Anatomy and Classification of the Mesophyllaceae (Corallinales, Rhodophyta), Based on Phylogenetic Principles
Authors: Athanasiadis Athanasios , Ballantine David L. 
Published: February 2024

A phylogenetic analysis shows the Mesophyllaceae comprise the subfamilies Clathromorphoideae Athanas. et D. L. Ballant. subfam. nov., Protomesophylloideae Athanas. et D. L. Ballant. subfam. nov., and Mesophylloideae Athanas. et D. L. Ballant. subfam. nov., the last one including the main core of species previously assigned to Mesophyllum and Leptophytum. The Clathromorphoideae comprise the genera Clathromorphum, Neopolyporolithon, Callilithophytum, and the monotypic Clathmoroa Athanas. et D. L. Ballant. gen. nov. based on C. tubiformis (Y. M. Chamb., R. E. Norris, et G. W. Maneveldt) Athanas. et D. L. Ballant. comb. nov. from South Africa. Protomesophylloideae is monotypic, based on Protomesophyllum ameleteton Athanas. et D. L. Ballant. sp. nov. from southern Australia, New Zealand, and the Chatham Islands. The Mesophylloideae comprise the tribes Amphithallieae Athanas. et D. L. Ballant. trib. nov., Melyvonneeae Athanas. et D. L. Ballant. trib. nov., and Magnephyceae Athanas. et D. L. Ballant. trib. nov. Amphithallieae include the genera Amphithallia, Synarthrophyton, Carlskottsbergia, Capensia, and the monotypic Kerguelena Athanas. et D. L. Ballant. gen. nov. (type: K. dickiei Athanas. et D. L. Ballant. comb. et nom. nov.) and Masoniana Athanas. et D. L. Ballant. gen. nov. (type: M. kraftii Athanas. et D. L. Ballant. comb. et nom. nov. from southern Australia). Melyvonneeae include the genera Phragmope, Mesophyllum, Melyvonnea, Perithallis, Thallis, Sunesonia, Printziana (comprising the type and P. insignis (Foslie) Athanas. et D. L. Ballant. comb. nov. from New Zealand), and the new monotypic Macroblastum Athanas. et D. L. Ballant. gen. nov. based on the Mediterranean M. dendrospermum Athanas. et D. L. Ballant. comb. et nom. nov.Magnephyceae include the genera Kvaleya, Leptophytum, Leptothallia Athanas. et D. L. Ballant. gen. nov. (based on L. acervata (Foslie) Athanas. et D. L. Ballant. comb. nov. from South Africa), Macedonis Athanas. et D. L. Ballant. gen. nov. (including the Aegean generitype M. tethygenis Athanas. et D. L. Ballant. comb. et nom. nov. and the NE Pacific M. julieae (Athanas. et W. H. Adey) Athanas. et D. L. Ballant. comb. nov., M. lamellicola (Athanas. et W. H. Adey) Athanas. et D. L. Ballant. comb. nov., and M. kymatodis (Athanas.) Athanas. et D. L. Ballant. comb. nov.), Hyperandri Athanas. et D. L. Ballant. gen. nov. (including the generitype from Pacific Mexico H. dawsonii Athanas. et D. L. Ballant. comb. et nom. nov., the Canarian-Caribbean H. bisporum (Foslie) Athanas. et D. L. Ballant. comb. nov., and the Thai H.siamense (Foslie) Athanas. et D. L. Ballant., comb. nov.), the monotypic Ectocarpa Athanas. et D. L. Ballant. gen. nov. (based on E. capverdensis Athanas. et D. L. Ballant., comb. et nom. nov.), Magnephycus Athanas. et D. L. Ballant. gen. nov. (including the Caribbean generitype M. ornatus (Foslie et M. Howe) Athanas. et D. L. Ballant. comb. nov., the southern Australian M. engelhartii (Foslie) Athanas. et D. L. Ballant. comb. nov., and the Indo-Pacific M. simulans (Foslie) Athanas. et D. L. Ballant. comb. nov.), Mastophoropsis, and Phymatolithopsis (the last genus being incertae sedis). As outgroups are selected two genera of Melobesiaceae: Melobesia (Melobesioideae) and Orthocarpa Athanas. et D. L. Ballant. gen. nov. (type: O. epicklonia Athanas. et D. L. Ballant. sp. nov. from southern Australia, placed in Orthocarpoideae Athanas. et D. L. Ballant. subfam. nov.). They share production of a fusion cell/gonimoblast just below the carpogonia and development of both lateral and orthostichous carposporangia, whereas the Mesophyllaceae develop carposporangia mainly laterally and produce a fusion cell/gonimoblast at the level of supporting cells. A further character distinguishing the Mesophyllaceae is the development of a cell tube, a prerequisite to transfer the zygote beyond the hypogynous cell to the subtending supporting (auxiliary) cell. Orthocarpa also accommodates several species previously placed in Synarthrophyton: Orthocarpa eckloniae (Foslie) Athanas. et D. L. Ballant. comb. nov., O. haptericola (Foslie) Athanas. et D. L. Ballant. comb. nov. (=Synarthrophyton schielianum), O. magellanica (Foslie) Athanas. et D. L. Ballant. comb. nov., O. papillata (G. W. Maneveldt, D. W. Keats, et Y. M. Chamb.) Athanas. et D. L. Ballant. comb. nov., O. munimenta (D. W. Keats et G. W. Maneveldt) Athanas. et D. L. Ballant. comb. nov., O. robbenensis (D. W. Keats et G. W. Maneveldt) Athanas. et D. L. Ballant. comb. nov., O. pseudospora A. S. Harv., Woelk., et A. Millar) Athanas. et D. L. Ballant. comb. nov., and O. chejuensis (J. Kim, H. Chung, D. Choi, et I. Lee) Athanas. et D. L. Ballant. comb. nov. The new family Lithothamnionaceae Athanas. et D. L. Ballant. nom. nov. (=“Lithothamniaceae H. J. Hees 1886” nom. illeg.) and the new combination Titanoderma chamberlainianum (Woelk. et S. T. Cambell) Athanas. et D. L. Ballant. comb. nov. (=Lithophyllum chamberlainianum) are proposed. A key to Mesophyllaceae subfamilies, tribes, and genera is presented.