Western Australian Cretaceous pliosaurid 
265 
Figure 2 Attempted reconstruction of the skeleton of Leptocleidus clemai sp. nov. showing relative completeness of 
remains so far recovered shown in black. Skull and other proportions are based on Peloneustes and 
Leptocleidus sp. 
The sequence reflects a transgressive pulse that 
was part of the progressive submergence of vast 
areas of the Australian continent during the Early 
Cretaceous (Dettmann el. al. 1992). This late 
Hauterivian-Barremian transgressive pulse is 
recognized in widely separated basins in Australia, 
and may represent a synchronous continent-wide 
sea-level rise. A similar sea-level rise is seen in the 
Algoa Basin (and other smaller basins) on the 
South African south-east coast, where Leptocleidus 
capensis has been recovered from Valanginian 
inshore deposits (Cruickshank 1997; McLachlan 
and McMillan 1977; McMillan in prep.). The earlier 
date for the South African deposits reflects a 
probable earlier phase of the break-up of (east) 
Gondwana. 
Institutional abbreviations used in this paper: 
WAM - fossil collections of the Department of 
Earth and Planetary Sciences; SAM - fossil 
collections in the Division of Palaeontology, South 
African Museum; NHM - fossil collections in the 
Palaeontology Department, The Natural History 
Museum, London. 
MATERIAL AND METHODS 
(a) WAM 92.8.1-1 to 68. The first specimen to be 
recovered comprises numerous vertebral centra, 
left and right femora, right tibia and fibula, left 
tibia, a possible partial ulna, base and part of the 
shaft of a left ilium, a badly damaged head of a 
humerus, broken parts of the pectoral girdle 
(scapula?) and pelvic girdle elements, part of a 
neural arch, and several rib fragments. The centra 
are distributed as follows: 11 cervical, 3 pectorals, 
17 dorsal, 2 sacrals(?), 5 caudals and one so badly 
preserved that its position is not identifiable, but it 
is possibly a dorsal. In addition to the elements 
which can be confidently assigned to a pliosaur, 
there are three heavily ossified portions of what 
appear to be the mid-part of a lower jaw, lacking 
teeth, which if reconstructed would be far too big 
for the assumed size of this pliosaur. 
(b) WAM 94.1.6-1 to 100. The second best 
preserved of the three. It comprises a length of the 
vertebral column encased in a nodule extending 
over about 15 vertebrae, and the following 
individual bones which can be identified: 9 cervical 
vertebrae, about 20 dorsal vertebrae as well as 
some fragments, 4 sacrals, one caudal, a fragment 
of scapula, portions of two ilia and, a piece of 
pubis, two humeri, one possible phalanx, an 
unidentifiable epipodial and five pieces of rib, 
apart from some very poorly preserved lengths of 
rib still in tlie nodule. 
A very badly preserved, but elongate, centrum 
found near the specimen is not plesiosaurian but is 
from the mid-caudal region of a medium-sized 
theropod dinosaur, and is described elsewhere 
(Long and Cruickshank 1997). 
(c) WAM 96.5.2. The material comprising this 
specimen is badly preserved and mostly 
unidentifiable as to taxon, except for some dorsal 
vertebrae which appear to be similar in size and 
proportion to those of the other two specimens. It 
is noted here only to complete the record. 
Figure 2 shows a generalised pliosaurid skeleton 
with the known remains from Leptocleidus clemai 
sp. nov. shaded in black, indicating the degree of 
completeness from the combined two partial 
skeletons. 
Excavation and preparation procedures used on 
this material were standard, using pneumatic 
airscribes and manual chisels to clear the friable 
sandy matrix and the thin layer of encrusting iron- 
rich cementing minerals from the specimens. 
Mends were made with proprietary organic glues 
dissolved in acetone, and therefore reversible, 
except for the joining together of the thicker bones 
(eg the humeri) in which epoxy resins were used. 
Some portions of the specimens were transported 
in plaster jackets and extracted from the matrix in 
the laboratory. Measurements were made to the 
nearest 0.1 mm, using sliding vernier calipers. 
