Mildenhall & Byrami-Redescription of Podosporites parvus

New Zealand Journal of Botany abstracts

A redescription of Podosporites parvus (Couper) Mildenhall emend. Mildenhall & Byrami from the Early Pleistocene, and late extinction of plant taxa in northern New Zealand

D. C. Mildenhall

Institute of Geological & Nuclear Sciences
P.O. Box 30 368
Lower Hutt, New Zealand

M. L. Byrami

School of Environmental and Marine Sciences
University of Auckland
Private Bag 92 019
Auckland, New Zealand

Abstract Numerous specimens of the conifer pollen grain Podosporites parvus, recorded at c. 1.32 Ma in the Pliocene-Pleistocene Puketoka Formation, suggest that the parent plants inhabited the fringes of lowland, coastal hardwood/podocarp forest. This pollen type has a botanical affinity with Microcachrys and Microstrobos (Podocarpaceae), which are prostrate to small shrubs currently inhabiting alpine and sub-alpine rocky outcrops, especially in wet areas, and around mountain tarns in Australia. The deposition site also features pollen of Nothofagus (Fuscospora), Dacrydium cupressinum, and several other tall trees, but is dominated by Nestegis. It also contains two extinct mesothermal taxa. The presence of a member of the Australian alpine conifer Microcachrys/Microstrobos group in an Early Pleistocene lowland pollen record from northern New Zealand suggests that such prostrate to small shrub-like conifers may have occupied different geographic and ecological ranges then than they do today. Moreover, it indicates that the vegetation assemblages have no modern New Zealand equivalent. P. parvus is re-described and diagnosis emended to highlight its distinctive irregular sacci and granulate-rugulate cappa, characteristics that distinguish it from other trisaccate grains attributed to Podosporites. The discovery of numerous pollen grains of an extinct species in these Early Pleistocene sediments is additional evidence that northern North Island was the last refuge for many New Zealand plants as they dwindled into extinction with the onset of cooler conditions.

Keywords palynology; fossil conifer pollen; Podocarpaceae; Podosporites parvus; Microcachrys; paleoenvironment; Pleistocene; Castlecliffian Stage; Auckland; extinct taxa

B02028 Received 27 March 2002; accepted 25 September 2002; published 31 March 2003
New Zealand Journal of Botany, 2003, Vol. 41: 147-160
0028-825X/03/4101-0147 $7.00 © The Royal Society of New Zealand 2003

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