New Zealand Journal of Marine and Freshwater Research abstracts
A recent sponge, Pleroma aotea Kelly (“Order” Lithistida: Family
Pleromidae), in the late Eocene Ototara Limestone of Otago, New Zealand
Michelle Kelly1
Daphne Lee2
Shane Kelly1
John S. Buckeridge3
National Institute of Water and Atmospheric Research Limited
Private Bag 109 695
Newmarket
Auckland, New Zealand
2Department of Geology
University of Otago
P.O. Box 56
Dunedin, New Zealand
3Earth and Oceanic Sciences Research Centre
Auckland University of Technology
Private Bag 92 006
Auckland, New Zealand
Abstract Numerous remarkably well-preserved lithistid
sponges recovered from the late Eocene-early Oligocene Ototara Limestone at
Kakanui, North Otago, represent the first sponge body fossils to be described
from the New Zealand Cainozoic. The sponges are scattered throughout a 1-3-m-thick
volcaniclastic limestone horizon immediately overlying the Kakanui Mineral
Breccia. The fossils are now solid calcite, the former siliceous skeleton
having been replaced during diagenesis. The Kakanui sponges are the only known
body fossils remaining from an extremely diverse sponge fauna which formed
a major component of the benthos in the Kakanui-Oamaru region in late Eocene-early
Oligocene times (c. 35-33 Ma). The sponge body fossils are described and
compared with living sponges that have a similar flattened globose morphology.
The fossils are morphologically indistinguishable from the living lithistid
sponge Pleroma aotea Kelly (“Order” Lithistida: Family Pleromidae)
from deep-water seamounts and banks off north-eastern New Zealand, and are
significant in that they represent a stratigraphic range for the species of
more than 35 million years. The present-day distribution of P. aotea,
limited to silica-rich deeper waters, is in marked contrast to the relatively
shallow warm water volcanic environments occupied during the Palaeogene. This
restriction, and that of related lithistid sponges to silica-rich deeper waters
off northern New Zealand, is paralleled in other demosponges and several calcareous
invertebrate groups such as barnacles, bryozoans, and crinoids.
Keywords fossil Porifera; Demospongiae; Lithistida;
Pleroma aotea; Ototara Limestone; Kakanui; Oamaru; Eocene; Oligocene; New
Zealand
M02022 Received 2 April 2002; accepted 26 July 2002; Published 20 March
2003
New Zealand Journal of Marine and Freshwater Research, 2003, Vol. 37:
129-148
0028-8330/03/3701-0129 $7.00 © The Royal Society of New Zealand
2003
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