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Baryonyx

Baryonyx is one of the largest piscivorous theropod dinosaurs. His crocodile-like head and dangerous claws made it a formidable predator of rivers and lakes. This dinosaur lived approximately 130 million years ago during the Lower Cretaceous period. It is now recognized as a member of the Spinosaurids family, although its affinities were obscure at the time of its discovery. This family of dinosaurs, the spinosaurs, are rather rare theropods.

Description

This spinosaur was very impressive. It was about 9 feet tall, 31 feet long and weighed about 2 tons. It was a huge beast but compared to other theropods of that time it was of medium size. It had two small arms, a small crest on its muzzle and a crocodile jaw that contained 95 serrated teeths. Like all other spinosaurids in the family to which it belongs, its muzzle is narrow and stretched forward. Although its arms were very short they were very powerful and its hands were provided with a huge nail claw that allowed it to pluck fish from the water without any difficulty.

Diet

Some researchers first hypothesized that it was piscivorous, fishing by hand and using its long thin snout to extirpate prey out of the water. Current crocodiles, who catch fish in this way, also sometimes have the same type of jaw. Its teeth, which were less flattened than most of those of other theropods, were rather jagged. This characteristic and the subtlety of its jaw led scientists to believe that it could not bring down large animals, which would suggest that its diet consisted mainly of fish. It is possible that Baryonyx hunted fish in the same way as modern grizzly bears; sweeping their claws back and forth across a river to pluck a fish. However, Iguanodon bones have been found in the bowels of a Baryonyx; perhaps it was targeting larger prey, but one could also think that this Iguanodon was already dead and that Baryonyx was also scavenger.

Fossils

Baryonyx fossil

This carnivore was discovered in 1983 by amateur paleontologist William Walker in a clay pit in Surrey, southern England. Walker initially found only the posterior part of the animal's huge claw. He returned to the same place a few weeks later and found the missing part of the claw and a number of bones. At the time of its discovery, it was one of the first carnivorous dinosaurs to be unearthed in England. Some time later, a group of paleontologists from the Natural History Museum in London visited the site and found many Baryonyx skeletons in Lower Cretaceous deposits. It is estimated that the original specimen (holotype), which may not have completed its growth, measured between 7.5 and 10 meters (25 and 33 feet) and weighed between 1.2 and 1.7 tons. It was named Baryonyx walkeri because of the impressive claw it had and as a tribute to the person who discovered it. The Baryonyx walkeri is mostly complete but lacks a number of pieces, including a large part of its tail and several cervical and dorsal vertebrae. Its skull is also incomplete. A reconstruction of the Baryonyx skeleton is currently on display at the Natural History Museum in London.

Evolution

Spinosaurs appear to have been widespread during the Barremian to Cenomanian Cretaceous stages, 130 to 95 million years ago, while the oldest spinosaur remains date all the way back to Middle Jurassic times. They all shared some unique features such as a long, narrow, crocodile-like skull and slightly jagged conical teeth with a circular section. In contrast, the typical feature of theropods was a long, narrow snout with teeth like blades. The adaptation of the skull of spinosaurs converges with that of crocodiles; the first comers had skulls similar to those of typical theropods and later developed an elongated snout and conical teeth. These adaptations are possibly the result of a change in diet; the carnivores became piscivores.

Classification

The baryonyx is unique enough to justify the addition of a new family of theropod dinosaurs: Baryonychinae. So this dinosaur is a baryonychinae spinosaurid.

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