2 NEW SPECIES OF PTEROSTOMA RS HILL FROM CENOZOIC SEDIMENTS IN AUSTRALASIA

Two new species of the probable zamiaceous cycad Pterostoma are descri bed from Australia and New Zealand. The Australian species, P. hirsutu s, from Early Eocene sediments in western Tasmania, represents the old est confirmed record of the genus, while the New Zealand species, P. d ouglasii, from Miocene sediments in the South Island, represents the m ost recent confirmed record and extends the known distrbution of the g enus away from southern Australia. Pterostoma has many morphological s imilarities with Dioonopsis, a zamioid cycad from the Palaeogene of Ja pan. The possible ecology of Pterostoma is discussed and the significa nce of its clean abscission of fronds at the prevailing very high lati tudes where it occurred is considered.