BARYONYX WALKERI 
FUNCTIONAL MORPHOLOGY AND MODE OF 
LIFE 
We (Charig & Milner 1986) have suggested for Baryonyx: 
(a) ichthyophagy (a diet consisting mainly of fish) but with the 
further possibility of a scavenging habit; 
(b) a terrestrial existence; and 
(c) quadrupedality, facultative at least. 
DIET AND METHODS OF FEEDING. Kitchener (1987) noted that 
‘The alternative lifestyle of a scavenger [had] received very little 
attention’ in our paper; he followed this with the full details of our 
case for a scavenging habit (as presented by us at meetings in 
Drumheller and Belfast in 1986 but omitted from our publication 
because of lack of space). Kitchener then went on to state his 
preference for the idea of a scavenging habit over that of 
ichthyophagy, a preference which we do not share. 
The characters suggesting a scavenging habit, as published by 
Kitchener, may be summed up as follows: 
. Stance facultatively quadrupedal. 
. Neck long (both 1 & 2 suitable for feeding at ground level). 
3. Fore-limbs massively developed, with huge claws (ideal for 
breaking into a carcase). 
4. Snout narrow (well suited to investigating the body cavity of the 
carcase). 
5. External nares placed far back from tip of snout (permitting 
simultaneous feeding and breathing). 
6. Premaxilla and maxilla connected by flexible hinge (allowing 
freer movement in the restricted space in the body cavity). 
7. Teeth slender and finely serrated (for processing the soft viscera). 
Noe 
However, we now know that there is no evidence for characters nos 
1, 2 and 6. 
Kitchener also put forward one character as evidence against a 
typical macropredacious habit: 
8. Mandible and teeth weakly developed (particularly unsuitable 
for killing and feeding on large herbivorous dinosaurs). Even 
crocodilians, after the birds the nearest living relatives of 
Baryonyx, have great difficulty in breaking through the skin of 
large prey. 
e€ also made two arguments against ichthyophagy: 
It is unlikely that such a heavy creature ‘could have been 
sufficiently manouverable [sic] to catch fast-moving fish’. 
10. Baryonyx has too many adaptations for fish feeding, viz. fore- 
limbs for hooking fish and teeth and jaws similar to the fish-eating 
gavial’s; ‘one adaptation would suffice’. 
N a critical reply to Kitchener, Reid (1987) cited three counter- 
‘guments: 
0 3 above: Most available carcases would probably already have 
been broken into by the primary predator. 
© 8 above: The teeth of modern crocodilians are more or less 
conical, not adapted to slicing, and are in no way comparable to 
the bilaterally compressed “steak-knife” teeth of typical theropod 
dinosaurs. (In fact, the condition in Baryonyx is intermediate 
between the two.) 
© 9 above: Large animals, e.g. grizzly bears, are capable of 
61 
catching fast-moving fish, at least in shallow water. Techniques 
analogous to ‘gaffing’ or trout-tickling could also have been 
employed. 
We add two further comments: 
To 7 above: The crowns of the teeth were not slender; in fact, they 
were less compressed laterally than those of other, more ‘typical’ 
theropods. 
To 10 above: There is no logic in the argument that, because an 
animal has two different adaptations that appear to have served 
the same purpose, neither of them can in fact have served that 
purpose. 
The information that may help us assess the diet and feeding 
methods of Baryonyx is as follows: 
1. There is direct evidence of what the animal had been eating. 
Within its smashed-up rib-cage, in its stomach region, were 
found: 
a. Acid-etched scales and teeth of the common Mesozoic fish 
Lepidotes (Fig. 47). These are of especially great significance. 
b. The disarticulated skeletal remains of a young Iguanodon 
[See Appendix B] showing some evidence of abrasion (and/or 
etching). 
2 There is also circumstantial evidence of the ichthyophagous 
habits of Baryonyx. Modern crocodilians have certain adapta- 
tions which are clearly effective in catching and swallowing 
fishes; analogous characters are found in Baryonyx: 
a. The jaws are long and very narrow from side to side; they are 
expanded horizontally at the anterior end, with enlarged teeth 
around the margins of the expansions (Fig. 2). In the upper jaw 
this spatulate expansion forms a ‘terminal rosette’, not unlike the 
corresponding region of the skull of a modern gavial. 
b. Seen from the side, both upper and lower jaws have sigmoid 
dentigerous margins (Fig. 1); the upper jaw has a downturned tip 
and a ‘subrostral notch’. Altogether this particular aspect of the 
animal has an appearance that is distinctly crocodile-like, albeit 
only superficially so. 
These similarities support the idea that Baryonyx caught small and 
moderate-sized fishes in a crocodilian manner, i.e., it seized them 
with the end of its pincer-like jaws and gripped them transversely in 
its subrostral notch and lateral teeth; the shape of the jaws and the 
nature of the teeth accord well with the suggestion that they some- 
how helped the grasping and manoeuvring of slippery prey. The 
animal might then have tilted its head back and manoeuvred the fish 
around so that the fish slid head-first down the gullet into its 
stomach, as do modern crocodilians. We believe that Baryonyx ate 
fish habitually, though not necessarily exclusively. 
Whatever the nature of Baryonyx’s preferred diet, the animal 
seems ill-equipped to have been a typical theropod macropredator of 
the type that relied largely on short, powerful jaws and blade-like 
teeth with serrated edges to capture, kill and dismember its prey. 
This is because: 
1. The middle part of each bony ramus of the mandible is wafer- 
thin. 
2. The teeth are only slightly compressed from side to side, thus 
differing from those of typical macropredacious dinosaurs like 
Allosaurus. 
3. The denticles on the carinae of the teeth are remarkably fine 
(about 7 per millimetre). 
