Baryonyx walkeri

Baryonyx walkeri transformed scientific understanding of spinosaurids because its holotype preserved much more of the skull and body than the fragmentary Spinosaurus material known at the time. The animal had a long, narrow snout expanded into a terminal rosette, many lightly serrated conical teeth, strong forelimbs and a very large claw on the first finger. Fish remains and juvenile iguanodontian bones found in the body cavity show that it was an opportunistic carnivore rather than a fish-only specialist. Its exact relationship with water remains debated: shoreline or shallow-water foraging is plausible, but the skeleton does not by itself demonstrate a highly aquatic lifestyle.

Its fossils occur between approximately 130 and 125 million years ago. Values shown here are approximate and reflect the current curated seed dataset.

Holotype NHMUK PV R 9951 preserves much of the skull, jaws, neck and trunk, both shoulder girdles and upper arms, parts of the forelimbs, pelvis, hind limbs and feet. The snout's expanded tip and recessed notch interlocked with the lower jaw, while numerous subcircular teeth were suited to gripping. The famous first-finger ungual measures about 31 centimetres around its outer curve before adding the keratin sheath present in life.

• Long, low snout with nostrils set back from the tip
• Expanded rosette at the front of the upper and lower jaws
• Numerous conical teeth with fine serrations
• Low ridge along the top of the snout
• Powerful shoulder and forelimb bones
• Enlarged first-finger claw about 31 centimetres around the bony curve
• Shallow dorsal neural spines rather than the tall sail of Spinosaurus

Amateur fossil collector William J. Walker noticed the tip of a large claw in Smokejacks brickworks clay pit near Ockley, Surrey, in January 1983. He brought the pieces to the Natural History Museum, whose team excavated the rest of the partial skeleton in May and June. Alan Charig and Angela Milner named Baryonyx walkeri in Nature in 1986; the genus means 'heavy claw' and the species honours Walker. Their detailed 1997 monograph documented the skeleton and the stomach-region remains that established fish consumption.

Discovery credit: William J. Walker, Natural History Museum field team.

Naming authors: Alan J. Charig, Angela C. Milner.

The Weald Clay Formation records a low-lying floodplain crossed by rivers and dotted with lakes, marshes and vegetated wetlands. Baryonyx lived alongside fish, turtles, crocodilians, pterosaurs and dinosaurs including iguanodontians and armoured forms. The Smokejacks deposit accumulated in and around a freshwater setting, but a wet habitat alone does not prove that Baryonyx spent most of its life in water.

Fish scales and teeth in the body cavity provide direct evidence that Baryonyx ate fish, while etched bones from a juvenile iguanodontian show consumption of terrestrial dinosaur tissue. Whether that animal was hunted or scavenged cannot be determined. The narrow jaws, conical teeth and strong forelimbs are consistent with grabbing slippery prey, but the exact use of the thumb claw is unknown. Claims of underwater pursuit, quadrupedal walking or specialised diving exceed what the holotype directly demonstrates.

• The first fossil recognised by William Walker was the tip of the animal's enormous thumb claw.
• The holotype gave palaeontologists the first substantially complete picture of a spinosaurid skeleton.
• Its stomach-region contents preserve one of the clearest direct dietary records known for a non-avian theropod.
• The reconstructed skeletal mount often photographed in London combines casts and restored elements; it is not an entirely original articulated skeleton.

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1. 01
   The Paleobiology Database

   Open source
2. 02
   Baryonyx, a remarkable new theropod dinosaur

   Alan J. Charig, Angela C. Milner · Nature · 1986

   Open source
3. 03
   Baryonyx walkeri, a fish-eating dinosaur from the Wealden of Surrey

   Alan J. Charig, Angela C. Milner · Bulletin of the Natural History Museum, Geology Series · 1997

   Open source
4. 04
   How did Baryonyx change what we knew about spinosaurs?

   Natural History Museum, London

   Open source
5. 05
   Dinosaur collection

   Natural History Museum, London

   Open source