| 
BARYONYX WALKERI 
reptiles. One might speculate that its functional significance in 
' Baryonyx might be somehow connected with the gripping and 
| manipulation of food, the lower teeth forming a closely spaced series 
_ of piercing and holding points that opposed the more widely spaced 
| upper teeth. 
_ In connexion with the animal’s feeding habits, it should also be 
mentioned that an apparent gastrolith was found within the rib-cage 
| of the Baryonyx. 
_ On balance, we still envisage Baryonyx as mainly a fish-eater. It 
probably crouched on the banks of lakes, creeks and rivers or waded 
in the shallows (Frontispiece), and it secured its prey by direct 
‘seizure with the jaws and perhaps also by ‘gaffing’. Small fishes 
would have been swallowed whole, larger ones broken up by the 
e fore-limbs with their huge claws. Fishing, however, was 
| 
not the only source of food; there is also: 
1. Circumstantial evidence that it may well have been both an active 
predator (using its powerful fore-limbs and claws rather than its 
jaws and teeth) and/or an opportunistic scavenger. 
2. Positive evidence (i.e. recognisable bony remains within its rib- 
cage) that it had eaten a small /guanodon, though whether this 
was the result of active predation or scavenging cannot be 
determined. 
\TERRESTRIALITY. If we accept that fish formed a significant part of 
the diet of Baryonyx, then we must consider the possibility that the 
Janimal led an aquatic or semi-aquatic existence. Nevertheless, its 
anatomy gives no indication of any modifications towards that mode 
of life. For example, it certainly had no flipper-like modifications of 
the limbs and it lacked the dorso-ventrally flattened skull with 
dorsally situated external nares typical of crocodiles. Indeed, the 
UF sition of the nostrils on the side of the skull would be disadvanta- 
ous to an animal spending much of its time in the water. However, 
a could probably swim, as can most land vertebrates, de- 
pte their lack of any special adaptations. 
STANCE AND GAIT. Despite our previous suggestions of 
‘quadrupedality (Charig & Milner 1986), the anatomy of Baryonyx 
7 
; 
affords no evidence of a gait any different from that of any other 
poe The length of the humerus of Stegosaurus, which is most 
‘certainly a quadruped, varies between 43% and 55% of the length of 
‘its femur; the corresponding ratio for Baryonyx is only 39% (based 
. n an unprejudiced estimate of the femoral length). On the other 
i] 
and, if Baryonyx really was a fish-eater, then it would have been 
pbliged to capture its aquatic prey from a crouching or quadrupedal 
dosition, either on the edge of the water or actually in it; and its 
"massive fore-limbs certainly possessed sufficient mechanical strength 
nd adequate musculature for the quadrupedal posture. 
he details of the fossilisation of the Baryonyx walkeri holotype 
_jsome of which have already been published in Charig & Milner, 
986) are as follows: 
ANNER OF OCCURRENCE. Most of the bones were encased in 
jideritic siltstone nodules of irregular shape and were directly 
jurrounded by uneven accumulations of extremely fine sand and 
ilts; such accumulations are not found anywhere else. The rest of 
: : bones lay unprotected in clay. 
IEGREE OF ARTICULATION. 
d somewhat scattered. 
The bones were largely disarticulated 
63 
METRES 
- Skull 
- lower jaw 
= teeth 
- dorsal ribs 
- abdominal ribs 
pectoral girdle 
- pelvic girdle 
- cervical vertebrae 
- dorsal vertebrae 
- caudal vertebrae 
- hind limb 
Fig. 48 Plan of the excavation at Smokejack’s Brickworks, Ockley, May- 
June 1983, indicating the in situ positions of the numbered blocks and 
the distribution of skeletal elements. 
O<PrOevarom 
