South polar greenhouse insects (Arthropoda: Insecta: Coleoptera) from the mid-Cretaceous Tupuangi Formation, Chatham Islands, eastern Zealandia

Abstract

Stilwell, J.D., Vitacca, J. & Mays, C., April 2016. South polar greenhouse insects (Arthropoda: Insecta: Coleoptera) from the mid-Cretaceous Tupuangi Formation, Chatham Islands, eastern Zealandia. Alcheringa 40, xxx–xxx. ISSN 0311-5518

Rare insect body fossils have been discovered for the first time after 175 years of research on the Chatham Islands, eastern ‘Zealandia’. The coleopteran (beetle) insects, dated to ca 95 Ma and extracted from fine-grained, upper delta plain facies in the lower Upper Cretaceous (Cenomanian–lowermost Turonian) Tupuangi Formation at Waihere Bay on the remote Pitt Island, represent the most southern, polar-latitude (ca 70–80°S) faunal assemblage from the Cretaceous recorded to date. Three species are represented in the insect fauna: a portion of a segmented abdomen of a probable carabid? ground beetle and two distinct coleopteran elytra, one preserved with a brilliantly iridescent carapace upon discovery, comparable with Cretaceous taxa within the Buprestidae (metallic wood borers), but identification with the Chrysomelidae (leaf beetles) or Tenebrionidae (darkling beetles) can not be discounted entirely. Another specimen has more weakly preserved greenish iridescence and has a morphology consistent with Carabidae; given the preservational deficiencies and rarity of material, the specimens are attributed to Buprestidae? genus et species indeterminate and Carabidae? genus et species indeterminate A and B, respectively. These coleopteran fossils represent the only recorded iridescence in Mesozoic invertebrates from Zealandia. Importantly, these mid-Cretaceous insects existed in South Polar forests near the height of the ‘hothouse’ phase of relatively warm, alternating intervals of full daylight in the summer months and total darkness during the winter, before eastern Zealandia diverged at ca 83 Ma from the Marie Byrd Land region of West Antarctica, as part of the final break-up of Gondwana.

Jeffrey D. Stilwell* [[email protected]], Jesse V. Vitacca [[email protected]] & Chris Mays [[email protected]], School of Earth, Atmosphere and Environment, Monash University, Clayton VIC 3800, Australia. *Also affiliated with the Australian Museum, 6 College Street, Sydney NSW 2000, Australia.

Key words:

• fossil beetles
• New Zealand
• iridescence
• Cenomanian–Turonian
• high-latitude
• Cretaceous greenhouse

Acknowledgements

Many individuals and institutions have supported this project, since the discovery of the first insects from the Chatham Islands in early 2012; they are: the Lanauze, Gregory-Hunt, Preece, and Tuanui families of the Chatham Islands; John Simes, GNS Science, Lower Hutt; Steve Morton, Monash University; Pedro Viegas and Hannah Carle, Monash University, for their expertise in the field and notes on insect herbivory in the Tupuangi Formation; Chava Rodriguez, Melbourne, for fossil preparation and fieldwork assistance; Sarah Martin, Geological Survey of Western Australia, Perth, and Dan Bickel, Australian Museum, Sydney for their collective expert advice on the fossil coleopterans. Alcheringa Editor, Stephen McLoughlin, Julián Petrulevicius and an anonymous reviewer improved the manuscript greatly, and we thank them for their efforts. This research was supported by an Australian Research Council Linkage Project (ARC-LP0989518) to JDS. We wish to dedicate this paper to the late New Zealand palaeontologist Joan Wiffen (1922–2009), who became fascinated well into her 80s by the frontier research and new fossil discoveries on the Chatham Islands, especially Cretaceous terrestrial ecosystems of eastern Zealandia. We acknowledge the Moriori people as the original landowners of Rangiauria (Pitt Island).