INTRODUCTION

The Miocene covers a period of extraordinary global climate change, extending though for example, the early Middle Miocene Climate Optimum (Flower and Kennett 1994; Shevenell et al. 2004; although Böhme et al. 2007 identify a German optimum slightly earlier) and the profound drop in temperature which rapidly followed (Miller et al. 1991; Zachos et al. 2001). During the optimum rainforest was widespread and thermophilic plant species grew poleward of their current extent. The succeeding temperature drop saw rainforest retreat and its replacement with deciduous forest while some deciduous forest became scrubland or grassland (Flower and Kennett 1994).

Southern New Zealand has proven to be an important source of Early Miocene plant fossils. The fluvial-lacustrine Manuherikia Group of Central Otago (Douglas 1986) lay to the north of the coastal fluvial-deltaic East Southland Group (Isaac and Lindqvist 1990). Extensive palynological studies have been carried out in both areas (e.g. Pocknall and Mildenhall 1984; Mildenhall and Pocknall 1989). Leaf and fruit impressions found in the Manuherikia Group include Eucalyptus (Pole 1993a), Allocasuarina (Campbell and Holden 1984) and a legume (Pole 1992). They demonstrate the variety of vegetation types which existed in the Early Miocene and from which significant climate change can be inferred (Pole 2003). Palynological studies also indicate the importance of burning during part of the deposition of the Manuherikia Group (Mildenhall 1989; Pole and Douglas 1998). Along with the vegetation there was a fauna which is becoming increasingly well-known (Feldman and Pole 1994; McDowall and Pole 1997; Pole et al. 2003; Worthy et al 2006, 2007). Earlier work on plant macrofossils focused on impressions (see Pole 1993b and references therein) although the pioneering investigations of Holden (1987) documented the presence of leaf cuticle in the East Southland Group. More recently dispersed cuticle has been central to research in the field (Pole 1997, 1998a, 2007a, 2007b) and has resulted in the discovery of two cycads (Hill and Pole 1994, Pole 2007b), 16 conifers (Pole 2007b), and 11 Proteaceae (Pole 1998a) and 25 Lauraceae (Pole 2007a) and 17 monocots or possible monocots (Pole 2007c). The identification of these taxa may help quantify aspects of the warmer global climate at a time when New Zealand was further south than it is today. For instance, the southern limit of the Lauraceae family lies within New Zealand today, where only four species of broad-leaved Lauraceae are present (Allan 1982; Wright 1984). However, in the Early Miocene 25 species are known (Pole 2007a). In the debate over the importance of long distance dispersal in the origin of New Zealand's flora (Knapp et al. 2005; McGlone 2005; Pole 1994; Winkworth et al. 2002) genetic data provided by extant plants seems to be strongly favouring the dispersal option, but good plant fossil evidence is still needed to date nodes on phylogenetic trees and to demonstrate where extinction has entirely eliminated taxa from major biogeographic regions. Basic description of cuticle morphologies will also prove useful for stratigraphic purposes. While previous papers have documented the more diverse taxonomic groups (see previous discussion) and a further paper documents the presence of families currently endemic to New Caledonia, the aim of this paper is to complete the documentation of the dispersed fossil leaf cuticle morphologies currently known from the Manuherikia and East Southland Groups. To this end it has no taxonomic focus, and includes a large proportion of taxonomic unknowns but is a necessary step prior to a synthesis of the vegetation.