Journal of the Royal Society of New Zealand Early ...

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Early Miocene flora of the Manuherikia Group, New Zealand. 4. Palm remains Mike Pole

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Department of Geology , University of Otago , P.O. Box 56, Dunedin , New Zealand Published online: 14 Jun 2013.

To cite this article: Mike Pole (1993) Early Miocene flora of the Manuherikia Group, New Zealand. 4. Palm remains, Journal of the Royal Society of New Zealand, 23:4, 283-288, DOI: 10.1080/03036758.1993.10721226 To link to this article: http://dx.doi.org/10.1080/03036758.1993.10721226

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©Journal of The Royal Society of New Zealand, Volume 23, Number 4. December 1993, pp 283-288

Early Miocene flora of the Manuherikia Group, New Zealand. 4. Palm remains Mike Pole*

Downloaded by [121.75.216.62] at 18:21 12 October 2014

The fossil palm Seaforthia zeelandica Ettingshausen from the early Miocene fluviallacustrine Manuherikia Group of Central Otago, New Zealand, is redescribed as Phoenicites zeelandica. The redescription is based on new material including fronds, inflorescences and fruits. Keywords: Nikau, Phoenicites, Rhopalostylus sapida, paleobotany

INTRODUCTION One of the New Zealand plant fossils described in the pioneering work of Ettingshausen (1887, 1891) is the palm, Seaforthia zeelandica. Recent collecting in Miocene strata of the Manuherikia Group in Central Otago, South Island, has provided several specimens of palm fronds which appear to be identical to Ettingshausen' s illustrations, but which are more complete. It is possible that they may come from the type locality of S. zeelandica. The new material, which includes reproductive organs, allows redescription of the taxon, and in light of more recent philosophy, a revised taxonomic placement. LOCALITIES AND AGE The plant-bearing Manuherikia Group was deposited during the Miocene as a complex of fluvial, lacustrine, and associated facies on top of a deeply weathered, and possibly peneplained, schist basement. Douglas (1986) has produced a detailed analysis of Manuherikia Group sedimentology, stratigraphy and paleogeography. The palm fossils come from three localities within the Manuherikia Group which are cited according to the New Zealand Geological Society Fossil Record system (Fig. I). The most important, F41/f245, crops out in the north bank of the Kawarau River about 3 km upstream of its confluence with the Clutha River. It is interpreted to have been a well drained swamp. This locality has been inundated with water by Lake Dunstan, which formed behind the Clutha Dam. The other two localities, F41/f218 and F41 /f236, lie 2.5 km to the south west, in the valley of the Bannockburn, 400 m upstream of its confluence with the Kawarau River. F41/f218 is interpreted as accumulating in a poorly drained swamp and F41/f236 in an interdistributary bay. They have narrowly avoided being flooded by Lake Dunstan. Palynological evidence (Mildenhall, 1989; Mildenhall and Pocknall, 1989) does not constrain the age of the plant fossils in the lower Manuherikia Group closer than Early to Middle Miocene (Otaian to Lillbumian local stages). Localities F41/f236 and F41/f218 are roughly lateral equivalents. Specimens prefixed with OU- are catalogued in the collection of the Department of Geology, University of Otago. Specimens prefixed with 1 L- were collected and catalogued privately several years ago. All material is currently housed in the Department of Geology, University of Otago.

*Department of Geology, University of Otago, P.O. Box 56, Dunedin, New Zealand. Present address: Department of Plant Science, University of Tasmania, G.P.O. Box 252C, Hobart, 7001 Australia.

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Journal of The Royal Society of New Zealand, Volume 23, 1993

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Fig. I - Locality map.

METHODS Organic material is not preserved, except for masses of carbon in the palm seeds; the fronds are preserved only as three dimensional impressions. The material was prepared using a vibrating chisel powered by compressed air, and some of the larger specimens were first plaster-jacketed in a manner similar to that used for vertebrate fossils. SYSTEMATICS Ettingshausen ( 1887, 1891) placed his palm specimens into the genus Seaforthia Brown, an Australian plant, later synonymised with Ptychosperma, Labill. by Bentham ( 1878). Read and Hickey ( 1972) have pointed to the great difficulty in identifying modem palms accurately from their leaves alone, and state that "no attempt should be made to place fossil palm fragments in genera of modem palms unless unquestionably identifiable with them". The fossil material from Central Otago fits two of the criteria listed by Read and Hickey which indicate placement in the family Palmae: the leaf segments are plicate, and they have a strong, uniform mid-vein. However, instead of the mid vein being bounded on either side by two orders of parallel veins, the fossil specimens display another three vein orders, and veins of the two highest orders alternate with each other. This observation prompted a closer look at several extant palm taxa, in which the number of vein orders was found to be similar. Read and Hickey have formalised a system of organ genera to be used for fossil palm material in the absence of characters other than general leaf morphology. Ettingshausen' s species is placed into the appropriate organ genus, Phoenicites, which covers "unarmed, simple or compound pinnate-leaved palm remains with reduplicate pinnae" (Read and Hickey, 1972). It may be used until better preserved reproductive material is discovered.

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Pole -Miocene palm, Manuherikia Group

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e Fig. 2 - palm remains, (a) schematic representation of venation in a single pinna of Seaforthia zeelandica, (b) portion of inflorescence OU29961, F41/f245, (c) Seaforthia zeelandica midrib and pinnae attachment OU29955, (d-f) Seaforthia zeelandica fronds, (d) OU29955, F41/f245, (e) 1L544, F41/f218, (f) OU29962, F41/f245.

TAXONOMY Family PALMAE Genus Phoenicites, (A.Brongniart) Read and Hickey 1972 Type species: Phoenicites pumila, A.Brongniart, 1828.

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Fig. 3 -Palm remains - Seaforthia zeelandica, (a) Midrib and proximal portions of pinnae (OU2995), (b) Three palm spikes (OU29961, arrowed), with a spike of a Recent Nikau (Rhopalostylus sapida) for comparison, (c) Dense accumulation of palm fruits (0U29424), (d) Close-up of a spike of a Recent Nikau (Rhopalostylus sapida), (e) Close up of a spike of Seaforthia zeelandica (OU29961).

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Pole -Miocene palm, Manuherikia Group

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Phoenicites zeelandica Fig. 2, 3 Seaforthia zeelandica Ett. 1887 Seaforthia zeelandica Ett. 1891: 261 Plate 24, fig. 25.


Lectotype (Designated by Gregg, 1975) Canterbury Museum specimen zp169. Paralectotype: Otago Museum specimen c.48.45. Slab containing fragments of the mid portions of several pinnae.

Vegetative material Fig. 2, 3a Occurrence and referred specimens F41/f218 1L544 F41/f236 OU13229 F41/f245 OU29955 OU29957 OU29958 OU29962 OU29963 OU29968 OU29969 OU29973 OU29975 OU29976 OU29977 OU29997 OU29998 Type locality The label attached to the paratype states "Gold Fields Department District of Dunstan. Clay containing fossils from Kawarau Basin". This makes it very likely that it comes from the Bannockburn - Cromwell region, while the appearance of the matrix makes it highly probable that it is from locality F41/f245. Description Frond pinnate, simple. Rachis over 700 mm long, straight, at least 30 mm wide, not tapering significantly over 700 mm. Pinnae reduplicate on axial surface, often constricted at base, evenly spaced, length may exceed 390 mm, tapering from 41 mm to 19 mm. Maximum pinna width 52 mm. Pinnae have central midrib (Venation subset A) about 1.0 mm wide. This flanked on either side by normally two equally spaced veins of subset B, spaced 5.0-6.8 mm apart, about 0.5 mm wide, and possibly also by a vein, or remains of one, forming margin of each pinnule. In between are equally spaced (0.6 mm) veins of subset C, 0.15 -0.20 mm wide. Midway between each C vein a vein of subset D, 0.05 - 0.10 mm wide.

Palm Inflorescences Fig. 3 (b, e) Occurrence and referred specimens F41/f245 OU29956 OU29961 Description Flowering spike (or spadix), 5-6 mm in diameter, reaching at least 270 mm in length, possibly as branches of panicle. Flowering units appear spirally arranged along axis, 2.02.5 mm in diameter and 1.5-2.5 mm apart. Flowering units themselves are not preserved, or indistinguishable, and impossible to tell if solitary or in triads.

Palm -Nuts Fig. 3 (c) Occurrence and referred specimens F41/f218 OU12448 F41/f221 OU12585 F41/f228 OU12264 F41/f245 (numbers refer to blocks of sediment with large numbers of "nuts") OU29424 OU29425 OU29959 OU29960 OU29964 OU29965 OU29966 OU29970 OU29971 OU29972 OU29980-0U29996 49

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Description Smooth, sub-globular, indehiscent, fruits or seeds, about 10 mm in diameter, flattened parallel to plane of deposition.


Note The sometimes abundant nuts placed within zones of palm-frond concentrations suggests the affinities are with the Palmae. At locality F41/f245 these nuts form dense layers amongst palm fronds, reaching densities of 43 nuts per 50 square em (see spec. OU29424). Comparisons P. zeelandica fronds compare well with the single extant New Zealand palm, Rhopalostylus sapida Wendl. et Drude (an arecoid palm), in size and arrangement of the pinnae, and the structure of the inflorescence. The form of R. sapida is reported to show considerable geographical variation (Esler, 1975); however there are differences which are significant enough to preclude specific identity. I. R. sapida pinnae, when living, are often tightly folded, and in abcised fronds appear so without exception (based on observations made in the Punakaiki, Kaihoka Lakes and W aitakeri Ranges). However, all the P. zeelandica specimens have pinnae which open out consistently close to the rachis. This is similar to the extant Lord Howe Island palm, Howeaforsteriana ( which has distinctive glands at the base of each pinna, not present on P. zeelandica or R. sapida ). 2. The venation arrangement in R. sapida pinnae is slightly different; the outermost veins corresponding to the B subset in P. zeelandica are generally larger than the inner ones. This has not been noted in P. zeelandica, though it may be a preservational loss. The size difference in the Recent leaves is much easier to see in cross-sections of the leaves than in plan view. 3. The nuts of R. sapida are similar in size to P. zeelandica, but are distinctly elongate. P. zeelandica nuts are much more globular. The palm Phoenicites zeelandica is specifically distinct from the single extant New Zealand palm Rhopalostylus sapida, but may be a closely related arecoid taxon.

ACKNOWLEDGEMENTS I thank my supervisor, J.D. Campbell, and also R.S. Hill, J.D. Lovis and M.E. Dettmann who reviewed the manuscript at various stages, and the Patterson family of Bannockburn who allowed access on their property. Don Weston took the photographs and prepared the plate. In particular I thank Mr and Mrs B. Duder of Dunedin who let me cut chunks off their historical nikau palm and even gave me one of its progeny. This work was financed by a UGC scholarship.

REFERENCES Bentham, G., 1878. Flora Australiensis, volume 7. Lovell Reeve and Co. London. Douglas, B.J., 1986. Lignite resources of Central Otago. New Zealand Energy Research and Development Committee. Publication P104. Esler, A.E., 1975. The Nikau palm. New Zealand's Nature Heritage 4: 532-534. Ettingshausen, C. von, 1887. Beitrage zur Kenntniss der Fossilen Flora Neuseelands. Denkschriften der Akademie der Wissenschaften, Wien 53: 143-194. Ettingshausen, C. von, 1891. Contributions to the knowledge of the fossil flora of New Zealand. Transactions of the N.Z. Institute 23: 237-310. Gregg, D.R., 1975. Type and figured specimens of fossil plants in the Canterbury Museum. Records of the Canterbury Museum 9: 259-276. Mildenhall, D.C., 1989. Summary of the age and paleoecology of the Miocene Manuherikia Group, Central Otago, New Zealand. Journal of the Royal Society of N.Z. 19: 19-29. Mildenhall, D.C. and Pocknall, D.T., 1989. Miocene-Pleistocene spores and pollen from Central Otago, South Island, New Zealand. N.Z. Geological Survey Paleontological Bulletin 59. Read, R.W. and Hickey, L.J., 1972. A revised classification of fossil palm and palm-like leaves. Taxon 21: 129-137. Received 25 November 1991; accepted 23 February /993

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