Mike Pole

Can long-distance dispersal be inferred from the New Zealand plant fossil record?

New Zealand is generally thought to have been physically isolated from the rest of the world for over 60 million years. But physical isolation may not mean biotic isolation, at least on the time scale of millions of years. Are New Zealand’s present complement of plants the direct descendants of what originally rafted from Gondwana? Or has there been total extinction of this initial flora with replacement through long-distance dispersal (a complete biotic turnover)? These are two possible extremes which have come under recent discussion. Can the fossil record be used to decide the relative importance of the two endpoints, or is it simply too incomplete and too dependent on factors of chance? This paper suggests two approaches to the problem—the use of statistics to apply levels of confidence to first appearances in the fossil record and the analysis of trends based on the entire palynorecord. Statistics can suggest that the first appearance of a taxon was after New Zealand broke away from Gondwana—as long as the first appearance in the record was not due to an increase in biomass from an initially rare state. Two observations can be drawn from the overall palynorecord that are independent of changes in biomass: (1) The first appearance of palynotaxa common to both Australia and New Zealand is decidedly non-random. Most taxa occur first in Australia. This suggests a bias in air or water transport from west to east. (2) The percentage of endemic palynospecies in New Zealand shows no simple correlation with the time New Zealand drifted into isolation. The conifer macrorecord also hints at complete turnover since the Cretaceous.

Eocene Nypa from Regatta Point, Tasmania

A new species of the mangrove palm Nypa, N. australis, is formally described from Lower Eocene sediments from near Strahan, western Tasmania. Fossil material comprises fronds (with cuticle), fruits, and pollen. Coming from a paleolatitude of approximately 65°S, it is the most polar Nypa known.

Early Miocene flora of the Manuherikia Group, New Zealand. 2. Conifers

Abstract Remains of six conifer taxa are described from early Miocene sediments of the Manuherikia Group, New Zealand. Two of these are new, Retrophyllum vulcanense sp. nov. and Podocarpus alwyniae sp. nov.. The others are Araucaria sp. sect. Eutacta, present as impressions of vegetative shoots and isolated ovuliferous cone scales, shoots of Dacrycarpus dacrydioides (A. Rich.) de Laubenf.; a single impression of a Phyllocladus sp. phylloclade; and an impression of an unidentified shoot. This is the first record of the genus Retrophyllum from New Zealand.

Plant macrofossils from the Foulden Hills Diatomite (Miocene), Central Otago, New Zealand

Twenty eight taxa of angiosperm fossils are described from the Early Miocene (c. 20 Ma) Foulden Hills Diatomite, not far from Dunedin, New Zealand. Some leaves include cuticle, and this has sometimes facilitated identification. Families confidently identified include Euphorbiaceae, Lauraceae, Myrsinaceae, Myrtaceae, Sapindaceae, and Smilacaceae, and, less confidently, Cunoniaceae and/or Elaeocarpaceae, Hernandiaceae, Leguminosae, Meliaceae or Rutaceae, Sterculiaceae, Tiliaceae, and Winteraceae. There is a notable absence of Nothofagus macrofossils, and only a single conifer, a broad‐leaved Podocarpus. The original community was probably moderately diverse and growing on a nutrient‐rich substrate. Floristics and climate were probably similar to northern New South Wales and southern Queensland today.

The terrestrial Miocene biota of southern New Zealand

Abstract Known Early‐Middle Miocene terrestrial strata of southern New Zealand are represented by alluvial plain and lacustrine sediments. A vertebrate fauna including fish, ducks, and crocodiles populated Lake Manuherikia, with abundant mussels, gastropods, and stromatolites occupying the near‐shore areas of the lake. A diverse vegetation covered the surrounding broad fluvial plains that extended to the coastal margins. Initially this was largely rainforest, which varied according to habitat and to changing climate. In particular, the climate and ecology appear to have fluctuated across the two major thresholds of fire/no‐fire and of peat accumulation and no‐peat. A major climate change, possibly the sharp global deterioration in conditions at about 14 Ma, profoundly changed the vegetation. Rainforest continuity fragmented, and herblands became widespread. Leaf fossils effectively disappear from the record at this time.

Structure of a near-polar latitude forest from the New Zealand Jurassic

A tidal platform at Curio Bay near the southernmost point of the South Island, New Zealand, preserves the petrified remains of an in situ Middle Jurassic forest. The forest grew close to the palaeo-polar circle, but data are not precise enough to tell on which side it lay. A mapped portion of the forest floor provides data on tree density and population structure, allowing comparison with recent forests and with records of other fossil forests. The forest has tree densities similar to many forests growing in low to mid-latitudes today; it appears to have had emergents projecting through a low canopy, and a well-developed undergrowth of smaller gymnosperms and osmundaceous ferns. No aspect of the forest structure uniquely distinguishes it from that of non-polar latitude forests. An extended discussion is given on reconstructing tree height from stump diameter. On the basis of this, a reinterpretation of the structure of an Early Cretaceous fossil forest from Alexander Island, Antarctica, is offered.

Mid-cretaceous conifers from the Eromanga Basin, Australia

Mid-Cretaceous (latest Albian–earliest Cenomanian) sediment in sevenbore cores from the Eromanga Basin (south-western Queensland) was sampled fororganically preserved plant macrofossils. Among those recovered, 26 taxa ofconifers have been distinguished. Families Araucariaceae, Podocarpaceae, andCheirolepidiaceae were prominent. The Araucariaceae includeAraucaria sp., while the remainder are considered torepresent extinct genera. Podocarpaceae are all species of extinct genera andtwo new genera are described: Eromangia andThargomindia. There are two species ofCheirolepidiaceae. One of these, Geinitzea tetragonaCantrill & Douglas, is made the type of a new genus,Otwayia, with two species,O. tetragona and O. cudgeloides,both occurring in the Eromanga Basin. No unequivocalCupressaceae/Taxodiaceae were recognised.

Early Miocene flora of the Manuherikia Group, New Zealand. 10. Paleoecology and stratigraphy

A stratigraphic sequence of vegetation is recognised from macrofossil assemblages in Lower-Mid Miocene fluvial-lacustrine sediments of the Manuherikia Group, New Zealand. Temperature, water-level, drainage, fire and rainfall were probably the factors that divided the distribution of plant taxa into several distinct communities. These communities are compared with structural vegetation types presently recognised in eastern Australia, including notophyll vine forest (sometimes with podocarp conifers), microphyll forest, araucarian notophyll vine forest, tall open-forest (at times probably closed forest with sclerophyll emergents), notophyll feather palm vine forest, and fern fields. The earliest assemblage in the Cromwell region represents Nothofagus forest (microphyll fern forest or microphyll vine forest), or at least a forest in which Nothofagus was probably an important element. Rainfall was high, but the associated presence of Allocasuarina indicates forest edge conditions, or perhaps disturbance by fi...

A quantitative palynostratigraphy of the Miocene Manuherikia Group, New Zealand

A quantitative palynostratigraphy is presented for the Manuherikia Group, New Zealand Six stratigraphic sections were studied from the northern Manuherikia basin where the relative proportions of six pollen taxa were compared Nothofagus ‘brassu type’, Nothofagus ‘fusca type’, Casuannaceae, Myrtaceae, Arecaceae, Asteraceae, and Chenopodiaceae A consistent order of dominance is apparent and zone boundaries are erected based on dominance of the latter five taxa over that of Nothofagus ‘brassu type’ Four new zones are proposed the Nothofagus ‘brassu type’ Zone, the Arecaceae‐Myrtaceae Zone, the Casuannaceae Zone, and the Asteraceae‐Chenopodiaceae Zone The latter is essentially a redefinition of the Chenopodipolhs chenopodiaceoides Zone of Mildenhall and Pocknall Correlation with the International time scale is attempted the N ‘brassu type’ Zone is Early Miocene, while the base of the Casuannaceae Zone or the Asteraceae‐Chenopodiaceae Zone may correlate with major global cooling recognised at approximately 14 Ma

A large galaxiid fossil (Teleostei) from the Miocene of Central Otago, New Zealand

A fish fossil of Miocene age from the Manuherikia group, from a site near Bannockburn in Central Otago, New Zealand, is described and identified as a galaxiid, probably genus Galaxias. The fish was large, estimated at 383 mm, and thus larger than all extant New Zealand Galaxias except G. argenteus, which is known to reach 580 mm. However, it appears to have been of quite slender form. There was, therefore, in Miocene times, a large, slender, perhaps lacustrine Galaxias in Palaeo‐lake Manuherikia in Central Otago.