During the early Cretaceous, the Wealden Lake covered the majority of what is now northern Europe. River plains and deltas spread from the uplands surrounding modern London, England and eventually met this great lake. It is in the area of these deltas that the dinosaur Baryonyx ("heavy claw") was discovered. In 1983, an amateur fossil hunter named William Walker came across an enormous claw sticking out the side of a clay pit in Surrey. He received some help in retrieving the specimen, which - while the only recovery yet made - is a good one. He then dutifully passed the skeleton to Dr Alan J. Charig and Dr Angela C. Milner of The Natural History Museum in London. They published their description of the type species, B. walkeri, in 1986, and gratefully named it after Mr Walker. The skeleton was about 70% complete, and crucially included the skull. Therefore paleontologists can make many useful deductions about Baryonyx from just a single find. It was the first carnivore discovered in England.
Baryonyx was about 8 to 10 metres long, and around 5 metres tall. It probably weighed in the region of 2000kg, but we cannot know for certain if our specimen was of average weight. In fact, analysis of the bones suggests that it was not yet fully grown. It probably ate fish. It lived in the Barremian period of Early Cretaceous, around 125 million years ago.
Baryonyx is a very unusual carnosaur indeed. The design of its hips and pelvis suggests that it was bipedal for the purposes of walking from place to place. However, its forelimbs were absurdly large for a theropod, suggesting that it also spent much of its time on all fours. Like many other theropods, it had two large claws - measured at about 31cm. However, where most dinosaurs had one on each rear foot, Baryonyx had them on the front pair of feet - or so it is believed. Of course, the skeleton was not arranged exactly as it would have been in life, so the scientists reconstructing it placed them on the front feet because these legs were so powerful. The bone structure suggests a massive bulk of muscle ran down the sides of these front legs, and it therefore seems probable that the claws were placed here. The long neck was fairly inflexible and not S-shaped as in many theropods, and the skull was set at an acute angle; not the 90° angle that one would expect from many similar dinosaurs. The long jaw was distinctly crocodilian, and with 96 teeth, it had twice as many as many of its relatives. 64 of the teeth were placed in the lower jaw, and 32 large ones in the upper. The snout probably bore a small crest.
The crocodile jaws and large number of finely serated teeth suggested to scientists that Baryonyx was a fish-eater. As confirmation, a number of scales and bones from the fish Lepidotes were also discovered in the body cavity. It seems Baryonyx would sit on a river bank, resting on its powerful front legs, and then sweep fish from the river with its powerful striking claw. The image is very similar to that of a modern grizzly bear. The long but low stance and angled head then begin to make sense. This makes Baryonyx the only known piscivorous (fish-eating) dinosaur. On the other hand, bones of an Iguanadon were found with the Baryonyx skeleton. Although not definitive proof, it seems possible that Baryonyx scavenged any extra meat it could find.
There is only one specimen of Baryonyx, so there is little debate about classification. There is a similarity to the theropod Becklespinax but there is no evidence that Baryonyx had elongated spines on the back of the neck.