CONTRIBUTIONS FROM THE MUSEUM OF PALEONTOLOGY THE UNIVERSITY OF MICHIGAN VOL. 23, NO.8, p. 105-169 (2 pls., 10 text-figs.) FEBRUARY22, 1971 EVOLUTION OF THE FERN FAMILY OSMUNDACEAE BASED ON ANATOMICAL STUDIES BY CHARLES N. MILLER, JR. Department of Botany, University of Montana, Missoula 59801 MUSEUM OF PALEONTOLOGY THE UNIVERSITY OF MICHIGAN ANN ARBOR CONTRIBUTIONS FROM THE MUSEUM OF PALEONTOLOGY Director: ROBERTV. KESLING The series of contributions from the Museum of Paleontology is a medium for the publication of papers based chiefly upon the collection in the Museum. When the number of pages issued is sufficient to make a volume, a title page and a table of contents will be sent to libraries on the mailing list, and to individuals upon request. A list of the separate papers may also be obtained. Correspondence should be directed to the Museum of Paleontology, The University of Michigan, Ann Arbor, Michigan 48104. VOLS.2-22. Parts of volumes may be obtained if available. Price lists available upon inquiry. 1. The rodents from the Hagerman local fauna, Upper Pliocene of Idaho, by Richard J. Zakrzewski. Pages 1-36, with 13 text-figures. 2. A new brittle-star from the Middle Devonian Arkona Shale of Ontario, by Robert V. Kesling. Pages 37-51, with 6 plates and 2 text-figures. 3. Phyllocarid crustaceans from the Middle Devonian Silica Shale of northwestern Ohio and southeastern Michigan, by Erwin C. Stumm and Ruth B. Chilman. Pages 53-71, with 7 plates and 4 text-figures. 4. Drepanarter wrighti, a new species of brittle-star from the Middle Devonian Arkona Shale of Ontario, by Robert V. Kesling. Pages 73-79, with 2 plates. 5. Corals of the Traverse Group- of Michigan. Part 13, Hexagonaria, by Erwin C. Stumm. Pages 81-91; with 4 plates. 6. The Pliocene rodent Microtoscoptes disjunctus (Wilson) from Idaho and Wyoming, by Claude W. Hibbard. Pages 95-98, with 2 text-figures. 7. A new microtine rodent from the Upper Pliocene of Kansas, by Claude W. Hibbard. Pages 99-103, with 1 plate and 1 text-figure. EVOLUTION OF THE FERN FAMILY OSMUNDACEAE BASED ON ANATOMICAL STUDIES CHARLES N. MILLER, JR. Department of Botany, University of Montana, Missoula 59801 ABSTRACT-The fern family Osmundaceae has only 16 living species, but nearly 100 fossil species have been named on the basis of various detached organs. Most important of these are 29 species based on petrified axes which provide a partial but substantial record of the family from the Late Permian to the present. These axes and some of the Recent species have been important in the formulation of concepts of stelar evolution and in our understanding of the evolutionary relationships of living ferns, but an intensive investigation of the evolution of the species of the Osmundaceae has never been made. Thus, the purpose of the present work is to investigate the phylogenetic interrelationships of the species of the family as interpreted from anatomical and morphological characters of their stems, leaf-bases, and roots. Types or representative materials of 14 Recent and 21 fossil species were examined for variable characters. Information about nine additional species of petrified axes came from descriptions in the literature. These species were then analyzed by the ground plan method of multiple character correlation in three samples: (1) analysis of 43 species based on six characters, (2) analysis of 31 species based on 13 characters, and (3) analysis of 14 Recent species based on 18 characters. By this means the species were arranged according to lines of specialization, and when these lines are considered with respect to geologic time, nine groups of phylogenetically related species are resolved. Five of the groups are represented by the present-day genera and subgenera and their fossil members. Three groups are subdivisions of Osmundacaulis, and the remaining group includes the extinct protostelic forms. The results show large gaps between these groups. This indicates that the fossil record of the family contains only a small number of those species that existed in the past. It is evident, however, that the modern species evolved from protostelic ancestors by intrastelar origin of a pith and subsequent (or concurrent) dissection of the xylem cylinder by leaf-gaps. The living species and most of the fossil forms are products of slight modifications of the dictyoxylic-siphonostele plan of organization. However, two of the groups of species became highly specialized in the Mesozoic but died out near the close of that era. The Recent genera Todea and Leptopteris are as distinct from one another as each is from the subgenera Osmun- da, Osmundastrum, or Plenasium, but their fossil records are not sufficient to indicate their origin. Osmunda, Osmundastrum, and Plenasium were distinct lines of evolution in the Paleo- cene, and Osmunda and Plenasium are represented by foliage remains in the Cretaceous. No definite source for Osmunda and Osmundastrum can be determined, but Plenasium shares a number of characters with Osmundacaulis atherstonei and 0. natalensis, both of which are from the Lower Cretaceous, and they may have evolved from forms similar to these species. The Osmundaceae probably arose during Early Permian or Pennsylvanian time from forms similar to Grammatopteris baldaufi or G. rigolloti, but neither of these species can be considered a precursor of the family. Further, no ancestors of other fern taxa can be found amonq the known Osmundaceae. Taxonomically, the protostelic forms are treated in the subfamily Thamnopteroideae with the remaining species forming the subfamily Osmundoideae. CONTENTS Introduction ............................................................................................................................................................................. 107 Acknowledgments. ...................................................................................................................................................................107 Classlficatlon ............................................................................................................................................................................. 108 History of investigation ....................................................................................................................................................... 110 Materials and methods ........................................................................................................................................................... 111 Anatomy and morphology. -. ................................................................................................................................................... 112 Stem .................................................................................................................................................................................. 112 Stele ........................................................................................................................................................................... 112 Cortex ......................................................................................................................................................................... 118 Leaf-trace ................................................................................................................................................................. 119 Petiole base ....................................................................................................................................................................... 122 Root .................................................................................................................................................................................. 124 Stem branching ............................................................................................................................................................... 124 Growth habit ................................................................................................................................................................... 125 106 CHARLES N . MILLER. JR . Systematic descriptions based on stem. root. and leaf-base characters ...................................................................... 125 Order Filicales ........................................................................................................................................................................ 125 Family Osmundaceae ............................................................................................................................................................ 125 Key to the subdivisions based on anatomical characters ........................................................................................ 125 Subfamily Osmundoideae ....................................................................................................................................................... 127 Genus Osmunda ............................................................................................................................................................... 127 Subgenus Osmunda ......................................................................................................................................................... 127 0. regalis. ..................................................................................................................................................................