264 
A.R.I. Cruickshank, J.A. Long 
Figure 1 Locality and stratigraphic setting of the pliosaurs from near Kalbarri, Carnarvon Basin, Western Australia. 
Scale bar =500 km 
recovered from the Birdrong Sandstone outcrop 
near Kalbarri in the Carnarvon Basin, Western 
Australia and isolated sauropterygian remains 
were also recovered from outcrops in the northern 
Carnarvon Basin, near Coral Bay (McLoughlin et 
al. 1995; Hocking et al. 1987) (Figure 1). The 
skeletons all lack skull material, but are well 
enough preserved to be ascribed to a new species 
of the 'Wealden' (Early Cretaceous) genus 
Leptocleidus Andrews 1922 on size differences of 
their postcranial bones. This genus is known from 
England and South Africa (Andrews 1911; 1922; 
Cruickshank 1997), and probably from the Albian/ 
Aptian of Coober Pedy, Australia (Schroeder in 
prep.), although the new species described herein 
becomes the first species of the genus to be 
formally named ed from Australia. 
Incorporated in the material described below are 
a few anomalous bones which do not seem to be 
part of plesiosaurian skeletons. One (found near 
the specimen may be a mid-caudal vertebra from a 
theropod dinosaur, and three others, from another 
skeleton (WAM 92.8.1) could possibly be from a 
jaw too big to belong to a pliosaur of the presumed 
size of the species described here. The purpose of 
this paper is put these discoveries on record, 
pending a fuller review of other Leptocleidus 
occurrences in the Early Cretaceous. 
The Birdrong Sandstone 
In the Carnarvon Basin the Cretaceous rocks 
generally lie on an erosion surface cut into Permian 
strata (Figure 1), although in Kalbarri the 
Cretaceous sequence rests unconformably above 
the ?Silurian Tumblagooda Sandstone. The 
Birdrong Sandstone is the basal unit and is ca 10 m 
thick, being overlain by 56 m of the Muderong 
Shale, a carbonaceous mudstone-siltstone. The 
Birdrong Sandstone belongs to the Muderongia 
australis Zone of late Hauterivian-Barremian age, 
as does the lower part of the Muderong Shale 
(McLaughlin et al. 1994). The age of the upper 
Muderong Shale is uncertain, as is the age of the 10 
m thick sandstone unit which separates the 
Muderong Shale from the late Aptian Windalia 
Radiolite. Changes in sediment composition, 
palynomorph assemblages and forminiferal 
biofacies reflect retrogradation of marine facies 
during deposition of the Birdrong Sandstone and 
lowermost Muderong Shale, followed by 
aggradation through most of the Muderong Shale, 
with a maximum water depth of never more than 
50 m. At its type section on Mardathuna Station, 
northeast of Carnarvon, the Birdrong Sandstone 
begins with a fluviatile phase of deposition, 
followed by deltaic and shallow marine facies 
(Hocking et al. 1987). 
