Fossil imbricate-leaved Podocarpaceae from tertiary sediments in Tasmania

Aust. Syst. Bot., 1989, 2, 387-423

Fossil Imbricate-leaved Podocarpaceae from Tertiary Sediments in Tasmania

Penelope M. Wells andRobert S . Hill

Department of Plant Science, University of Tasmania, G.P.O. Box 252C, Hobart, Tas. 7001.

Abstract

Fifteen new species belonging to five genera (one, Mesibovia, newly described) of the Podocarpaceae with imbricate leaves are described from Oligocene-Early Miocene localities in Tasmania. Nine of these species belong to Dacrycarpus, which is now extinct in Australia, and their living affinities are widespread in latitude and altitude from New Zealand to New Guinea. Three species of Dacrydium s. str. demon- strate that this genus was diverse in Tasmania in the Tertiary, although it is now extinct in Australia. A species of Microstrobos, which is very similar to the extant alpinelsubalpine Tasmanian endemic M. niphophilus, occurs in both high- and low-altitude sites, and suggests that this type was once more widespread. The Oligocene Lagarostrobos marginuta is intermediate between the two extant species of Lagarostrobos, and suggests a closer relationship between them than do other lines of evidence. Mesibovia rhomboideu, recovered from three localities, shares features with several extant genera, and is of importance in understanding evolution within this group. The significance of the fossils for climatic and vegetation reconstruction is discussed.

Introduction

Sediments from the Tertiary Period of southern Australia contain a great diversity of Podocarpaceae macrofossils (Ettingshausen 1888; Cookson and Pike 1953a, 1953b, 1954; Florin 1963; Townrow 1965; Blackburn 1981; Hill and Macphail 1983, 1985; Greenwood 1987; Hill 1989). However, there are many species which have not been properly described or even reported. This has largely been due to the fact that most fossils consist of only vegetative remains, and the vegetative morphology of the living podocarps has not been well understood. However, Wells and Hill (1989) have investigated the vegetative morphology of the extant imbricate podocarps in detail, and it is now possible to attempt to identify fossils of a similar vegetative form.

In this study, new species of Tasmanian fossil podocarp twigs bearing imbricate leaves are identified and described using features of leaf arrangement and cuticular micrornorphology. Phyllocladus macrofossils have recently been treated in this way (Hill 1989), and it is our intention to extend this study to the broad-leaved podocarps in the future.

Fossil Deposits

Bells Plains

The fossiliferous sediments from this locality are from diamond drill hole core sections from BHP drill holes E.L. 33/79 (Fig. 1). Rocks from two drill holes, WA2 (41°21'S., 145O35'E.) and WY2 (41°20'S., 14S036'E.), were studied. The land surface at the top of the holes is about 600 m above sea level, and the fossiliferous formation occurs between approximately 100 and 150 m below this. The rocks are fine-grained micaceous grey mudstones

388 P. M. Wells and R. S. Hill

interbedded between Tertiary basalt flows (Brown and Forsyth, unpublished data). The mudstone probably formed in a basalt-dammed basin, inferred from the presence of basalt flows beneath the sedimentary layers.

The palynology of this deposit has been interpreted by Brown and Forsyth (unpublished data), who suggest that the presence of Cyatheacidites annulatus indicates that the palynoflora is no older than the Proteacidites tuberculatus Zone of Stover and Partridge (1973), while Foveosporitespalaequetrus, Nothofagiditesflemingii, Beaupreadites verrucosus and Periporopollenites vesicus indicate that the assemblage is no younger than this zone. Furthermore, N. flemingii and P. vesicus suggest a maximum age limit of the Middle P. tuberculatus Zone, and B. verrucosus an upper age limit of the Lower P, tuberculatus Zone. Despite possible differences between the time of first and last appearances between Tasmania and Victoria, this correlation with the Gippsland Basin suggests an Oligocene age, and probably Early Oligocene based on the presence of B. verrucosus.

Little Rapid River 4 1'

Bells Plains

A Monpeelyata

Pioneer

Fig. 1. Map of Tasmania showing the position of the fossil localities.

The Pioneer deposit (41°05'S., 147'56'E.) is located in a tin mine approximately 1 km north of the Pioneer township, on the eastern margin of a large Tertiary sedimentary basin (Fig. 1). Hill and Macphail (1983) described the site and the palynoflora which they assigned to the Lower Proteacidites tuberculatus Zone of Stover and Partridge (1973). A second source of data useful for dating the deposit comes from basalts which overlie the Tertiary sedimentary basin to the west of Pioneer (Morrison 1980). These have been dated, using K-Ar isotopic analysis (Brown, unpublished data) at about 16 Myr, therefore fixing an upper age of the sediments at the Early /Middle Miocene boundary (Hill and Macphail 1983). Overall, the data strongly indicate an Oligocene age for the flora, and possibly Early Oligocene.

Little Rapid River

The fossiliferous sediment outcrops in a cutting situated on an abandoned logging road approximately 2 km south of the Little Rapid River (4lo09'S., 145"14'E., Fig. 1). The deposit is composed of two different lithological units, each corresponding with a separate environ-

Fossil Imbricate-leaved Podocarpaceae 389

ment of deposition. The change from the older, lower unit (LRR2) to the younger, upper unit (LRR1) is sudden, and clearly marked by a band of black organic material 20-40 cm thick mixed with sand and silt. Within this layer are pieces of logs, some with a diameter of up to 10 cm and in an excellent state of preservation.

The lower unit is at least 2 m in depth and is composed of a very fine-grained dark grey mudstone characterised by many layers of black organic material containing macrofossils. Above the organic layer which separates the two units the sediment changes suddenly to a coarser grained material composed of dark grey sands, once again rich in black organic material. The plant remains do not form laminations as markedly as in the lower unit. The upper sandy unit (approximately 50 cm thick) becomes lighter in colour higher up in the cutting, and eventually gives way to several metres of very pale-coloured sand with only fine particulate organic matter scattered through it. Both upper and lower units are consolidated when dry but become plastic when wet.

Dating of the Little Rapid River deposit is based on palynology. Stratigraphy is uncer- tain; there are no associated basalts or correlative geomorphological features. M. K. Macphail (reported in Hi11 (1987) and personal communication) has assigned the palynoflora to the Lower Proteacidites tuberculatus Zone of Stover and Partridge (1973) based on the presence of Cyatheacidites annulatus, Chenopodiipollis sp. and Foveotriletes crater, which all range no higher than this zonule in the Gippsland Basin. Acaciapollenites myriosporites, which Stover and Partridge (1973) use to define the base of the Middle P. tuberculatus Zone, is absent from the sediment.

The Middle and Lower P. tuberculatus Zones are normally assigned to the Oligocene (approximately 25-36 Myr). More precise dating is difficult, since sediments of this age are rare in the offshore Gippsland Basin and the probability of simultaneous extinctions of taxa between Victoria and Tasmania is low (M. K. Macphail, personal communication). Never- theless, Macphail suggests that the Little Rapid River mudstones are slightly younger than the Oligocene Pioneer sediments due to the lack of many typically Eocene species present at Pioneer (e.g. Ilexpollenites anguloclavatus, Latrobosporites crassus, Nothofagidites deminutus, Parvisaccites catastus, Periporopollenites demarcatus, Propylipollis annularis and Tricolpites simatus). While it is possible that this may reflect differences in depositional environments or regional vegetation, the overall data support a Late Oligocene age. No difference in age between the two lithological units, LRRl and LRR2, can be determined.

It is likely that the Little Rapid River deposit represents a Tertiary lake which has under- gone a dramatic change in depositional regimes. The lower unit is characteristic of a low energy environment such as the centre of a lake with low stream input. Organic laminations would be the result of fluctuating stream flow (possibly seasonal), the plant matter most probably being derived from vegetation lining inflowing creeks and streams or from the lake edge itself.

A 20-40 cm band separates the lower (LRR2) mudstone from the stratigraphically younger (LRRl) sandy mudstone. Evidence for this being a single event rather than a slow accumulation of sediment includes:

(1) the band is horizontally continuous throughout the deposit and is not repeated any- where else in the exposure;

(2) large logs and branches (up to 10 cm diam.) tightly packed within the horizon suggest very rapid deposition;

(3) the wide range in grain size (mud up to coarse sand size) and lack of sorting of grains throughout the layer also suggest rapid deposition; and

(4) the excellent preservation of wood structure within the large logs is consistent with sudden burial.

A landslide or mudflow is the simplest explanation for this since it would also partly explain the change in lithology represented in the top unit. Massive movement of earth or mud may have dammed or altered the course of the major inflow to the lake, bringing its entry point into closer proximity with the site of deposition exposed in the cutting. The coarser upper unit would then simply be the result of deposition in a higher energy environment than the finer grained lower unit.

An alternative, although unlikely, scenario is that the higher energy deposition in the upper rock type reflects a shift in climate to one with a much higher rainfall.

Stratigraphic correlation of the deposit is difficult since the top contact appears to be eroded and obscured by talus derived from dolerite capping the hill immediately to the south. The dolerite occurs as dykes within Precambrian basement rocks.


Monpeelyata

During the early Tertiary, north to north-west trending faults developed over a widespread area in Tasmania, including the Midlands area and the Central Plateau. This faulting often resulted in the formation of topographic depressions in which Tertiary sediments were deposited in lakes or lagoons. Later, Tertiary volcanism and associated lava flows caused the damming of many of the fault controlled valleys and pre-existing river valleys, and gave rise to deeper and more enclosed basins in which further sedimentation could take place (Forsyth and Gulline 1979).

The fossiliferous sediment at Monpeelyata on the Central Plateau (42'04'S., 146"40'E., Fig. 1) is probably an example of a lake which formed in this manner, since the deposit is closely associated with basalt flows in the area (Hill 1988). Also, Tertiary faulting occurred on the Plateau during the Palaeocene (Forsyth and Gulline 1979) and the deposit has been dated as much younger than this (see below).

The Monpeelyata deposit is exposed in a canal cut by the Hydro-Electric Commission to connect the two impoundments of Little Pine Lagoon and Lake Echo. It is a small mudstone lens, approximately 15 m long and about 1.5 m thick (Hill 1988) and lies between Jurassic dolerite at its base and tholeiitic Tertiary basalt above. The mudstone is visible at the top of the channel cutting as an orange-red fine-grained sediment with only particulate organic matter and little macrofossil evidence. Its coloration and lack of well preserved fossils are probably partly due to low thermal metamorphism caused by the overlying lava flow and also due to heavy leaching and downward transportation of iron from the basalt. Beneath the orange-red layer and continuous with it is a richly fossiliferous fine-grained greenish mudstone. The macrofossils were obtained from this part of the lens.

From the abundance of Isoetes remains in the lens, it is probable that the depositional environment was a shallow freshwater lake or tarn similar to the many alpine lakes which currently occur in the Tasmanian highlands (Hill 1988). The current altitude of the site is approximately 900 m above sea level, and there is evidence to suggest that the relative altitude was similar at the time of deposition (Ollier 1986).

Pollen taxa in the Monpeelyata mudstone suggest that the sediment belongs to the Upper Proteacidites tuberculatus Zone of Stover and Partridge (1973) (M. K. Macphail and S. M. Forsyth, personal communication). This is based on the occurrence of Cyatheacidites annulatus and Acaciapollenites rnyriosporites, which make their first appearance in this zone, and the presence of Foveotriletes palaequetrus, Ilexpollenites sp., Nothofagidites flerningii and Periporopollenites dernarcatus, which do not range above this zone. According to Stover and Partridge (1973), the Upper P. tuberculatus Zone spans the Early Miocene, which suggests an age for the Monpeelyata flora of between 24.6 and 18 Myr.

The area around Great Lake is covered in many places by large basalt flows, which have been dated in five localities using K-Ar analysis. All fall within the age range 23.6-21.8 Myr (Sutherland et al. 1973). The nearest dated basalt to the weathered lava overlying the Monpeelyata mudstone occurs on the Skittleball Plains next to Little Pine Lagoon. The basalt is the oldest one dated on the Central Plateau (23.6 Myr) and underlies a sequence of younger flows that have been provisionally correlated with basalts bordering Great Lake, one of which is 22.9 Myr (Sutherland et al. 1973). Although the basalt at the Monpeelyata site is unsuitable for dating and cannot be precisely correlated with the Skittleball Plains basalt, it is unlikely that it is any younger than 21.8 Myr due to the very narrow range of ages determined for other Central Plateau basalts. These results agree with the palynological data, and an earliest Miocene age is therefore proposed for the Monpeelyata deposit, with the probable age falling within the period 21.8-23.6 Myr (M. K. Macphail, personal communication).

Regatta Point

The site occurs in a road cutting only a few metres above sea level at Regatta Point, Macquarie Harbour (42"09'S., 145'20'E., Fig. 1). In situ sediments have not been found, the fossiliferous mudstone being located as large blocks (up to 1 m long) contained within a glacifluvial outwash gravel (Hill and Macphail 1985). The gravel lies above an Early Eocene mudstone. The mudstone blocks are composed of quartz grains, black organic fragments, whole plant structures and cream-coloured mud flakes all dispersed through a dark brown- grey mudstone matrix. It is unlikely that the blocks have been transported far since they show little erosion, are large and angular, and occur very close together.


Although these rocks are not in situ, some information about their depositional environment can be derived from their lithology. The fine-grained nature of the sediment matrix indicates distal deposition in a low-energy environment such as a lake, river estuary or a shallow inland harbour such as the one existing there today. A freshwater environment is more likely than estuarine conditions, however, since there is no evidence of bioturbation, carbonate deposits or marine fossils. The presence of cream-coloured mud flakes up to 1 mm in diameter suggests that there may have been periodic influxes of slightly faster flowing water. The mud flakes are likely to have come from a proximal source, since they are much larger (relatively) than the mud grains making up the rock matrix. Their source is inferred to be a mud flat close by.

Evidence for the age of the Regatta Point sediments has been considered in detail by Hill and Macphail (1985). Since the fossiliferous blocks of mudstone have been transported to the site of deposition from an unknown location, relative age dating through stratigraphic means is not possible. However, by an analysis of the palynoflora and macroflora, along with studies of glacial outwash trains (e.g. Kiernan 1983), the sediments are considered to be Late Pliocene-Early Pleistocene.

Materials and Methods

All fossil specimens considered were organically preserved, and therefore were available for cuticular analysis. Fragments of fossiliferous mudstones were broken down by heating them gently in a mixture of water, hydrogen peroxide and tetrasodium pyrophosphate until the reaction became self-sustaining. After the reaction was complete the residue was washed through a 300 pm sieve to retain large organic fragments that were examined for podocarpaceous remains.

Podocarp twigs were cleaned of any siliceous particles by immersion in 40% wlw hydrofluoric acid for approximately 1 h. Some twigs were then placed directly onto aluminium stubs using double-sided adhesive tape for scanning electron microscope (SEM) study; others were used for cuticular analysis. Fossil cuticles were prepared using one of two methods: (1) immersion in cold 10% chromium trioxide for 1-2 h; or (2) immersion in concentrated nitric acid for 1 h and further clearing for a short time in 5% aqueous ammonia. The first method was preferred, since the chromium trioxide is reported to dissolve cellular material without degrading the cuticle surface (Alvin and Boulter 1974). Concentrated nitric acid tends to attack the surface of leaf cuticles, obscuring the finer structural details. However, where fossils were badly preserved, the second method proved the more successful, since chromium trioxide completely dissolved the cuticle. Some of the better preserved twigs (e.g. Pioneer and Bells Plains) had to be softened slightly by gentle heating in dilute hydrogen peroxide before either method for cuticle preparation was successful.

Following this preparation, cuticles were washed, and either stained in 1% aqueous safranin 0 and mounted in phenol glycerine jelly for light microscopy, or mounted unstained onto aluminium stubs using double-sided adhesive tape for SEM study. Specimens on aluminium stubs were gold-coated in a high vacuum evaporative coating unit to a maximum thickness of 20 nm and studied using a Philips 505 SEM operated at 15 kV. In all, about 250 specimens were studied under the SEM, and many more were either examined or photographed under the light microscope. The living species used for compari- son with the fossils were discussed by Wells and Hill (1989).

Taxonomic Descriptions

Order Coniferales Family Podocarpaceae

Dacrycarpus (Endl.) de Laubenf. (1969)

Dacrycarpus mucronatus Wells & R. Hill, sp. nov. (Figs 2,4-6)

Diagnosis

Foliage uniform, spirally arranged, leaves bifacial, narrow to falcate, decurrent, imbricate, appressed, strongly keeled, 1 9 (1 .3-2.7) mm long, 0.4 (0-3-0.5) mm wide, apex mucronate, incurved. Leaf base contracted, about 0.2 mm wide. Margins entire. Cuticle amphistomatic; stomata in four distinct zones, two narrow bands either side of midvein on


both surfaces, extending to apex on adaxial surface. Stomata in uniseriate rows, sometimes disordered or discontinuous or merging with others, rows parallel with long axis of leaf and typically separated by 1-3 epidermal cells; stomata absent near leaf margin, across midvein, across abaxial surface. Stomata1 zone 1-4 rows wide (typically 2-3). Stomata unequally amphicyclic, encircling cells usually missing from polar regions, often spanning adjacent subsidiary cells in lateral regions; polar subsidiary cells typically shared between adjacent stomata in a row, square or rounded with smooth anticlinal walls or granular periclinal walls;

Fig. 2. SEM of part of a branchlet of Dacrycarpus mucronatus (LRR2-043) showing the spirally arranged, loosely imbricate, mucronate leaves. Scale: 1 mm. Fig. 3. SEM of part of a branchlet of D. vieillardii showing the foliage with very similar morphology and arrangement to D. mucronatus. Scale: 1 mm. Figs 4-6. SEMs of the cuticle of D. mucronatus. Fig. 4. Inner cuticular surface (LRR2-043) showing the epidermal and subsidiary cells with thin, smooth anticlinal walls and granular periclinal walls. Scale: 25 pm. Fig. 5. Inner cuticular surface (LRR2-044) showing the stomatiferous zone. Scale: 50 pm. Fig. 6. Outer cuticular surface (LRR2-042) showing the Florin ring and stomata1 pore sunken below the leaf surface. Scale: 10 pm. Fig. 7. SEM of the inner cuticular surface of D. vieillardii showing the stomatiferous zone. Scale: 25 pm.


lateral subsidiary cells crescentic with a thick band of cuticle displaying prominent lateral and polar extensions adjacent to the guard cell, periclinal walls granular to smooth. Polar subsidiary cells 2, lateral subsidiary cells 2-4. Stomatal apparatus normally ovate, sometimes irregular. Stomatal pore elongate, orientation parallel to the long axis of the leaf, 20 x 7 pm. Florin ring indistinct, sunken below leaf surface. Epidermal cells within stomatiferous zones square to rectangular, irregular, shorter than non-stomatiferous epidermal cells. Non-stomatiferous epidermal cells are narrow parallelograms forming rows parallel to long axis of leaf, anticlinal walls thin, smooth, sometimes pitted, periclinal walls flat, granular.

Holotype. LRR2-044; Department of Plant Science, University of Tasmania. Type locality. Lower mudstone unit, Little Rapid River. Etymology. The specific epithet refers to the mucronate apex of the leaf. Specimens examined. LRR2-041-044.

Discussion

The specimens of D, mucronatus studied in detail all consisted of small pieces of stem bearing 7-12 spirally arranged leaves (Fig. 2). These specimens were readily assignable to Dacrycarpus because of the distinct combination of thin falcate foliage, and the acute to mucronate incurving leaf apex (Fig. Z), amphistomatic cuticle, four zones of uniseriate stomatal rows arranged parallel with the long axis of the leaf and rows of rectangular epidermal cells, thin, smooth epidermal cell anticlinal walls and granular periclinal walls (Fig. 4).

In gross vegetative morphology D. mucronatus most closely resembles the extant species D. vieillardii (New Caledonian endemic) (de Laubenfels 1969) which has mucronate, imbricate to closely imbricate foliage appressed on the penultimate branches, although more spreading on the ultimate branches (Fig. 3). The dimensions of D. mucronatus are similar to D. vieillardii (Figs 2,3) and some features of the cuticle are alike. Both are amphistomatic with rows of stomata on each surface nearly reaching the apex. Other uniformly small bifacial imbricate-leaved species such as D. compactus have only small zones of stomata near the base of the abaxial surface. Additionally, D. mucronatus and D. vieillardii have 2-3 stomatal rows per stomatal zone (Figs 5,7), and the stomatiferous areas are narrow.

However, other features of the cuticle clearly distinguish D. mucronatus from D. vieillardii and all other extant Dacrycarpus species. The stomatal rows and the shape and arrangement of subsidiary cells are relatively disordered in D. mucronatus compared with the ordered arrangement in D, vieillardii (Figs 5,7). D. vieillardii also lacks prominent lateral extensions on the guard cell cuticular flange, and does not have the flat granular subsidiary cell periclinal walls that are present in D. mucronatus (Figs 4,7). The Florin ring of D. mucronatus is usually sunken and often indistinct (Fig. 6). These differences therefore warrant the description of a new species to incorporate the fossil specimens.

Three fossil species of Dacrycarpus have been recorded previously from Australia: D. eocenica Greenwood; D. praecupressinus (Ett.) Greenwood; and D. setiger (Townrow) Greenwood (Greenwood 1987). Dacrycarpus praecupressinus has dimorphic foliage with neither leaf type closely resembling the leaves of D. mucronatus. Dacrycarpus mucronatus differs from D. eocenica and D, setiger in the absence of long bilaterally flattened distichous foliage. It can be further differentiated from D, setiger in that it lacks the marginal bristles of the latter, and can be distinguished from D. eocenica because it is clearly amphistomatic. Dacrycarpus eocenica has stomata restricted to one surface (Greenwood 1987). However, while Greenwood (1987) describes D. eocenica as hypostomatic (stomata restricted to the abaxial leaf surface), we believe that it is actually epistomatic (stomata restricted to the adaxial leaf surface) as shown and described in Greenwood's (1987) figure 6C.

Although the specimens of D. mucronatus examined to date have uniform foliage, it is possible that dimorphic foliage existed (as in many of the extant Dacrycarpus species).

Dacrycarpus involutus Wells & R. Hill, sp. nov. (Figs 8,9,12,13)

Diagnosis

Foliage uniform, spirally arranged; leaves bifacial, imbricate, appressed to loosely spreading, strongly keeled, decurrent, elongate scales 2.5 (2.0-3.0) mm long, 0.8 (0.7-0.9) mm


wide at widest point. Leaves strongly tapering from widest point, base slightly constricted. Apex acute, curved inward. Margins entire. Cuticle epistomatic, stomata in two zones near base of adaxial surface, either side of stomata free midvein. Stomata in short ordered uniseriate rows parallel to long axis of leaf, stomatal zones 3-4 rows wide, polar subsidiary cells normally shared between adjacent stomata of row, lateral subsidiary cells commonly in contact between rows, sometimes shared. Guard cells completely enclosed by cutin envelope with distinct T-shaped polar extensions. Stomata1 pore elongate, orientation parallel to leaf axis; Florin ring indistinct, smooth. Epidermal cells outside stomatal zones elongated, forming long narrow parallelograms arranged in rows parallel to stomatal rows. Within stomatal zones epidermal cells less elongated with thinner anticlinal walls. Adaxial surface epidermal cells with thin, smooth, slightly beaded anticlinal walls (<2.5 pm), abaxial epidermal cells with thicker buttressed anticlinal walls, 4-6 pm thick.

Holotype. M-2023; Department of Plant Science, University of Tasmania. Type locality. Mudstone lens, cutting, Monpeelyata canal. Etymology. The specific epithet refers to the cuticle enveloping the guard cells. Specimens examined. M-232, 237, 243, 244, 2023, 2024. Of the 830 podocarpaceous

specimens examined from Monpeelyata, 164 could be placed in this species based on vegetative morphology. Twelve specimens were investigated for cuticular preservation, but only six yielded well enough preserved cuticle for taxonomic investigation.

Discussion

All specimens of D. involutus exhibit the highly distinct cutin envelopes with T-shaped polar extensions covering the guard cells (Figs 8,9) which, among extant species, are unique to D. dacrydioides (Figs 10,ll). Some features of the fossils, such as the buttressed abaxial anticlinal walls (Fig. 12), which would otherwise be considered characteristic of Dacrydium, fall within the range exhibited by Dacrycarpus dacrydioides. Dacrycarpus dacrydioides, a New Zealand species, has buttressed abaxial anticlinal walls (Fig. 10) which, in addition to the cutin envelope over the guard cells, make this species strikingly different from all other extant Dacrycarpus species. Its cuticular morphology suggests closer relations with extant Dacrydium, but there is no doubt that the reproductive structures of D. dacrydioides are of the Dacrycarpus type (Allan 1961; de Laubenfels 1969; Moore and Irwin 1978; Salmon 1985).

Dacrycarpus involutus is similar to D. dacrydioides not only in its unusual cuticular features but also in its gross vegetative morphology. Semi-adult and adult leaves of D. dacrydioides are scale-like, imbricate to slightly spreading and 2-3 mm long (Salmon 1985), characters which closely match those of the fossil (Figs 13,14).

Nevertheless, the fossils are not identical to D. dacrydioides. Dacrycarpus dacrydioides is distinctly amphistomatic while D. involutus appears to have stomata located on the base of the adaxial surface only, though it is conceivable that stomata may occur on the abaxial surface but were not visible due to poor preservation. Buttressing does not seem to occur on the adaxial epidermal cell anticlinal walls in the fossils, whereas it is a common feature in D. dacrydioides. These differences, as well as the temporal and spatial gap between the fossil specimens and extant species, have justified the proposal of a new specific name for the fossils.

Dacrycarpus eocenica is the only previously described Dacrycarpus fossil which has an epistomatic cuticle. Florin (1931) and Buchholz and Gray (1948) considered amphistomatic cuticle diagnostic of Dacrycarpus, but there is considerable plasticity within the genus. For example, D. compactus has very few stomata on the abaxial surface. Therefore it is not surprising that in the past some Dacrycarpus species, including D. eocenica and D. involutus, were stomata-free on the abaxial surface. However, the long distichous bilaterally flattened and spreading foliage in D. eocenica clearly separates it from D, involutus.

Dacrycarpus praecupressinus, which has been recovered from several localities in south- eastern Australia and has been compared with many extant Dacrycarpus species, including D. dacrydioides (Cookson and Pike 1953b), is distinct from D, involutus. This is not only because it is amphistomatic but also because of its marginal frill located on the bifacial leaves and the bilateral, spreading, distichous nature of leaves on the dimorphic branches. Dacrycarpus setiger, described from sediments in southern Tasmania (Townrow 1965), has much larger foliage than D. involutus and distichously arranged leaves with an amphistomatic cuticle.


Figs 8 and 9. SEMs of the inner cuticular surface of Dacrycarpus involutus (M-2023) showing the stomatiferous zone with the distinct cuticular envelopes surrounding the guard cells (Fig. 8, scale: 25 pm) and T-shaped extensiuns ul" cutiil (arrowea] at the poles of the guard cells (Fig. 9, scale: 10 pm). Figs 10 and 11. SEMs of the inner cuticular surface of D. dacrydioides showing stornatal rows adjacent to epidermal cells with thickened, buttressed anticlinal walls (Fig. 10, scale 25 p n ) and stomata with cuticular envelopes surrounding the guard cells and T-shaped extensions of cutin (arrowed) at the poles of the guard cells (Fig. 11, scale: 25 pn) . Fig. 12. SEM of the inner cuticular surface of D. involutus (M-244) showing the slightly buttressed epidermal cell anticlinal walls. Scale: 25 pm. Figs 13 and 14. SEMs of part of a branchlet of D. involutus (M-232, Fig. 13, scale: 1 mrn) and D. dacrydioides (Fig. 14, scale: 1 mm) showing the spirally arranged, imbricate foliage.


Dacrycarpus acutifolius Wells & R. Hill, sp. nov. (Figs 15-18)

Diagnosis

Foliage uniform, spirally arranged; leaves bifacial, decurrent, broad rhomboidal, imbricate, closely appressed, keeled scales, 1 - 6 (1 3-1 -9) mm long, 0.7 (0.6-0.8) mm at widest point. Apex acute, strongly incurved. Margin entire. Cuticle epistomatic, stomata in two distinct zones either side of thin, stomata-free midvein, extending 2/3 leaf length. Apical region stomata-free. Stomata in ordered, closely packed uniseriate rows, parallel to long axis of leaf, rarely separated by more than one epidermal cell width, stomatal zones broad, 4-6 rows wide. Stomata elongate and normally paratetracytic, polar subsidiary cells 2, often shared between adjacent stomata of row, square in outline, granular periclinal wall; lateral subsidiary cells 2-4 sometimes in contact with adjacent subsidiary cells, sometimes shared,

Figs 15-18. SEMs of Dacrycarpus acutifolius (M-235) . Fig. 15. Part of a branchlet showing acute incurved leaves. Scale: 1 mm. Fig. 16. Inner cuticular surface showing the stomatal band with paratetracytic stomata oriented longitudinally to form rows. Scale: 10 pm. Fig. 17. Inner cuticular surface showing a stomatiferous zone adjacent to a band of rectangular epidermal cells. Scale: 25 pm. Fig. 18. Outer cuticular surface showing the stomatal pores. Scale: 10 pm.

shape crescentic, periclinal wall granular. Guard cell cuticle oval in outline, bordered by thickened cuticular rim, lateral extensions absent, polar extensions poorly developed. Stoma- tal pore rectangular, 11-13 pm long, 2 pm wide, parallel with stomatal rows. Florin ring prominent to indistinct, raised above leaf surface, elongate, smooth. Epidermal cells rectangular, arranged in files parallel with long axis of leaf, longer in non-stomatiferous regions; granular, flat, periclinal walls; thin, smooth, straight anticlinal walls.

Holotype. M-235; Department of Plant Science, University of Tasmania. Type locality. Mudstone lens, cutting, Monpeelyata canal. Etymology. The specific epithet refers to the acute apices of the leaves. Specimens examined. M-235, 236, 238, 1178. Of the 830 podocarpaceous specimens at

Monpeelyata, 274 could be assigned to this species on the basis of vegetative morphology. Seven of the 10 specimens investigated had reasonably well preserved cuticles.


Discussion

This fossil type is placed in Dacrycarpus because of the presence of the acute incurving leaf apices (Fig. 15), two zones of uniseriate stomatal rows on the adaxial cuticle surface arranged parallel to the long leaf axis, rows of rectangular epidermal cells between stomatiferous areas, thin, smooth epidermal cell anticlinal walls and granular periclinal walls, and paratetracytic stomata (Figs 16,17).

On gross morphology this species most obviously resembles varieties of extant D. imbricatus. Adult foliage of D. imbricatus is scale-like, 1-1.8 mm long, strongly keeled and acute, but neither flattened nor distichous (de Laubenfels 1969), matching very closely the foliage of D. acutifolius. Dacrycarpus imbricatus grows throughout the Indo-Malesian area including New Guinea (de Laubenfels 1969). Dacrycarpus acutifolius is nevertheless distinct from all extant Dacrycarpus species in that it appears to be epistomatic, although this feature is shared with the fossil species D. eocenica and D. involutus. It also differs from modern and other fossil species by possessing a round cuticular flange separating the guard cells from the subsidiary cells. The flange is without marked lateral or polar extensions and is bordered, usually around its entire circumference, by a thickened rim of cuticle (Fig. 16). Florin ring development is highly variable but predominantly indistinct (Fig. 18).

Dacrycarpus lanceolatus Wells & R. Hill, sp. nov. (Figs 19,23,24)

Diagnosis

Foliage uniform, spirally arranged, leaves bifacial, decurrent, imbricate, appressed, linear-lanceolate, keeled, 2.3 (2.0-2.5) mm long, 0.5 (0.4-0.8) mm wide. Apex acute, slightly inwardly curved or straight. Margin entire. Cuticle epistomatic, stomata in two distinct zones either side of wide stomata-free area across midvein. Stomata in ordered uniseriate rows parallel to long axis of leaf; rows rarely separated by more than one epidermal cell width. Stomata1 zones narrow, 2-3 rows wide. Stomata rounded in outline, amphicyclic; polar subsidiary cells two, square to rectangular, often shared between adjacent stomata of row; granular periclinal wall; lateral subsidiary cells two, rarely divided, crescent- shaped, often shared or in contact with subsidiary cells of stomata in adjacent rows, periclinal wall granular. Guard cell cuticle rectangular in outline with distinct polar and lateral extensions. Lateral extensions thin towards outer edge. Epidermal cells rectangular, longer in non-stomatiferous areas, arranged in longitudinal files; periclinal walls granular, flat; anticlinal walls thin, smooth, slightly pitted along tapering edge.

Holotype. M-1186; Department of Plant Science, University of Tasmania. Type locality. Mudstone lens, cutting, Monpeelyata canal. Etymology. The specific epithet refers to the lanceolate-shaped leaves. Specimens examined. M-242, 1186, 1187.

Discussion

The specimens examined have poorly preserved cuticle, although the twigs were apparently well preserved when extracted from the mudstone. After several attempts, only small fragments could be obtained for SEM examination. Much of the finer detail of cuticular morphology could not be observed and the extent of stomatal rows along the adaxial surface could not be determined. In addition, no pieces of cuticle could be obtained which might illustrate the external stomatal morphology. None of the whole twigs examined showed stomata on the abaxial surface, so it was assumed that this fossil type, like the other two Dacrycarpus species from Monpeelyata, possessed an epistomatic cuticle.

The specimens have been placed into Dacrycarpus because of the close similarities between their cuticle and that of modern species in the genus. The only major difference is the epistomatic nature of the cuticle, but this may be accounted for by the plasticity seen in extant Dacrycarpus species.

In the lack of a distinctly incurved pungent apex, the fossil species (Fig. 19) is similar to some specimens of extant D. compactus (Fig. 20), D. dacrydioides and occasionally D. imbricatus and D. cumingii. In most respects, however, D. compactus (a New Guinean species) more closely resembles the fossil since they share the features of linear-lanceolate imbricate leaves (Figs 19, 20), narrow stomatal bands (3-4 rows wide, Figs 21-23),


paratetracytic stomata (Fig. 24), and a thick cuticular flange between the guard cells and subsidiary cells that has distinct polar and lateral extensions (Figs 22, 23). Dacrycarpus compactus also has extremely few stomata on the abaxial surface, a situation which comes very close to the epistomatic cuticle of D. lanceolatus, and has uniform foliage lacking dimorphic or distichous leaves. On the other hand, D. compactus has, on the whole, much longer and slightly more spreading foliage than the fossil and in the majority of specimens the apex is more noticeably incurved.

Dacrycarpus lanceolatus is distinguishable from the fossils D, praecupressinus and D. setiger by the amphistomatic nature of the cuticle of the last two, and it differs from D. eocenica in the lack of bilaterally flattened distichous foliage, the size of leaves and the imbricate nature of the foliage.

Figs 19 and 20. SEMs of part of a branchlet of Dacrycarpus lanceolatus (M-242, Fig. 19, scale: 1 mm) and D. compactus (Fig. 20, scale: 1 mm) showing the spirally arranged linear-lanceolate leaves. Figs 21 and 22. SEMs of the cuticle of D. compactus. Fig. 21. Outer cuticular surface showing the poorly developed stomatal zone on the abaxial leaf surface. Scale: 200 pm. Fig. 22. Inner cuticular surface showing stomata with distinct polar and lateral extensions (arrowed). Scale: 50 pm. Figs 23 and 24. SEMs of the inner cuticular surface of D. lanceolatus, showing the stomatiferous zone (M-1187, Fig. 23, scale: 25 pm) and the stomatal complex (M-1186, Fig. 24, scale: 10 pm).

Fossil Imbricate-leaved Podocarpaceae

Dacrycarpus linifolius Wells & R. Hill, sp. nov. (Figs 25-27, 30)

Diagnosis

Foliage uniform, spirally arranged; leaves bifacial, decurrent, imbricate, closely appressed, distinctly linear, keeled, 4-5 mm long, 0.5-0.7 mm wide at broadest point, tapering to acute apex, base constricted, 0-2-0.4 mm wide. Margin entire. Apex straight or curved outwards. Cuticle amphistomatic, stomata in four distinct zones, two narrow bands on each side of wide stomata free zone across midvein on both leaf surfaces, nearly extending as far as apex on adaxial surface, but much less than '13 of leaf length on abaxial surface. Stomata in uniseriate rows, sometimes discontinuous or merging with others; rows parallel to longitudinal leaf axis, sometimes with stomata in contact or separated by 1-3 rows of epidermal cells. Stomatal zone 1-3 rows wide. Stomata extremely elongated, paratetracytic; polar subsidiary cells 2, square to rounded, often shared between adjacent stomata of a row; periclinal walls granular; lateral subsidiary cells 2, rarely divided, narrow rectangular to narrow crescent shaped, periclinal walls smooth to granular. Cuticular flange between guard cells and subsidiary cells elongate with distinct polar and lateral extensions, the latter sometimes reaching the opposite wall of lateral subsidiary cell. Subsidiary cell outer anticlinal walls deeper than epidermal cell anticlinal walls. Stomatal pore elongate, 18-25 pm long. Florin ring absent or very indistinct. Epidermal cells rectangular, arranged in longitudinal files, sometimes shorter within stomatiferous zones, granular flat periclinal walls, thin, smooth, sometimes pitted anticlinal walls. Anticlinal walls on abaxial surface often with lateral extensions covering the wall from sight under SEM.

Holotype. LRR1-851; Department of Plant Science, University of Tasmania. Type locality. Upper mudstone unit, Little Rapid River. Etymology. The specific epithet refers to the linear nature of the foliage. Specimens examined. LRR1-851, 1174.

Discussion

The long, linear, appressed, imbricate leaves of D. linifolius (Fig. 25) are unlike the foliage seen in any fossil or extant species of Dacrycarpus, even though its cuticle has all the diagnostic features of extant Dacrycarpus. The foliage of extant Dacrycarpus sometimes becomes very linear and appressed along fertile branches (e.g. D. steupii, D. cumingii) but the twig itself is actually much thicker than D. linifolius. However, it is possible that D. linifolius represents branchlets from fertile regions, either from one of the fossils described here or from an as yet undescribed species. Because of this possibility, it is difficult to compare this species with other Dacrycarpus species, which have had only their vegetative branches described in detail (Cookson and Pike 1953b; Townrow 1965; Greenwood 1987; Wells and Hill 1989).

If the fossil twigs represent vegetative branchlets then their foliage morphology and cuticle type distinguish them quite clearly from other fossil Dacrycarpus species. The cuticle of D. linifolius most closely resembles extant D. steupii in the elongate paratetracytic nature of the stomatal apparatus (Figs 26-29), the elongate stomatal pore lacking a Florin ring (Figs 30, 31), and the loosely spaced small number of stomatal rows within narrow stomatal bands. The vegetative foliage of D. steupii, which is a tropical species growing in New Guinea, Sulawesi and Borneo, is quite unlike the leaves of D. linifolius.

Dacrycarpus arcuatus Wells & R. Hill, sp. nov. (Figs 32-34)

Diagnosis

Foliage bifacial, spirally arranged, leaves bifacially flattened to acicular, decurrent, loosely imbricate, strongly keeled, 2.0-2.5 mm long, 0.3-0.5 mm wide. Apex acute, inwardly curving. Margins entire. Cuticle amphistomatic, stomata in four distinct zones; two narrow bands either side of a wide stomata-free area over the midvein on both the adaxial and abaxial surfaces. Full extent of stomatal bands unknown but covering at least half of leaf length. Stomata in disordered, uniseriate rows, sometimes discontinuous or merging with others; rows 2-3 per band, longitudinally oriented, separated by rarely more than one row of epidermal cells. Stomata elongate, more paratetracytic than amphicyclic.


Figs 25-27. SEMs of Dacrycarpus linifolius (LRR1-851). Fig. 25. Part of a branchlet showing the long, linear, appressed leaves. Scale: 1 mm. Fig. 26. Inner cuticular surface showing the stomatiferous zone composed of elongate paratetracytic stomata, adjacent to a zone of rectangular epidermal cells. Scale: 50 prn. Fig. 27. Inner cuticular surface showing the elongate stomata. Scale: 25 pm. Figs 28 and 29. SEMs of the inner cuticular surface of D, steupii showing the stomatiferous zone (Fig. 28, scale: 50 prn) and the elongate stomata (Fig. 29, scale: 25 pm). Figs 30 and 31. SEMs of the outer cuticular surface of D. linifolius (LRR1-851, Fig. 30, scale: 25 pm) and D. steupii (Fig. 31, scale: 25 pm) showing the elongate stornatal pores lacking Florin rings.

Fossil Imbricate-leaved Podocarpaceae 40 1

Subsidiary cells irregularly shaped and arranged; polar subsidiary cells 2, usually distinct, sometimes shared or in contact with adjacent stomata of row or sometimes lying obliquely or laterally in contact; periclinal wall granular, flat; lateral subsidiary cells 2-4, may extend past polar cells, variable shapes, giving stomatal complex an irregular outline, periclinal walls flat, granular. Cuticular flange between guard cells and subsidiary cells with fully developed polar extensions and distinct lateral extensions which sometimes connect with the opposite wall of the lateral subsidiary cell. Epidermal cells narrow, rectangular, arranged in longitudinal files, shorter in stomatiferous areas, periclinal walls flat, granular, anticlinal walls thin, straight, smooth, sometimes pitted.

Holotype. LRR1-243; Department of Plant Science, University of Tasmania. Type locality. Upper mudstone unit, Little Rapid River. Etymology. The specific epithet refers to the bow-shaped curve of the leaves. Specimens examined. LRR1-243, P-232, 871, 891, 902.

Discussion

Only one specimen of this species was recovered from Little Rapid River, but several were found at Pioneer. The combination of vegetative and cuticular features in this fossil is typical of Dacrycarpus and despite the irregularity in arrangement of both the lateral and polar subsidiary cells in the stomatal complex (Fig. 34), there is little doubt that this species belongs in this genus. The acute, nearly acicular, loosely spreading foliage is similar to semi- adult foliage of D. compactus, D. cumingii and D. dacrydioides (Figs 32, 14, 20), while the narrow stomatal bands with loosely spaced rows (Fig. 33), which extend at least halfway along the leaves and possibly further (an entire cuticle was not recovered from this specimen), indicate an affinity with D. imbricatus (Wells and Hill 1989). However, no one extant species possesses the entire range of characters observed in D. arcuatus and thus it is difficult to determine where its closest affinities lie.

Of the three fossil species described by previous authors, D. arcuatus is possibly closest to D. praecupressinus. However, the latter has thick, strongly pitted walls and foliage types not observed in D. arcuatus.

Dacrycarpus crenulatus Wells & R. Hill, sp. nov. (Figs 35-37)

Diagnosis

Foliage spirally arranged, leaves bifacial, decurrent, strongly keeled, loosely imbricate, short falcate to linear needles 1-1.8 mm long, 0.2-0.4 mm wide. Apex acute, incurved. Margin entire. Cuticle amphistomatic; stomata in four distinct zones, two either side of stomata-free area across midvein on both leaf surfaces; zones nearly extending to apex on adaxial surface, but only '12 leaf length on abaxial surface. Stomata in ordered uniseriate rows; rows 2-3 per band, often in contact, occasionally separated by 1-2 epidermal cells near band margin. Stomata rounded, amphicyclic with polar encircling cells usually missing, lateral encircling cells usually in contact with polar and lateral subsidiary cells; polar subsidiary cells 2, often shared between adjacent stomata of a row, round in outline, anticlinal walls deeper than those of epidermal cells, periclinal walls smooth; lateral subsidiary cells 2 sometimes divided to give 3, crescent-shaped, periclinal wall distinctly grooved and inclined downwards to meet cuticular flange of guard cell, outer anticlinal wall sometimes frill-like or crenate due to continuation of grooves from the periclinal wall. Cuticular flange between guard cells and subsidiary cells extensively developed with prominent lateral flaps and polar extensions. Stomata1 pore elongate 8-16 pm x 2.5-4.5 pm. Florin ring indistinct, sunken. Epidermal cells narrow, rectangular, arranged in longitudinal files, shorter in stomatiferous regions, periclinal walls granular, anticlinal walls smooth, deep, strongly pitted.

Holotype. P-221; Department of Plant Science, University of Tasmania. Type locality. Pioneer tin mine, Pioneer. Etymology. The specific epithet refers to the crenulate nature of the subsidiary cells. Specimens examined. P-221, 222, 231, 251, 252, 261, 881, 882.

Discussion

Of the 197 imbricate podocarp specimens examined from Pioneer, 171 had a leaf morphology falling within the range described above. Eight specimens were cleared for cuticular

402 P. M. Wells and R. S . Hill


examination and all yielded extremely well preserved whole leaf cuticles with identical morphologies. The combination of features described for D. crenulatus leaves no doubt that this species lies within the genus Dacrycarpus (see discussion in Wells and Hill 1989).

Dacrycarpus crenulatus has distinctly grooved lateral subsidiary cell walls (Figs 36, 37), a feature seen in some extant Dacrycarpus species including D. cinctus (fig. 6 in Wells and Hill 1989), D. compactus, D. cumingii and D. vieillardii (Fig. 7). These extant species all show development of distinct polar and lateral extensions to the guard cell cuticular flange (e.g. Figs 22, 39), which is also common to D. crenulatus (Fig. 37). However, D. compactus can readily be distinguished from D. crenulatus due to its much poorer development of stomata on the abaxial surface, and D. vieillardii has distinctly mucronate foliage (Fig. 3) not observed in D. crenulatus (Fig. 35). The markedly crenulate outer edges of the subsidiary cell cuticle distinguishes D. crenulatus from all other extant Dacrycarpus species.

The foliage of D. crenulatus is variable, with some leaves being almost linear (Fig. 3 9 , similar to those in D. cumingii (Fig. 38), and others short to falcate acicular needles. Although this could be considered a dimorphism in the leaves, none of the foliage exhibited the distichous arrangement found in juvenile or young leaves of most extant Dacrycarpus species and the fossil species described by previous authors. In this respect, D. crenulatus is similar to all other fossil Dacrycarpus species described here.

Dacrycarpus cupressiformis Wells & R. Hill, sp. nov. (Figs 40-43)

Diagnosis

Foliage uniform, spirally arranged. Leaves bifacial, decurrent, keeled, imbricate, appressed, elongate scales, 0 . 9 - 1 . 3 mm long, 0 .4 -0 .5 mm wide. Apex basically rounded but sometimes with a small point slightly incurved. Margin entire. Cuticle amphistomatic. Stomata in four zones extending from base almost to apex on both surfaces on either side of stomata-free midregion. Zones comprising 4-5 short uniseriate rows rarely more than 6 stomata long and separated by 1-2 epidermal cells. Stornatal complex amphicyclic, rounded in outline, polar and lateral subsidiary cells distinct. Polar subsidiary cells 2, often shared between stomata of a row, square to rectangular, granular periclinal walls, smooth, thin anticlinal walls; lateral subsidiary cells 2, often bisected, crescent-shaped, periclinal wall granular, anticlinal wall smooth, thin. Guard cell cuticular flange elongate with polar extensions continuous with short lateral extensions. Florin ring distinct, sunken. Epidermal cells rectangular, in parallel longitudinal rows, forming narrow zone across midregions. Anti- clinal walls thin, smooth, basically straight; periclinal wall flat, granular.

Holotype. LRR2-023; Department of Plant Science, University of Tasmania. Type locality. Lower mudstone unit, Little Rapid River. Etymology. The specific epithet refers to the small, closely appressed scale leaves. Specimens examined. LRR2-023, 024.

Discussion

This is an unusual Dacrycarpus species because of its blunt apex and scale-like leaves that are not markedly falcate (Figs 40, 41). These features are rare in Dacrycarpus, although blunt scale leaves were noted on some specimens of D. dacrydioides. Nevertheless, features of the cuticle of D. cupressiformis such as files of epidermal cells and stomatal bands parallel

Figs 32-34. SEMs of Dacrycarpus arcuatus (LRR1-243). Fig. 32. Part of a branchlet with acute, nearly acicular, loosely imbricate foliage. Scale: 1 mm. Fig. 33. Inner cuticular surface showing the narrow stomatal bands between broad zones of rectangular epidermal cells. Scale: 100 pm. Fig. 34. Inner cuticular surface showing the stomatal complex with irregularly arranged subsidiary cells. Scale: 10 pm. Figs 35-37. SEMs of Dacrycarpus crenulatus (P-221). Fig. 35. Part of a branchlet showing the linear imbricate foliage. Scale: 0.5 mm. Fig. 36. Inner cuticular surface showing rows of stomata with crenulate subsidiary cell walls. Scale: 25 pm. Fig. 37. Inner cuticular surface showing the stomata with crenulate subsidiary cell walls and polar and lateral extensions on the guard cell cuticular flange. Scale: 10 pm. Figs 38 and 39. SEMs of D. cumingii. Fig. 38. Part of a branchlet showing the linear imbricate foliage. Scale: 1 mm. Fig. 39. Inner cuticular surface showing the stomata with crenulate subsidiary cell walls. Scale: 25 pm.


to the long axis of the leaf and thin epidermal cell walls (Figs 42, 43) are distinctly Dacrycarpus-like, most closely resembling those of the extant species D. imbricatus. How- ever, D. cupressiformis lacks the prominent acute to pungent inwardly curving apex of D. im bricatus.

Dacrycarpus cupressiformis is markedly different from both the fossil species D. eocenica and D. setiger but does closely resemble the bifacial form of D. praecupressinus as described by Cookson and Pike (1953b). However, D. cupressiformis does not have the distinct marginal frill of D. praecupressinus.

Figs 40-43. SEMs of Dacrycarpus cupressiformis. Fig. 40. Part of a branchlet (LRR2-024) showing the spirally arranged, appressed imbricate foliage. Scale: 0.5 rnm. Fig. 41. Single scale leaf (LRR2-024) showing the stornatal pores each surrounded by a distinct, sunken Florin ring. Scale: 100 pm. Fig. 42. Inner cuticular surface (LRR2-023) showing the stomatiferous zones on the abaxial surface parallel to the long axis of the leaf. Scale: 100 prn. Fig. 43. Inner cuticular surface (LRR2-023) showing the stomatal complex and epidermal cells with thin anticlinal walls. Scale: 25 pm.

Dacrycarpus linearis Wells & R. Hill, sp. nov. (Figs 44-49)

Diagnosis

Leaves long, slender, decurrent, spreading, strongly keeled, acicular to bilateral needles 4-8 mm long, 0 .3 -0 .5 mm wide. Apex acute, straight. Margin entire. Cuticle with two full length stomatal zones on adaxial surface at least, zones may be wide, comprising 3-5 discontinuous, merging or ordered uniseriate stomatal rows, separated by 1-3 epidermal cells. Stomatal complex ovate, mostly amphicyclic; polar subsidiary cells often shared between the stomata of a row. Subsidiary cells regularly arranged, polar cells 2, rounded or square, anticlinal walls smooth, thin, periclinal wall slightly granular; lateral subsidiary cells 2, occasionally bisected, anticlinal walls thin, smooth, periclinal wall slightly granular and inclined towards hollow corresponding with the outer Florin ring. Guard cell cuticular flange rectangular in outline, with polar extensions and possibly lateral extensions. Florin ring usually distinct, smooth, rounded. Stomatal pore rounded, 8-10 pm long, 5-6 pm wide.


Epidermal cells narrow, rectangular, arranged in longitudinal files, shorter within stomatiferous zones, anticlinal walls thin, smooth, basically straight; periclinal walls granular.

Holotype. LRR2-051; Department of Plant Science, University of Tasmania. Type locality. Bottom mudstone unit, Little Rapid River. Etymology. The specific epithet refers to the linear nature of the leaves. Specimens examined. LRR1-241, 242, LRR2-05 1, 052, 053.

Fig. 44. Branchlet of Dacrycarpus linearis (LRR1-1901) showing the spreading, dense foliage. Scale: 5 mm. Figs 45-49. SEMs of D. linearis. Fig. 45. Awl-shaped needle-leaf (LRR1-053). Scale: 2 mm. Fig. 46. Inner cuticular surface (LRR2-051) showing rows of stomata forming discrete bands, and zones of thin- walled, non-buttressed epidermal cells. Scale: 100 p m Fig. 47. Inner cuticular surface (LRR2-052) showing stomata surrounded by epidermal cells with slightly granular periclinal walls. Scale: 25 pm. Fig. 48. Inner cuticular surface (LRR1-242) showing the stomata and granular-walled epidermal cells. Scale: 25 p n . Fig. 49. Inner cuticular surface (LRR1-242) showing a single stomate. Scale: 10 pm.

Discussion

The foliage of D. linearis (Figs 44, 45), with its non-falcate, almost needle-like leaves, is more like some extant species of Dacrydium than Dacrycarpus. However, the cuticular pattern is unmistakably that of Dacrycarpus, with the distinctly thin, straight, smooth epidermal cell anticlinal walls and slightly granular periclinal walls (Figs 46-49). Dacrycarpus


linearis appears to be epistomatic, since no stomata were observed on the abaxial surface of the leaves. It is impossible to suggest extant affinities for this species, since the foliage is clearly distinct from all extant species. It is possible that this species represents an extinct genus, but in the absence of reproductive structures the assignment to Dacrycarpus is suggested.

A key to the Australian macrofossil species of Dacrycarpus is given in Appendix 1.

Dacrydium Soland. ex Lamb. (1807)

Dacrydium tasmanicum Wells & R. Hill, sp. nov. (Figs 50-53)

Diagnosis

Spiral phyllotaxy; leaves uniform, short, decurrent, strongly keeled, loosely imbricate, somewhat bifacial needles, 1 a 7 (1.4-1.9) mm long, 0.4 (0.3-0.5) mm wide. Apex acute, straight or slightly incurved. Margin entire. Cuticle amphistomatic; stomata in four distinct zones, two either side of a stomata-free area across midvein; adaxial stomata1 zones extending from base to just below apex, abaxial zones from near base to half way along leaf or in small cluster near midpoint. Zones composed of 2-3 closely spaced uniseriate rows, becoming wider near base with up to 5 rows. Stomatal complex rounded, amphicyclic, polar encircling cells usually missing. Subsidiary cells compact, rectangular arrangement, polar subsidiary cells 2, rounded to rectangular outline, anticlinal and periclinal walls smooth; lateral subsidiary cells 2, sometimes bisected to form 3-4, crescent-shaped; periclinal wall smooth or occasionally grooved or papillate, sloping downward to meet hollow corresponding with outer Florin ring, anticlinal wall smooth, pitted, continuous with periclinal wall. Guard cell cuticular flange oval shaped with distinct polar extensions, prominent lateral extensions absent. Epidermal cells narrow, rectangular, arranged in parallel longitudinal files between stomatiferous zones, shorter and irregularly shaped within stomatiferous zones; periclinal walls smooth; anticlinal walls distinctly buttressed on abaxial surface giving thick sinuous appearance, sometimes obscured (under SEM) by lateral cutin extension at edge of anticlinal flange, thin on adaxial surface with little or no buttressing and no lateral cutin extensions. Stomatal pore elongate, 13-18 pm x 5-7 pm; Florin ring distinct, elongate to round in outline, smooth.

Holotype. LRR1-1031; Department of Plant Science, University of Tasmania. Type locality. Upper rnudstone unit, Little Rapid River. Etymology. The specific epithet refers to the species being recovered from Tasmanian

sediments. Specimens examined. LRR1-1031, 1032, 1172.

Discussion

Specimens of this species are extremely well preserved and whole leaf cuticles can be examined. The distinctly sinuous cell walls on the abaxial epidermal surface (Fig. 51), the marked difference between anticlinal wall ornamentation of the abaxial and adaxial surfaces, the shape and arrangement of stomata and the small imbricate helically arranged needles (Fig. 50) leave no doubt that this species belongs to Dacrydium. Other podocarpaceous genera such as Decussocarpus and Prumnopitys often exhibit buttressed or sinuous epidermal cell walls but these species have much larger, broader and distichously arranged leaves (Greenwood 1987).

Dacrydium tasmanicum does not closely resemble the long, thin, needle-leaved Dacrydiurn species such as D. xanthandrum, D. nidulum, D. lycopodioides, D. guillauminii, D. gibbsiae or D. beccarii. Dramatic foliage dimorphism does not occur in extant Dacrydium, as it can do in Dacrycarpus (de Laubenfels 1969), and thus separation of groups on the basis of gross leaf morphology is possible, particularly between the longer, needle- leaved species and the shorter, needle- or scale-leaved species.

On the basis of cuticle morphology, D. tasmanicum can readily be distinguished from D. araucarioides, D. balansae, D. elatum, D. nausoriensis and D. pectinatum since they all have extremely sinuous epidermal cell anticlinal walls on both the adaxial and abaxial surfaces. Dacrydium tasmanicum has this feature developed to a small degree on the abaxial leaf surface (Fig. 51) but not at a11 on the adaxial surface (Fig. 52). Dacrydium novo-guineense


can also be differentiated from the fossil due to its closely appressed imbricate scale-like foliage with distinct marginal frills along the apical and lateral leaf margins.

Dacrydium cupressinum (Figs 54-56), a New Zealand endemic, is the only extant species which shows a close affinity with D. tasmanicum. In all aspects of vegetative and cuticular morphology, D. tasmanicum falls within the character ranges of D. cupressinum. The simi-

Figs 50-53. SEMs of Dacrydium tasmanicum (LRRl-1031). Fig. 50. Part of a branchlet with small, spirally arranged imbricate leaves. Scale: 1 mm. Fig. 51. Inner cuticular surface showing epidermal cells with buttressed anticlinal walls giving them a sinuous appearance. Scale: 100 pm. Fig. 52. Inner surface of the adaxial cuticle showing amphicyclic stomata and smooth epidermal cell walls. Scale: 1Opm. Fig. 53. Outer cuticular surface showing the Florin ring development. Scale: 25 pm. Figs 54-56. SEMs of D. cupressinum. Fig. 54. Part of a branchlet showing small, spirally arranged, loosely imbricate leaves. Scale: 1 mm. Fig. 55. Outer cuticular surface showing the smooth, rounded Florin rings. Scale: 100 pm. Fig. 56. Inner surface of the adaxial cuticle showing amphicyclic stomata. Scale: 25 pm.


larity of the stomatal complex morphology between the fossil and this extant species is illustrated in Figs 52, 53, 55 and 56. Despite this close similarity, the fossil has been given separate specific status for the following reasons. Firstly, not all extant Dacrydium species have been examined (see Table 1, Wells and Hill 1989) and it is possible that the fossils may also lie within the character ranges of species which have not been seen. Secondly, no fertile material of the fossil species has been recovered, and therefore it cannot be compared with D. cupressinum at that level. Thirdly, there is a large spatial and temporal gap (30-35 Myr) between the two species, which suggests that the evidence should be overwhelming before the fossils are placed in that extant species.

No Dacrydium species occur in Australia today, and only one occurs in New Zealand. In addition, only two fossil species from Australian Tertiary sediments have previously been placed in Dacrydium, D. rhomboideum from the Yallourn coal deposits in Victoria (Cookson and Pike 1953a) and D. cupressinoides (Ettingshausen 1888) from Vegetable Creek. There is doubt about the generic identity of D. cupressinoides (Cookson and Pike 1953a), because of the lack of a description of the cuticular morphology, and it could be a species of Dacrycarpus based on its vegetative morphology alone. Dacrydium rhomboideum is distinct from D. tasmanicum since it has relatively shorter, broader, scale- like leaves and a marginal frill. The two new Dacrydium species described below (D. sinuosum and D. aciculare) differ from D. tasmanicum in their markedly sinuous anticlinal epidermal cell walls.

Dacrydium sinuosum Wells & R. Hill, sp. nov. (Figs 57-60)

Diagnosis

Leaves uniform, short, decurrent, strongly keeled, loosely imbricate needles, 2-25 mm long, 0.35-0.6 mm wide. Apex acute, straight or slightly inwardly curved. Margin entire. Cuticle amphistomatic; stomata in four distinct zones, two either side of stomata-free midvein; adaxial stomatal zones narrow, extending from base to just below apex; abaxial zones very narrow, extremely short, occurring at base of leaf only; zones composed of 2-3 ordered, uniseriate rows rarely separated by more than one epidermal cell. Stomata1 complex rounded, amphicyclic, polar encircling cells missing. Subsidiary cells compact, regularly arranged; polar subsidiary cells 2, varying outline, anticlinal walls usually buttressed, periclinal walls smooth; lateral subsidiary cells 2, sometimes bisected, periclinal wall smooth, sloping downward towards hollow formed by Florin ring, anticlinal wall thin, smooth. Guard cell cuticular flange rectangular with prominent polar extensions, but little or no lateral extension development. Epidermal cells narrow, rectangular, arranged in parallel longitudinal files between stomatal zones, irregular within stomatal zones; anticlinal walls thick, strongly buttressed giving distinctly sinuous appearance on both adaxial and abaxial surfaces, slightly thinner on adaxial surface; periclinal walls smooth. Florin ring prominent on outer epidermal surface, sometimes double-ringed, level with surface or sunken. Stoma- tal pore elongate 16(12-18) pm long, 3.5(3-4) pm wide.

Holotype. P-631; Department of Plant Science, University of Tasmania. Type locality. Pioneer tin mine, Pioneer. Etymology. The specific epithet refers to the very sinuous anticlinal walls. Specimens examined. P-262, 63 1.

Figs 57-60. SEMs of Dacrydiurn sinuosurn (P-631). Fig. 57. Single leaf. Scale: 0.5 mm. Fig. 58. Inner cuticular surface showing stomata on the abaxial surface and strongly buttressed epidermal cell anticlinal walls. Scale: 25 pm. Fig. 59. Inner cuticular surface showing stomata with buttressed polar subsidiary cell anticlinal walls. Scale: 25 pm. Fig. 60. Outer cuticular surface showing the Florin ring. Scale: 25 pm. Fig. 61. Juvenile branchlets of D. elaturn showing the spreading needle leaves. Scale: 1 cm. Figs 62-64. SEMs of the cuticle of D. elaturn. Fig. 62. Inner surface showing stomata and buttressed epidermal cell anticlinal walls. Scale: 25 pm. Fig. 63. Inner surface showing stomatal complexes. Scale: 25 pm. Fig. 64. Outer surface showing stomata with Florin rings arranged longitudinally along the leaf surface. Scale: 100 pm.



Discussion

Specimens of this species are very well preserved as single leaves (Fig. 57), and cuticle samples were easily prepared. The features of vegetative and cuticular morphology are all in accord with the generic assignment to Dacrydium. The gross morphological features of the fossils are almost identical to those of D. tasrnanicum (Fig. 57) but cuticular features such as the scarcity of stomata on the abaxial surface, the marked sinuosity of the adaxial surface anticlinal walls (Figs 58, 59), buttressing of polar subsidiary cell anticlinal walls (Fig. 59), relatively sinuous abaxial anticlinal cell walls and the rectangular guard cell cuticular flange in D. sinuosurn prevent it being conspecific with D. tasmanicum.

Long-needled extant species, such as D. xanthandrum, D. nidulum, D. guillaurninii and D. beccarii, and D. aciculare, the fossil species described below, have recognisably different foliage from D. sinuosurn as have the scale-leaved species D. araucarioides and D. novoguineense. Dacrydiurn elatum (Figs 61-64), a south-east Asian species, also has scale leaves in its adult form and its cuticle is very similar to D. sinuosum, since both have narrow stomatal zones composed of only 2-3 stomatal rows, buttressed polar subsidiary cell anticlinal walls (Figs 59, 63), relatively sinuous abaxial and adaxial epidermal cell anticlinal walls (Figs 58, 59, 62, 63), similarly shaped stomatal complexes (Figs 59, 63) and distinct Florin rings (Figs 60, 64). Foliage very similar to that in D. sinuosurn occurs in semi-mature leaves of D, elaturn (Fig. 61). However, D. elaturn has a considerably higher density of stomata on the abaxial leaf surface and has scale leaves in the adult phase. Therefore, although it is closely related to D. elatum, D. sinuosurn is distinct from all living species. It is also distinct from the fossil species D. rhomboideum for the same reasons given for D. tasrnanicum above.

Figs 65-67. SEMs of Dacrydium aciculare. Fig. 65. Single needle leaf (LRR1-441). Scale: 1 mm. Fig. 66. Inner cuticular surface (LRR1-482) showing the stomata and highly sinuous epidermal cell walls. Scale: 25 pm. Fig. 67. Inner cuticular surface (LRR1-482) showing the highly sinuous epidermal cell walls. Scale: 25 pm.

Dacrydium aciculare Wells & R. Hill, sp. nov. (Figs 65-67)

Diagnosis

Foliage uniform; leaves long, slightly decurrent, strongly keeled, awl-shaped needles, 4-8 mm long, 0.4-0.6 mm wide. Apex acute, straight. Margin entire. Cuticle with uniseriate rows of amphicyclic stomata at least 5 rows per stomatal band, epidermal cells arranged in longitudinal parallel files, anticlinal walls extremely sinuous.


Holotype. LRR1-441; Department of Plant Science, University of Tasmania. Type locality. Upper mudstone unit, Little Rapid River. Etymology. The specific epithet refers to the long needle-shaped leaves of this fossil. Specimens examined. LRR1-441, 482.

Discussion

Few details of this species could be recorded since the cuticle is very poorly preserved. Nevertheless, the long acicular leaves (Fig. 65) and the extremely sinuous anticlinal walls (Figs 66, 67) are sufficient evidence to place this species within Dacrydium. This find is significant since it is the only long, needle-leaved Dacrydium to have been discovered in Australia. Its foliage allies it closely with tropical species such as D. xanthandrum and D. guillauminii, which are the only two extant species investigated that have the combination of long, awl-shaped leaves and extremely sinuous anticlinal walls. Further correlation is impossible due to the poor preservation of the fossil material.

Lagarostrobos Quinn (1982)

Lagarostrobos marginatus Wells & R. Hill, sp. nov. (Figs 68-71)

Diagnosis

Spiral phyllotaxy; leaves bifacial, decurrent, keeled, elongate, closely appressed, imbricate scales, 1-1.5 mm long, 0.3-0.4 mm wide. Apex acute to blunt. Margin entire. Cuticle amphistomatic; stomata arranged randomly across both leaf surfaces, stomata not always longitudinal. Small stomata-free zone along base of midvein on adaxial surface and along midvein and apical regions of abaxial surface. Stomata usually solitary, subsidiary cells rarely touching. Stomatal complex rounded, amphicyclic; subsidiary cells 4-6, only occasionally differentiated into distinct polar and lateral cells, subsidiary cell periclinal walls sometimes with discontinuous irregular cutin thickening arising from guard cell complex. Guard cell cuticular flange rectangular with no lateral extensions and only poorly developed polar extensions. Epidermal cells polygonal, randomly oriented except over lower midvein where cells are rectangular and arranged in files; anticlinal walls thin, straight or curved, periclinal walls granular. Florin ring pronounced, sunken level with leaf surface, slightly elongate, smooth. Stomatal pore 13-22 pm long, 4-6 pm wide.

Holotype. LRR1-701; Department of Plant Science, University of Tasmania. Type locality. Upper mudstone unit, Little Rapid River. Etymology. The specific epithet refers to the entire margined leaves. Specimens examined. LRR1-701

Discussion

Only one specimen of this species has been recovered (Fig. 68). It has been classified within the 'Group C' Dacrydiums (Florin 1931; Wells and Hill 1989) because of the randomly scattered, isolated, regularly shaped, amphicyclic stomata (Figs 69-71), the random orientation of polygonal epidermal cells (Fig. 70), and the general lack of distinction between polar and lateral subsidiary cells. The periclinal walls are not distinctly U-shaped as in Lepidothamnus (e.g. fig. 30 in Wells and Hill 1989), and the anticlinal walls do not exhibit the slightly buttressed and beaded appearance typical of Halocarpus (e.g. figs 20, 21 in Wells and Hill 1989). However, the combination of the characteristic 'Group C' features with the deep, thin, smooth, epidermal cell anticlinal walls and rectangular-shaped guard cell cuticular flanges (Fig. 71 and figs 24-26 in Wells and Hill 1989) suggest affinity with Lagarostrobos. The conspicuous cutin thickenings which incompletely cover the subsidiary cell periclinal walls of the fossil (Fig. 71), a feature previously noted only in L. franklinii (Fig. 72 and figs 24, 25 in Wells and Hill 1989) is further evidence for placing the fossil in this genus.

Although this last feature promotes a strong relationship between L. marginatus and L. franklinii, other features such as the square, extended polar regions of the guard cell cuticular flange (Fig. 71) and the well defined Florin ring sunken level with the leaf surface (Fig. 69) are shared with L. colensoi (Figs 73, 74) and not apparent at all in L. franklinii. Lagarostrobos marginatus is distinct from both extant species in lacking their conspicuous marginal fringe and in having stomata with a slightly more regular arrangement.


Figs 68-71. SEMs of Lagarostrobos marginatus (LRR1-701). Fig. 68. Part of a branchlet showing elongate closely appressed scale leaves. Scale: 0.5 mm. Fig. 69. Entire-margined leaf showing randomly scattered stomata with prominent Florin rings. Scale: 100 pm. Fig. 70. Inner cuticular surface showing the stomatal distribution and the randomly oriented polygonal epidermal cells. Scale: 100 pm. Fig. 71. Inner cuticular surface showing a stomatal complex with unevenly thickened periclinal walls on the subsidiary cells. Scale: 10 pm. Fig. 72. SEM of the inner cuticular surface of L. franklinii showing a stoma with an uneven subsidiary cell periclinal wall. Scale: 25 pm. Fig. 73. SEM of the inner cuticular surface of L. colensoi showing the stomatal complex with a rectangular guard cell cuticular flange. Scale: 10 pm. Fig. 74. SEM of the outer cuticular surface of L. colensoi showing the well developed Florin rings. Scale: 100 pm.


Lagarostrobos franklinii (Hook. f.) Quinn (1982)

Discussion

Hill and Macphail (1985) reported macrofossils of this species at Regatta Point, but did not substantiate the identification. In all respects the fossil material is identical with extant L. franklinii (Figs 75-78, cf. figs 22-24 in Wells and Hill 1989). This morphological similarity, based on vegetative material, demonstrates that L. franklinii was extant by the Pliocene at least.

Figs 75-78. SEMs of Lagarostrobos franklinii. Fig. 75. Part of a branchlet (RPU-190) showing the closely appressed small scale leaves. Scale: 0.5 mm. Fig. 76. Stomata1 distribution on the abaxial leaf surface (RPU-190). Scale: 100pm. Fig. 77. Inner cuticular surface (RPU-111) showing the stomata separated by isodiametric epidermal cells. Scale: 50 pm. Fig. 78. Inner cuticular surface (RPU-111) showing stomata with unevenly thickened subsidiary cell periclinal walls. Scale: 10 pm.

Microstrobos Garden & L. A. S. Johnson (1950)

Microstrobos microfolius Wells & R. Hill, sp. nov. (Figs 79-82)

Diagnosis

Ultimate leafy shoots less than 1 mm in diameter bearing spirally arranged leaves. Leaves small, bifacial, strongly keeled, decurrent, closely appressed imbricate scales, 0.5-0.9 mm long, 0.4-0.6 mm wide. Apex blunt, incurved slightly. Margin with distinct continuous frill from widest points of leaf to apex, 30-60 pm in length from leaf edge. Cuticle episomatic, stomata in one large zone extending from base to apex on adaxial surface, small stomata- free zones near margins and in the region at base of midvein. Stomata lying in uniseriate rows, rarely separated by more than 1 epidermal cell, polar subsidiary cells often shared between stomata within the same row, lateral subsidiary cells sometimes in contact or shared

P. M. Wells and R. S. Hill


between stomata of adjacent rows. Stomata1 complex neither paratetracytic nor amphicyclic since subsidiary cells elongate, narrow, and of considerably varying lengths; polar subsidiary cells 2, square to elongate rectangular, anticlinal wall often deeply pitted. Guard cell cuticular flange considerably elongate, usually with marked polar extensions, but lateral extensions not conspicuous. Epidermal cells outside stomatal zones rectangular, narrow, in longitudinal files; periclinal walls slightly granular, anticlinal walls thick, beaded.

Holotype. M-1155; Department of Plant Science, University of Tasmania. Type locality. Mudstone lens, cutting, Monpeelyata Canal. Etymology. The specific epithet refers to the small scale leaves. Specimens examined. M-801, 1155, LRR2-021, 022

Discussion

This species is represented by nine leafy shoots at Monpeelyata (Fig. 79) and eight from the lower mudstone unit at Little Rapid River. The specimens from the two localities are virtually indistinguishable, alkhough the pid River specimens are slightly more acute at the leaf apex. .j:

Microstrobos micro f@L&*(~i~s 79 ingly similar to the extant M. niphophilus (Figs 83-86) in both vkge.&tive and lar morphology. Both have imbricate, closely appressed tiny scale leaves with a marginal frill (Figs 79, 80), which bear cuticle markedly different from all other imbricate podocarps. Microstrobos microfolius has a stomatal complex morphology (Fig. 81) that is unique to Microstrobos and Microcachrys within the imbricate Podocarpaceae and has a similar distribution and arrangement of stomata to extant Microstrobos. The spiral phyllotaxy of M. microfolius distinguishes it from Microcachrys tetragona which has opposite and decussate foliage.

The only notable differences between M. microfolius and M. niphophilus are the slightly smaller foliage and lack of distinct lateral extensions on the guard cell cuticular flange of M. microfolius (Fig. 81 cf. Fig. 85). The first difference is not enough to warrant the erection of a new species, and the second could merely be the result of poor preservation. However, the large temporal gap between the fossils (Miocene) and the first indisputable M. niphophilus ( 4 0 0 000 years B. P., Colhoun and van de Geer 1987) is, in our opinion, sufficient reason to warrant the erection of a new species. One other fossil species of Microstrobos, M. sommervillae, has been described by Townrow (1965) but this, along with the other extant species M. Jitzgeraldii, is distinguished from M. microfolius by its more elongate and spreading foliage with acute apices.

Mesibovia Wells & R. Hill, gen. nov. (Figs 87-94)

Diagnosis

Foliage uniform, spirally arranged; leaves bifacial, imbricate, elongated, rhomboidal scales. Apex acute, slightly inwardly curved. Margin entire. Cuticle very unequally amphistomatic, stomata arranged in two crowded zones from near base almost to apex either side of stomata-free midregion on adaxial surface. Abaxial stomata in small crowded basal zones either side of midregion. Stomata amphicyclic, randomly oriented, not in rows. Epi- dermal cells other than subsidiary cells rare in stomatal zones; epidermal cells between zones rectangular, in files parallel to long axis of leaf.

Figs 79-82. SEMs of Microstrobos microfolius (M-1155). Fig. 79. Part of a branchlet showing small, overlapping, spirally arranged scale leaves. Scale: 250 pm. Fig. 80. Scale leaf showing the distinct marginal frill. Scale: 100 p m Fig. 81. Inner cuticular surface showing the stomatiferous zone with elongate guard cell cuticular flanges and irregularly distributed subsidiary cells. Scale: 10 pm. Fig. 82. Inner cuticular surface showing rectangular epidermal cells arranged in longitudinal files. Scale: 10 pm. Figs 83-86. SEMs of Microstrobos niphophilus. Fig. 83. Part of a branchlet showing small, overlapping, spirally arranged scale leaves. Scale: 0.5 mm. Fig. 84. Scale leaf with a well developed marginal frill. Scale: 100 pm. Fig. 85. Inner cuticular surface showing stomata with strongly developed lateral extensions on the guard cell cuticular flange. Scale: 25 pm. Fig. 86. Inner cuticular surface showing the thick, beaded epidermal cell anticlinal walls. Scale: 25 pm.



Type species. Mesibovia rhomboidea. Etymology. The genus is named for Mr Bob Mesibov, who discovered the Little Rapid

River deposit.

Discussion

A new genus is proposed here to encompass foliage types found in three deposits of similar age that possess cuticles with a combination of features not observed in any of the other genera examined. The generic name refers to the imbricate nature of the foliage.

Mesibovia rhomboidea Wells & R. Hill, sp. nov. (Figs. 87-94)

Diagnosis

Leaves decurrent, not strongly keeled, 1-8-2.2 mm long, 0.7-0.9 mm wide. Stomata tightly packed in crowded zones, two zones extending almost from base to apex either side of wide stomata-free midregion on adaxial surface, two much smaller zones on basal corners of abaxial surface. Zones composed of randomly oriented, amphicyclic stomata, normal epidermal cells rare. Stomata1 complex irregular in outline, separated from neighbours by subsidiary cells only. Subsidiary cells 4-6, of irregular shapes and sizes, almost always shared with adjacent stomata, periclinal walls flat and granular, anticlinal walls thin, smooth, polar ends rounded, polar and lateral subsidiary cells indistinguishable. Guard cells' cuticular flange ovate in outline, polar ends rounded, lateral and polar extensions not developed. Epidermal cells between stomata1 zones along adaxial midregion and most of the abaxial surface, rectangular, narrow, oriented parallel to long axis of leaf, periclinal walls granular, anticlinal walls thin, smooth, straight.

Holotype. WA2-002; Department of Plant Science, University of Tasmania. Type locality. BHP drill hole WA2, E.L.33179, from Bells Plains, Murchison Highway. Etymology. The specific epithet refers to the rhomboidal scale leaves. Specimens examined. WA2-001,002, LRR1-244, P-621.

Discussion

This species was recovered from three different locations, Little Rapid River (upper mudstone unit), Pioneer and the WA2 borehole (Bells Plains), all of which are Oligocene. The LRRl and WA2 specimens are identical while the Pioneer specimens exhibited only minor differences (e.g. slightly wider spacing of stomata within stomatiferous zones) that were not sufficient to warrant segregation into separate species or even varieties.

Mesibovia rhomboidea possesses a combination of cuticular features hitherto unknown in imbricate Podocarpaceae. The arrangement of stomata into two distinct zones either side of a stomata-free midregion composed of rows of rectangular epidermal cells (Figs 88, 93) is reminiscent of Dacrycarpus and Dacrydium species. The thin, smooth, straight anticlinal walls and flat granular periclinal walls (Figs. 89, 92), although unlike those of Dacrydium, are also common to Dacrycarpus, but the similarities end there.

The outer cuticular surface of the specimens examined is not well enough preserved to enable description of the Florin ring structure. Nevertheless, degraded structures could be observed (Fig. 91) and it was therefore possible to determine the distribution of stomata on the abaxial surface.

Figs 87-94. SEMs of Mesibovia rhomboidea. Fig. 87. Part of a branchlet from Bells Plains (WA2-001) showing the closely appressed imbricate foliage. Scale: 0.5 mm. Fig. 88. Inner surface of the adaxial cuticle (WA2-002). Scale: 100 pm. Fig. 89. Inner cuticular surface (WA2-002) showing the stomata with ovate guard cell complexes. Scale: 25 pm. Fig. 90. Part of a branchlet from Pioneer (P-621) showing the closely appressed imbricate foliage. Scale: 0.5 mm. Fig. 91. Outer cuticular surface (P-621) showing degraded Florin rings. Scale: 50 pm. Fig. 92. Inner cuticular surface (P-621) showing the subsidiary and epidermal cells with thin, smooth, straight anticlinal walls and flat, granular periclinal walls. Scale: 25 pm. Fig. 93. Inner cuticular surface (LRR1-244) showing the rectangular epidermal cells arranged in files. Scale: 25 pm. Fig. 94. Inner cuticular surface (LRR1-244) showing the stomatiferous region. Scale: 50 pm.


Most other features of the cuticular morphology indicate a relationship with the Dacrydium 'Group C' genera. The closely appressed imbricate foliage (Figs 87, go), randomly oriented stomata (Fig. 89), ovate guard cell complex (Figs 89, 92, 94), lack of distinct polar and lateral subsidiary cells (Figs 89, 92, 94), and lack of uniseriate stomatal rows are characteristics which are normally diagnostic of this group. Thus cuticular evidence suggests close affinities with the 'Group C' Dacrydium genera, but M. rhomboidea is unique amongst the group and cannot be clearly allied with any one of the three genera Halocarpus, Lagarostrobos or Lepidothamnus.

Discussion

Dacrycarpus

Tasmanian Dacrycarpus fossils, whose closest modern relative grows in New Zealand (D. dacrydioides), exhibit the greatest diversity of all the imbricate genera studied from the Tertiary period of Tasmania. Of the 16 imbricate fossil species examined here, nine belong to Dacrycarpus, with six coming from the Oligocene and three from the Early Miocene.

The most notable aspect of the morphology of these Dacrycarpus species is the distinct lack of conspicuously dimorphic foliage. All but one of the extant species of Dacrycarpus exhibit strongly distichous, bilaterally flattened juvenile or young foliage which is considerably different from the spirally arranged falcate needles or lanceolate leaves of the adult foliage (de Laubenfels 1969). The exception is D. compactus which grows at high altitdues (3200-3900 m), particularly along the treeline, in New Guinea, and which has uniform spirally arranged, lanceolate foliage (Fig. 20) throughout its life (de Laubenfels 1969). The three Early Tertiary fossils previously described, D, eocenica, D. praecupressinus and D. setiger (Cookson and Pike 19538; Townrow 1965; Greenwood 1987) also exhibit the strongly dimorphic foliage seen in extant species, and the same is true of an undescribed Early Eocene specimen from the west coast of Tasmania (Hill and Wells, unpublished data).

One Oligocene fossil was retrieved which had bilaterally flattened falcate foliage of the kind normally seen in juveniles of many extant species, but the cuticle was poorly preserved, and the species cannot be described until more specimens are located. The general absence of two distinct foliage types in the Oligocene and Miocene appears to be a real occurrence rather than just an accident of preservation, since no other bilaterally flattened leaves have been seen in the deposits involved among several thousand plant fragments examined.

If the lack of juvenile bilaterally flattened foliage in Oligocene and Miocene species is real, then a possible reason for its loss may have been the significant drop in high latitude southern hemisphere temperatures that occurred at the onset of the Oligocene. Prior to the Oligocene, conditions were relatively warm and humid (Kemp 1978), possibly similar to the subtropical/ tropical conditions that prevail today in the Indo-Malaysian region where all but one of the modern Dacrycarpus species occur (the exception being D. dacrydioides which grows in lowland swampy forest in New Zealand). The only uniform-leaved species today is D. compactus which grows at high altitudes under relatively cool conditions. However, D. dacrydioides also grows in relatively cool conditions, and has distinct and persistent distichous, bilaterally flattened juvenile foliage and therefore it cannot be assumed that decreasing temperatures favoured the loss of dimorphic foliage.

It is interesting to speculate where Dacrycarpus species lacking dimorphic foliage orig- inated. In the fossil record species lacking this feature have only been recorded from Tasmanian Oligocene-Miocene sediments. Although there are no known uniform-leaved Dacrycarpus species in the Tasmanian fossil record prior to the Oligocene, it seems unlikely that they evolved in situ in such a short period after separation from Antarctica, since at least nine distinctly different uniform-leaved Dacrycarpus species occur in the Tasmanian sediments, which is a large number given the apparently conservative evolution in Dacrycarpus and Dacrydium during the Tertiary in Tasmania. Thus it is more probable that the uniform foliage of these fossil species existed prior to the Oligocene and hence prior to the total separation of Tasmania from Antarctica.

All extant Dacrycarpus species have amphistomatic leaves, although the stomatal band development on the abaxial surface varies. Some species (D. imbricatus, D. vieillardil) have fully developed bands, while D. compactus has only a small stomatiferous region at the base of the abaxial surface. The Oligocene fossil species also exhibit differing degrees of abaxial stomatal development, with D. cupressiformis having full length abaxial stornatal areas and D. linifolius exhibiting very short abaxial stornatal areas covering much less than one-third


of the total leaf length. However, unlike the amphistomatic Oligocene and modern species, the Miocene Monpeelyata Dacrycarpus species (D. involutus, D. lanceolatus, D. acutifolius) are all epistomatic. The only epistomatic Dacrycarpus species previously described is D. eocenica, erroneously described as hypostomatic by Greenwood (1987).

The Monpeelyata mudstone occurs at 920 m above sea level and is considered to be a cool climate subalpine flora (Hill and Gibson 1986; Hill 1988; Macphail et al., unpublished data). The two imbricate scale-leaved podocarps (Microcachrys tetragona and Microstrobos niphophilus) that occur in subalpine to alpine terrain in Tasmania today are both epistomatic, and so it may be that the epistomatic cuticles found on the Monpeelyata Dacrycarpus species are a response to cool, higher altitude conditions. Alpinelsubalpine regions are often subject to considerable water stress in both winter and summer. The location of stomata on only the inner surface of the leaves closely appressed to the stem would much reduce water loss.

Table 1. List of the fossil species showing the deposit(s) where they were found and the living species (with their geographic range) to which they have their closest affinity

(? signifies doubtful affinity)

Fossil species Living affinity

Dacrycarpus acutSfolius (Monpeelyata)

D. arcuatus (Little Rapid River, Pioneer) D. crenulatus (Pioneer) D. cupressiformis (Little Rapid River) D. involutus (Monpeelyata) D. lanceolatus (Monpeelyata) D. linearis (Little Rapid River) D. linifolius (Little Rapid River) D. mucronatus (Little Rapid River) Dacrydium aciculare (Little Rapid River)

D. tasmanicum (Little Rapid River) D. sinuosum (Pioneer)

Mesibovia rhomboidea (Bells Plains, Little Rapid River, Pioneer)

Lagarostrobos franklinii (Regatta Point) L. marginatus (Little Rapid River)

Microstrobos microfolius (Little Rapid River, Monpeelyata)

Dacrycarpus imbricatus (Indo-Malesia, including New Guinea)

Dacrycarpus D. cumingii? (Philippines, Borneo, Sumatra) Dacrycarpus D. dacrydioides (New Zealand) D. compactus (New Guinea) Dacrycarpus D. steupii ? (New Guinea, Sulawesi, Borneo) D. vieillardii (New Caledonia) Dacrydium guillauminii (New Caledonia) and

D. xanthandrum (Borneo and the Philippines to the Solomons)

D. cupressinum (New Zealand) D. elatum (Thailand and Tonkin to central

Sumatra and Sarawak) Dacrycarpus, Dacrydium, group C Dacrydium

Lagarostrobos franklinii (Tasmania) L. colensoi (New Zealand) and L. franklinii

(Tasmania) Microstrobos niphophilus (Tasmania)

The nearest living relatives of the nine fossil Dacrycarpus species described in this paper come from a wide geographic range (Table 1). Dacrycarpus mucronatus has very close affinities with the extant D. vieillardii which currently grows throughout New Caledonia, but particularly on serpentinite rock, along rivers and in moist areas generally where flooding is common (de Laubenfels 1969). Dacrycarpus involutus is almost identical to the extant New Zealand species D. dacrydioides, which grows throughout the north and south islands in forests up to 600 m altitude, where it is usually the dominant tree in swampy areas (Salmon 1985). Dacrycarpus cupressiformis and D. acutifolius both resemble the extant species D. irnbricatus which occurs throughout the Indo-Malesian region in tropical rainforests from sea level to 3300 m. However, seemingly small differences in morphology between fossil and extant species may signify completely different ecological tolerances. Thus any conclusions regarding climate and associated vegetation and regional setting must be drawn with caution unless supported by evidence from other sources.


Nevertheless, it is clear from the macrofossil evidence that Dacrycarpus was far more diverse in the Australasian region during the Tertiary, having existed formerly across Gondwana, and now represented by single species in New Caledonia and New Zealand. In relatively recent times, however, radiation appears to have occurred throughout the South- East Asian tropics (Greenwood 1987), with seven species being found across the Malesian-Melanesian region.

Dacrydium

Dacrydium species were found as macrofossils only in Oligocene sediments. The only previously described and adequately substantiated fossil species of Dacrydium, D. rhomboideum, is also from Oligocene sediments at Yallourn, Victoria (Cookson and Pike 1953a). Since Dacrydium no longer occurs in Australia, the three fossil species described here, D. aciculare, D. tasmanicum (Little Rapid River) and D. sinuosum (Pioneer), provide valuable information regarding the past distribution of Dacrydium in the Australasian region. Although D. aciculare is poorly preserved and hence difficult to relate to modern species with any certainty, D. sinuosum and D. tasmanicum exhibit characters very close to extant species (Table 1). Dacrydium tasmanicum is virtually indistinguishable from the extant species D. cupressinum, which occurs throughout New Zealand in podocarplbeech rainforest from sea level to 600 m (Salmon 1985). The closest living relative to D. sinuosum, however, is D. elatum, a species now restricted to warm, humid mountain forests from north-central Thailand to central Sumatra and Sarawak (de Laubenfels 1969).

These comparisons with living species suggest that a moist rainforest vegetation with Dacrydium species as prominent members existed close to the two deposits at the time of deposition. Evidence supporting humid conditions comes from palaeoclimatic sources (Kemp 1978) and from the presence of humid habitat indicator organisms such as epiphyllous fungal germlings (Lange 1978) which were present on some of the fossil leaves. From this evidence it appears that Dacrydium species occurred in humid rainforest habitats across south-eastern Australia at least up until the Late Oligocene.

Lagarostrobos

Since Quinn (1982) split Dacrydium s.1. into four genera, Dacrydium sstr . , Halocarpus, Lepidothamnus and Lagarostrobos, there has been considerable discussion as to the validity of the reclassification. Wells and Hill (1989) found excellent agreement between the cuticle groups which emerged and three of the genera, Dacrydium, Halocarpus and Lepidothamnus. The two species of Lagarostrobos, however, are no more similar to each other than they are to members of the other genera. The pollen grains of L. colensoi and L. franklinii are also quite different from one another (Tengner 1965; M. K. Macphail, personal communication). Other differences between the two Lagarostrobos species include karyotype (Hair and Beuzenberg 1988) and biflavones (Quinn and Gadek 1981). Hence the evidence suggests that L. franklinii and L, colensoi may not be as closely related to each other as suggested by Quinn (1982).

The discovery of the fossil L. marginatus from the Oligocene deposit at Little Rapid River is significant because it has features of both extant species. Thus this Oligocene species links the two extant species (neither of which appear in the macrofossil record until very near or even after the close of the Tertiary period) and may represent a common ancestor or a close relative of one.

In summary, it seems likely that Lagarostrobos was present at least as early as the Late Oligocene with a species existing that shared characteristics with both extant species, thus providing evidence in support of Quinn's (1982) classification.

Microstrobos

The most important feature associated with the fossil M. microfolius is that it was recovered from two deposits with completely different regional settings: one a lowland site of Oligocene age (Little Rapid River); the other a high altitude locality of Early Miocene age (Monpeelyata). There is no evidence to suggest that either deposit has altered in relative altitude since their time of deposition. The climate during the Oligocene was relatively cool with high rainfall occurring over south-eastern Australia (Kemp 1978). The first evidence of the development of colder high altitude regions is found in the Early Miocene at Monpeelyata (Hill and Gibson 1986; Hill 1988; Macphail et al., unpublished data). Thus it is apparent

Fossil Imbricate-leaved Podocarpaceae 42 1

that M. microfolius was adapted to the subalpine conditions at Monpeelyata, but was also present in cool temperate, lowland vegetation types (e.g. Little Rapid River). If, as appears likely, M. microfolius is closely allied with extant M. niphophilus or is perhaps even its immediate predecessor, then it appears that the ecological preferences of the species have narrowed or altered through time.

There are thus two possible scenarios for the early evolution of M. microfolius. It may have been present as a lowland species during the Oligocene and was gradually forced into highland areas due to high competition from the rapidly radiating angiosperms (see Hill and Bigwood 1987), or by increases in temperature during the Early Miocene (Kemp 1978). Alternatively, it may have already been present in both lowland and highland areas during the Oligocene, but for the reasons suggested above it became unable to compete in the lowlands, and by the Miocene or even later became restricted to alpine regions. Some time after the Early Miocene and before the Pleistocene it seems likely that M. microfolius evolved to the form now recognised as M. niphophilus.

Mesibovia

This genus, clearly a member of the Podocarpaceae, is unknown in the modern flora. Now extinct fossil genera which have been proposed in the past (e.g. Coronelia (Florin 1940)), have affinities that lie elsewhere in the Podocarpaceae, while Mesibovia is the first to show clear affinities with the 'Group C' Dacrydium genera, although still displaying certain characteristics in common with Dacrycarpus. Other than the rare Lagarostrobos fossil, 'Group C' species remain obscure in the fossil record. Thus it is possible that this group had their origins in the Dacrycarpus/Dacrydium complex via Mesibovia or a closely related genus. Evidence in favour of this proposal is that no 'Group C' Dacrydium species have been found in the fossil record earlier than the Late Oligocene, while Mesibovia has been recovered from Early Oligocene sediments and Dacrycarpus macrofossils date back to the Eocene. More fossil evidence is required to test this hypothesis.

Acknowledgments

This study was supported by a grant from the Australian Research Grants Committee. Our thanks to Dr J. Read for discussion on the ecology of the fossil species, and to Dr M. K. Macphail and Mr S. M. Forsyth for palynological interpretations.

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Appendix 1. Key to the fossil species of Dacrycarpus recovered from Australian Tertiary sediments

1. Leaves epistomatic ..................................................................................................... 2. Leaves amphistomatic ................................................................................................ 6 .

2. Cuticle with distinct cutin envelopes surrounding guard cells ............................... D. involutus Cuticle without cutin envelopes around guard cells .......................................................... 3.

3. Leaves 5 3 mm long ................................................................................................ 4 . Leaves >3 mm long ................................................................................................... 5.


4. Leaf apex strongly incurved; stomata1 bands 4-6 rows wide .............................. D. acutifolius Leaf apex only slightly incurved, if at all; stomata1 bands 2-3 rows wide ........... D. lanceolatus

5. Leaves strongly dimorphic, with early leaves distichous, bilateral ........................... D. eocenica Leaves not strongly dimorphic, never distichous .............................................. D linearis

6. Leaves with a distinctly pungent or mucronate apex ........................................ D mucronatus Leaves with an acute apex ........................................................................................... 7.

7. Leaves >2.5 mm in length, spirally or distichously arranged ............................................. 8. Leaves 1 2 . 5 mm in length, never distichous ................................................................. 10.

8. Leaves uniform, spirally arranged, distinctly linear, stem clasping ........................ D. linifolius Leaves dimorphic, early leaves distichous ....................................................................... 9.

9. Bilateral distichous leaves 4-12 mm long, margins with bristles ................................ D. setiger Bilateral leaves mostly 2.5 mm long, no bristles on margin ........................ D. praecupressinus

10. Lateral subsidiary cells with deeply striated periclinal walls and crenately margined anticlinal walls, stomata1 apparatus and aperture elongate ........................................................ D crenulatus Lateral subsidiary cell periclinal walls flat, granular to smooth, never striate, anticlinal walls smooth with irregular margins .............................................................................................. . l 1.

11. Leaves 2-2.5mm long, 0.3-0.5mm wide, acicular, acute; stomatal aperture elongate ................................................................................................................. D arcuatus

Leaves appressed elongate scales, blunt; 0.9-1.3 mm long, 0.4-0.5 mm wide, stomatal aperture rounded .............................................................................................. D. cupressiformis

Manuscript received 22 November 1988, accepted 2 March 1989

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Fossil imbricate-leaved Podocarpaceae from tertiary sediments in Tasmania