a shoot tip transcriptome of Huperzia selago (Lycopodiales) to examine the genes involved in microphyll leaf formation in the simpex SAM. We discovered the presence of HsYABBY expression and the absence of any ARP gene expression activity in H. selago shoot tips. Phylogenetic analysis showed that HsYABBY gene is a sister to YABBY proteins from euphyllophytes. Thus, YABBY genes have been appeared in the last common ancestor of vascular plants. Localization of HsYABBY transcripts in the H. selago SAM and the comparison with the expression pattern of ARP in the monoplex SAM of Selaginella kraussiana based on literature data showed that the development of microphylls does not require the combined activities of ARP and YABBY.