An Early Tertiary macroflora from West Dale, southwestern Australia

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An Early Tertiary macroflora fromWest Dale, southwestern AustraliaRobert S. Hill a & Hillary E. Merrifield ba Department of Plant Science , University of Tasmania , GPOBox 252C, Hobart, Tasmania, Australia , 7001b 25 Jecks Street, Rockingham, Western Australia, 6168Published online: 27 Nov 2008.

To cite this article: Robert S. Hill & Hillary E. Merrifield (1993) An Early Tertiary macroflora fromWest Dale, southwestern Australia, Alcheringa: An Australasian Journal of Palaeontology, 17:4,285-326, DOI: 10.1080/03115519308619596

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An Early Tertiary macroflora from West Dale, southwestern Australia

ROBERT S. HILL AND HILLARY E. MERRIFIELD

HILL, R.S., & ME~ItWn~, H.E., 1993:03:29. An Early Tertiary maeroflora from West Dale, southwestern Australia. Alcheringa 17, 285-326. ISSN 0311-5518. The Middle Eocene - Oligocene macroflora from West Dale in southwestern Australia is

described. The majority of fossils are leaves, and 35 tara are described and illustrated, including 12 new fossil species and three previously described species (two fossil, one extant). There are clear floristi¢ similarities with Eocene - Oligoeene macrofloras in eastern Australia (e.g. Agathis, Dacrycarpus, Oymnostoma, Cunoniaceae, Nothofagus, Lanraceae, BanksieaephyUum), but the West Dale flora is unique in the predominance of Myrtaeeae and, to a lesser extent, Proteaeeae. The West Dale macroflora offers support for the hypothesis that the Australian sclerophyU flora e~lved primarily in response to low nutrient levels (especially phosphorus) and was pre-adapted to developing xeric climates. However, alternative hypotheses cannot be ruled out.

Robert S. Hill, Department of Plant Science, University of Tasmania, UPO Box 252C, Hobart, Tasmania, Australia 7001; and Hillary E. Merrifield, 25 Jecks Street, Rockingham, Western Australia 6168; received 6 December 1991; received 6 December 1991.

Keywords: Early Tertiary, plant macrofossils, southwestern Australia, scleromorphy.

AUSTRALIAN Early Tertiary macrofloras are common in the southeast of the continent (e.g. Hill, 1990a), but have rarely been reported elsewhere. This has led to a major bias in reconstructions of vegetation for that time. Macrofloras are known in southwestern Aus- tralia, but they are either impression floras (see review in Wilde & Backhouse, 1977) or dispersed cuticles (e.g./_amge, 1978). The discov- ery of a diverse macroflora at West Dale in southwestern Australia is therefore of particular significance, since the specimens are preserved as complete or near complete organs with ex- cellent surface cellular preservation. This flora provides the first detailed vegetation reconstruc- tion for this region of Australia.

Material and methods Well preserved plant macrofossils including leaves, stems, wood and infructescences have been discovered in a small siltstone deposit on the Darling Plateau at West Dale, 76 km east southeast of Perth and 325 km west southwest

0311/5518/93/020285-42 $3.00 ©AAP

of Beverley, Western Australia (32 ° 13.6' S, 116 ° 36.2' E, Fig. 1). The deposit lies on privately owned land and the precise location is on record in the Department of Earth and Plan- etary Sciences, Western Australian Museum. The WAM specimens on which this report is based are part of the Western Australian Museum's fossil plant collection.

The fossil-bearing outcrop lies about 270 m above sea level on the eastern slope of the drainage divide between the west-flowing Dar- kin and the east-flowing Dale Rivers. The Darkin River joins the Helena River and the Dale flows into the Avon-Swan system, both of which eventually flow west through the Darling escarpment to the Swan Coastal Plain (Fig. 1).

The outcrop is a low, tree-topped ridge trend- ing westsouthwest on the eastern side of the divide on a genre slope leading down to a small tributary of the Dale River. The ridge is roughly oval in shape and approximately 150 m long and 70 m at its widest part. The northern side of the ridge is composed of fossiliferous siltstone and the southern of ferruginous sandstone. The siltstone area is surrounded by small tabulate siltstone 'floaters' for about 10 m on

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286 R. S. HILL AND H. E. MERRIFIELD ALCHERINGA

- 31 " "

32"-

33*-

.I

Fig. I . Map of southwestern Augralia, showing the position of the West Dale deposit in relation to the Darkin and Dale Rivers.

the northern side, with some also on the eastern and western ends. The siltstone crops out as a thin stratum along the crest of the ridge axis and overlies the sandstone. A laterite profile has developed in the area and towards the western end of the ridge erosional remnants of a ferrn- ginous duricrnst can be found ((3. Kendrick, pets. comm.).

The fossil matrix is a yellowish-brown siltstone with inclusive small lenses of sand. The siltstone is fissile and the tabulate floaters produced from it split readily to reveal the fossil plants which have been preserved in iron oxides with some limonitic deterioration. The under- lying ferruginous sandstone is red-brown in eolour. The coarse pisolitic duricrust vestige has a base of cobble-sized angular clasts of siltstone material and was estimated to have a

thickness of 350 mm ((3. Kendrick, pers. comm.).

The age of the siltstone is uncertain. Neither it nor the associated sandstone in the ridge are indicated on the relevant geological map (Pin- jarra, 1:250,000, Sheet SI/50-2, Geological Survey of Western Australia, 1980) though lateritisation in the area has been considered to be possibly Tertiary in age.

The Darling Plateau has an average elevation of 300 m (Wilde & Low, 1980) and constitutes an ancient low-relief erosion surface (peneplain) once drained by sluggish water channels (Mulcahy et al., 1972). Uplift of the plateau is believed to have occurred in the Pliocene (Clarke et al., 1967) and it has since been much eroded and dissected by rejuvenating streams which have incised new channels through the Darling Range to the Swan Coastal Plain. At West Dale, stream channel incision has exposed the fossil-bearing siltstone layer which appears to be part of the old drainage system now represented by sediments on the divides.

The fine grain of the siltstone and the preservation of plant material by iron oxide replacement are consistent with low energy and anaerobic fossilisation conditions. The presence of sand suggests the silt.stone was part of a sluggish river system, perhaps a billabong, but open to occasional direct discharge.

Present day remnants of this old drainage system are believed to be preserved in the Goonaping-Darkin swamp system on the other side of the divide to the northnorthwest of the West Dale locality (Mulcahy eta/., 1972). Drill samples taken at 21 and 34-37 m during a search for hydrocarbons in the Darkin Swamp, 16 km northwest of the fossil site yielded microfossils of Late Eocene to Early Oligocene age (Balme, 1967 and pets. comm.). These samples yielded a somewhat similar flora to the West Dale macrofossils, but there is no way of correlating the two deposits because of the lack of microfossils in the siltstone. Palynomorphs are not preserved organically in the sediment and thin sections of the sediment which were cut and examined with a transmitted light microscope did not yield identifiable palynomorphs.

The presence of siltstone clasts in the overly- ing laterite suggests that prior to lateritisation the siltstone unit was exposed to erosion, possi-

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ALCHERINGA EARLY TERTIARY MACROFLORA, W. A. 287

FrERII~PHYTES One unidentified species

GYMNOSPERMS AP.XOC.Am~a~

Agathis kendrickii sp. nov. PODOCARPACEAE

Dacrycarpus patulus sp. nov. Rewophyllum australe sp. nov. Podocarpaceae sp.

ANGIOSPERMS CASUAR[SAt"~J~

Gynmostoma sp. CUNONUC'EAE

of. Callicoma FRG~'EAE

Nothofagus tasmantca Hill LAUR~W.AE

Laurophyllum striatum ~p. nov. MY~ACEAE

Myrtactphyllum striatum sp. nov. M. sinuatwn ~p. nov. M. brochldodromum sp. nov. M. westdaliense sp. nov. M. annulatum sp. nov. M. sp. Agonis cf. flcruosa (Spreng.) Schau. Rhodomyrms austra//s sp. nov.

Bank~ieaephyllumfastigalwn Cookson & Duigan R westdaliense sp. nov. R longifolium sp. nov. of. Alloxylon el. Stenocatpus Proteaceae sp. 1-6

MISCELLANEOUS ANGIOSPERMS Angiosperm sp. 1-7

Tablel. List of rmerofossil taxa identified in the West Dale sediment.

bly due to change of watercourse or lowering of ground water level; this is consistent with eu- static changes and drier palaeoclimate in the Oligocene (Kemp, 1978; Finlde & Fairbridge, 1979). The soil profile resulting from weathering was lateritised, with siltstone clasts incor- porated into the lowest layer of the laterite. Palaeomagnetic studies in the Perth Basin have suggested that southwestern Australia under- went extensive weathering processes resulting in widespread lateritisation in the Mid Tertiary (Schmldt & Embleton, 1976). As yet, there is no information available on the possible age of laterites in the West Dale area, though it has been suggested that laterite duricrust formation

on the Darling Plateau began in the Oligocene and continued through the Miocene (Finlde & Fairbridge, 1979).

If the postulated sequence of events at West Dale is correct, then the upper age limit for the plant fossils in the siltstone layer ~ u l d possibly be Oligoeene. The lower limit is unknown, but is presumed to be within the Early Tertiary. Some of the maerofossils identified later in this report are of limited stratigraphic use. Pollen of Nothofagus subgenus Lophozonia (Hill & Read, 1991; Hill & Jordan, 1993) first appears in Australia in the Middle Eocene (Dettmann et oJ., 1990) and the oldest maerofossils described to date are Late Eocene (Hill, 1988). Gym- nostoma macrofossils are common from the Early Eocene and may also limit the maximum age of the sediments, although Paleocene sediments are not well studied for macrofossil content in Australia. The oldest unequivocal Agathis macrofossil in Australia is from the Middle Eocene sediments at Maslin Bay (Christophel, 1981). Thus macrofossil evidence suggests a maximum age of Middle - Late Eocene, although this must be considered as preliminary, since there is clearly danger in extrapolating essentially southeastern Austra- lian age ranges to southwestern Australia.

On a gross morphological scale, the leaves and occasional reproductive structures are often fragmentary, but in many cases the general leaf form and the venation pattern is well preserved. However, the most remarkable feature of the fossils is the preservation of the leaf surface. The organic content of the macrofossils has been lost, and has been replaced by very fine- grained sediment or crystals. During the replacement process little or no surface detail has been lost. When leaf fragments are examined using scanning electron microscopy (SEM), surface cell detail is often as finely preserved as in living plants. However, there is no internal cellular preservation, and so only the surface can be viewed. In many of the fossils, the cuticle does not appear to have preserved well, so that the surface viewed by SEM is actually that of the epidermal cells rather than the outer cuticular layer. In such cases the result is similar to viewing a light microscope prepara- tion of a leaf cuticle, with all epidermal cell detail present. In other fossils the cuticle is still

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288 R. S. HILL AND H. E. M E R R ~ I E L D ALCHERINGA

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Fig. 3. A-C, holotypc o f Retrophyllum australe OVAM P.88.96). A, whole specimen, showing many pairs of oppmite leaves which are heterofacially flattened in the shoot. Scale = 1 era. 13, SEM of the outer leaf surface showing stomate~ in irregular rows, but not aligned in bands. Scale = 200/~m. C, SEM of the outer leaf mrface showing a single stomate with the typical oval shape of the subsidiary cells around the guard cells and the well developed Florin ring. Scale = 10/~m. D-F, Podocarpaceae ap. (WAM 1).88.187). D, whole specimen, showing the broad lamina and well developed primary vein. Scale = 1 cm. E, SEM of the outer leaf surface showing a single stomate, with most of the cuticle still intact around the stomatal opening. Scale = 10/~a. F, SEM of the outer non-stomatai leaf surface. The cuticle has not preserved and the sinuous and probably buttressed epidermal cell walls are clearly visible. Scale -- 100/zm.

Fig. 2. A, part o f a ~erile fern pinnule (WAM 1).87.261). Scale = 5mm. B-E, Agath/s kendrickii. 13, holotype (WAM P.84.29), showing most of a leaf with the base and apex missing. SCale = 5ram. C, apical part of a leaf (WAM P.84.30b), showing the falcate shape. Scale = 5mm. D, SEM of the outer leaf surface (WAM 1).84.29), showing stomatal rows with stomates at varying angles to the long axis of the leaf, which runs from left to right. Scale = 100 #m. E, SEM of the outer leaf surface (WAM P.84.30b), showing three stomatea, one of which is completely plugged. Scale = 50 #m. F-I, Dacrycarpuspatulus (holotype, WAM P.84.34a,b). F, G, counterparts of the whole specimen showing the relatively spreading foliage in a bifacially flattened arrangement. Scale = 2ram. H, SEM of the leaf surface showing stomatal rows. Scale = 100/~m. I, SEM of the outer leaf surface showing two stomates, with a clear stomatal plug in the one on the fight. Scale = 20ram.

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intact, and this often hampered the search for diagnostic taxonomic characters.

Initially whole specimens were photographed using reflected light at various angles to best highlight the venation pattern and any other important features. This was carried out in the Western Australian Museum. Small fragments of the mineralised leaf tissue were then removed from the specimens and transferred to the Uni- versity of Tasmania for SEM study. The leaf fragments were attached to aluminium stubs using double sided adhesive tape. Stubs were coated in a high vacuum evaporative coating unit to a maximum thickness of 20 nm, and examined with a Philips 505 Scanning Electron Microscope operated at 15 kV. All fossils are stored in the Western Australian Museum. Leaves of several hundred extant species from Western Australia (from the Western Australian Herbarium) and eastern Australia were available for comparison with the fossils and were prepared in the same way as the fossils for SEM study. This was necessary since leaf morphological characters are still poorly known for many extant Australian plant groups.

Identification of macrofossils All but one of the macrofossils described below consist of vegetative organs, which were by far the most common specimens. Identification varied from those which were assigned to species and/or genera through to those which could not even be assigned to a family. Comparison was made on the basis of all available characters and, in the best preserved specimens, this consists of leaf form, venation pattern and epidermal cell detail. In this regard these fossils rival the best preservation found in Tertiary leaves in Australia to date. Many of the fossils belong to families for which there is a very poor under- standing of the leaf morphology of the extant species. Where these families are large, an

exhaustive survey was beyond the scope of this study, and taxonomic determinations have thus been limited. However, research on these fossils will continue, and it is anticipated that the identity of many species will become clearer in the future. A summary of the macrofossil taxa considered in this report is given in Table 1.

Pteridophytes The sediments yielded numerous fragments of vegetative fern pinnules (Fig. 2A). In the ab- senee of reproductive structures the affinities of these ferns are uncertain, but their presence is of great environmental significance.

Gymnosperms

Araucariaceae

Several large leaf fragments are preserved which can be assigned to the family Arau- cariaceae. The leaves are relatively large ( > 6 cm long and > 1 em wide, Fig. 2B), obovate, and taper to an acute, often falcate apex (Fig. 2C) and base. The visible venation pattern is made up of numerous (about 20) parallel veins which terminate at the leaf margin or apex (Fig. 2C). Stomates occur in loosely defined rows between the veins, and have a random orientation (Fig. 2D). Most of the stomates are plugged, although the plug is often degraded (Fig. 2E). Subsidiary cells are not always easily observed, but the most common number appears to be four, with two lateral and two polar cells (Fig. 2E). Cells over the veins are elongate in comparison with normal epidermal cells.

The Araucariaceae comprise two extant genera. The features of these fossils are characteristic of Agathis, and in particular the leaf size and shape, and the random stomatal orientation (Bigwood & Hill, 1985). The large-leavedAr- aucaria species have stomates aligned parallel

Fig. 4. A, photosynthetic branch of Oymnoswma (WAM P.84.75b). Note the leaf whorl about one third of the way up from the base and the marked groove down the stem between each leaf palr. Scale = lmm. B, approximate transverse section through a Gymnostoma 'cone' (WAM P.84.60), showing the central axis and exerted valves. Scale = 2ram. C, leaf of 0f. CaUicoma (WAM P.88.84A). Scale ffi 1 cm. D, cleared leaf of Callicoma serratifolia. Scale = 1 cm. E, SEM of the outer leaf surface of of. Callicoma (WAN[ P.88.84A) showing elongated epidermal cells over a vein and normal epidermal cells with occaisoml stomates. Scale ffi 100/an. F, SEM of the outer leaf surface of of. CaUicoma (WAM P.88.84A) showing stomates surrounded by epiphyllous fungus. Scale = 25 pm. G, SEM of the outer leaf surface of Callicoma serratifolia, showing stomates and trichomes. Scale ffi 2 5 / ~ a .

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ALCHERINUA EARLY TERTIARY MACROFLORA, W. A. 291

D

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Fig. 5. Nothofagus tasmanica (WAM P.84.80). A, whole specimen. Scale = I cm. ]a, part of the leaf showing the fine venation and the leaf margin. Scale -- 5mm. C, SEM of the outer stomatiferous leaf surface, showing the randomly oriented stomates within an areole. Scale = 100/an. D, SEM of the outer stomatiferous leaf surface, showing two stomates with the thin cutlcular covering mostly intact. Scale = 10 #tin. E, SEMI of the outer stomatiferoua leaf surface showing a single large glandular trichome. Scale -- 25 #tm. F, SEM of the outer non-stomatiferotm leaf surface.

to the long axis (Bigwood & Hill, 1985; Hill, 1990b), whereas those Araucaria species with randomly oriented stomates (Section Euctacta) have relatively small leaves (Stockey & Ko, 1986).

Bigwood & Hill (1985) and Hill & Bigwood (1987) plotted the frequency of different stoma-

tal orientations in fossil and living Agathis species. The West Dale fossils most closely resemble the extant Agathis australis (which currently occurs on the north island of New Zealand) in stomatal orientation but, in the absence of information on the inner cuticular surface, this comparison cannot be carried fur-

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Fig. 6. Holotype of LaurophyUum striatum (WAM P.84.94b). A, whole specimen showing an entire margined leaf with brochidodromous venation. Scale = 1 cm. B, SEM of the non-stomatiferous leaf inflate, showing a large gland (base of figure) with the euticular mriatiom radiating away from it. Scale = 250/tin. C, SEM of the outer, probably stomatiferous, leaf surface. Epidermal cells are clearly defined, but stomatal openings have not been located. Scale ffi 100/an.

ther. These fossils are clearly distinct in this character from all other fossil Agathis species, and they are therefore assigned to a new species, A. kendrickii.

Podocarpaceae

Several specimens can be assigned to the Podo- earpaeeae. One fossil consists of a shoot section bearing several small, possibly spirally ar ranged imbricate leaves (Fig. 2F, G). Stomates occur in 4--5 rows for the entire leaf length on either side of the main vein on both leaf surfaces (Fig. 2H). There are two polar and two or three lateral subsidiary cells per stomate, and one or two cells separating stomates in a row (Fig. 21). All stomates are

aligned parallel to the long axis of the leaf and some are plugged. All epidermal cells appear to have straight walls. The leaf size and arrangement, stomatal alignment, and epidermal cell wall shape are all characteristic ofbifacially flattened foliage of the genus Dacrycarpus (Wells & Hill, 1989a). This genus is very well represented by macrofossils in Tertiary sediments from southeastern Australia (Cookson & Pike, 1953; Wells & Hill, 1989b; Hill & Car- penter, 1991). Many of the characters used by Wells & Hill (1989a,b) to differentiate vegetative material of the fossil and living Dacry- carpus species rely on being able to observe the inner cutieular surface. That is not possible for the West Dale fossil. However, the leaf size, shape and angle of departure from the axis of the West Dale Dacrycarpus is clearly distinct from all previously described fossil species and, for that reason, it is placed in a new species, D. patulus.

Several well preserved shoots have been recovered which have up to 14 pairs of opposite leaves in a decussate arrangement (Fig. 3A). The cuticular morphology of these shoots (Fig. 3B,C) clearly allies them with the Podo- carpaceae and, within that family, this leaf arrangement is highly diagnostic. Hill & Pole (1992) describe heterofacially flattened shoots as those where leaves on opposite sides of the axis both twist at the base in an anticlockwise direction to form a two-dimensional shoot where the abaxial leaf surface is seen on the left hand side of the shoot axis and the adaxial surface on the right hand side. Such an arrangement, in conjunction with the presence of a single primary vein in the leaf is diagnostic of RetrophyUum among extant genera, but is also found in the fossil genera WiUungia and Smithtonia (Hill & Pole, 1992). The West Dale fossils have several characters which ally them with RetrophyUum. The shoots are very long (Fig. 3A), like the lateral shoots of that genus; the leaves are amphistomatic, with stomates in long rows, but with no obvious bands present (Fig. 3B); Florin rings are prominent around the stomatal opening (Fig. 3C), which is often plugged; and epidermal cell walls are consis- tently straight (Fig. 3B, C). These specimens represent the first fossil record of Retrophyllum in Australia and are assigned to the new species, R. australe. There are five extant species of

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D

_

Fig. 7. A, holotype ofRhodomyrtus austra//s (WAM P.88.86A), showing the characteristic paired veins arising from the primary vein near the leafhase. Scale ffi I cm. B, cleared l ea fo fR , ele&ans. Scale ffi I cm. C, SEM of the outer leaf surface ofR. austra//s (WAM P.88.86A), showing stomates in an areole and a probable trichome base (arrowed). Scale ffi 50/~m. D, SEN[ of the outer leaf surface ofR. australis (WAM P.88.86A), showing a single stomate with • stomatal plug and a pair oflongltudlnal subsidiary cells. Scale -- 10/an. E, SEM of the outer lcafsurface ofR. elegans, showing gomatea in an areole and a trichome base. Scale = 50/.tm.

RetrophyUum (Page 1988) which occur in Fiji, New Caledonia and South America.

One specimen has been recovered which consists of the basal half of a relatively large leaf (the preserved portion is 37 x 8 r a m , F i g . 3D). The leaf is apparently lanceolate, petiolate, and has a strongly striated primary vein and petiole. Parallel rows of stomates occur on either side of the primary vein on at least one leaf surface.

The leaf surface is well preserved, and the presence of a thick cuticle often obscures cell detail and, although stomates were observed (Fig. 3E), little could be concluded except that they conform to the general podocarpaceous type. In some areas highly sinuous epidermal cell outlines were seen (Fig. 3F), but these occur in more than one of the extant broad- leaved podocarpaceous genera.

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Angiosperms

Casuarinaceae

Several branchlets and infructescences ('cones') of Casuarinaceae have been recovered and, although the twigs are not connected to the cones, they conform to the same type and are considered to be part of the same taxon. The twigs are always four-parted and square in section. Each face of the twig has a clear line running down the centre (Fig. 4A) which is interpreted as a groove. The surface of these twigs was examined using a dissecting microscope, and structures which were thought to be stomates were observed on the faces of the twigs. However, stomates could not be seen on twig sections which were examined with the SEM. The cones are all preserved in section, and they are sometimes difficult to interpret (Fig. 4B). However, the valves are highly exserted, and occur in alternate whorls of four, so that eight valves can be seen in section. All these features are characteristic of the genus Gymnostoma (Christophel, 1980; Dilcher et al. , 1990) and, although some diagnostic characters (e.g. subsidiary cell arrangement and stomatal distribution) could not be observed, the affinity of these fossils with Gymnostoma is clear. The fossils are remote both spatially and temporally from extant Gyranostoma, and for that reason they are not assigned to an extant species. A large number of very well preserved Gym- nostoma fossils from several Tertiary localities in southeastern Australia awaits description, and it is appropriate to wait for the work on those fossils to be published before the specific affinity of the West Dale Oymnostoma is considered further.

Cunoniaceae

One specimen is very well preserved and represents most of a highly serrate leaf, with prominent secondary veins which terminate in the serrafions in a craspedodromous pattern (Fig. 4C). Tertiary veins are well formed and prominent in parts of the leaf at least. Surface detail is not clear, but stomates are restricted to one leaf surface (Fig. 4E), and trichome bases were not observed. The affinities of this leaf are not completely certain, but the leaf shape and venation pattern are typical of families such

as Elaeocarpaceae and Cunoniaceae. Within these families, the cunoniaceous species CaUicoma serratifolia stands out as having a very similar leaf morphology. The leaf size, shape and venation pattern is very similar (Fig. 4C cf. D), although the serrations have dis- finctly different morphology. The stomates of the fossil are not well preserved, but resemble those of C. serratifolia in the presence of a ridge of cutin around the outside of the stomatal pore (Fig. 4F cf. G). However, the characteristic trichomes of C. serratifolia are absent from the fossil, and in the absence of detailed morphological comparison with many other living species, the fossil wil l be re fer red to as Cunoniaceae cf. CaUicoma.

Fagaceae

A single specimen has been recovered which can be assigned to Nothofagus. The leaf is incomplete, but is prominently serrate, with secondary veins which terminate in the serration or, more usually, the sinus above it in a typical craspedodromous pattern (Fig. 5A,B). Tertiary veins are prominent and well formed at an angle of greater than 90 ° to the primary vein. The leaf surface is quite well preserved. Stomates are restricted to one leaf surface, are randomly oriented, and there are no specialised subsidiary cells (Fig. 5C, D). The guard cells form almost circular stomates which are quite variable in size. Trichomes have not been observed on this leaf surface, but a single large gland was located on the leaf fragment examined (Fig. 5E). The non-stomatiferous leaf surface is featureless (Fig. 5F).

This leaf has the gross morphology, venation pattern and serrafion type typical of extant species of Nothofagus, and in particular N. moorei in subgenus Lophozonia (Hill & Read, I991; Hill & Jordan, 1993). However, diagnostic cuticular characters are required to confirm this identification. The fossil has stomates typical of the subgenus, with their random orientation, circular guard cell shape and variable size, along with the apparent absence of a T-piece of cutin at the poles (although this may be difficult to observe even if present). The gland on the stomatiferous surface is also typical of Nothofagus in general, and places its generic identity beyond doubt. The absence of other trichomes is unusual, but the extant spe-

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296 R. S. HILL AND H. E. MERRIFIELD ALCHERINUA

i~i ~ ~.J~-~": ..-,--~,;~, ,:~

i ,~i • i~'i~ . ~ ..... ; ~ Z - ~ .~. . . . . . . ~,~ .... ~! ~! , ~ ~,!~ ~ ~ J~x~,~ ~ ,~ ~, ~i

.~ii~ ,~, .... ii ~,, .... ~J

~ ~ i~ '-'; ~!i '~,~ ~' ~ ....

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ties which the fossil most closely resembles, N. moorei, is also often very nearly glabrous, and on small leaf fragments like those examined here they may be missed.

Leaf fossils of this general type are common in southeastern Australia from the Late Eocene onwards, and Hill (1983) assigned Early Terti- ary leaves from Tasmania which were very similar to extant N. moorei to N. tasmanica. The West Dale leaf differs from N. tasmanica only in having a relatively narrow base, but given the apparent damage to the leaf this could be an artifact of an abnormal development or of preservation. In any event this character is not sufficient to warrant the erection of a new species and therefore the West Dale leaf should be assigned to N. tasmanica. This leaf represents the first macrofossil record of Nothofasus with cellular preservation from the western two thirds of Australia.

Lauraceae

Lauraceous leaves are common in Early Terti- ary macrofloras in Eastern Australia (Hill, 1986, 1988). However, because of the large number of extant species (2000 to 2500 species in 31 genera according to Kostermans, 1957), many of which are very poorly known, it is difficult to determine the affinities of fossil leaves at higher taxonomic resolution within this family. For this reason, Hill (1986) argued that fossil species should be placed in the genus Laurophyllum until such time as more comparative work on the leaf anatomy of extant species is undertaken.

One specimen from West Dale can be assigned to the Lauraceae. The leaf is nearly complete (Fig. 6A), although both the base and apex are missing. It is linear-elliptical in shape and has very well defined brochidodromous venation. The secondary veins are relatively widely spaced along the primary vein, weak intersecondary veins arise from the primary

vein occasionally, and the tertiary veins are sometimes well defined, but more often somewhat random in their course. The surface of this leaf is not well preserved, but a single secretory cell has been located (Fig. 6B) which is very similar to that produced by other extant and fossil lanraceous species (see illustrations in Hill, 1986). This leaf surface, which is probably non-stomatiferous, is covered in fine striations which are usually randomly oriented, but radiate away from the secretory cell. Stomates have not been located on the other leaf surface (Fig. 6C), but it is a common feature of lauraceous leaves that stomates can be very difficult to see on the outer leaf surface, where they often produce little more than a small slit (see fossil species in Hill, 1986). The venation pattern of this specimen is similar in some respects to LaurophyUum arcuatum and L. brochidodromum, but it differs in some important aspects and is considered to represent a distinct species, Laurophyllum striatum.

Myrtaceae

The Myrtaceae are of particular interest in the Australian fossil record because of their domi- nance in the modern flora, especially in the form of Eucalyptus. However, there are few described myrtaceous leaf fossils. Hill & Mae- phail (1983) illustrated a leaf with cuticular preservation from Tasmanian Oligoeene sediments, and Christophel & Lys (1986) described a new organ genus, Myrtaciphyllum, to encom- pass leaves of two species from the Eocene sediments at Anglesea. There are numerous earlier reports of myrtaceous leaves, but they lack organic preservation and the comparative work with extant species is poor.

There are many myrtaceous leaves at West Dale. While some have good epidermal cell detail, it is more ot~en poor, and it seems that leaf specimens of this family have degraded more than most in this deposit or, more proba-

Fig. 8. A, fossil leafofAgon/s cf.flexuosa (WAM P.87.268). Scale = 1 cm. 13, cleared leaf of extant A. flexuosa. Scale = I cm. (2, SEM of the outer leaf surface o f fossilA, ef.flexuosa (WAM R87.268), showing the poorly preserved stomates as raised areas. Scale = 50 /an . D, SEaM of the outer leaf surface ofextantA.flexuosa, showing the raised stomates. Scale ffi 50 pan. E, SEM of the outer non-stomatiferous leaf surface of fossil A. cf.flexuosa (WAM R87.268). Scale = 50 pro. F-H, holotyp¢ ofMyrtaciphyllum striatum (WAM P.87.265). F, whole specimen, showing the basal ha l fo f a leaf. Scale -- 5mm. G, SEM of the outer leaf surface showing the well preserved stomates, the small, unicellular trichome bases with the foot cell embedded in the epidermis, and the large, multicellular, glandular triehome. Scale ffi 50 pm. H, SEM of the outer non-stomatiferous leaf surface. Scale -- 50 fan.

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298 R. S. HILL AND H. E. MERRIFIELD ALCHER1NGA

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bly, the cuticle is still intact. The myrtaceous leaves can be divided into at least eight species. All are broad-leaved and have the characteristic myrtaceous intramarginal vein. Two of these species have enough diagnostic characters to warrant their inclusion in extant genera, but the remainder have less certain affinities and are referred to the genus MyrtaciphyUum.

One specimen, which is preserved for most of its length, with only the apex missing, consists of an elliptical leaf with prominent paired basal secondary veins arising just above the insertion of the petiole (Figs 7A, 21A). While this type of venation is found in many families, and in particular is often associated with the Lauraceae, the leaf surface detail confirms its myrtaceous affinity. The paired basal secondary veins are interpreted as intramarginal veins which, by phyletic slide from an ancestral type, now appear well inside the margin. These intramarginal veins are robust, and the true secondary veins are relatively minor, and join the primary vein to the intramarginal veins. T ~ extant myrtaceous genera exhibit this venation pattern, Rhodamnia and Rhodomyrtus (Fig. 7B). The cuticular patterns of these genera are quite distinctive, and the fossil clearly matches Rhodomyrtus. On the stomatiferous surface stomates are arranged at random, have two or three large subsidiary cells in an anomocytic arrangement, are superficial, and are almost always plugged (Fig. 7C, D). $tomates are also confined to one surface on Rhodo- myrtus, and the stomates are very similar in size, a l i~ment and structure (Fig. 7E), except that they have not been observed to be plugged in any of the extant species examined. Epider- mal cells over the veins on the fossil are straight walled, very long and narrow (Fig. 7C), as_in Rhodomyrtus. Trichome bases occur fre- quently on the stomatiferous surface of the fossil. They are unicellular, with the basal cell

being embedded in the epidermis, but the base clearly extends over surrounding cells (Fig. 7C). The trichomes are not preserved. Rhodo- myrtus contains similar trichome bases (Fig. 7E). The non-stomatiferous surface of the fossil has only one feature of note, i.e. similar trichome bases to those on the stomatiferous surface occur over the veins. Again, a similar distribution is noted in Rhodomyrtus. Thus there appears to be only one feature of the fossil which distinguishes it from the extant Rhodo- myrtus species examined -- the presence of stomatal plugs. These plugs may be present in other extant Rhodomyrtus, but in any case their significance is likely to be related to water availability (see Discussion) and their presence is therefore unlikely to be diagnostic of a distinct genus. This fossil is therefore assigned to a new species of Rhodomyrtus, R. australe.

The second species is the most common among the Myrtaceae. The leaves are narrow lanceolate with a strongly developed primary vein, and closely spaced, steeply angled secondary veins which occasionally branch or anasto- mose before merging into a strongly developed intramarginal vein (Fig. 8A). The venation pattern of this leaf type is very similar to some species of Agonis and, in particular, could not be separated from the largest-leaved extant species, A. flexuosa (Fig. 8]3). The leaf surface of this type shows little cellular detail, although stomates are observed to be restricted to one leaf surface, where they are randomly arranged and extend above the general leaf surface (Fig. 8C). A very similar stomatal arrangement and morphology is seen among the extant species of Agonis (e.g. Fig. 8D). Very large, probably glandular structures are common on the non- stomatiferous surface of the fossil (Fig. 8E). The surface details of extant Agonis species match those of the fossil very closely, and we consider that there are no characters which

Fig. 9. A-E, holotype ofMyrtaciphyllum sinua~,n (WAM 1).84.70). A, part e r a leaf. Seal© = I cm. K SEM of the outer leaf surface shooing the well preserved stomates and the characteristic two-celled oil gland. Scale = 50 #m. C, cloaz up of the ell gland shown in B. Scale = 5 0 / a n . D, close up of stomatcs showing the atomatal plugs and the anomocytio subsidiary cell m'rangoment. Scale = 25 #m. E, SEM of the outer non-stomatifcrous leaf Jna'face dlooing a trlchorna basz with radiating cells surrounding the foot call. Scale = 25 #m. F-H, holotypc of Myrtactphyllum brochidodromum ONAM P.84.63b). F, whole specimen, which is the basal half of a leaf with a cloar intran~rginal vein which is looped to form a brochidodromous venation paucrn. SCalo= 5ram. G, SEM of the outer leaf ~trfacc showing randomly arranged stomates covered by an almost intact cuticle. Scale = 25 #m. H, closz up o f a single s'~omate where the cuticle is not prc~rved, mhowing paired subsidiary calls flanking the guard cells. Scale = 10 #m.

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separate the fossils fromA, flexuosa. However, in the absence of details of the reproductive structures of the fossil species we assign the fossils to A. cf. flexuosa.

The first Myrtaciphyllum species has the clearest epidermal cell surface of the myrta-

ceous species but is represented by only the basal half of one leaf (Figs 8F, 21B). The secondary veins are strongly developed, unbranched, and run parallel to one another until they change angle abruptly when they reach the intramarginal vein. Stomates are restricted to

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one leaf surface and the subsidiary cell arrangement is typically anomocytic (Fig. 8G). Small, unicellular trichome bases are numerous on the stomatiferous surface, and large, multicellular, probably glandular structures also occur there (Fig. 8G). The epidermal cells are finely striated. The non-stomatiferous surface is poorly preserved, but appears to be striated (Fig. 8H). This leaf type is assigned to a new species of MyrtaciphyUum, M. striatum.

The second MyrtaciphyUum species is represented by at least two specimens, neither of which is complete. The secondary venation pattern is strongly developed, with an intramarginal vein just inside the margin, but the secondary vein course is not as clearly parallel and unbranched as in M. striatum (Figs 9A, 21C, G). Tertiary veins are random reticulate. On both specimens the cuticle appears to have largely disintegrated, leaving the epidermal cells visible, with a few fragments of cuticle attached. Stomates are present on only One leaf surface, and have an anomocytic subsidiary cell arrangement (Fig. 9B, D). Epidermal cells on this surface are highly sinuous, and the typical myrtaceous two-celled oil glands are prominent (Fig. 9B, C). Trichomes are absent from the stomatiferous surface. On the other leaf surface epidermal cells may be slightly sinuous, but are more often straight-walled (Fig. 9E). Trichome bases with a unicellular foot cell embedded in the epidermis and radiating surrounding cells (Fig. 9E) are relatively common on this surface. This leaf type is assigned to a new species of Myrtaciphyllum, M. sinuatum.

The third Myrtaciphyllum species is represented by a single specimen. About half the leaf is present, and has a fine venation pattern, with secondary veins which depart at a relatively oblique angle to the primary vein and loop into a relatively poorly formed intramarginal vein (Figs 9F, 21D). Stomates are confined to one

leaf surface, where they are randomly arranged (Fig. 9(3). The cuticle is missing from part of that surface, showing that the subsidiary cell pattern may be brachyparacytic (Fig. 9H). Epi- dermal cell walls are straight, and trichome bases are absent. The epidermis of the other leaf surface is featureless, except for occasional pits which may represent glandular openings. The leaf type is assigned to a new species of MyrtaciphyUum, M. brochidodromum.

The fourth MyrtaciphyUum species is represented by a single specimen which is part of the apical half of a leaf (Figs 10A, 21E). The secondary veins arise at a relatively large angle from the primary vein, and run more or less straight to the intramarginal vein. The secondary veins are widely spaced, and intersecondary and random reticulate tertiary veins are prominent. The leaf surface is poorly defined. Stomates are restricted to one leaf surface, and are randomly arranged (Fig. 10B). Occasional very large stomates are scattered amongst the ordinary stomates (Fig. 1013, C), and may be associated with veins, although this is difficult to determine. The subsidiary cell arrangement cannot be determined, but epidermal cells are sinuous (Fig. 10(2). Cuticle is lacking from the other leaf surface, where epidermal cells are highly sinuous (Fig. 10D). Trichome bases are absent from both leaf surfaces, although depressions on the non-stomatiferous surface (Fig. 10D) may represent the position of glands. This leaf type is assigned to a new species of Myrtaci- phyUum, M. westdaliense.

The fifth Myrtaciphyllum species is represented by a single specimen. The base and apex of the leaf are missing, but the leaf is clearly lanceolate, with a prominent venation pattern (Figs 10E, 21F). The secondary veins are well-defined and relatively closely spaced. They run straight from the primary vein to the intramarginal vein at a relatively high angle,

Fig. 10. A-D, holotype of MynaciphyUum westdaliense ONAM P.84.76). A, whole specimen, which shows part of a leaf tapering towards the apex. Scale ffi I cm. 13, SEM of the outer leaf surface J-hewing randomly arranged stomates of distinctly different sizes. The cuticle is intact on this leaf surface. Scale = 100/an. C, close up o f part of 13, showing a very large stomate, possibly over a vein, in the bottom of the figure and normal g~na tes towards the top. Scale = 50 /an . D, SEM of the outer non-~omatifemus leaf surface showing very sinuous epidermal cells where cuticle is not preserved and a depression, which may be the site of an oil gland. Scale ffi 10 p.m. E--H, hoiotype ofMyrtaciphyUum wmulamm (WAM P.84.97). E, whole specimen, showing the top ha l fo fa leaftepering towards the apex. Scale -- I cm. F, SEM of the outer leaf surface showing the r~omates and epidermal cells which are not covered by cuticle. Some of the stomates show remnants o f plugs. Scale ffi 25 tan. G, close up of a single stomate. Note the circular shape of the pair o f guard cells and the distinct ring around the gomatal opening where the thick cuticle terndnatsd. Scale = 10/tm.

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302 R. S. HILL A N D H. E. MERRIFIELD ALCHERINGA

~ ......... ~:~! i ~ i ~ ii~ i~! ~

: ~ 11

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ALCHERINGA E A R L Y T E R T I A R Y M A C R O F L O R A , W . A . 3 0 3

Fig. 12. Banksieaephyllum longifoliton. A, holotype (WAM E84.47), showing the basal part o f a leaf with an entire margin and prominent secondary veins. Scale -- 5ram. B, apical part o f a leaf (WAM P. 84.99). Scale --- 5ram. C, SEM of the outer leaf surface (WAM P.84.47) showing stomatea within the areolea. Scale = 100 ~m. D, close up o f the stomate8 in C. Note also the small, unicellular trichome foot cells embedded among the epidermal cells. Scale = 25 /an . E, SEM of the epidermal cells over a vein (WAM P.84.47). Note the small, unicellular trlchome foot cells embedded among the epidermal cells. Scale -- 25/~m. F, SEM of the outer non-stomatiferous leaf surface. Scale -- 250/~m.

Fig. 11. A-D, specimen ofBanksieaephyllumfastlgatum (WAM P.84.46). A, whole specimen, showing the middle section of a long, narrow leaf with regular serrations at the termination of the secondary veins. Scale -- 5ram. B, SEM of the outer leaf surface showing the stomates confined to the areolea. The epidermal cells over veins are highly modified and many unicellular trlchome foot cells are present. Scale ffi 50 / an . C, closeup of stomates. The subsidiary cells are difficult to detect. Scale = 10 /an . D, SEN[ of the outer non-stomatiferous leaf surface. Scale -- 100 /an. E-H, holotype o f Banksieaephyllwn westclaliense (WAM P.84.51). E, whole specimen, showing the basal part o f a lobed leaf. Now the extremely small leaf size. Scale = 2ram. F, SEM of the outer leaf surface showing randomly oriented stomates above the general epidermal cell level and small, unicellular trlchome foot cells embedded among the epidermal cells. Scale = 50 /an. G, close up of stomates. The subsidiary cells are difficult to detect. Scale -- 10 #m. H, SEM of the outer non-stomafiferous leaf surface. Scale -- 50/ml .

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and tertiary veins are quite well formed between them. The cuticle is not preserved on either leaf surface. Randomly arranged stomates are restricted to one leaf surface, and have an anomocytic subsidiary cell arrangement (Fig. 10F, G). The guard cells form almost circular stomates, many of which are heavily plugged (Fig. 10G). Epidermal cells are straight-walled or slightly undulating. On the non-stomatiferous surface epidermal cell walls are also straight or slightly undulating (Fig. 10H) and trichome bases are absent from both leaf surfaces. This leaf type is assigned to a new species of Myrtaci- phyllum, M. annulatum.

The sixth Myrtaciphyllum species is represented by a single specimen which preserves almost the entire leaf length (Fig. 21H). The leaf is lanceolate, with a well preserved venation pattern, showing a prominent intramarginal vein and secondary venation pattern. Although the venation pattern of this leaf appears to be distinct from the other fossils considered, the leaf surface is so poorly preserved that no detail could be observed. Because of this, it is noted that this specimen probably represents a distinct myrtaceous species, but it is not assigned a species name and is referred to as Myrtaci- phyllum species 1.

Proteaceae

The largest number of specimens and the great- est diversity was found within the family Pro- teaceae. This family is well represented in the Tertiary macrofossil record from southeastern Australia (Cookson & Duigan, 1950; Black- burn, 1981; Christophel, 1984; Carpenter & Hill, 1988; Hill & Christophel, 1988; Hill, 1990c; Carpenter, 1991) and dispersed cuticle has been recovered from Tertiary sediments in Western Australia (Lange, 1978). Many genera in the family have highly distinctive foliage, and

the cuticular pattern is usually easily identified by the characteristic trichome bases and brachyparacytic subsidiary cell arrangement.

One of the best represented groups in the southeastern Australian maerofossil record is the tribe Banksieae, which contains the extant genera Banksia, Dryandra, Austromuellera and Musgravea. Leaf fossils cannot yet be identified with an extant genus because of a lack of diagnostic characters, and so they are assigned to Banksieaephyllum if cuticular characters can be observed, or Banksieaeformis for impression fossils with no cell detail preserved (Hill & Christophel, 1988). Three species from West Dale can be assigned to BanksieaephyUum.

The first species, represented by only a single specimen, is comparable to R fastigatum, described by Cookson & Duigan (1950) from the Yallourn brown coal in Victoria. The leaf is incomplete, but is long and narrow, and finely serrate, with a secondary vein ending in each serration, and another in each sinus (Fig. llA). Stomates are restricted to one leaf surface, and occur in areoles which are clearly marked by the veins (Fig. liB). Cookson & Duigan (1950), in describing R fastigatum, noted that there are two subsidiary cells per stomate lying parallel to the pore, but they are inconspicuous and the neighbouring epidermal cells project over them slightly. The West Dale fossil may have a similar arrangement, since the pair of subsidiary cells cannot be seen in surface view, even though the cuticle is often missing (Fig. l 1 C). Furthermore, the very small trichome bases described by Cookson & Duigan (1950) for R fastigatum are also present on the West Dale fossil (Fig. 11B). The upper epidermis of the West Dale fossil has no particularly diagnostic characters (Fig. l lD), but again is very similar to R fastigatum. There are some differences between the West Dale specimen and

Fig. 13. A-G, specimens ofcf . AUarylon. A, part of a leaf showing brochidodromous venation (WAM P.84.64). Scale -- 1 cm. B, part of a leaf (WAM P.84.61d), showing the general leaf shape. Scale = 1 cm. C, SEM of the outer leaf surface (WAM P.84.61d) showing the stomates, most of which are plugged. Scale = 50 /an . D, close up of the s~omates, showing the form of the slomatai plug and the paired subsidiary cells running parallel to the guard cells. Scale = l0 #m. E, SEM of the outer leaf surface (WAM P.84.73) showing mostly unplugged stomates. Scale = 1130 #m. F, SEM of the outer leaf mrfac© (WAM P.84.64) showing a multi-celled trichome base. Scale = 50 ttm. G, SEM of the outer non-stomatiferous leaf surface showing a two-celled trichome base. Scale = 50 #m. H, cleared leaf of AUoxylon wickhamii. Scale -- 1 cm. I, cleared leafofA, pinnata. Scale = 1 cm.

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ALCHERINGA EARLY T E ~ Y MACROFLORA, W. A. 305

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Fig. 14. Specimen of of. Stowcarpus (WAM P.88.217A). A, whole specimen, showing part of a large, deeply lobed leaf. Scale -- 2 cm. B, SEM of the outer leaf surface showing the plugged stomates and We-celled trichome bases. Scale = 50 lan. (2, SEM of the outer leaf surface opposite to that shown in B. Stomates are present, but are less frequent. Trichome bases are also prominer~. Scale = 50/ms. D, close up of a plugged stomate showing the subsidiary cells running parallel to the long axis of the guard cells. Scale = 10 ian.

R fastigatwn. The stomatal areas in the West Dale leaf are level with the general leaf surface, and the individual stomates are not sunken. This contrasts with R fastigatum, which has stomates in slight depressions, and the individual stomates are sunken slightly below the general leaf surface. However, this difference is not considered sufficient to warrant the erection

of a new species, and the West Dale specimen is assigned to R fastigatum.

The second species of BanksieaephyUum at West Dale is also represented by a single specimen. Neither the base nor apex is preserved, and the specimen consists of several lobes, which are equivalent to serrations which extend in to the primary vein of the leaf (Fig. l lE) . The leaf fragment is very small, relatively narrow and the lobes are small. This leaf form, with lobes extending to the primary vein, is today restricted to western Australian members

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ALCHERINGA E A R L Y T E R T I A R Y M A C R O F L O R A , W . A . 3 0 7

Fig. 15. A-C, Proteaceae species I (WAM 1'.84.55). A, two long, narrow leaves, side by side. Scale = I cm. B, SEM of the outer leaf surface showing stomates among numerous trichome bases. Scale = 100 ~tm. C, close up of B, showing two stomates and a trichome base among heavily ridged epidermal cells. Scale : 7.0 ~tm. D-G, Proteaceae species 2 (WAM 1'.84.50). D, whole specimen showing part of a leaf with prominent serretions. Scale ffi 4ram. E, SEM of tba outer leaf mrface showing e~on~ttea among prominent trlchome bases. The cuticle is present on this specimen making it difficult to interpret. Scale ffi 50 /an . F, close up o f E, showing stometes and triahome bases. Scale ffi 20/ml . G, SEM of the outer non-stomatiferous leaf surface, showing a finely griated leaf surface and numerous very large trichome bases. Scale ffi 50 pan.

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of the tribe, although it is common in fossil species from eastern Australia (Hill & Christophel, 1988). There is evidence for at least three major veins per lobe, each extending from the primary vein towards the margin, with

the central one terminating in the apex of the lobe. Areoles are well developed in this specimen. The leaf surface is well preserved, although the cuticle is usually missing. On the stomatiferous surface randomly aligned

Fig. 16. A-C, Proteaceae species 3 (WAM P.84.49). A, whole specimen, showing part e r a leaf with a distinctly serrate margin and prominent primary vein. Scale = 5ram. 13, SEM of the outer leaf surface. This is the stomatal surface, but it is quite degraded, making the stomates difficult to see. Triehome bases are evident on some epidermal cells. Scale = 25 #m. C, SEM of the outer non-stomatiferous leaf surface. Note the fine surface striations and the multicellular trichome base. Scale ffi 25 pro. D-F, Proteaeeae species 4 (WAM P.88.155). D, whole specimen, showing part o f a deeply incised leaf. Scale = 2ram. E, SEM of the outer leaf surface showing several plugged s~omates aligned more or less parallel to the long axis of the leaf. Scale = 50 /an . F, SEM of the outer leaf surface opposite to that shown in E. A triehome base is shc~vn over a vein with a s~omate just below it. Stomates are uncow_n~n on this leaf surface. Scale ffi 50/~m.

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stomates are confined to the areoles (Fig. l lF) , which are surrounded by elongate cells which occur over the veins. The stomates may occur within slight depressions between the veins, but there are no marked pits on the leaf surface. Stomates are superficial on the leaf surface (Fig. 11F, (3). Small, unicellular trichome bases are common and appear as holes between the epidermal cells over and between the veins (Fig. 11F, G). The trichomes are not preserved. No trichome bases were observed on the non- stomatiferous leaf surface (Fig. 11H). The leaf and cuticular morphology of this specimen are distinct from all extinct and extant species, and so it is assigned to a new species, Banksieae- phyllum westdaliense.

The third species of BanksieaephyUum is represented by two specimens, neither of which contains a base or an apex, although one clearly represents the basal part of a leaf(Fig. 12A) and the other the apical part (Fig. 1213). The leaves are long and relatively narrow, with a more or less linear elliptical shape and an entire margin. The venation pattern is very regular, with numerous secondary veins arising at an angle which approaches 90 ° in the basal and mid portions of the leaf, but becomes more acute towards the apex. The secondary veins bifurcate very close to the leaf margin and loop into the adjacent secondary veins with a brochidodromous pattern. There is one very prominent intersecondary vein between each pair of secondary veins, which follows a similar course but branches into higher order veins well short of the leaf margin. Other, less prominent intersecondary veins may also be present between each pair of secondary veins. Areoles are well def ined and are c lear ly marked on the stomatiferous surface by modified epidermal cells which are relatively long and narrow (Fig. 12C). Small, unicellular trichome bases are common and appear as holes between the epidermal ceils over and between the veins (Fig. 12D, E). The trichomes are not preserved, but the basal cell is often present and terminates at the level of the epidermal cells. Stomates are superficial on the leaf surface (Fig. 12C, D). The non-stomatiferous surface is featureless (Fig. 12F). This leaf type is distinct from all other fossil and extant species and is therefore assigned to the new species BanksieaephyUum longifolium.

The tribe Banksieae is unusual in the Pro- teaceae in having been well studied at the leaf anatomical level. The rest of the Proteaceae has been studied in this way spasmodically, but a major project is now underway at the Depart- ment of Plant Science, University of Tasmania, in an attempt to describe the leaf architecture and cuticular characters of the large number of living and fossil proteaceous leaves. It is too early to be able to compare non-Banksieae proteaceons leaves adequately with extant genera, and hence the approach taken here is to describe the different species, and suggest possible affinities where they are known. How- ever, the comparison has not been exhaustive, and further work may lead to a different conclu- sion.

The most common proteaceous species consists of a broad leaf with prominent brochidodromous venation (Fig. 13A, B). The secondary veins loop well inside the leaf margin, and higher order vein loops occur toward the margin. The leaf is entire-margined, and the base and apex are unknown. Randomly aligned stomates are restricted to one leaf surface, are relatively large, and often plugged (Fig. 13C, D) although in one specimen stomatal plugs are absent (Fig. 13E). The subsidiary cells are brachyparacyfic, with the pair of cells often narrow relative to the epidermal cells (Fig. 13D). One- or two-celled trichome bases occur infrequently (Fig. 13E, F). The non-stomatal epidermis has straight-walled epidermal cells and occasional one- or two-celled trichome bases (Fig. 13G). Fine striations occur over the leaf surfaces.

These fossils are very similar to extant species ofAlloxylon (Weston & Crisp, 1991). The leaf size and shape and venation pattern are identical (Fig. 13H, I) and the cuticular pattern is very similar, with the major difference being the presence of sinuous epidermal cell walls in the two extant species examined. There are four extant species of Alloxylon, but only two were available for examination. The importance of epidermal cell wall shape in the Proteaceae is not yet known, but apart from that character this fossil leaf type corresponds well to Alloxylon, and will be referred to as Proteaceae cf. Al- /oxy/on.

One proteaceous specimen consists of what is interpreted as part of a deeply dissected leaf,

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with long, narrow, alternately arranged lobes which terminate in an acute apex (Fig. 14A). The individual lobes have a thick primary vein which is prominent on the leaf surface, but other venation cannot be observed. Epidermal cell detail is clear on the leaf surface, since the cuticle often appears to be missing. Randomly aligned stomates occur on both leaf surfaces, but are more common on one (Fig. 1413 cf. C). The brachyparacytic subsidiary cells are narrow (Fig. 14D), and epidermal cells have straight walls (Fig. 1413). Occasional single- and multi- celled trichome bases occur on both leaf surfaces (Fig. 1413, C).

This leaf type is very similar in size, shape, and surface pattern to some extant species of Stenocarpus. However, there are other possible affinities which have not been fully tested, and the leaf is referred to as Proteaceae of. Steno- carpus.

Six other proteaceous species are represented which have typical features of the family, but at this stage cannot be allied to extant genera. These specimens are referred to as Proteaceae species 1 to 6.

Proteaceae species 1 has very long, narrow leaves, with neither base nor apex preserved (Figs 15A, 22A). The stomatiferous leaf surface is particularly distinctive, with highly striated epidermal cell walls (Fig. 15B, C). Prominent circular, unicellular trichome bases are common, with the striations on surrounding epidermal cells radiating away from them (Fig. 1513, C). Stomates are randomly oriented and superficial on the leaf surface (Fig. 15C). The non-stomatiferous surface is poorly preserved and exhibits no distinctive features.

Proteaceae species 2 is represented by a single specimen which is the middle section of a leaf wi th p rominen t se r ra t ions and semicraspedodromous venation (Figs 15D, 22B, C). The leaf surface details of this type are unusual

and have not been observed in any other member of the family. It is made difficult to interpret since it is one of the few specimens where the cuticle is apparently intact and cell wails cannot be observed. The stomatiferous surface has relatively regularly spaced, randomly oriented, superficial stomates, with no sign of epidermal cell outlines between them (Fig. 151/). How- ever, the surface is marked by large and very deep holes which are interpreted as trichome bases (Fig. 15E, F). While these bases resemble those of some of the BanksieaephyIlum species, they are substantially larger. The trichomes associated with these bases are unknown. The non-stomatiferous surface is covered in fine striations which radiate out from large circular trichome bases which are very common (Fig. 15G). These trichome bases are not well preserved and it is not possible to determine whether they were uni- or multicellular.

Proteaceae species 3 is represented by a single specimen which is a long, narrow leaf with regularly spaced, prominent serrations and semicraspedodromous venation (Figs 16A, 22D, E). The higher order venation is prominent and areoles are well developed. Neither the base nor the apex is preserved. On the stomatiferous surface randomly oriented stomates are located superficially within the areoles, which are marked by epidermal cells which are somewhat longer and narrower than normal epidermal cells (Fig. 1613). Trichome bases with a narrow basal cell over one or two large cells in the epidermal layer are common both over and between veins (Fig. 16B). The rest of the trichome is not preserved. On the non-stomatiferous surface cells are very finely striated and large, multicellular trichome bases are prominent (Fig. 16C). This specimen may have affinities with Banksieaephyllum, but di-

Fi 8. 17. A-E, Proteaceae species 50VAM P.84.79). A, whole apeclrnen, showing part of two leaves, po , ib ly from the same plant, or even leaflets from a compound leaf. Scale = 1 am. B, SEM of the outer leaf surface showing randomly arranged ltomates. Scale -- 50/,(m. C, SEM of the outer leaf aurface showing a actuate and a two-celled trichome base. Scale ffi 25 ttm. D, SEM of the outer non-stomatiferous leaf surface, shelving large one- or two-celled trichome bases and a striated surface. Scale = 100 pan. E, SEM of the outer non-ftomafiferons leaf a,affaca. A second trichome type may be present (arrowed), although this may represent damage to the leaf. Scale ffi 50 p.m. F-H, Proteaceae ~ .¢ ies 6 (WAM 1).84.48). F, whole specimen, consisting of part of • leaf with prominent brochidodromous venation. Scale = 5mm. (3, SEM of the outer leaf surface showing probable, but poorly defined, t~mates. Scale -- 25/an . H, SEM of the outer non-stomatiferons leaf, showing sinuous-walled epidermal cells with a thick, striated cuficular covering. Scale = 25/.an.

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agnostic characters are not well enough preserved to be certain.

Proteaceae species 4 is represented by one specimen which is the apical part of a single leaf

(Fig. 16D). The leaf is deeply and irregularly lobed around a primary vein and, although each lobe has at least one vein, the venation pattern cannot be clearly observed. $tomates occur on

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Fig. 18. Angiosperm species 1. A, almost complete leaf (WAM P.g4.30A), showing the clear venation pattern and dliptieal leaf shape. Scale = 1 cm. B, basal part of a leaf 0/dAM P.g4.75A) showing the asymmetrical leaf base. Scale = 1 era. C, SEM of the outer leaf surface (WAM R 84.105) showing stomate.s, possible complex trichome bases (arrowed) and papillate epidermal cells. Scale = 50/~m. D, SEM of the outer leaf surface (WAM P.84.30A) showing the detail of the gomates and papillate epidermal cells. Scale = 25 ~m. E, SEM of the outer non-stomatiferous leaf surface (WAM P.g4.75A). Scale = 50 tan.

both leaf surfaces, but are much more frequent on one. On this surface the stomates are more or less aligned with the long axis o f the leaf(Fig. 16E) and have a brachyparacytic subsidiary cell arrangement. Prominent c i rcdar to elliptical trichome bases consisting o f one or two cells occur over and between veins (Fig. 16E). The veins are not dear ly defined by specialised epidermal cells. The other leaf surface is very similar except that the stomates are much more sparse, and tend to occur mainly near the major vein in each lobe (Fig. 16F).

Proteaceae species 5 is represented by two leaves which are in close proximity to one another, suggesting that they may be leaflets from a compound leaf or at least leaves f rom the same plant (Figs 17A, 22F). One specimen represents the top half o f a leaf which is tapering to an acute apex, while the other represents the middle section o f a leaf with both base and apex missing. The leaves are slightly falcate, and the venation pattern is brochidodromous. On the s tomat i fe rous sur face r a n d o m l y or ien ted stomates are superficial within areoles, and the

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Fig. 19. A-C, angiosperm species 2 (WAM P.88.161). A, B, counterparts of the apical part o f the leaf showing the large serrationa and prominent venation pattern. Scale = 1 cm. C, SEM of the outer leaf surface, showing the poorly preserved stomates. Scale ~ 100/J~a. D, angiosperm species 3 CvVAM P.84.85), showing the basal part of a leaf. Scale ~ 1 cm. E, F, angiosperm species 4 (WAM P.84.65). E. Whole specimen, showing a fragmentary part of a leaf. Scale ~ 1 cm. F, SEN[ of the outer leaf surface showing the characteristic stometes. Scale = 10/mL

veins are marked by highly modified epidermal cells which are longer and narrower than normal epidermal cells (Fig. 17B). Large, one- or two-celled trichome bases of a circular to elliptical shape occur occasionally over the veins

(Fig. 17C), but trichomes are not preserved. Epiphyllous fungus is common on the leaf surface. The non-stomatiferous surface probably has two types of trichome bases. The most prominent are similar in morphology to those

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on the stomatiferous surface, but they are much more common (Fig. 17D). Striations over the leaf surface radiate away from these trichome bases. The second possible trichome base type is probably multicellular, and is raised above the general leaf surface with an irregular opening where the trichome was attached (Fig. 17E). Trichomes are not preserved. This structure is possibly not a trichome base at all, but may represent the effect of insect or pathogen attack.

Proteaceae species 6 is represented by two specimens, neither of which have the base or apex preserved (Fig. 17F). The leaves are long and narrow, with the margins more or less parallel for most of their length, suggesting a very linear form. Poorly defined serrations occur irregularly and infrequently along the margin. The venation pattern is brochidedrom- ous, with the secondary veins arising at an angle close to 90 ° to the primary vein and running almost straight towards the margin. These veins bifurcate just inside the margin and the branches change course abruptly in a basal and apical direction respectively to loop into branches from adjacent secondary veins. Short branches from these loops terminate in serrations. Higher order venation is not well ordered, but areoles are distinct. Cell detail on the leaf surface is poor, probably because the cuticle is well preserved. The stomatiferous surface contains regularly spaced, randomly oriented, superficial stomates, but no sign of trichome bases (Fig. 17(3). The non-stomatiferous surface consists of small cells with slightly sinuous walls, and the cuticle is covered in striations which run more or less parallel to one another (Fig. 17H). The cell detail is not well enough preserved to determine the familial affinity, but in this leaf type the venation pattern is highly reminiscent of the Proteaceae and so it is considered to belong to that family. However,

affinities of this type are less certain than for those described previously.

Miscellaneous angiosperms

There are many other angiosperm species which have not been identified even to the familial level. Some broad-leaved specimens have well preserved venation patterns, but no surface details, whereas others have well preserved surface details which do not, at this stage, assist in their identification. Several species are well enough preserved to warrant further discussion.

Angiosperm species 1 is very common ill the deposit. The venation pattern is well preserved, as is the leaf surface detail. The leaves are usually symmetrical and elliptical, although the base is always highly asymmetrical (Fig. 18A, B). The primary vein is robust and has a straight course. Secondary veins are also robust, and arise at an angle of about 60 ° and curve towards the margin. Some secondary veins branch near the margin, while others appear to be unbranched. The secondary veins gradually become thinner towards the margin, where they appear to merge with a thin but well defined vein just inside the margin. This vein is probably better described as a fimbrial vein than an intramarginal vein. Intersecondary veins occur occasionally, and follow a similar course to the secondary veins. Tertiary veins are well defined and percurrent (Fig. 18B).

Stomates are confined to one leaf surface, are randomly oriented, and appear to have an anomocytic subsidiary cell arrangement (Fig. 18C, D). This leaf surface is highly papillate, with a single papilla on every epidermal and subsidiary cell, becoming somewhat less pro- nounced over the veins (Fig. 18C, D). Unicel- lular trichome bases are present, with the small foot cell embedded in the epidermis (Fig. 18C). Traces of the trichomes are preserved, but none in enough detail to allow a description of their

Fig. 20. A--C, angiosperm species 5 (WAM P.84.73b). A, whole specimen, lhowing a damaged section of a finely senate leaf. Scale = 1 cm. B, SEM of the outer leaf surface showing the stomates surrounded by sinuous-walled epidermal cells. Scale = 25 ~tm. C, SEM of the outer non-stomatiferous leaf mtrface, showing the epidermal cells and trichome foot cells embedded in the epidermis. Scale = 100/~m. D, E, angiosperm species 6 (WAM P.84.106). D, whole specimen showing part of a leaf with brochidodromous venation. Scale -- 5mm. E, SEM of the outer leaf surface showing poorly preserved stomates and probable trichome bases. Scale = 50 #m. F-I, angiosperm species 7 (WAM P.88.101B). F, whole specimen, showing a long, parallel-aided leaf or photosynthetic stem. Scale ffi 1 cm. (3, SEM of the outer mfface showing elongated epidermal cells over a vein at the top and large i~omates at the bottom. Scale ffi 50/an. H, close up of the stomates, mtrrounded by epidermal cells with sinuous walls. Scale ffi 25/~m. I, SEM of the outer non-stomatiferous surface showing the epidermal cells. Scale -- 100m.

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morphology. The non-stomatiferons leaf surface is featureless apart from the isodiametric epidermal cells (Fig. 18E).

This leaf form has a very distinctive morphology. However, none of the characters observed are considered diagnostic for any known taxonomic group.

Angiosperm species 2 consists of a single specimen which is the apical part of a leaf (Fig. 19A, B). Secondary veins are prominent and arise at an angle of nearly 90* to the primary vein. They proceed in a shallow arch to the margin where they terminate in rounded serrations, forming a craspedodromous pattern. Weak intersecondary veins are present, but higher order venation is not well defined. Sur- face detail is poor, but stomates occur at random within very shallow depressions between the veins (Fig. 1913). No trichomes or glandular structures were observed. The affinities of this leaf are unknown.

Angiosperm species 3 consists of the basal part of a large and apparently thin leaf (Fig. 19D). The secondary veins are not well defined and form a weak semicraspedodromous pattern. Short branches from the secondary vein loops proceed to the margin and terminate in small, possibly glandular serrations. Intersecondary veins are common and higher order venation is prominent but not well ordered. The leaf surface detail on this specimen is very poor and nothing of importance can be said about the cell details. The affinities of this leaf are unknown.

Angiosperm species 4 is represented by only a single leaf fragment which shows part of a brochidodromous venation pattern (Fig. 19E). However, the surface detail of this leaf is well preserved, and shows the stomates, which are restricted to one surface, to have a morphology which is distinct from all other species at West Dale (Fig. 19F). The affinities of this leaf are unknown.

Angiosperm species 5 is represented by a single leaf fragment which shows semicraspedodromous venation, with small serrations at the margin (Figs 20A, 22G). The leaf surface is well preserved. Stomates are restricted to one surface, are superficial, randomly or iented, and have anomocytic subsidiary cells (Fig. 20B). On the non- stomatiferous surface unicellular trichome bases are prominent, but the trichomes are not

preserved (Fig. 20C). The affinities of this leaf are unknown.

Angiosperm species 6 is represented by a single leaf fragment whleh is entire margined and has brochidodromous venation (Fig. 20D). Intersecondary veins are prominent and regular between each pair of secondary veins, but higher order venation lacks resolution. The stomatiferous surface of this leaf is well preserved and has abundant superficial stomates and trichome bases (Fig. 20E). However, the precise structure of these features is difficult to determine because of the unusual undulation of the surface and because the well preserved cuticle obscures details of the epidermal layer.

Angiosperm species 7 is linear, relatively thick in section, with fine parallel striations which may represent parallel venation (Fig. 20F). The surface shows that stomates are restricted to one side of the leaf or stem, are very large, oriented more or less with the long axis of the leaf and are surrounded by undiffer- entiated, sinuous-walled epidermal cells (Fig. 20G, H). Epidermal cells over the veins are markedly different in morphology, being long and narrow, with straight walls (Fig. 20G). The other leaf or stem surface is covered in irregularly shaped epidermal cells (Fig. 20I). This leaf may represent a monocotyledon, but its exact affinities are unknown.

Taxonomic descriptions

Order CONIFERALES

Family ARAUCARIACEAE

Agathis R.A. Salisb. 1807

2~pe species. Agathis loranthifolia.

Agathis kendrickii sp. nov. (Fig. 2B-E)

Diagnosis. Leaf often falcate. Most stomates aligned within 30* of the long axis of the leaf, no stomates aligned at 90* to the long axis of the leaf.

Holotype. WAM P.84.29.

Specimens examined. WAM P.84.28, P.84.29, P.84.30b.

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Etymolog 3 Named in honour of George Kendrick, whose advice on various aspects of this project was greatly appreciated.

Family PODOCARPACEAE

Dacrycarpus Laubenfels 1969

Type species. Dacrycarpus imbricatus.

Dacrycarpus patulus sp. nov. (Fig. 2F-l)

Diagnosis. Leaves bifacially flattened, up to 3 mm long, diverging from the axis at an angle of 30-40 °. Leaves epistomatic.

Holotype. WAM P.g4.34a, b, counterparts, only specimen observed.

Etymology. Named for the spreading nature of the foliage.

Retrophyllum C.N. Page 1988

Type species. Retrophyllum vitiense.

Retrophyllum australe sp. nov. (Fig. 3A-C)

Diagnosis. Leaves in up to 15 opposite pairs in a heterofacially flattened shoot. Leaf length about 7 ram. Loaves amphistomatic, stomates in long rows, but no obvious bands present. Florin rings prominent.


Specimens examined~ WAM P.84.56, P.84.57, R84.58, P.88.94, P.88.95, P.88.96, P.88.128, P.88.129.

Etymology. Named for the most southerly occurrence of this genus as a macrofossil and its first record in Australia.

Discussion. It is impossible to separate some of the extant species of Retrophyllum on the basis of gross leaf morphology and external cuticular detail alone. Thus while it is possible that this fossil belongs to an extant species, the state of preservation does not allow us to determine whether this is the case. The recognition of a new fossil species highlights the signifi-

canoe of this fossil and can be justified on its age and geographical location, although this should not be given too much weight.

Order LAURALES

Family LAURACEAE

Laurophyllum Goeppert 1853

Type species, non designatus.

Laurophyllum striatum sp. nov. (Fig. 6A-C)

Diagnosis. Lamina symmetrical, elongate, base and apex unknown. Leaf length about 8 cm, width 1.7 cm. Venation pattern brochidodromous. About 13 secondary veins arise at irregular distances along the primary vein and generally curve abruptly upwards about 2/3 of the way to the margin to loop into the super- adjacent secondary vein. Intersecondary veins common. Tertiary veins sometimes clearly percurrent. Stomates not visible on outer leaf surface, epidermal cells on probable stomatal surface clearly marked by cell walls recessed below the general leaf surface. Non-stomatal surface marked by large glands with surface striations radiating away from them.

Holotype. WAM P.84.94b, only specimen observed.

Etymology. The specific epithet refers to the striate nature of the cuticle on the non-stomatal leaf surface.

Order MYRTALES

Family MYRTACEAE

Rhodomyrtus Reichb. 1841

Type species. Rhodomyrtus tomentosa.

Rhodomyrtus australis sp. nov. (Fig. 7A, C- E)

Diagnosis. Leaf about 11 cm long, about 3.7 cm wide, venation perfect suprabasal acro- dromous. Stomates restricted to one leaf surface. On stomatiferous surface stomates

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arranged at random, with tin3 or three large subsidiary cells in an anomocytic arrangement, superficial, almost always plugged. Epidermal cells over veins straight walled, very long and narrow. Unicellular trichome bases, with the basal cell being embedded in the epidermis, but the base clearly extending over surrounding cells are common on stomatiferous surface and over veins on non-stomatiferous surface. Tri- chomes not preserved.

Holotype. WAM P.88.86A, only specimen observed).

Etymology. Named for the southerly distribution of this species.

Myrtaciphyllum Christophel & Lys 1986

Type species. Myrtaciphyllum undulatum.

Myrtaciphyilum striatum sp. nov. (Fig. 8F- H)

Diagnosis. Only the basal half of the leaf known. Secondary veins are strongly developed, unbranched, and run parallel to one another until they change angle abruptly when they reach the intramarginal vein. Stomates restricted to one leaf surface, subsidiary cell arrangement typically anomocytic. Small, unicellular trichome bases numerous on stomatifer- otis surface, and large, mnlticellular, probably glandular structures also occur there. Epider- mal cells finely striated. Non-stomatiferous surface poorly preserved, striated.

Holotype. WAM P.87.265, only specimen observed.

Etymology. Named for the striate leaf surface.

Myrtaciphyllum sinuatum sp. nov. (Fig. 9A- E)

Diagnosis. Leaves about 6 cmlong, 2 cm wide, elliptical. Secondary venation pattern strongly

developed, with an intramarginal vein just inside the margin; secondary vein course sub-parallel and branching. Tertiary veins random reticulate. Stomates restricted to one leaf surface, with an anomocytic subsidiary cell arrangement. Epidermal cell walls highly sinuous, two-~elled oil glands prominent. Tri- chomes absent. On the non-stonmtiferous surface epidermal cells may be slightly sinuous, or more often straight-walled. Trichome bases with a unicellular foot cell embedded in the epidermis and radiating surrounding cells are relatively common. Trichomes not preserved.


Specimens examined. WAM P. 84.38, P. 84.63a, E84.70.

Etymology. Named for the sinuous cell walls on the stomatiferous leaf surface.

Myrtaciphyllum brochidromum sp. nov. (Fig. 9F-H)

Diagnosis. Only the basal half of the leaf known. Venation pattern fine, secondary veins depart from the primary vein at a relatively oblique angle and loop into a relatively poorly formed intramarginal vein. Stomates confined to one leaf surface, randomly arranged. Sub- sidiary cell pattern probably brachyparacytic. Epidermal cell walls straight, trichomes absent. Epidermis ofnon-stomatiferous surface featureless, except for occasional pits which may represent glandular openings.

Holotype. WAM E84.63b, only specimen observed.

Etymology. Named for the slight looping of the venation pattern near the margin, forming a brochidromous pattern.

Myrtaciphyllum westdaliense sp. nov. (Fig. 10AD)

Fig. 21. Line drawings of selected fossil leaves. Scale -- 5ram. A, Rhodomyrms austra//s (WAM P.88.86A). B, Myrtaciphyllum striatum (WAM P.87.265). C, MyrtaciphyUum sinuatum (WAM P.84.70). D, Myrtaciphyllwn brochidodromum (WAM P.84.63b). E, Myrtaciphyllum westdaliens¢ (WAM P.84.76). F, Myruw/phy//wn annu/atwn (WAM P.84.97). G, Myrtaciphyllwn sinuatum (WAM P.84.38). H, MyrtaciphyUum species 1 (WAM P.87.464).

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A_LCHERING/I EARLY TERTIARY MACROFLORA, W. A. 319

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Diagnosis. Only part of the apical half of the leaf known. Secondary veins arise at a relatively oblique angle from the primary vein, and run more or less straight to the intramarginal vein. Secondary veins widely spaced, intersecondary and random reticulate tertiary veins prominent. Leaf surface poorly defined. Stomates are restricted to one leaf surface, randomly arranged. Occasional very large stomates, which may occur over veins, are scattered amongst ordinary stomates. Subsid- iary cell arrangement indeterminable, epidermal cell walls sinuous. On non-stomatiferous surface epidermal cell walls highly sinuous. Trichomes absent from both leaf surfaces, although depressions on the non-stomatiferous surface may represent the position of glands.


Etymo/ogy. Named for the locality which yielded the fossil specimens.

Myrtaciphyllum annulatum sp. nov. (Fig. IOE-H)

Diagnosis. Leaf lanceolate, base and apex unknown. Secondary veins well-defined and relatively closely spaced, running straight from the primary vein to the intramargiual vein at a relatively oblique angle; tertiary veins prominent. Randomly arranged stomates restricted to one leaf surface, subsidiary cell arrangement anomocytic. Guard cells form almost circular stomates, many of which are heavily plugged. Epidermal cell walls straight or slightly undulating on both leaf surfaces. Trichomes absent.


Etymo/ogy. Named for the circular appearance of the pair of guard cells in the stomate.

Order PROTEALES

Family PROTEACEAE

Banksieaephyllum Cookson & Duigan 1950

~pe species. BankMaephyllum angustum.

Banksieaephyllum westdaliense sp. nov. (Fig. 11E-H)

Diagnosis. Leaf relatively narrow (about 3 ram) and lobed, base and apex unknown. At least three major veins per lobe, each extending from the primary vein towards the margin, with the central one terminating in the apex of the lobe. Areoles well developed. Stomates restricted to one surface, randomly aligned, superficial, confined to areoles, which are surrounded by elongate cells over the veins. Stomates may occur within slight depressions in areoles. Small, unicellular trichome bases common over and between veins, trichomes not preserved. Trichomes not observed on non- stomatiferous leaf surface.


Etymology. Named for the locality which yielded the fossil specimens.

Banksieaephyllum longifolium sp. nov. (Fig. 12A-F)

Diagnosis. Leaf long (at least 7.5 cm) and relatively narrow (about I cm), with a more or less linear elliptical shape and an entire margin. Venation pattern very regular, with numerous secondary veins arising at an angle which approaches 90 ° in the basal and mid portions of the leaf, but becomes more acute towards the apex. Secondary veins bifurcate very close to the leaf margin and loop into the adjacent secondary veins, forming a brochidodromous pattern. One very prominent intersecondary vein occurs between each pair of secondary veins, which follows a similar course but branches into higher order veins well short of the leaf margin. Other, less prominent intersecondary veins may also be present between each pair of secondary veins. Areoles well

FL#. 22. Line drawings of selected fossil leaves. Scale = 5ram. A, Proteaceae species I (WAM P.84.55). B, C, Counterparts of Protcace,~ epecies 2 (WAM P.84.50). D, E, Counterparts ofProteaceae epecies 3 (WAM E84.49). F, Proteaoea© epecicl 5 (WAM P.84.79). G, angiosperm species 5 (WAM P.84.73b).

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ALCHERlNGA EARLY TERTIARY MACROFLORA, W. A. 321

defined and clearly marked on the stomafiferous surface by modified, relatively long and narrow epidermal cells. Small, unicellular trichome

bases are common between epidermal cells over and between veins. Trichomes not preserved, but the basal cell is often present and terminates

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322 R. S. HILL AND H. E. MERRJFIELD ALCHERINGA

at the level of the epidermal cells. Stomates superficial on the leaf surface. Non-stomatiferous surface featurdess.

Holotype. WAM E84.47.

Specimens examined. WAM P.84.47, P.84.99.

Etymo/ogy. Named for the long, narrow leaf form.

Discussion The southwestern corner of Australia is re- nowned as a region of remarkable extant botanic diversity. This high species diversity is of particular interest, since the region has a low relief and subdued topography. Hopper (1979) noted that 2,450 (68 %) of the 3,600 species known in the region by the mid 1960s were endemics. He concluded that four geohistorical circumstances contributed to the high degree of diversity and endemism. They are:

1. Tectonic stability, low relief, and slow, local patterns of erosion have preserved some Early Tertiary landscapes on the Great Plateau, which has in tam provided habitat continuity over a long geological period, thereby saving many relict species from extinction.

2. Marine, edaphic or climatic barriers to migration on all sides of the southwest since the Eocene have effectively isolated most components of the flora from related groups in eastern Australia, and have been responsible primarily for the maintenance of high specific endemism in the region.

3. Extensive lateritic soil formation on the Great Plateau in the Oligocene and/or Miocene, and its continued formation in areas of seasonal rainfall to the present day has, following weathering, given rise to nutrient deficient sands and gravels which favour a sclerophyllous flora pre- adapted to the progressive aridity of the Late Tertiary and Quaternary. The unique character of much of the modern southwestern flora is due to the prolific speciation and adaptive radiation of heathland genera.

4. Erosional dynamism and recurrent climatic stresses in the transitional rainfall zone during the Late Tertiary and Quaternary produced a mosaic of landforms and soils together with labile population structures in the transitional- zone flora. Populations on the older plateau

surfaces were fragmented; rates of migration, isolation, extinction, confluence, and hybridisa- tion were increased among species adapted to younger soils; and accelerated rates of speeia- tion resulted. Habitat and climatic stability were greater in the high rainfall zone during these periods and hence favoured the persistence of a more conservative relict flora.

The West Dale flora contains a unique mixture of angiosperms, gymnosperms and ferns which offer evidence in support of some of Hopper's conclusions. There is a clear broad-leaved rainforest component to the flora, including Notho- fagus tasmanica, Cunoniaceae cf. CaUicoma, Laurophyllum striatum, cf. Alloxylon, possibly of. Stenocarpus and some of the unidentified angiosperms (some of which have well developed drip tips, although the specimens were not well enough preserved to warrant illustration). This component is typical of the rainforest species observed in Eocene - Oligocene rainforest in eastern Australia. For example, the Little Rapid River, Pioneer and Cethana macrofloras in Tasmania all contain Nothofagus, Lauro- phyllum and Callicoma (or at least some broad- leaved member of the Cunoniaceae) (Hill & Macphail, 1983; Hill, 1990a; Carpenter, 1991). While all these taxa are still present in eastern Australian rainforests today, they, along with mesomorphie rainforest in general, are extinct in southwestern Australia.

Although Nothofagus and I.aurophyUum may have relatively thick leaves, they are not generally regarded as sclerophyllous. However, there are dearly some sclerophyllous dements in the West Dale flora. The flora is dominated by Myrtaceae and Proteaceae and, in both families, many of the fossil taxa are thick-leaved and have typically sclerophyllous characteristics. Some of the other taxa present also demonstrate sclerophyllous characteristics. Agathis, Dacrycarpus and Retrophyllum are all thick-leaved gymnosperms, and Gymnostoma has highly reduced leaves and photosynthetic branches.

This part of the flora makes an interesting comparison with Eocene - Oligocene floras of Eastern Australia. Myrtaceous species had a relatively low diversity in eastern Australian Eocene - Oligocene rainforests. For example, there is only one species in each of the Little Rapid River, Pioneer and Cethana macrofloras

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(Hill & Macphail, 1983; Hill, 1990a; Carpen- ter, 1991), and those taxa have clear rainforest affinities (thin cuticle, and a well developed drip tip). However, Blackburn (1985) recognised 10 species of myrtaceous leaves in seven genera from the Morwell open cut coal mine in Victo- ria, although this material probably represents several vegetation types, at least some of which should not be considered as rainforest.

Similarly, proteaceous leaves are uncommon in most Eocene - Oligocene sediments in eastern Australia, but they are prominent at Cethana, where there are more than 18 taxa (Carpenter, 1991) and Morwell, where there are six leaf species and many more known only from dispersed cuticle (Blackburn, 1985). Other components of the West Dale flora, e.g. Agathis, Dacrycarpus, and Gymnostoma, all occur in Eocene - Oligocene rainforests in southeastern Australia. For example, all occur at Little Rapid River, Cethana (Carpenter, 1991) and Morwell (Blackburn, 1985). Retro- phyUum is unkncrom in Australia outside West Dale, but occurs in Miocene sediments in New Zealand (Hill & Pole, 1992).

It is clear that on a broad level there is a great deal in common among the Eocene - Oligocene floras of eastern Australia and that at West Dale. However, at a more specific level it is equally clear that the preponderance of myrtaceous and proteaceous leaves at West Dale is unnuttched in eastern Australia at that time. Furthermore, the leaves in these families at West Dale are often thick and usually lack obvious rainforest characteristics such as drip tips, and this also tends to distinguish them from their eastern Australian counterparts.

Scleromorphy is recognised as being a response to growth in a low nutrient environment, and in particular in a soil depleted of available phosphorus (Loveless, 1961,1962; Beadle, 1966). Low levels of phosphorus affect the synthesis of protein, and so the leaves are protein deficient, which makes them relatively fibre-rich. The morphological expression of scleromorphy is often small cells and leaves, thick cuticle, and other features which are often regarded as xeromorphic. However, as Hill (1990a) noted, scleromorphy and xeromorphy are not interchangeable terms. Scleromorphy, which is a condition associated with low phosphorus levels, is expressed morphologically in

characteristics which can be regarded as xeromorphic (e.g. small, thick, fibrous leaves with a thick cuticle). However, xeromorphy strictly refers to features of the plant which assist survival in conditions of low water availability, and there are some xeromorphic features which are clearly independent of scleromorphy (e.g. the herbaceous ephemeral strategy). Hill (1990a) noted some more subtle features of xeromorphy which could be expected to be independent of scleromorphy, and which could be detected in the fossil record.

Hill (1990a) reiterated the hypothesis that scleromorphy may have been a general pre-adaptation for xeromorphy in the Australian flora, and proposed that there were ways to test this hypothesis. Many perennial plants exist in Aus- tralia today under conditions which produce both scleromorphic (because of low soil nutri- ents) and xeromorphic (because of high temper- atures and low rainfall in summer) adaptations. The southwest of Australia is a prime example. However, there are xeromorphic features of plants which can be separated from scleromorphy. Chief among these is the degree of protection of stomates, which is an adaptation to increase the boundary layer and hence reduce transpiration, but is not necessarily expected in plants growing in a phosphorus-poor environment (which are scleromorphic) but with a high rainfall (and hence no need to reduce transpirational load).

Many of the perennial shrubs of Australian ecosystems in the Mediterranean climatic belt exhibit forms of stomatal protection, including stomates in hair-filled pits, deeply sunken stomates, plugged stomates, leaf rolling etc. These adaptations can be regarded as purely xeromorphic. Hill (1990a) noted that in south° eastern Australia Early Tertiary members of the tribe Bank~ieae have many scleromorphic adap- tafiens, but tittle or no stomatal protection, suggesting that water was readily available to these plants, which were probably growing in nutrient-deprived conditions. However, later in the Tertiary morphological protection of the stomates is seen, particularly in the Latrobe Valley coal, presumably in response to increasing aridity. A similar change is seen in the Casuarinaceae.

The West Dale fossils have little or no stomatal protection. In all cases the stomates are

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superficial on the leaf surface, there are no significantly revolute leaf margins, and no pits which contain stomates. Some specimens have plugged stomates, and this would have served the purpose of increasing the boundary layer for those stomates, but this is probably among the less extreme xeromorphic adaptations. Fur- thermore, Hill & Carpenter (1991) demonstrated a succession of forms of Dacrycarpus in Early Tertiary sediments in Tasmania which gradually restricted stomatal distribution, presumably in response to reduced water availability. Dacrycarpus patulus at West Dale still has stomates on both leaf surfaces, suggesting relatively wet conditions. This strongly suggests that rainfall at West Dale in the Oligocene was high enough and consistent enough throughout the year to stop transpirational loss being a major problem, a suggestion supported by the presence of numerous fern fronds and the prominent epiphyllous fungal populations on many of the leaf surfaces. However, phosphorus- poor soils may have been present, because scleromorphic adaptations are present among most of the leaves.

R is possible to speculate on the fate of the taxa at West Dale as the climate became drier and probably hotter towards the present. Pre- sumably the mesomorphic leaf types would have been unsuited to such a climate, and would have quickly become locally extinct. However, the scleromorphic taxa had some pre-adaptation to water stress (small, thick leaves with a thick cuticle), and would have survived some degree of climatic drying. Some of the taxa may have had the ability to evolve in response to a drying climate, especially in the direction of greater stomatal protection, and among these the Pro- teaceae and Myrtaceae are notable examples. However, some other scleromorphic taxa at West Dale may not have had this ability, and eventually even their scleromorphic adaptations were not enough to protect them from the drying climate. Thus taxa such as Agathis, Retro- phyUum, Dacrycarpus and Gymnastoma, with their superficial stomates, became locally extinct, and occur today in wet climates, but often on nutrient-poor soil.

However, there is another possibility which must be considered. Few of the proteaceous or myrtaceous taxa at West Dale can be clearly linked phylogenetieally with extant taxa in such

a way that the evolution of stomatal protection or a general increase in xeromorphy can be demonstrated. Probable exceptions are Agonis and Banksia/Dryandra. Thus it is possible that few of the West Dale taxa represent ancestral forms to extant species in the region. It may be that xeromorphic taxa were already present in the Eocene - Ofigocene in restricted dry sites (e.g. ridgetops, sand dunes etc.). These taxa may have already evolved morphological means of stomatal protection. When the climate dried these taxa extended their range and replaced all the rainforest, whether it had scleromorphic adaptations or not. The Casuarinaceae are a clear example of this. Gymnostoma is a common fossil in Australia in the Early Tertiary, and it is clear that this genus is scleromorphic. However, its stomates are superficial and there is little impediment to transpirational water loss. Today Gymnostoma has been almost completely replaced in Australia by Casuarina and Al- locasuarina, which are also selerophyllous, but have their stomates in deep, hair filled grooves on the photosynthetic stems. However, there is no evidence to suggest that Casuarina and AI- /ocasuar/na have recently evolved from Gym- nostoma, and indeed this seems unlikely. Instead this represents a genuine replacement and it is probable that the more xeromorphic Casuarina and Allocasuarina expanded into areas previously inhabited by Gymnostoma during the Late Tertiary increase in aridity.

Thus the West Dale flora provides some evidence for Hopper's (1979) geohistorical circumstances for the high degree of diversity and endemism in southwestern Australia. Firstly, although the proportions of families are different to other Oligocene floras, there is taxonomic overlap at the specific, generic and familial levels, suggesting that the post-Eocene barriers to migration (and in particular Miocene marine incursions) suggested by Hopper were not yet having a major effect. Secondly, the extensive lateritic soil formation of the Oligocene may be reflected in the relatively high scleromorphic component of the West Dale flora, but the pre-adaptive significance of these scleromorphic features is uncertain.

The West Dale flora gives us the first macrofossil picture of vegetation in Western Australia during the Eocene-Oligocene and suggests some patterns which segregate this vegetation

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from that in eastern Australia. More data are required to test some of the hypotheses concern- ing the evolution of the vegetation in this region, and the search for appropriate fossil floras should be given high priority.

Acknowledgements This research is supported by an ARC grant to RSH. We gratefully acknowledge the support of the Western Australian Museum and in particular George Kendrick and Ken MeN.mare. Bruce Maslin, of the Western Australian Her- beduin, supplied leaves of many extant Western Australian species for comparison with the fos- s/Is, and Karl-Heinz Wyrwoll of the Geography Department, University of Western Australia and Basil Balm. of the Geology Department, University of Western Australia freely offered specialist advice.

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326 R. S. HILL A N D H. E. MERRIFIELD ALCHERINGA

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Documents

An Early Tertiary macroflora from West Dale, southwestern Australia