| BARYONYX WALKERI 
| 
51 
| Fig. 40 Baryonyx walkeri, holotype, BMNH R9951; proximal part of left femur. A, lateral view: B, proximal; C, medial. x 0.25. 
Be erging as gentle concave curves; the lateral margin develops a 
“distinct lip, protruding laterally. The profile of the posteroventral 
edge is weakly concave, so that the pubis expands a little 
Jposteroventally towards the distal end. However, the end itself 
“does not expand extensively either anteriorly or posteriorly to form 
a ‘pubic boot’, as it does in many other theropods; indeed the distal 
asic of the medial or lateral surface forms a smooth convex 
‘curve. The medial surface is perceptibly concave towards its distal 
nd. 
_ISCHIUM (Fig. 39B). A large part of the left ischium is preserved, 
including most of the shaft (total length of the element as preserved 
470 mm). It lacks only the distal end of the shaft and a small part of 
the anterior edge of the pubic peduncle. Of the right ischium there 
remain only four fragments of the proximal end, none of which can 
de fitted together directly; one of them includes the pubic articula- 
ion with a small part of the acetabulum, another includes the 
obturator flange (see below), a third small piece is a further length of 
he acetabular margin, and a fourth piece is a length of the upper part 
x the shaft. 
_ The element as preserved is a fairly typical ischium, shaped 
omewhat like a Y. Between the two peduncles is the most ventral 
ortion of the acetabular ring, narrower in the centre and widening in 
either direction towards the articulating surfaces for the pubis and 
_ lium respectively; the iliac surface is the larger of the two. Both 
i deduncles (and of course the margins of their articulating surfaces) 
“are convex on their lateral sides and concave medially. Ventral to this 
_egion the ischium forms a broad plate which has a stout posterior 
“Margin; just below the iliac peduncle this plate is weakly concave 
_detween two longitudinal ridges. Towards its anterior margin, below 
he pubic peduncle, the plate tapers to a slender flange. The ventral 
dart of this flange with its distinctive fluted margin might be 
_/nterpreted as the equivalent of an obturator process, but the evident 
“absence of any notch or embayment proximal thereto suggests that 
there was no process projecting anteroventrally, such as is found in 
Allosaurus. There is, however, a slight notch in the anterior edge of 
jhe ischium distal to this region; we therefore propose to call this part 
- 
of the bone the obturator flange. This condition is very similar to that 
found in ceratosaurs, in particular Dilophosaurus (Welles 1984) and 
Carnotaurus (Bonaparte, Novas & Coria 1990). 
The posterior surface of the shaft is broad and flat, but anteriorly 
it is produced into a thin flange that widens towards the broken distal 
end. The medial surface of this flange is more or less planar, but the 
lateral surface is weakly concave. 
Hind limb 
FEMUR (Figs 40,41). Both femora suffered extreme damage from 
clay-winning operations before the presence of the dinosaur skel- 
eton was recognized. The only fragments rescued were (from the left 
femur) the proximal end with the uppermost part of the shaft, 
together with the tibial condyle, and (from the right femur) the distal 
40% or so of the bone. There was no overlap between the two sides, 
and it is therefore impossible to make an accurate estimate of the 
length of the entire element; 1,200 mm is probably a reasonable 
approximation. 
Unfortunately, in this limited material many of the external 
features had either been destroyed without trace or would have been 
on regions of the bone that were not preserved; these include the 
internal and fourth trochanters. 
The proximal end of the femur appears not to have been crushed 
but is nevertheless somewhat flattened anteroposteriorly. The 
inturned head is oval in outline and its articulating surface is 
directed, not medially, but rather posteromedially; it is separated 
from the much larger greater trochanter by a broad U-shaped 
vertical channel on the posterior side. The greater trochanter is 
elongated in a mediolateral direction and tapers towards the lateral 
side, with its anterior surface lightly convex and its posterior sur- 
face concave. The lateral edge, narrow proximally, swells out more 
distally into a distinct protuberance with a convex anterior margin 
and a straight posterior margin. 
The shaft of the femur is more or less circular in cross-section. 
The distal end shows the usual two condyles, both well preserved; 
