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Bull. nat. Hist. Mus. Lond. (Geol.) 53(1): 11-70 Issued June 1997 
Baryonyx walkeri, a fish-eating dinosaur from 
| the Wealden of Surrey 
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ALAN J. CHARIG AND ANGELA C. MILNER 
: Department of Palaeontology, Natural History Museum, Cromwell Road, London SW7 5BD 
CONTENTS 
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SYNOPSIS. The well-preserved skeleton of a large theropod dinosaur, Baryonyx walkeri Charig & Milner, 1986, from the 
Wealden (Barremian, Lower Cretaceous) of Surrey, is described in detail. It is a large theropod with some resemblance to 
Megalosaurus or Allosaurus, but is sufficiently different to merit its earlier designation as the type of the new family 
Baryonychidae. Its distinguishing characters include: the prenarial extension of its snout into a spatulate rostrum, a unique 
increase in the number of the dentary teeth (which are more than twice as numerous per unit length of jaw as the opposing 
| maxillary teeth), an unusually robust fore-limb, and at least one pair of huge manual talons. Lack of fusion between the 
components of both skull and vertebrae suggests that this 10 metre long animal was immature. 
Few other specimens might be referred to Baryonyx: a maxilla fragment of B. walkeri is recorded from the Barremian of Spain; 
two snout fragments from the Aptian of Niger, which are virtually identical to the conjoined premaxillae of Baryonyx; two 
isolated tooth crowns, one from the Hauterivian of East Sussex, and one from Surrey; and seven from the Barremian of the Isle 
of Wight are compared to the genus. On the evidence of jaws and teeth only, the families Baryonychidae and Spinosauridae 
(Spinosaurus, Angaturama, and perhaps Irritator) are placed in the superfamily Spinosauroidea. An investigation of the wider 
affinities of Baryonyx, based on a modified version of Holtz’s 1994a data-matrix on the Theropoda, suggests that the 
Spinosauroidea is a basal member of the Tetanurae and sister-group to the whole of the Neotetanurae (i.e. the Coelurosauria sensu 
Gauthier plus a variable collection of ‘allosauroids’), with Megalosaurus and Torvosaurus as progressively more distant 
outgroups. 
The associated fossil fauna is dominated by Jguanodon and many insects, which lived in the vicinity of a sub-tropical delta. 
Baryonyx was terrestrial, a fish-eater, probably a scavenger, and possibly an active predator of small to medium-sized land 
animals. It made greater use of its fore-limbs and talons in attack and defence than its jaws and teeth, which were used mainly for 
seizing fish and entrails. The taphonomy of the holotype suggests that the animal is unlikely to have been transported from 
elsewhere and probably died where found. Its skeletal remains lay in sediments that were mostly submerged in shallow water but 
exposed to the air for brief periods; the bones were trampled and broken before fossilization. 
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Natural History Museum, 1997 
