High-Latitude Austral Fauna and Flora from the uppermost Cretaceous-lowermost Paleogene Takatika Grit, remote Chathams Islands, SW Pacific: the emergence and flooding of "Zealandia"

Before the 21st Century, avian and non–avian dinosaurs from the Mesozoic were unknown from any remote Southwest Pacific islands. In 2003, theropod dinosaur remains were discovered from the Takatika Grit, Chatham Islands (ca.865 km east of New Zealand, lat. 44°S, 176°W) in a mixed association of both terrestrial and marine fauna and flora. Further expeditions from 2004 to 2009, sponsored by the National Geographic Society Committee for Research and Exploration, have resulted in a previously unrecognized diversity of many groups of animals and plants in this condensed unit. Although scarcely 10m thick, the Takatika Grit preserves the remains of many species of theropod dinosaurs and possible other groups; partially articulated and associated skeletons of amongst the oldest recorded modern sea birds (at least four new groups); elasmosaur and mosasaur marine reptiles with associated skeletons; some nine families of fish; and diverse macroinvertebrates comprising bivalves, gastropods, cephalopods, and poriferans. Plants include exquisitely preserved conifer cones, gymnosperm and angiosperm wood and leaf shoots. Following its Late Cretaceous divergence from Marie Byrd Land, West Antarctica, the Chatham Peninsula was characterized by a tectonically dynamic, volcanic landscape with eroding horst blocks adjacent to flood plains and deltas with thick sediments being deposited in the half-grabens. Terrestrial organisms such as the dinosaurs would have evolved in isolation for millions of years after the separation from the Gondwanan margin, with the Chathams region becoming a refuge. The high biotic diversity on land and in shallow waters along this low-lying, narrow, crustal extension of Zealandia, reflects the greenhouse environmental conditions and associated upwelling centers off the Zealandian coast.