Early Cretaceous macrofloras 
57 
these plants were adapted to a seasonal climatic 
regime. A deciduous habit for other plant groups 
in the Western Australian assemblages is less 
obvious although the complete and sometimes 
matted fronds of bennettitaleans such as 
Ptilophyllum cutchense in the Broome Sandstone 
may reflect deciduousness. 
The range of fern and lycophyte species in the 
collections suggests a humid microthermal to 
megathermal climate based on the distributions of 
related extant taxa. However, most of the 
fossiliferous units were deposited in lowland 
deltaic environments where high water table 
(rheotrophic) rather than necessarily high rainfall 
(ombotrophic) conditions may have aided the 
growth of pteridophytes. Modern cycadophytes 
typically grow in mesothermal to megathermal 
conditions and most forms probably occupied 
similar climates in the past (Douglas and Williams 
1982). The abundance of bennettitalean foliage in 
the studied assemblages favours interpretation of a 
relatively warm (though seasonal) climate. Some of 
the bennettitaleans have comparatively small 
fronds (e.g., Ptilophyllum boolensis) which may have 
been a foliar response to local water stress. 
Differential representation of plant groups 
between the various Western Australian 
Neocomian-Barremian assemblages is relatively 
minor and probably reflects local differences 
between depositional settings (e.g., alluvial valley 
versus coastal environments). The Nanutarra 
Formation yields a small macroflora mixed with a 
marine invertebrate fauna (Cox 1961) and was 
probably deposited within paralic to shallow 
marine conditions. The coastal to nearshore 
sediments of the Birdrong Sandstone lack leaf 
remains but contain abundant mollusc-bored fossil 
wood, ammonoids, and marine vertebrates 
(McLoughlin et al. 1994). Whilst some of the plant 
remains in the Broome Sandstone are clearly 
allochthonous, autochthonous root beds and 
Nathorstianella corms are evident in exposures at 
Gantheaume Point, Broome. This coarse-grained 
unit also contains diverse dinosaurian trackways 
(Long 1990) and sparse bivalves (Yeates et al. 1984) 
and was probably deposited within a deltaic 
setting. The plant-bearing Callawa Formation and 
Cronin Sandstone, although not examined during 
this study, lack invertebrate fossils and were 
probably deposited within proximal fluvial 
(alluvial valley/ alluvial plain) settings. The 
Leederville Formation consists of interbedded 
sandstones, siltstones, and claystones and was 
deposited within paralic to shallow marine 
environments (Cockbain 1990). The correlative 
Bullsbrook Formation is dominantly composed of 
sandstone but contains local plant-bearing 
overbank shale lenses and was deposited within 
fluvial environments (Cockbain 1990). 
CONCLUSIONS 
Thirty-two fossil plant and fungi taxa have been 
described from five Early Cretaceous 
lithostratigraphic units in Western Australia. Four 
new species (viz., Phyllopteroides westralensis, 
Roebuckia spalulata, Elatocladus ginginensis, and 
Carpolithes bullsbrookensis) are defined while several 
others are described under open nomenclature 
owing to insufficient or inadequately preserved 
material prohibiting comparisons to established 
taxa. The fossil assemblages comprise lycophytes, 
ferns, pteridosperms, pentoxylaleans, 
bennettitaleans, and araucarian and podocarpacean 
conifers. Bennettitaleans, pentoxylaleans, and 
conifers are the numerically dominant elements of 
the flora. Macrofossil suites from the Broome 
Sandstone (Canning Basin), Nanutarra Formation 
and Birdrong Sandstone (Carnarvon Basin), and 
Leederville and Bullsbrook Formations (Perth 
Basin) are correlated with Douglas' (1969) 
Ptilophyllum-Pachypteris austropapillosa Zone (Zone 
B) of Victoria and indicate a Neocomian- 
Barremian age. The Nanutarra Formation is a 
diachronous marginal marine to paralic unit and 
its age may locally extend to the Aptian based on 
invertebrate assemblages (Cox 1961). The Western 
Australian Early Cretaceous floras are most closely 
comparable with coeval assemblages from South 
Australia and the Northern Territory. Lesser 
similarities are evident with eastern Australian and 
Indian floras and fewer species are shared with 
South America, Antarctica, and South Africa. Few, 
if any, species are shared with extra-Gondwanan 
assemblages. The representation of plant groups, 
together with wood growth indices, 
palaeomagnetic data, and oxygen isotope 
signatures, suggests that the Western Australian 
marginal basins experienced humid seasonal 
mesothermal climates in mid-latitudes during the 
Neocomian-Barremian. Local variations between 
assemblages are probably attributable to 
differences in depositional settings, seasonal 
effects, and taphonomic factors rather than 
significant climatic or stratigraphic anomalies 
between localities and host formations. 
ACKNOWLEDGEMENTS 
Thanks are due to the numerous museum and 
university officers and members of the public who, 
over the past three decades, have contributed 
Cretaceous plant fossils from various localities to 
the Western Australian Museum and the 
University of Western Australia. Dr Ken 
McNamara and Dr John Long of the Western 
Australian Museum are thanked for arranging the 
loan of the museum's specimens. Dr David Haig 
(University of Western Australia) and Mr Glynn 
Ellis (University of Lausanne) assisted with 
