Baryonyx

Taxobox
name = "Baryonyx"
fossil_range = Early Cretaceous

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image_caption = "Baryonyx walkeri"
image_width = 250px
regnum = Animalia
phylum = Chordata
classis = Sauropsida
superordo = Dinosauria
ordo = Saurischia
subordo = Theropoda
familia = Spinosauridae
subfamilia = Baryonychinae
genus = "Baryonyx"
genus_authority = Charig & Milner, 1986
subdivision_ranks = Species
subdivision =
* "B. walkeri" Charig & Milner, 1986 (type)
synonyms =
* "Suchosaurus"? Owen, 1841
* "Suchomimus"? Sereno "et. al", 1998

"Baryonyx" (pronEng|ˌbæriːˈɒnɪks meaning "heavy claw", referring to its large claw (Greek "βαρως"/"barus" meaning 'heavy' and "ονυξ"/"onyx" meaning 'claw' or 'nail') is a genus of carnivorous dinosaur first discovered in clay pits just south of Dorking, England, and later reported from fossils found in northern Spain and Portugal. It contains one species, "Baryonyx walkeri". Its fossils have been dated to the Barremian period of Early Cretaceous Period, around 125 million years ago.

"Baryonyx" is one of the few known piscivorous (fish-eating) dinosaurs, with specialized adaptions like a long low snout with narrow jaws filled with finely serrated teeth and gaffe hook-like claws to help it hunt its main prey.

Description

"Baryonyx" was about 8.5 m (28 ft) longCharig, A.J. and Milner, A.C. (1997). "Baryonyx walkeri", a fish-eating dinosaur from the Wealden of Surrey." "Bulletin of the Natural History Museum of London", 53: 11–70.] and weighed in the region of 1,700 kg.cite book |last=Paul |first=Gregory S. |title=Predatory Dinosaurs of the World |year=1988 |publisher=Simon & Schuster |location=New York |isbn=0-671-61946-2 ] However, analysis of the bones suggests that the most complete specimen was not yet fully grown, so "Baryonyx" may have grown even larger.

"Baryonyx" had a large claw on the thumb of each hand, which measured at about 35 cm (14 in). Its long neck was not as strongly S-curved as in many other theropods. The skull was set at an acute angle, not the 90° angle common in similar dinosaurs. The long jaw was distinctly crocodilian, and had 96 teeth, twice as many as its relatives. Sixty-four of the teeth were placed in the lower jaw (mandible), and 32 large ones in the upper (maxilla). 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.

Discovery and naming

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 the side of a clay pit, Smokejacks Pit at Wallis Wood, Ockley near Dorking in Surrey. 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 of "Baryonyx" or other 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 in Carisbrooke 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.Buffetaut, E. (2007). "The spinosaurid dinosaur "Baryonyx" (Saurischia, Theropoda) in the Early Cretaceous of Portugal." "Geological Magazine", 144(6): 1021-1025. doi:10.1017/S0016756807003883]

Classification

Another crocodile-like fish-eater, "Suchomimus", was described in 1998, and placed together with "Baryonyx" in the subfamily Baryonychinae.Sereno, Beck, Dutheil, Gado, Larsson, Lyon, Marcot, Rauhut, Sadleir, Sidor, Varricchio, Wilson and Wilson. (1998). "A Long-Snouted Predatory Dinosaur from Africa and the Evolution of the Spinosaurids." "Science", 282(5392): 1298–1302.] The Baryonychinae is a subdivision of the family Spinosauridae, 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 as "Baryonyx tenerensis" due new discoveries that showed the vertebrae of "Baryonyx" were more similar to those of "Suchomimus" than previously thought.Hutt, S. and Newbery, P. (2004). "A new look at "Baryonyx walkeri" (Charig and Milner, 1986) based upon a recent fossil find from the Wealden." "Symposium of Vertebrate Palaeontology and Comparative Anatomy". ( [http://www.svpca.org/2004/abstracts/svpca-papers_a.htm online abstract] ).]

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 related "Spinosaurus". 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.

Paleoecology

The crocodile-like jaws and large number of finely serrated 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 of the English specimen.

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

Until the discovery of the closely-related "Suchomimus", "Baryonyx" was the only known piscivorous (fish-eating) dinosaur. On the other hand, bones of an "Iguanodon" were also found in association with the "Baryonyx" skeleton. Although not definitive proof, it seems possible that "Baryonyx" scavenged any extra meat it could find.

References

* Paul Barrett and José Luis Sanz. "Larousse de los Dinosaurios", Larousse, 2000.
*

External links

* [http://64.233.161.104/search?q=cache:KBvMvb8DPJ0J:www.geocities.com/dinowight/baryonyx.html+Baryonyx+walkeri&hl=en&client=firefox-a Many teeth from this species can be found on the Isle of Wight.]
* [http://www.dinosaurpark.org/baryonyx.htm Baryonyx walkeri]
* [http://www.dinohunters.com/History/Baryonx.htm A Baryonyx page]
* [http://www.dinosaurios.net/gdm/dmg_bary.htm "Baryonyx" in "Dinosauriomanía" (Spanish)]