56 
N. W. ARCHBOLD 
most beds of the Wooramel Group which is 
identical with the fauna found in the immedi¬ 
ately overlying Byro Group, reflecting “the 
deepening of the basin and the initial develop¬ 
ment of more definite off-shore marine con¬ 
ditions in those places”. This fauna, found in the 
top of the Keogh and Billidee Formations, was 
included in Stage D by Dickins (1963). The oc¬ 
currence of the ammonoids Neocrimites sp. and 
Bamyaniceras sp. in beds high in the Billidee 
Formation (Cockbain 1980) also links this fauna 
with the lowest fauna of the Byro Group, gen¬ 
erally regarded as being early Baigendzhinian in 
age. 
While there is little disagreement as to the age 
of the uppermost Wooramel Group faunas, this 
is not the case for the bulk of the Wooramel 
Group. Dickins (1963) considered that the close 
relationship of his Stage C assemblages with 
those of his Stage B assemblages indicated an age 
for Stage C of Early Artinskian (Aktastinian). He 
considered Stage C to be immediately younger 
than the Sterlitamakian fauna of the underlying 
Callytharra Formation with, by implication, the 
disconformity between the two stratigraphical 
units representing a very minor interval of 
time. 
However, the discovery of a specimen of the 
ammonoid Pseudoschistoceras from beds near 
the top of the Cordalia Sandstone (a lateral 
equivalent of the Nunnery Sandstone) resulted 
in Cockbain (1980) considering the entire Woo¬ 
ramel Group to be of early Baigendzhinian age. 
Pseudoschistoceras is generally considered to in¬ 
dicate a Baigendzhinian age (Glenister et al. 
1983) but is only known from three described 
localities and is listed from the Kungurian by 
Bogoslovskaya (1988), indicating that it’s full 
stratigraphical range may not be fully under¬ 
stood. Runnegar (1969) and Waterhouse (1970) 
regarded the recognition of Stage C as unwar¬ 
ranted and so merged it with Stage B. As a result 
Cockbain (1980: 104) considered that Stage B 
had a “fairly long time range and occurs at a 
number of shelly horizons, often of limited 
extent, and hence cannot be used for detailed 
biostratigraphical correlation”. 
AGE OF WOORAMEL GROUP 
The fossils figured and described herein include 
the following: 
IStreptorhynchus sp. 
Pennorthotetes sp. 
Neochonetes (Sommeriella) hockingi sp. nov. 
Strophalosia jimbaensis Archbold, 1986 
Aulosteges sp. 
Fusispirifer sp. 
Neospinfer sp. 
ICleiothyridina sp. 
lAviculopecten sp. 
While the preservation of specimens as natu¬ 
ral ferruginous casts and internal and external 
moulds is of variable quality, the overall affinity 
of the fauna is closer to that of the Callytharra 
Formation than to that of the overlying fauna of 
the Madeline/Coyrie Formation. Nevertheless 
the Wooramel Group species are distinctive, 
and of particular importance are species of 
Neochonetes (Sommeriella) and Strophalosia. 
Chonetid brachiopods evolved rapidly during 
the Permian in Western Australia (e.g. see Arch- 
bold 1981) and are invaluable for correlation, 
while Strophalosia species are also important for 
biostratigraphy (e.g. see Clarke 1990). 
A formal zone is proposed herein forWoora- 
mel Group faunas, namely the Strophalosia jim¬ 
baensis zone, based on a species that is found in 
both the One Gum and Billidee Formations. The 
species is also present in the Jimba Jimba Cal- 
carenite where the distinctive species Globiella 
jlexuosa (Waterhouse) is also found (Archbold 
1983). The Jimba Jimba fauna, currently being 
investigated by me, appears to be related to that 
of the Callytharra Formation but is distinct at 
the species level, adding support to the biostrati¬ 
graphical recognition of Stage C of Dickins 
(1963). 
In view of the relatively close relationship of 
many of the Wooramel Group species to those 
from the Callytharra Formation (see compari¬ 
sons below), I agree with Dickins (1963) that the 
disconformity between the two units does not 
represent a major break in time (perhaps just the 
late Sterlitamakian). As a result, not withstand¬ 
ing the significance of the occurrence of the 
ammonoid Pseudoschistoceras sp., 1 prefer an 
Aktastinian age assignment for the Wooramel 
Group. Comparison of a few species of the fauna 
with forms from Sterlitamakian or Aktastinian 
horizons elsewhere also strengthens the pro¬ 
posed Aktastinian age. 
COLLECTIONS AND LOCALITIES 
All specimens are registered with the Geological 
Survey of Western Australia (GSWA F), Perth or 
with the Commonwealth Palaeontological Col¬ 
lections (CPC) of the Bureau of Mineral Re¬ 
sources, Geology and Geophysics, Canberra. 
