New Zealand Journal of Marine and Freshwater Research abstracts

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An early Paleogene sponge fauna, Chatham Island, New Zealand

Michelle Kelly

National Centre for Aquatic Biodiversity
and Biosecurity
National Institute of Water and Atmospheric
Research Limited
Private Bag 109 695, Newmarket
Auckland, New Zealand
email: m.kelly@niwa.co.nz

John S. Buckeridge

Earth and Oceanic Sciences (EOS) Research Institute
Auckland University of Technology
P.O. Box 92 006
Auckland, New Zealand

Abstract  A late Paleocene-early Eocene (c. 60-53 Ma) poriferan fauna, comprising hexactinellids (Class Hexactinellida), astrophorids (Class Demospongiae: Family Astrophorida), and lithistids (“lithistid” Demospongiae) has been identified from the Tutuiri Greensand outcropping on the north coast of Chatham Island, New Zealand. Most of the fossils are hexactinellids, comprising extremely delicate siliceous networks embedded in friable sandstone. The sediment matrix within and around these skeletons contains numerous siliceous demosponge spicules, many of which are exceptionally well preserved. The soft friable matrix of the Tutuiri Greensand has made extraction a relatively simple process, making taxonomic identification of the material, and comparison with adjacent Recent and other New Zealand Eocene faunas possible. These sponge body fossils and spicule microfossils indicate a fauna that was once dominated by hexactinellids, lithistid, and astrophorid demosponges. A qualitative comparison of the abundance and diversity of the Tutuiri Greensand sponge fauna with the present-day Chatham Rise sponge fauna indicates that the late Paleocene-early Eocene fauna is as diverse as the Recent fauna, for the hexactinellid sponges and astrophorid demosponges, and much more diverse for lithistid sponges. The paleoecology of the Tutuiri Greensand has been interpreted as inner to mid shelf water depths (50-250 m) but the poriferan fauna described here is more like that of the present-day soft sediment benthic environment of the Chatham Rise at 800-1200 m.

Keywords  Porifera; Hexactinellida; Demospongiae; lithistid; Paleocene; Eocene; paleobathymetry; Tutuiri Greensand; Oamaru Diatomite; Chatham Rise; Chatham Island

M04127; Online publication date 17 June 2005 Received 19 July 2004; accepted 14 February 2005
New Zealand Journal of Marine and Freshwater Research, 2005, Vol. 39: 899-914
0028-8330/05/3904-0899 © The Royal Society of New Zealand 2005

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