Baryonyx, meaning “heavy claw,” was a genus of carnivorous dinosaur from the Hauterivian to early Barremian stages of the Early Cretaceous Period (130-125 million years ago). It was first discovered in clay pits just south of Dorking, England, and later also found in northern Spain and Portugal. Only one species is known, B. walkeri, named in honor of its discoverer, amateur fossil hunter William Walker.

Walker discovered the creature when he came across an enormous claw sticking out of the side of a clay pit in Surrey, England. The skeleton was in a relatively intact state and was excavated by a team of paleontologists from the Natural History Museum of London. The description of the dinosaur was published in 1986. About 70 percent of the skeleton was recovered and is now housed at the Natural History Museum.

Another specimen was discovered some years later, along with abundant fossil tracks near Burgos Province, Spain. The tracks have been identified as either belonging to Baryonyx or another similar theropod genus. Two more claws have also been found in Niger Republic in West Africa, and another in 1996 on the Isle of Wight. In December 1997, a store of old fossils in the Isle of Wight Museum yielded a forearm of a Baryonyx. These remains had apparently been unearthed decades earlier on the southwest coast of the island, and had sat unclassified in a box in Carisbrooke Castle since that time.

Baryonyx was about 28 feet long and weighed around 3750 pounds. Analysis of the bones suggests that the most complete specimen was not yet fully grown, so it is possible Baryonyx may have been much larger than this. It had a large claw on the thumb of each hand, which measured about 14 inches long. It had a long neck and the skull was set at an acute angle, rather than the 90 degree angle seen in similar dinosaurs. The long jaw was crocodilian and had 96 teeth, twice as many as its relatives. The snout probably bore a small crest. The upper jaw had a sharp angle near the snout, a feature seen in crocodiles that helps to prevent prey from escaping. A similar feature is also seen in shrikes.

The crocodilian jaws and the large number of finely serrated teeth suggested to scientists that Baryonyx was a fish-eater. If so, it would be one of the few known fish-eating dinosaurs. Confirming this theory, a large number of scales and bones from the fish Lepidotes were also discovered in the body cavity of the dinosaur.

Scientists speculate that Baryonyx would sit on a riverbank, resting on its powerful front legs, and then sweep fish up from the river with its powerful claw, in similar fashion to the modern grizzly bear.