A new Eocene fossil of the genus Phycopeltis (Ulvophyceae, Chlorophyta)

A fossil of the aerophytic green algal genus Phycopeltis (Trentepohliaes, Ulvophyceae) dated to 35 mya, is reported from the Pikopiko Fossil Forest, Southland, New Zealand. Previous reports of fossilized Phycopeltis have been subsequently synonymised with fungi by other authors; however, our specimen is not vulnerable to their criticisms. Inflated cells present in two approximately concentric rings are interpreted as gametangia, with irregular structures resembling the gametangial pores of modern material; sporophytic material is absent. The fossil resembles the modern disc-forming species P. novae-zelandiae, P. expansa, and P. arundinacea. The limited material available prevents the assignation of a specific epithet, but the habit and dimensions of the fossil clearly fall within those of modern representatives of the genus. Its single cell thickness throughout, absence of distinct melanisation, and larger size demonstrate that it is not a fungal shield. The specimen constitutes arguably the most convincing fossil belonging to Trentepohliales, and the first unambiguously for the genus Phycopeltis. It is consistent in age with other known fossils of the order that, when combined with molecular evidence, suggests a terrestrial radiation far more recent than that of land plants.