The mostly submerged continent of Zealandia may have been much closer to land level than previously thought, providing pathways for animals and plants to cross continents from 80m years ago, an expedition has revealed.

Zealandia, a for the most part underwater landmass in the South Pacific, was declared the Earth's newest continent this year in a paper in the journal of the Geological Society of America. It includes Lord Howe Island off the east coast of Australia, New Caledonia and New Zealand.

On Wednesday researchers shared findings from their two-month-long expedition, one of the first extensive surveys of the region, announcing fossil discoveries and evidence of large-scale tectonic movements.

"The discovery of microscopic shells of organisms that lived in warm shallow seas, and spores and pollen from land plants, reveal that the geography and climate of Zealandia was dramatically different in the past," said Prof Gerald Dickens of Rice University.