The first Early Pleistocene (ca 1 Ma) fossil terrestrial vertebrate fauna from a cave in New Zealand reveals substantial avifaunal turnover in the last million years

Abstract

New Zealand has a rich Late Pleistocene–Holocene vertebrate fossil record with numerous sites across the country in dune, cave and wetland deposits, collectively providing detailed knowledge on the composition and distribution of the immediately pre-human avifauna. In contrast, older Pleistocene terrestrial vertebrate fossil deposits are unknown in New Zealand caves and are otherwise limited to the Early Pleistocene Marton beach deposit and isolated bones (mainly dinornithiforms) from Early–Middle Pleistocene marine sediments. The Late Pleistocene to late Holocene record reveals no species turnover in the avifauna until human arrival in the latest Holocene (ca 750 years before present [ybp]) precipitated a cascade of extinctions and faunal replacement. However, substantial differences between the avifaunas of the Early Miocene St Bathans Fauna and the Holocene reveals major turnover also occurred prior to the Late Pleistocene but the timing and hence drivers of this turnover are unknown. Here we report the discovery of the first Early Pleistocene vertebrate fauna from a New Zealand cave. It derives from deposits in Moa Eggshell Cave, near Waitomo Caves, North Island, that are constrained in age by the presence of two key marker tephra beds, from the earlier 1.55 million year (Ma) old Ngaroma and later 1 Ma Kidnappers eruptions and a 535 thousand year (ka) old speleothem date on the sediment’s top surface. This fauna includes four species of frog (Leiopelma spp.) and 12 species-level taxa of birds of which minimally four and probably six are not known from Late Pleistocene avifaunas. Two species are described as new, Strigops insulaborealis sp. nov. (Strigopidae) and Porphyrio claytongreenei sp. nov. (Rallidae), and a phabine species of columbid is reported from the New Zealand avifauna for the first time. This pre-Kidnappers-tephra fauna therefore reveals 33–50% species turnover in the avifauna in the last 1 Ma that coincides with the increased magnitude of glacial-interglacial climate oscillations during this period. The timing and presence of deposits from the 1 Ma Kidnappers supereruption suggests, however, that volcanism may have also influenced species turnover at this crucial time interval, with widespread pyroclastic flows and thick ashfall impacting on many ground-dwelling bird species. Zoobank LSID of publication: urn:lsid:zoobank.org:pub:A16F0299-038B-45A3-AD58-CDE1BCE2A2B2 Trevor H. Worthy* [trevor.worthy@flinders.edu.au], College of Science and Engineering, Flinders University, PO Box 2100, Adelaide, South Australia, Australia. R. Paul Scofield [pscofield@canterburymuseum.com], Canterbury Museum, Private Bag 4744, Christchurch 8154, New Zealand; Sneha Suresh [snehasuresh.24@gmail.com], School of Environment, University of Auckland, PO Box 92019, Auckland, New Zealand; Simon J. Barker [simon.barker@vuw.ac.nz], School of Geography, Environment and Earth Sciences, Victoria University of Wellington, PO Box 600, Wellington 6140, New Zealand; Colin J. N. Wilson [colin.wilson@vuw.ac.nz], School of Geography, Environment and Earth Sciences, Victoria University of Wellington, PO Box 600, Wellington 6140, New Zealand; Paul W. Williams [p.williams@auckland.ac.nz], School of Environment, University of Auckland, PO Box 92019, Auckland, New Zealand; Joel A. Baker [joelallenbaker@gmail.com], School of Environment, University of Auckland, PO Box 92019, Auckland, New Zealand.