Credit: ROYAL SOCIETY

Proc. R. Soc. B. doi:10.1098/rspb.2008.1785 (2009)

Two conflicting theories explain the heritage of New Zealand's current flora and fauna.

Sea levels rose 25 million–22 million years ago, and some believe that the landmass was completely submerged during this time and then repopulated later by transoceanic voyagers. Others hold that the land was only ever partly submerged, and that the ancestors of some of today's resident species have been there since New Zealand separated from other continents, 82 million–60 million years ago.

Marc Jones of University College London and his colleagues identified fossil jaw bones and teeth (pictured) of a rhynchocephalian reptile, a relative of the extant New Zealand tuatara. Given the fossil's age — 19 million–16 million years — these lizard-like creatures would have had less time to repopulate the landmass than had previously been thought, suggesting that New Zealand was never fully underwater and has been home to the tuatara's ancestors since the time of the dinosaurs.