An Unusual New Rheophytic Species of the Liverwort Genus <i>Cephaloziella</i> from Panama

Abstract— During bryophyte surveys in the Antón River watershed, Coclé Province, Panama, we discovered a minute rheophytic liverwort representing an undescribed species of Cephaloziellaceae. Phylogenetic analyses based on nuclear ITS1‐2 and plastid rbcL DNA markers placed the new species within Cephaloziella , where it resolved in a clade with C. microphylla , C. kiaeri , and C. recurvifolia in the ITS tree, and with C. microphylla alone in the rbcL tree. We describe the species as Cephaloziella minutiloba . The new species is morphologically distinct by its minute size, flagelliform shoots, scattered violet rhizoids, succubous and highly unequally conduplicate leaves with a prominent ventral lobe and a strongly reduced dorsal lobe bent over the ventral lobe, and crenate-dentate leaf margins. The gynoecia on short ventral branches are made up of 2‐3 series of highly connate, crenate bracts and a 5-plicate perianth with a fringed mouth. This new species expands our understanding of morphological diversity and rheophytic adaptation within Cephaloziella . The morphological affinities of the species are discussed, and the importance of integrative taxonomic approaches in liverwort systematics is emphasized.