ASPECTS OF PERMIAN PALAEOBOTANY AND PALYNOLOGY. VI. TOWARDS A FLEXIBLE SYSTEM OF NAMING PALAEOZOIC CONIFERS

Abstract

SUMMARY A natural classification of extinct conifers requires the recognition of natural taxa. In conifers reproductive organs provide the most successful characters for delimiting natural genera and families. Based on assembled species, a genus should at least be diagnosed in terms of overall morphology of leafy shoots in combination with the organization of ovuliferous organs. In addition, detailed statements about the epidermal structure are of great practical value. However, most taxa of fossil conifer remains are artificial by implication. Most genera are form-genera, established for all kinds of isolated organs. They have a highly variable degree of artificiality, ranging from taxa comprising fragments which only supposedly belong to conifers, to taxa which can be attributed to a natural family. Fossil conifer taxonomy should recognize the variable status of the taxa to which plant fragments may be assigned. Within a framework of natural genera and varied form-genera, it is possible to integrate taxonomic progress through a “promotion” of taxa. If better preserved material permits a more thorough analysis, species may be transferred to more precisely defined form-genera or even to a natural genus. Some form-genera may gain a natural status through adequate redefinition. Such a flexible procedure is introduced as a possibility to rationalize Late Carboniferous – Permian conifer taxonomy. Within the Walchiaceae one may recognize the three natural genera Walchia Sternberg, Ernestiodendron Florin and Ortiseia Florin. Form-genera explicitly related to this family are Culmitzschia Ullrich (foliage with preserved epidermal structure), Walchiostrobus Florin (ovuliferous organs) and Walchianthus (polliniferous organs). The present state of species assignment is reviewed. The new form-genus, Hermitia Kerp et Clement-Westerhof is established in order to accommodate part of the many species, formerly assigned to Walchia, which can only be diagnosed in terms of overall leaf morphology; the included species are not explicitely related to the Walchiaceae. The following new combinations are introduced (Kerp et Clement-Westerhof): Culmitzschia parvifolia, Hermitia arnhardtii, H. bertrandii, H. carpentieri, H. dawsonii, H. gallica, H. geinitzii, H. germanica, H. imbricatula, H. minuta, H. rigidula, H. schlotheimii, H. schneideri, H. stephanensis, and H. whitei.