miocene conifers from the manuherikia group, new zealand

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Miocene conifers from theManuherikia Group, New ZealandMike Pole a ba Department of Plant Science , University of Tasmania , GPOBox 252C, Hobart, TAS, 7001, Australiab Department of Botany , University of Queensland , St Lucia,Brisbane, QLD, 4072, AustraliaPublished online: 30 Mar 2010.

To cite this article: Mike Pole (1997) Miocene conifers from the Manuherikia Group,New Zealand, Journal of the Royal Society of New Zealand, 27:3, 355-370, DOI:10.1080/03014223.1997.9517543

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O1 Journal of The Royal Society of New ZealandVolume 27 Number 3 September 1997 pp 355-370

Miocene conifers from the Manuherikia Group,New Zealand

Mike Pole*

Eight genera of conifers in two or three families are documented from Miocenesediments of the Manuherikia Group, Central Otago, New Zealand They includeAcmopyle masonu sp nov , Dacrycarpus dacrydioides Lepidothamnus intermedius,Podocarpus sp 'Mata Creek', Prumnopitys taxifoha, and Retrophyllum vulcanense inthe Podocarpaceae, an indeterminate genus in either the Podocarpaceae or Taxaceae,and a single representative of the Cupressaceae Seven species occur in one deposit

Keywords palaeobotany Podocarpaceae Taxaceae, Cupressaceae Dacrycarpus, Lepidothamnus, Podocarpus,Prumnopitys Retrophyllum

INTRODUCTIONConifers are an important component of many New Zealand forests today, and palynology(e g Mildenhall 1980) has demonstrated their presence, in variable amounts, throughout theTertiary The taxonomy of extant podocarps has recently undergone much revision, withmany new genera being proposed Out of a milieu of species which had earlier been placed inPodocarpus, de Laubenfels (1969) separated seven genera, and then an eighth, Prumnopitys(de Laubenfels 1978) Quinn (1982) then split Dacrydium into four genera and Page (1988)segregated Sundacarpus from Prumnopitys Most recently Molloy (1995) described a newgenus Manoao, as a segregate from Lagarostrobos The recent taxonomic revisions, whilematching pollen diversity in the Podocarpaceae to some extent, have also made it moredifficult (using present criteria) to place some fossil grains in the correct genera Somemorphotypes among fossil podocarp pollen may represent several genera of extant plantsSome morphotypes may also represent extinct genera (e g Hill & Pole 1992) On the otherhand, the extant genera of Southern Hemisphere conifers can be readily distinguished on thebasis of gross morphology and cuticular details of the leaves (e g Greenwood 1987, Hill &Carpenter 1991, Wells & Hill 1989, Hill & Pole 1992, Pole 1992b) Excellent preservationexists in some of New Zealand's fossil localities (Pole 1992b), and recently developedtechniques and methodolology can now be utilised to document the history of our coniferswith much greater precision

The Manuherikia Group is an extensive (>5600 km2) deposit of Miocene fluvial (DunstanFormation) to lacustrine (Bannockburn Formation) basin fill in southern New Zealand Thestratigraphy and sedimentology have been detailed by Douglas (1986), the palynology byMildenhall (1989) and Mildenhall & Pocknall (1989) and the macropaleobotany by Pole(1993a) The oldest sedimentary units recognised by Douglas are braided river deposits (StBathans Member) filling incised valleys These are overlain by more extensive meanderingstream and floodbasin deposits (Fiddlers Member) In the north of the basm these units arewell exposed by gold- and coal-minmg activities At several localities lenses of carbonaceousmud within dominantly gravel-sand hthology contain organically preserved ('mummified')

* Department of Plant Science, University of Tasmania, GPO Box 252C, Hobart, TAS 7001, AustraliaPresent address Department of Botany, University of Queensland, St Lucia, Brisbane, QLD 4072,Australia

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356 Journal of The Royal Society of New Zealand, Volume 27, 1997

VinegarHill

H40/f4

H41/f72 Grey Lake

Blue Lake

NEW ZEALANDManuherikiaRiver

Fig. 1 Locality map, Manuherikia Group sites.

plant remains. Conifer remains from two such localities have already been described (Pole1992b). The aim of this paper is to describe vegetative conifer remains from four morerecently investigated localities (Fig. 1). The locality with the most diverse conifer assemblage,H41/f74, lies above the St Bathans paleovalley (Douglas 1986), within sediments of theFiddlers Member; a second is more or less laterally equivalent within the Fiddlers Member(H41/f77), and two are from the underlying St Bathans Member (H40/f4 and H41/72). Alllocalities are likely to date from the Early Miocene (Pole, unpublished data).

METHODSCarbonaceous mud was collected in bulk then disaggregated gently using warm water andhydrogen peroxide. Plant material was concentrated by sieving and further cleaned byimmersion in hydrofluoric acid. Intact material could then be viewed directly by mounting ona stub for scanning electron microscopy (SEM) or further processed for cuticle. This involvedimmersion in 10% chromium trioxide until all but the cuticle had been removed. Hydrogenperoxide was also tried, which gives better results for delicate cuticle (as in some angiosperms),but chromium trioxide appeared satisfactory for this conifer cuticle. Clean cuticle was

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Pole—Miocene conifers from the Manuherikia Group 357

stained in safranin and mounted on glass slides within glycerine jelly for transmitted lightmicroscopy (TLM) or dried on stubs for SEM.

Specimens mounted on slides are catalogued with the prefix "SB" and those on stubs with"S-". Specimens prefixed with "E/" refer to extant herbarium material, "B" to a preexistingfossil collection. All are stored in the Department of Plant Science, University of Tasmania.Fossil localities are numbered according to the Geological Society of New Zealand FossilRecord system.

TAXONOMYPodocarpaceaeAcmopyle

A fragment of leaf (SB 1188) from H41/f77 (Figs 2A, B) shows unicellular trichomesscattered over both surfaces, and a more complete, bilaterally flattened leaf from H41/f74(SB 1149; Fig. 2C) has unicellular trichomes near its apical margin. Both have the disorganisedstomatal complexes with poorly differentiated subsidiary cells and rows of hypoplasticstomates (Fig. 2B, D) which are characteristic of Acmopyle (Hill & Carpenter 1991). One ofthe two extant species of Acmopyle, A. sahniana Buchh. et Gray from Fiji, was reported byHill & Carpenter (1991) to be the only extant conifer to have unicellular trichomes on theleaves. In addition, two Australian fossil species, A. florinii R. Hill & Carpenter and A.setiger (Townrow) R. Hill & Carpenter, also have trichomes (Hill & Carpenter 1991). Theseauthors concluded that the trichomes are a derived character in Acmopyle and considered thethree species to form a monophyletic group.

Acmopyle florinii was described as having trichomes "near the leaf base over the midveinand along the leaf-bearing axis", while in A. setiger they occur along the abaxial leaf margin.The new fossil has trichomes scattered over both leaf surfaces (including some amongmature stomates) and on specimen SB 1149 they extend to the apex. In this way it differs fromthe Australian fossils. A. sahniana was stated by Hill & Carpenter to have trichomes, but theydid not detail how they were distributed on the lamina. In the herbarium specimens of A.sahniana available to me (E/1519) I have seen dense hairs along the margins of the small,scale-like leaves at the base of the shoots, but none on the bilaterally flattened leaves. Iprepared cuticle from four of the bilaterally flattened leaves of E/1519, and could locate onlya single trichome at the very base of one (E/1519c). A previously prepared slide (E/1029)shows no trichomes on what are obviously fragments of the bilateral leaves, but many alongthe margins of several small scale-like leaves. A small shoot fragment of scale-like leavesfrom H41/f74 mounted on an SEM stub (S-498; Fig. 3) has many trichomes and is regardedas a similar part of an Acmopyle shoot.

The new fossils clearly differ from A sahniana in having many trichomes on the bilateralleaves {A. sahniana also has stomates which almost completely cover one surface, whereas inthe fossils they are in a distinctly narrower band). The new fossils also differ from A. setiger.I have examined the lectotype (B-001), and confirm that the trichomes are mostly at the baseof the leaf, with a few extending about halfway along what Hill & Carpenter interpreted asthe abaxial margin of the bilaterally flattened leaves. The new fossils also differ in theirtrichome distribution from that of A. florinii. The New Zealand fossils are therefore distinctand are described as a new species of Acmopyle, A. masonii.

Acmopyle masonii sp. nov. (Figs 2, 3)Etymology: for G. Mason, who took me on my first trip to Mata Creek.Holotype: SB 1149Type locality : H41/f74Referred specimens: H41/f72 SB1161; H41/f77 SB1188Diagnosis: Differs from other species of Acmopyle in having trichomes on both surfaces ofthe bilaterally flattened leaves and which extend towards the apex.

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Fig. 3 Acmopyle masoniisp. nov., S498: (A) SEM,shoot with bilaterallyflattened foliage to left andright, separated by scaleleaves (scale 1 mm); (B)SEM, scale leaf withtrichomes, S 498 (scale1 mm).

Description: Shoot unknown. Main leaves flattened bilaterally (small, bifacial scales at baseof shoot), spreading; length unknown, width about 1.3 mm. Very unequally hypostomatic;stomates in two zones on one (functionally lower) surface, a few stomates near apex andabundant hypoplastic stomates on other (functionally upper) surface. Stomates in long, clearrows, orientation longitudinal, paratetracyclic, mostly amphicyclic, sometimes monocyclic.Polar subsidiary cells often shared between adjacent stomates. Lateral subsidiary cells inadjacent rows often in contact, sometimes shared. Epidermal cells bearing unicellular trichomeson both leaf surfaces.

DacrycarpusDacrycarpus shoots are common in the H41/f74 assemblage, occurring as bilaterally flattenedspreading shoots and as smaller imbricate shoots with bifacially flattened or unflattened

Fig. 2 Acmopyle masonii sp. nov.: (A) TLM, morphologically lower surface of leaf with stomatalrows and trichomes (arrowed) throughout, SB 1188 (scale 200 um); (B) TLM, morphologically uppersurface of leaf with scattered trichomes (dark spots, short rows of hypoplastic stomates, and a fewmature stomates (one is arrowed), SB 1188 (scale 200 um); (C) TLM, apical portion of leaf, withtrichomes extending to apex adjacent to arrow, SB1149 (scale 1 mm); (D) TLM, rows of hypoplasticstomates, SB 1149 (scale 50 um); (E) TLM, rows of typical irregular-shaped mature stomates, SB 1149(scale 50 um); (F) TLM, trichomes near edge of leaf, SB 1149 (scale 50 um); (G) TLM, detail of maturestomates, SB1149 (scale 20 Um); (H) TLM, single trichome and some stomates, SB1161 (scale 50 um).

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Fig. 4 Dacrycarpus dacrydioides fossil, SEM (scale of 1 mm segments):(A) shoot with bilaterally flattened leaves, S497; (B) shoot with bifaciallyflattened leaves, S493.

leaves. This range of foliage types is characteristically found on extant Dacrycarpus plants,and these fossil shoots are inferred to belong to a single species.

Dacrycarpus dacrydioides (A. Rich) de Laubenfels (Fig. 4)Referred specimens: H40/f4 SB1187; H41/f74 SB1151Description: see Pole (1992b).

LepidothamnusTwo specimens (SB 1174, S^-77; Fig. 5) are shoots with spirally disposed, very looselyimbricate or spreading, little-flattened leaves with rounded apices and rounded stomates. Thestomates are typical of the "Dacrydium group C" podocarps of Florin (1931), now includingHalocarpus, Lagarostrobos, and Lepidothamnus. Wells & Hill (1989) characterised theGroup C podocarps as having "randomly oriented" stomates, although within this groupLepidothamnus has reasonably well aligned stomates (pers. obs.). The new fossils havestomates with a general longitudinal lineation, although some stomates may be at right anglesto this trend. In gross morphology and cuticular characters the fossils are consistent withLepidothamnus, and are placed in this genus.

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Fig. 5 Lepidothamnus intermedius fossil: (A) SEM, portion of shoot, S^I-77 (scale 1 mm); (B) TLM,stomatal zone, SB1174 (scale 50 um); (C) TLM, detail of stomates, SB1174 (scale 20 urn); (D) SEM,outer leaf surface showing Florin rings, S^-77 (scale 0.1 mm); (E) SEM, inner surface, S785. Notesmooth U-shaped (cf. Wells & Hill 1989: 380) cross-section of epidermal cells (scale 50 um).

There are three extant species of Lepidothamnus and one fossil species. The extantPatagonian species, L.fonkii Phil., differs from all the other species in being tightly imbricate.One of the extant New Zealand species, L. laxifolius (Hook, f.) Quinn, is also unique inhaving leaves which are typically reflexed at right angles to the shoot axis (but not always -on one stem some may be reflexed, others not.: C. Burrows, pers. comm. 1997). Theremaining species, the extant New Zealand L. intermedius (T. Kirk) Quinn and the fossil L.diemenensis Pole from Tasmania (Pole 1992a), are very similar to the new fossil material. Idistinguished L. diemenensis partly on the form of the stomates, which often had clearlydistinct polar subsidiary cells. In this respect the new fossils compare with L. intermedius inhaving purely amphicyclic stomates. A marginal frill, present on both L. diemenensis and L.

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Fig. 6 Podocarpus sp. 'Mata Creek': (A) TLM, stomatal rows, SB H52 (scale 50 um); (B) TLM,epidermal cells showing parallel 'files' of cells, SB 1152 (scale 50 um); (C) TLM, detail of stomates,SB 1152 (scale 20 um); (D) SEM, inner surface of stomatal row (scale 50 um); (E) SEM, outer stomatalsurface (scale 50 um); (F) SEM, inner cuticle surface around stomate (scale 20 um).

intermedia, is not clearly visible on the two new fossils, but is not ruled out. I regard the newfossils as attributable to the living species, L. intermedius.

Lepidothamnus intermedius (T. Kirk) Quinn (Fig. 5)Reference specimen: S-632Reference locality : H4l/f74Referred specimens: H4l/f74, SB 1174Description: Leaves spirally disposed, very loosely imbricate or spreading on terminal shoots(Fig. 5A). Leaves little-flattened, with apices rounded; length about 2.0 mm, width about1.0 mm. Amphistomatic; stomates in four zones, well spaced, not in clear rows. Stomatalorientation generally longitudinal, although some stomates up to right angles to this trend;

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stomates amphicyclic; rounded subsidiary cells not shared (Fig. 5B, C, E). Florin ringsdistinct, sunken (Fig. 5D). Epidermal cells isodiametric, not in rows.

Podocarpus

In the H41/f74 assemblage fragments of flattened (presumably linear-lanceolate) leaves arereasonably common (e.g. SB 1152; Fig. 6). They are hypostomatic, with stomates in long,uniseriate rows. Epidermal cells are often elongate. On the non-stomatal surface epidermalcells often occur in lateral files, which clearly indicate derivation from a single cell. Thiscombination of characters is typical of Podocarpus.

The leaves of all extant species of New Zealand Podocarpus, as well as the fossil P.alwyniae (Pole 1992b), all have the stomates in two zones separated by a gap over themidvein. The width of the stomatal zones is approximately equal to the width of the gap.There is also a generous gap between the stomatal zone and the leaf margin. This contrastssharply with the condition in the new fossils, in which the stomatal zone is from four tonearly six times the width of the midvein gap with no appreciable gap near the margin,similar to the New Zealand fossil, broad-leaved P. travisiae (Pole 1993b), and to numerousother extant broad-leaved Podocarpus species from outside New Zealand. This indicates thatthe new fossils are not closely related to the extant New Zealand Podocarpus, which isclassed in Section Australis (de Laubenfels 1985), but are derived from an extinct species (atleast in New Zealand) from another section. They are clearly not P. travisiae, which is muchbigger. The cuticular morphology of the many species of broad-leaved Podocarpus is poorlyunderstood at present. Formal naming of these fossils would be premature, and instead Ipropose to give them an informal name, Podocarpus 'Mata Creek'.

Podocarpus sp. 'Mata Creek' (Fig. 6)Reference specimen: SB 1152Locality : H41/f74Referred specimens: H41/f74, S788Description: Shoot unknown. Leaf shape presumed linear-lanceolate, bifacially flattened;length unknown, width up to 4.5 mm. Hypostomatic, with stomates in two zones on eitherside of gap over midvein; stomatal zone from four to nearly six times width of midvein gap,with no appreciable gap near margin. Stomates paratetracyclic, in long, uniseriate rows (Fig.6A, C, D); orientation longitudinal. Polar and lateral subsidiaries well defined, with polarsubsidiaries of adjacent stomates in a row usually either abutted or shared (Fig. 6C, D, F).Encircling cells often distinct, but usually very irregular in shape and orientation. Epidermalcells often elongate (usually no more than L:W = 10:1), moderately buttressed on stomatalsurface. On non-stomatal surface epidermal cells not buttressed, or only slightly so, oftenoccurring in lateral files (Fig. 6B), clearly indicating derivation from a single cell.

PrumnopitysSeveral fragments of leaves (e.g. SB 1153; Fig. 7A) have epidermal cells with stronglybuttressed and slightly sinuous walls. The stomates are in two zones and in rows, butfrequently widely separated within each row, so that the next nearest stomate is often in theadjacent row. This combination of characters is typical of Prumnopitys (Pole 1992a).

All eight extant taxa of Prumnopitys were available for comparison with the fossils. Mostcan be clearly distinguished from the fossil on the basis of stomatal distribution and shape ofthe epidermal cells. One of the New Zealand species, P.ferruginea (D. Don) de Laubenfels,appears similar to the fossil, but it has stomates which are consistently well spaced, bothwithin and between rows. The fossil has stomates which are in very closely spaced rows,often with the stomates from adjacent rows in contact. Within the rows about half thestomates are well spaced, the other half forming short chains two or three stomates longwhere polar subsidiaries are in contact. In this feature, as well as epidermal cell shape,buttressing, and size of the leaf, the fossil is essentially identical to the other New Zealand

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Fig. 7 Prumnopitys taxifolia (A-F, fossil): (A) nearly complete leaf, SB1 153 (scale 1 mm); (B) upperepidermal cells, SB1 154 (scale 50 (im); (C) stomatal rows on lower epidermal surface, SB1 154 (scale50 |am); (D) detail of stomates, SB1154 (scale 20 |im); (E) SEM, inner stomatal surface, S814 (scale50 |Jm); (F) SEM, outer stomatal surface, S814 (scale 50 |im); (G) TLM, stomates of extant P. taxifolia,E/1948 (scale 50 urn); (H) TLM, upper epidermal cells of extant P. taxifolia, E/1925 (scale 50 |im).

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d g 8 R g vulcanense, SB 1148: (A)TLM basal pordon of ,eaf showmg twistmg offalse petiole at base (scale { mm). (B) TLMdetail of stomate (scale 20 urn).

species, P. taxifolia (Solander ex D. Don) deLaubenfels (Fig. 7G, H). The Chilean speciesP. andina (Poeppig ex Endlicher) deLaubenfels (the type of the genus) is alsorather similar, supporting Philipson & Molloy(1990) who regard it as a "close" relative ofP. taxifolia. It is subtly different from P.taxifolia and the fossil in having stomatal rowsslightly further apart and fewer 'linked'stomates within rows. The logicalidentification of the fossil is with P. taxifolia.

Prumnopitys taxifolia (D. Don.)Laubenfels (Fig. 7A-F)Holotype: SB 1154Locality : H41/f74Referred specimens: H41/f74 SB1153, 1155;H41/f77SB1163Description: Shoot unknown. Leaf bifaciallyflattened, usually falcate; length about 5.0 mm,width about 1.2 mm. Hypostomatic, withstomates in two zones in very closely spacedrows, stomates of adjacent rows often incontact. Within rows, about half the stomateswell spaced and half forming short chains twoor three stomates long, where polarsubsidiaries abut or, rarely, are shared (Fig.7C-E). Stomates oval, paratetracyclic;orientation longitudinal; polar and lateral subsidiary cells clearly defined. Epidermal cellswith strongly buttressed and slightly sinuous walls (Fig. 7B-E), elongate near stomates,isodiametric near margins and on non-stomatal surface.

RetrophyllumFragments of R. vulcanense Pole were identified on the basis of amphistomatic leaves,widely distributed stomates, typically wide polar subsidiary cells, and often more than foursubsidiary cells. A specimen from H41/f74 (SB1148; Fig. 8) shows the characteristic abruptnarrowing and twisting at the leaf base characteristic of the genus.

Retrophyllum vulcanense Pole (Fig. 8)Referred specimens: H41/f74 SB1148; H41/f77 SB1189Description: See Pole (1992b).

Podocarpaceae or TaxaceaeA single specimen (SB 1150; Figs 9A-C) is the apical portion of a leaf with a small frill at theapex. The stomates are in discontinuous rows, and the stomatal pores are surrounded byelongate papillae (this feature is distinct from the normal podocarp Florin ring, which simplycomprises a raised portion of the subsidiary cells). Encircling and epidermal cells on thestomatal surface are also covered with a mass of rough papillae (several small papillae percell). The encircling cells (adjacent to the subsidiary cells) are 'bridge-shaped' or contributeto a bridge shape. They curve around the subsidiary cells along one margin, while the otheris usually straight, forming a neat 'edge' to a row. Elongate papillae surrounding the stomatalpore are found in Cupressaceae, Podocarpaceae, and Taxaceae. In Cupressaceae the subsidiarycells are typically polygonal and poorly distinguished in shape from both ordinary epidermal

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Fig. 9 (A-C) Podocarpaceae/Taxaceae (gen. et sp. indet): SB1150, (A) TLM, leaf apex (scale200 um); (B) TLM, stomatal rows (scale 50 urn); (C) detail of stomates surrounded by elongatepapillae (scale 20 um). (D) Cupressaceae (Libocedrus or Papuacedrus) TLM, stomatal zone, SB885(scale 50 urn).

cells and each other. They are frequently shared obliquely, whereby a subsidiary at the poleof one apparatus forms a lateral subsidiary of another. This forms a kind of 'net' of relatedcells with no encircling cells. In contrast, Microstrobos (in Podocarpaceae) and members ofthe Taxaceae have well defined polar and lateral subsidiary cells. Subsidiary cell sharingalways involves polar subsidiary cells, and, importantly, there are clear encircling cellswhich are often bridge-shaped, forming the edges to the stomatal rows. There is only a singlespecies of Taxaceae in the Southern Hemisphere, Austrotaxus spicatus Compton, a genus andspecies endemic to New Caledonia. It does not have papillate subsidiary and epidermal cells.In Microstrobos there are small papillae on the encircling cells (see fig. 45 in Wells & Hill1989), but these do not extend to normal epidermal cells. Microstrobos leaves are short,scale-like, and imbricate. In contrast, the fossil appears to be the bifacially flattened apex ofa lanceolate leaf, although the small apical frill suggests it was part of an imbricate shootrather than a spreading one. Comparison is therefore difficult with any living taxon, and thefossil is likely to belong to an extinct genus. Formal diagnosis will wait until a complete leafis discovered.

Podocarpaceae/Taxaceae gen. et sp. indet (Fig. 9A-C)Reference specimen: SB 1150Locality : H41/f74Description: Shoot unknown. Leaf shape unknown, possibly lanceolate, bifacially flattened,small but with a distinct frill at acute apex (Fig. 9 A); length unknown, width about 1.0 mm.Stomates on one surface only, unclear whether in zones, but in discontinuous rows (Fig. 9B).Stomates basically paratetracyclic; orientation longitudinal; stomatal pores surrounded by

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Pole—Miocene conifers from the Manuhenkia Group 367

elongate papillae (Fig 9C) Polar subsidiary cells often abutting, sometimes shared Encirclingcells 'bridge-shaped', curving around subsidiary cells along one margin, the other usuallystraight, forming a neat 'edge' to row (Fig 9C) Both subsidiary cells and epidermal cells onstomatal surface covered with a mass of rough papillae Epidermal cells on non-stomatalsurface more elongate, not papillate

Cupressaceae

One small cuticle fragment (SB885, Fig 9D) also has prominent rings of papillae around thestomatal pores Other papillae are found on, and restricted to, all the subsidiary cells Thepapillae are smooth and discrete In other features the fragments fit the criteria given abovefor the Cupressaceae

If this cuticle type is Libocedrus, it belongs to neither of the extant New Zealand speciesL plumosa (D Don) Sarg has papillae restricted to the subsidiary cells, but these are poorlydeveloped (E/1162, and fig 4G in Hill & Carpenter 1989) Other Libocedrus species havepapillae, e g L austro-caledomca Brongn et Gns from New Caledonia, as do some speciesof Papuacedrus, eg P arfakensis (Gibbs) Li from New Guinea and the Moluccas (Hill &Carpenter 1989) Identification to genus requires more complete material, and probablyintact shoots (Hill & Carpenter 1989)

Cupressaceae gen. et sp. indet (Fig 9D)

Reference specimen SB885Reference locality H40/f4Referred specimens H40/f4 SB878, 885Description Shoot and leaf unknown Stomates in zones, but not in well defined rows,stomates amphicychc, orientation longitudinal Stomatal pores with a distinct raised rim ofpapillae arising from subsidiary cells Subsidiary cells typically polygonal, poorly distinguishedfrom both ordinary epidermal cells and each other (except for smooth and discrete papillae),frequently shaied obliquely, forming a 'net' of related cells Encircling cells absent Epidermalcells smooth (no papillae)

DISCUSSIONAll the conifer genera described here are extant, although one, Acmopyle, is now extinct inNew Zealand These are the first records of Acmopyle and a putative member of Taxaceaefrom New Zealand It is also the first macrofossil record of Lepidothamnus and Prumnopitysm New Zealand earlier than the Quaternary, although both have already been recorded fromthe Middle to Late Eocene of Tasmania (Pole 1992a) On macrofossil evidence there are nowthree extant New Zealand species of podocarps dating from the Miocene Dacrycarpusdatrydioides, Lepidothamnus intermedius, and Prumnopitys taxifoha Other extant speciesare likely to have been present at this time However, it is curious that other extant NewZealand species have remained elusive as Tertiary macrofossils Dacrydium cupressinumSoland ex Lamb , for instance, is a common conifer in many extant forests, forms a largeamount of robust leaf litter, and is recorded in many Tertiary palynological preparations

The locality H41/f74 contains at least seven genera of conifers and a similar number ofspecies (Table 1) The conifers there form a prominent background component to anangiosperm-dominated assemblage The three other localities studied (H40/f4, H41/f72, andH41/f77) have fewer conifer species, which formed much less of the biomass Most of theirspecies are shared with H41/f74 (Table 1) At locality H41/f74 Dacrycarpus is the mostnumerous conifer, with Podocarpus and Prumnopitys frequent, while Retrophyllum, Acmopyle,Lepidothamnus, and the possible taxacean were found as one to three specimens only

Flonstic affinities of the conifer component at the family level are strongest with NewCaledonia, where all three families are found today This is also true at the generic level, with

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all the identified genera living there. Acmopyle is today restricted to New Caledonia and Fiji,and Retrophyllum is restricted to New Caledonia and Peru (Enright & Hill 1995).

Although seven genera of conifers in a single horizon (H41/f74) is a modestly highdiversity it is still much lower than totals from some early Tertiary assemblages in south-eastAustralia. For instance, the Tasmanian Oligocene site of Little Rapid River has so far yielded21 species of conifer (Hill & Bigwood 1987; Hill 1989, 1990, 1995; Hill & Carpenter 1989,1991; Wells & Hill 1989; Hill & Pole 1992; Hill et al. 1993). A climatic difference mayaccount for the lower diversity of the New Zealand localities. The increasing seasonality ofrainfall throughout the Tertiary postulated by Kershaw (1984) and Hill (1992) is probably atleast partially the answer. Hill & Carpenter (1991) demonstrated a change in foliage type anda reduction of stomatal distribution on Acmopyle and Dacrycarpus throughout the earlyTertiary which they inferred to be a response to this climate change. The stomatal distributionon the Acmopyle described in this paper (very unequally amphistomatic) is consistent withthis view, and on Dacrycarpus (amphistomatic with both bilateral and bifacially flattenedfoliage) less so.

If New Zealand was starting to experience significant climatic seasonality by the Miocene,an apparent contradiction is raised. Araucaria was a dominant component of many of theearly Tertiary, conifer-rich deposits in south-eastern Australia as well as in the Late Cretaceousof New Zealand. In the scheme of Hill & Carpenter (1991), these deposits could be inferredto have formed under conditions of low rainfall seasonality. The cuticle of Araucaria isexceptionally robust and its apparent absence from the mummified Miocene plant assemblagesin this study area may be a real, local absence. However, a lack of Araucaria in New Zealandcoincident with apparent increasing seasonality is curious, given that Araucaria in Australiatoday is a characteristic tree of 'dry' rainforest or vineforest (e.g. Webb 1968). Araucariamacrofossils are present in a single horizon of the Fiddlers Member in the south of theManuherikia Group, where they were interpreted as indicating a marked seasonal aspect torainfall (Pole 1993a). Phyllocladus is perhaps similar - it is absent so far from thesemummified assemblages, but known from impressions further south in Otago (Pole 1992b),also from a possibly seasonally dry environment.

This paper extends the record of two extant species of New Zealand conifers, Prumnopitystaxifolia and Lepidothamnus intermedius, back into the Miocene. It also increases the'extinct' generic diversity with Acmopyle and perhaps Taxaceae joining the locally extinctRetrophyllum (Pole 1992b). The study of mummified conifer remains is resulting in a moredetailed understanding of this plant group in New Zealand than has hitherto been possible.

Table 1 Summary of conifer fossil distribution over the four localities included in thisstudy.

Locality H40/f4 H41/H2 H41/f74 H41/f77

Acmopyle masonii • • •Dacrycarpus dacrydioides • •Lepidothamnus intermedius •Podocarpus sp. "Mata Creek" •Prumnopitys taxifolia • •Retrophyllum vulcanense •Podocarpaceae/Taxaceae •Cupressaceae •

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Pole-Miocene conifers from the Manuhenkia Group 369

ACKNOWLEDGMENTSMost of this project was carried out in the Department of Plant Science, University ofTasmania, with funding provided via an ARC grant to R S Hill It was then completedin the Department of Botany, University of Queensland, with funding from an ARCgrant to M Dettmann and G Stewart I would like to thank all three for their support Iam also grateful to A M Pole, B J Douglas, G Mason, and A Dnnnan, who providedtransport to the localities on different occasions, and to the landowners, V Waldron andG Hamilton, who allowed access to their properties Thanks to L Scnven (RoyalTasmaman Botanic Gardens), who supplied comparative material of Taxus Themanuscript benefited from the comments of K. O'Connor, C Burrows, and a further,anonymous, referee

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370 Journal of The Royal Society of New Zealand Volume 27 1997

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Received 7 January 1997 accepted 5 March 1997

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miocene conifers from the manuherikia group, new zealand

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