SOME NEW PLANT FINDS FROM THE POSONGCHONG FORMATION OF YUNNAN, AND CONSIDERATION OF A PHYTOGEOGRAPHIC SIMILARITY BETWEEN SOUTH CHINA AND AUSTRALIA DURING THE EARLY DEVONIAN

The new plants documented here, including a representative of the trim erophytes Psilophyton primitivum sp. nov., a questionable rhyniophyte or trimerophyte Hedeia sinica sp. nov., a prelycopod Baragwanathia sp. and two species of zosterophyllophytes, Zosterophyllum australianum L ang and Cookson 1930 and Z. sp. 1, from the Posongchong Formation of s outheastern Yunnan, China, add to the known floral diversity of the Ea rly Devonian of this region. Two sections of the Posongchong Formation , Changputang section of Wenshan district and Gegu section of Mengzi d istrict also are introduced. After comparing the plants with those of the coeval flora of Australia and considering the data of recent paleo continental reconstructions, the authors suggest that there is a north eastern Gondwana phytogeographic unit during the early Devonian compri sing Australia, South China Block and perhaps Shan-Thai Block. The sim ilarity of the floral component between Australia and South China is d iscussed. Because both Australia and South China also have dominant or endemic taxa, each might be recognized as a subunit, separately chara cterized by Hedeia for Australia and Eophyllophyton for South China.