Western Australian Cretaceous pliosaurid 
271 
Referred material 
WAM 94.1.6-1 to 100 (94.1.6-1 through to 94.1.6- 
94), a less well preserved partial skeleton, 
dimensionally very similar, approximately 100 
associated, partially articulated bones found 
underneath a single large concretion (Figures 4, 7, 
13B, 15). 
Etymology 
In honour of Mr John M. Clema of Perth, Western 
Australia, who has generously supported and 
assisted in fossil collecting expeditions by the 
Western Australian Museum over the years 1993- 
1995. 
Diagnosis 
A species of Leptocleidus whose vertebrae are at 
least 30% greater in linear dimensions than those 
of either L. superstes or L. capensis, and whose 
propodials are 10% - 15% greater in size (WAM 
92.8.1-2, femur 274 mm long). The epipodials show 
a derived state when compared with L. capensis in 
being wider than long. 
Description of material 
Holotype (WAM 92.8.1, Figs. 3, 5,6, 8-12, 13A, C- 
E,14, 16). 
Distinguishing between the various parts of the 
vertebral column was difficult in both the principal 
specimens reported here due to the poor state of 
preservation and fracturing of vertebrae. It has 
been assumed that the distinction between cervical 
and sacral centra is that the former have a mid- 
ventral keel, and prominent sub-central foramina 
in addition to the facets for the cervical ribs, which 
possibly could be confused with one or other of the 
sacral series. Pectoral centra do not have the 
prominent mid-ventral keel, but tire most anterior 
pectoral centrum has a large part of its rib facet 
still on the centrum, which in a poorly preserved 
specimen also might cause confusion with one of 
the sacral series. Caudal centra, apart from the 
very first few, have haemal facets and should not 
be confused with any others. Dorsal centra do not 
have rib facets and often do not have prominent 
sub-central foramina nor mid-ventral keels. They 
are often very much more robust than others in the 
vertebral column. 
All the centra are spool-shaped (Figures 3-11), 
are concave on their faces, and none has its neural 
arch in position. Mostly the evidence points to the 
bases of the neural arches having come cleanly 
away from the centra, indicating lack of fusion and 
hence a sub-adult ('juvenile') age for the specimen. 
The centrum with the greatest length is a dorsal at 
about 42.4 mm. The shortest is a caudal at 22.5 
mm. All centrum widths are significantly greater 
than their lengths, and also greater than, or sub¬ 
equal to their heights. The cervical vertebrae are 
not markedly shortened (Figures 3A-E). They are 
only slightly shorter than the pectorals, but more 
so when compared with the dorsals (Table 1). 
However the overall impression is a vertebral 
column of uniformly proportioned centra, as far 
back as the caudal series, when some compression 
is seen. This is a markedly primitive vertebral 
column for a Cretaceous pliosaur (Andrews 1922; 
Brown 1981; Tarlo 1960; Taylor and Cruickshank 
1993), but seems to be very similar to the other 
species of Leptocleidus (L. capensis (Andrews 1911) 
and L. superstes Andrews 1922), differing only in 
the overall size of the individual elements. 
Of the femora, the right is best preserved (Figs 
13A, 14). Its dimensions are 274.0 mm long, 76.3 
mm across the head and 123.4 mm wide distally. 
Table 1 Some measurements of Leptocleidus specimens. The vertebral measurements are listed in sequence as 
'Length', 'Breadth' (Width) and 'Height'. The limb bone measurements are overall length, width of head in 
plane of the distal expansion, and width of distal end. 
Identity L. superstes L. capensis L. clemai L clemai 
BMNH R4824 SAM K-5822 WAM 92.8.1 WAM 94.1.6 
post cervical 
25 
38 
30 
19 
30 
35 
35.4 
63.3 
55.2 
39.4 
56 
55.5 
ant cervical 
22 
25 
25 
20 
34.2 
30.7 
mid cervical 
25 
36 
31 
35 
48.9 
44.6 
post cervical 
25 
38 
30 
19 
30 
35 
35.4 
63.3 
55.2 
39.4 
56 
55.5 
32 
43 
40 
21 
33 
27 
35.6 
62.3 
54.7 
dorsal 
31 
55 
48 
32 
50 
41 
40.5 
52.6 
52.1 
32.5 
55.8 
49.5 
28 
46 
41 
40 
60.9 
58.3 
35 
58 
53.5 
41.9 
63.9 
64.1 
41.2 
73.1 
68 
l.humerus 
245 
60 
124 
r. humerus 
270 
68.2 
127.6 
r.femur 
274 
76.3 
123.4 
