1254 TAXON 58 (4)  November 2009: 1254–1280 Bateman & Hilton  Palaeobotanical systematics INTRODUCTION Do not be hasty, that is my motto. But if I had seen you, before I heard your voices, … I should have just trodden on you, taking you for little Orcs, and found out my mistake afterwards. Very odd you are, indeed. Root and twig, very odd! — Treebeard to Merry and Pippin, in J.R.R. Tolkien, 1954: 78, The Two Towers. Unwin, London. Palaeobotanical systematics differs considerably from neobotanical systematics. This statement may appear pat- ently obvious, yet any taxonomic novice reading the latest manifestation of the International Code of Botanical No- menclature (ICBN: McNeill & al., 2006) could be forgiven for not realising the truth, and the far-reaching implica- tions, of this simple statement. Through the last 35 years the ICBN has been almost completely shorn of the spe- cial clauses previously awarded to fossil plants. Only the nebulous concept of the ‘morphotaxon’—“a fossil taxon which, for nomenclatural purposes, comprises only the parts, life-history stages, or preservational states repre- sented by the nomenclatural type” (McNeill & al., 2006: 4)—remains as an impractical vestige of once-functional and mutually supporting concepts of the organ-genus and the form-genus. Both of these crucial concepts ultimately reflected in part contrasting preservation states observable Palaeobotanical systematics for the phylogenetic age: applying organ- species, form-species and phylogenetic species concepts in a framework of reconstructed fossil and extant whole-plants Richard M. Bateman 1,2 & Jason Hilton 2 1 Jodrell Laboratory, Royal Botanic Gardens Kew, Richmond, Surrey, TW9 3DS, U.K. r.bateman@kew.org (author for correspondence) 2 School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, U.K. A typical vascular land-plant consists of ten to twelve definable organs. Most plant fossils have been disarticulated into their component organs, which must therefore be correlated if the fossil plant is to be understood holisti- cally and compared with its presumed descendants in the extant flora. The resulting conceptually reconstructed whole-plants are the crown jewels of palaeobotany, as they permit full morphological comparison with extant plants and provide templates that guide through reciprocal illumination further attempts at reconstruction. Each of the three lines of evidence facilitating whole-plant reconstruction (association/dissociation, morphological similarity and organic connection) yields only a probability statement that the organs in question have been successfully correlated. Disarticulation means (1) that phenotypic variation can be studied only at the level of individual organs, and (2) that in order to be distinguished from all other kinds of the same organ, an organ must bear a unique morphological character state (autapomorphy). In our terminology, each definable kind of organ is an organ-species. The few organ-species perceived as possessing autapomorphies (and thus as unique) are termed autapospecies, whereas the remaining organ-species characterise more than one whole-plant species and hence are termed form-species. The distinction between autapospecies and form-species is dependent on the range of taxa sampled and is wholly character-based; the age of the fossils under comparison is irrelevant, and the state of preservation is relevant only through its influence on the range of characters that can realisti- cally be scored. None of the many other species concepts recognised by (palaeo)biologists is applicable to fossil plants. Our ability to apply this phylogenetically-inspired approach and terminology to formal taxonomy has been increasingly compromised by modifications to successive editions of the International Code of Botanical Nomenclature, culminating in the 2001 and 2006 Codes which reduced palaeobotanical provision to the fatally over-generalised ‘morphotaxon’ concept. A more conceptually rigorous, palaeobotanically informed revision of the Code, placing nomenclature more clearly in the service of taxonomy, would strengthen the crucial roles of reconstructed plants within palaeobotany and of palaeobotany within 21st Century science. KEYWORDS: autapomorphy, autapospecies, core taxon, disarticulation, form-species, ICBN, organ- species, palaeobotany, reciprocal illumination, satellite taxon, species concepts, whole-plant reconstruction PALAEOBOTANY