O complexo Dadoxylon-Araucarioxylon, carbonífero e permiano do gondwana: Estudo taxonômico do gênero Dadoxylon

Abstract

The Upper Palaeozoic flora of Gondwanan Realm is divided into two main groups, according to their taxonomic composition, one typical of the Upper Carboniferous floras and another typical of the Permian floras. The first one was composed of lycopsids, pteridosperms, cordaitaleans and ginkgoaleans, and the second one had Glossopteris Brongniart as the most typical genus, and was composed of several species ecologically different. This flora is today represented in the fossiliferous register by leaves and reproductive organs preserved as impressions/compressions and by permineralyzed woods. These woods were described since nineteenth century, mostly of them as Dadoxylon Endlicher and Araucarioxylon Kraus. However, since their original definitions, somewhat accurate, these generic names are being applied to different types of woods, creating a taxonomic complex containing a number of not necessary related forms. In the first part of this revaluation will be analyzed the species of Dadoxylon based on recent publications of the new conceptions established by different authors and the rules of ICBN (International Code of Botanical Nomenclature). As a result of the present study, among the 20 species identified in the literature, three of them were combined in the genus Dammudoxylon (Maheshwari) Maheshwari: Dammudoxylon arberi, D. waltonii and D. sp. (D. australe?); nine were considered as invalid: Dadoxylon cf. D. indicum, D. cf. Eristophyton, D. kumarpurensis, D. sp. Arber, D. sp. Walton, D. sp. Moonje, D. sp. Jacob, D. sp. Narasimhan and D. sp. Seward; five kept unaffected due the absence of enough diagnostic features preserved: Dadoxylon angustum, D. binneyi, D. brisbanense, D. maitlandi and D. williamsoni; and three were considered as part of new genera which will not be subject of this contribution: Dadoxylon butiense, D. sudanense and D. tordoxyloïdes.