The classification of early land plants-revisited* Harlan P. Banks Banks HP 1992. The c1assificalion of early land plams-revisiled. Palaeohotanist 41 36·50 Three suprageneric calegories applied 10 early land plams-Rhyniophylina, Zoslerophyllophytina, Trimerophytina-proposed by Banks in 1968 are reviewed and found 10 have slill some usefulness. Addilions 10 each are noted, some delelions are made, and some early planls lhal display fealures of more lhan one calegory are Sel aside as Aberram Genera. Key-words-Early land-plams, Rhyniophytina, Zoslerophyllophytina, Trimerophytina, Evolulion. of Plant Biology, Cornell University, Ithaca, New York-5908, U.S.A. 14853. Harlan P Banks, Section ~ ~ ~ <ltm ~ ~-~unR ~ qro ~ ~ ~ f~ 4~1~"llc"'111 ~-'J~f.f3il,!"~, 'i\'1f~()~~<1I'f'I~tl'1l ~ ~1~il~lqo;l~tl'1l, 1968 if ~ -mr lfim;j; <fr'f ~<nftm~~Fmr~%1 ~~ifmm~~-.mtl ~if-.t~m~fuit ciit'!'f.<nftmciit~%1 ~ ~ ~ -.m t ,P1T ~ ~~ lfiu ~ ~ -.t 3!ftrq; ~ ;j; <mol ~ <Rir t ;j; w -.m tl FIRST, may I express my gratitude to the Sahni, to survey briefly the fate of that Palaeobotanical Sociery for the honour it has done reclassification. Several caveats are necessary. I recall me in awarding its International Medal for 1988-89. discussing an intractable problem with the late great May I offer the Sociery sincere thanks for their James M. Schopf. His advice could help many consideration. aspiring young workers-"Survey what you have and Secondly, may I join in celebrating the work and write up that which you understand. The rest will the influence of Professor Birbal Sahni. The one time gradually fall into line." That is precisely what I did I met him was at a meeting where he was displaying in 1968. enthusiastically an angiosperm flower embedded in I sought major trends among the so-called a translucent matrix that he had collected recently. Psilophytales that anyone could see and left aside all All of us were captivated by his infectious the peripheral genera that for one reason or another personaliry and concer'n for palaeobotany. As a did not fit. Perhaps they lacked fertile parts or young man, I spent considerable time seeking conducting cells or details of branching. Perhaps copies of his publications through book dealers. they were only short-lived geologically. Perhaps they Without question, he made a profound impact on illustrated aberrant body plans in which world palaeobotany. characteristics had been assembled evolutionarily in Almost a quarter century ago I suggested a unexpected ways producing organisms that were reclassification of some Devonian taxa (Banks, 1968) new to our biases. They were no more than dead­ particularly because Psilophytales had become a end variations related to no other organisms. catchall group for obviously unrelated organisms Edwards and Edwards (1986) expressed my thinking and for indeterminable fragmentary fossils. That was precisely when they wrote (p. 216) "We find it at the lOath anniversary of the founding of Peabody neither necessary nor desirable to fit every species Museum, Yale Universiry. It seems appropriate at into a lineage." If we can see characteristics so another lOath anniversary, of the birth of Birbal Essays In Evolu,Jonary Plan! Biology Ed/lors : B. S, Venkal.achala, David L Dllcher & Hari K. Maheshwari "Reprinted from GeophYlOlogy, voL 21, 1992. Publisher: Birbal Sahni Insrirute of PalaeobOlany, lucknow BANKS-CLASSIFICATION OF EARLY LAND PLANTS 37 assembled as to produce plants that illustrate major anisotomously, pseudomonopodially or trends or lineages leading to subsequent younger adventitiously, bore terminal sporangia on main axes floras, then we certainly can visualize the possibility or on laterals of limited growth, and probably had of so assembling characteristics as to produce centrarch xylem strands. ephemeral organisms outside the major trends. Such Edwards and Edwards (1986) excluded plants a scenario might parallel that in the Cambrian with overtopping and pseudomonopodial branching Burgess shale where animals thought to be from Cooksonia (p. 202) and suggested (p. 203) that arthropods proved to be constructed on body plans the change from dichotomous to pseudomonopodial different enough to constitute new phyla. But of all branching was a major change in development. I am the variations only four survived the Cambrian and convinced that this change in the activity at the apex persisted as the four lineages now seen in of the stem is sufficiently important to distinguish Arthropoda. Similarly, none of the- most aberrant rhyniophytes with predominantly dichotomous plants of the early flora appear to have survived branching from other groups. Hence, I prefer to omit Devonian time. JUSt as examples of such plants, I from Rhyniophytina plants with obvious think of Germanophyton, Enigmophyton, pseudomonopodial growth. For example, Edwards Pia typhyllum, Barrandeina, and DUisbergia. and Edwards (1986) suggested that Cooksonia I see no reason now to depart from Schopfs pertonii and C. hemisphaerica in Ananiev and advice nor to change my approach from a search for Stepanov (1969) be excluded from Cooksonia major trends. So this talk is but a quick overview of because they branch pseudomonopodially. They changes since 1968 and my revision thereof (Banks, would erect a new genus for the two plants. I agree 1975 ). but would go one step farther and exclude them Many papers are omitted for lack of time or from Rhyniophytina, restricting the latter to simple space and my own unfamiliarity with the organisms. dichotomous branching. I emphasize suprageneric categories and minimize Edwards and Edwards (1986) also pointed to generic descriptions of early land plants. The the number of genera of rhyniophytes for which citations will lead one to full descriptions of genera, neither true tracheids nor intact vascular strands species, and the dynamic aspects of the early flora. have been found in fertile specimens. Though The latter include the physiological requirements of wi II ing to consider these plants as members of the move to land, the life history strategies involved, Rhyniophytina, they suggested grouping them the ecological conditions under which the informally under the heading "rhyniophytoid", a transmigrants had to sUlvive, the evidence for life on term apparently coined by Pratt et at. (1978). The land as early as Ordovician time, the stories told by group so designated includes genera that clearly microfossils (spores, bits of cuticle, elongate tubes), look like rhyniophytes and even a genus, Cooksonia, the phytogeography of Siluro·Devonian time all of that has come to be regarded as the oldest vascular which are being developed rapidly. Papers such as plant. Gray (1984), Selden and Edwards (1989), Edwards Table 1 is a comparison of my (1975) (1982, 1986), Edwards and Fanning (1985), assignments to Rhyniophytina, those of Edwards and Raymond, Parker and Barrett (1985), Raymond Edwards (1986) and my present thinking. Comments (1987) and references therein will quickly introduce on the listing follow. a reader to some of these significant and intriguing Rhynia gwynne-vaughanii (Text-figure lA) as approaches to early land plant evolution. revised by David Edwards (1980) still is a relatively Simple, dichotomizing rhyniophyte despite Edwards' RHYNIOPHYTINA demonstration of the abscission of its sporangia, its adventitious branching, and the resulting tendency I proposed (1968) this subdivision of toward overtopping. Tracheophyta for plants with naked axes bearing Uskiella spargens Shute and Edwards (1989) fusiform or globose sporangia and with centrarch branches isotomously and bears terminal, elliptical xylem strands. sporangia with complex walls, has no dehiscence, Dianne Edwards and collaborators, using a and has a conducting system of tracheids. This multifaceted approach, have greatly expanded our recent addition (Text-figure IB) to the rhyniophytes knowledge of the earliest land plants. She and David becomes the most typical proven member of the Edwards (1986) summarized the taxonomic group if nearly all others fall into the rhyniophytoid conclusions and their paper is basic to my review. category. They broadened the concept of Rhyniophytina to I omit Hostinella and Aphyllopteris because they include naked axes that branch isotomously, are form genera for vegetative dichotomizing or 38 THE PALAEOBOTANIST Table I-Taxa Included In RhyoJopbytlna by Banks (1975), Edwards and Edwards (1986), and the present paper (for some omitted genera see Table 2) Banks 1975 Edwa,rds and Edwards 1986· This paper Rhyniophytina Rhyniophytina Rhyniophytina Rhyniaceae Rhyniaceae Rhyniaceae Rhynia Rhynia gwynne·vaughanii Rhynia gwynne'vaughanii Kidston & Lang 1917 Horneophylon Taeniocrada (T. decheniana) Uskiel/a spargens Shute & Edwards 1989 Cooksonia Renalia (pro parle) Sleganolheca Hoslinel/a (pro parle) Rhyniophytoids Salopel/a APhyl/opleris (pro parle) Cooksonia Lang 1937 DUloilea Eogaspesiea Daber 1%0 Eogaspesiea Rhyniophytoids Sleganolheca Edwards 1970 Eogaspesiea Sa/opel/a Edward~ & Richardson 1974 Questionable Rhyniophytina Cooksonia Eorhynia Ishchenko, 1975 Taeniocrada Sleganolheca Hedeia Cookson 1935 Hicklingia Sa/opel/alEorhynia Yarravia Lang & Cookson 1935 NOlhia HedeialYarravia Caia Fanning, Edwards & Richardson 1990 Yarravia Duloilea pu/chra H<t>eg 1930 Hedeia Questionable Rhyniophytina Duloilea Hsua Horneophylon Excluded Genera NOlhia Rhynia major (Ag/aophylOn) Hicklingia pseudomonopodial axes that might be derived from from unattached, presumed rhizomes. a wide range of plants, not