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Baryonyx (meaning "Heavy Claw") is a genus of carnivorous saurischian dinosaur first discovered in clay pits just south of Dorking, England, and later reported from fossils found in northern Spain andPortugal. It is known to contain only one species, Baryonyx walkeri. Its fossils have been recovered from formations dating from the Hauterivian to early Barremian stages of the earlyCretaceous Period, around 130-125 million years ago.[1]

Baryonyx is one of the few known piscivorous (fish-eating) dinosaurs, with specialized adaptations like a long low snout with narrow jaws filled with finely serrated teeth and gaff-hook-like claws to help it hunt its main prey.During the early Cretaceous, Wealden Lake covered the majority of what is now northern Europe.Alluvial plains and deltas spread from the uplands surrounding the area where London now stands and eventually ran into this great lake.

Baryonyx was discovered in these former deltas. In January 1983, an amateur fossil hunter named William Walker came across an enormous claw sticking out of the side of a clay pit - Smokejacks Pit at Wallis Wood, Ockley near Dorking in Surrey (United Kingdom). He received some help in retrieving the claw and several other fossil bones from the site. Subsequently he contacted the Natural History Museum in London about his find.

The skeleton was fortunately found to be in a relatively intact state and was excavated by a team led by Alan J. Charig and Angela C. Milner of the Natural History Museum. They published their description of the type species, B. walkeri, in 1986, and named it after Walker. The skeleton can now be seen mounted at the Natural History Museum in London. About 70% of the skeleton was recovered including the skull, enabling paleontologists to make numerous deductions about Baryonyx from just this first specimen.

Some years after the initial discovery in England, a partial skull of Baryonyx was found in the Sala de los Infantes deposit of Burgos Province, Spain. Some of the famous and abundant dinosaur fossil tracks of La Rioja, near Burgos, have been identified as tracks ofBaryonyx or another theropod genus very similar to it. Two more claws have been found in the 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 inCarisbrooke Castle since that time.

Jaw fragments and teeth from Portugal, originally thought to belong to Suchosaurus girardi, were later identified as Baryonyx walkeri by paleontologist Eric Buffetaut.[1]Another crocodile-like fish-eater, Suchomimus, was described in 1998, and placed together withBaryonyx in the subfamily Baryonychinae.[5] The Baryonychinae is a subdivision of the familySpinosauridae, which contains other giant Cretaceous forms from Africa and South America, including the genera Spinosaurus and Irritator.

In 2004, paleontologists Hutt and suggested that Suchomimus tenerensis should be redefined asBaryonyx tenerensis due to new discoveries that showed the vertebrae of Baryonyx were more similar to those of Suchomimus than previously thought.[6]

Additionally, the similarity between Baryonyx and Suchosaurus was noted by Buffetaut in 2007. Remains long attributed to Suchosaurus are now assigned to Baryonyx, and it is difficult to distinguish between remains of these two dinosaurs. Some minor differences do exist, such as ridges on the teeth of Suchosaurus. However, a similar range of variation exists among Baryonyx specimens, and even among various teeth assigned to the relatedSpinosaurus. Buffetaut suggested that this could mean that either various Baryonyx specimens should be broken up into separate taxa, or that Suchosaurus could be a senior synonym of Baryonyx. Buffetaut noted that if this is the case, the name Baryonyx would be replaced with Suchosaurus, which could be problematic given that the holotype specimen of Suchosaurus is only a single, worn tooth.[1]The crocodile-like jaws and large number of finely serrated teeth suggested to scientists thatBaryonyx was a fish-eater. As confirmation, a number of scales and bones from the fish Lepidoteswere also discovered in the body cavity of the English specimen.

It is speculated that Baryonyx would sit on a riverbank, resting on its front legs, and then sweep fish from the river with its powerful striking claw. This is similar to the modern grizzly bear.[7]

Until the discovery of the closely related Suchomimus, Baryonyx was the only known piscivorous(fish-eating) dinosaur. On the other hand, bones of the ornithopod dinosaur Iguanodon were also found in association with the Baryonyx skeleton.