Baryonyx
Skeletal reconstruction of Baryonyx
- Baryonyx walkeri
Baryonyx is a bipedal dinosaur from the family Spinosauridae, who lived in the Lower Cretaceous ( Barremian ). A nearly complete skeleton was found in England, it is considered one of the best preserved fossils of theropods ( carnivorous dinosaurs) in Europe.
He reached a length of about 8.5 meters; characteristic features include the crocodile-like skulls and an unusually large claw on both the forelimbs a thumb with. He subsisted on fish and other dinosaurs, according to chemical analysis of teeth he may have been partially water alive. The well-preserved skeleton of England is one of the most important finds of Spinosauriden. Fossil preserved stomach contents made it possible for the first time today generally accepted assumption that this group fed on fish.
Physique
Baryonyx is specified according to sources with 8.2 to 8.5 meters in length, its weight is estimated at 1700 to 2000 kilograms. As the most complete skeleton is probably derived from a not fully grown animal, an adult Baryonyx could have been larger.
The 91 -centimeter-long skull is disproportionately long, built narrow and crocodile -like flat, as with other Spinosauriden. He had 64 teeth in the upper jaw 32 and lower jaw - about twice as many as in non- spinosauriden theropods. The crowns were conical in shape and referred to the cutting edge very fine Sägungen on, about seven per millimeter. Thus, they differ significantly from typical non- spinosaurider theropod teeth that were formed as a laterally flattened, blade-like fangs with coarse Sägungen. At the tip of the snout teeth strongly meshed (terminal rosette ). As a characteristic of Baryonyx within the Spinosauridae the fused nasal bones, significant transverse constrictions of the sacrum and the vertebrae of the tail, a specially designed hinge joint between the scapula and coracoid ( coracoid ), the projecting distal edge of the pubic bone scoop ( pubic blade ) apply, and the only very shallow indentation of the fibula.
His neck vertebrae were provided comparatively long and short appendages. Baryonyx had three fingers; the thumb had a prolonged, the holotype 31 -centimeter-long claw. Plus its not the resulting coating of keratin they would have been much greater. His upper arm bone was very strongly built and flattened very broad and strong at both ends. Unlike other Spinosauriden no back sail is demonstrated for him.
Since a strong difference in size between the front legs and hind legs was suspected to a bipedal ( two-legged ) locomotion. The very strong compared to other theropods training of the front legs, especially the humerus, but could also indicate that he occasionally on four legs ( quadruped ) moved or rested.
Fund history
The amateur paleontologist William J. Walker discovered in January 1983 in a clay pit in Surrey ( England) one of the 30 -centimeter-long claws, the first known fossil of Baryonyx. He informed the British Museum of Natural History; this hid in May and June 1983 in the vicinity of the original reference a nearly complete skeleton of Baryonyx ( specimen number BMNH 9951 ), which only lacked the majority of the tail. The bones were mostly in the natural anatomical context; Displacements and damage to bones are largely due to the use of a bulldozer in the recovery. The find quickly pulled a large media attention, which made him known to a broad public. BMNH 9951 is considered one of the most important fossils of England until 1983, a partially preserved Eustreptospondylus was the only significant discovery of a theropod from England.
About three years later the first description Baryonyx walkeri than by the British paleontologist Alan Charig and Angela Milner. Baryonyx means " heavy claw " (from the ancient Greek, barys = difficult, onyx = claw ), the type - walkeri epithet honors William J. Walker. Originate also from England isolated teeth found and vertebrae, but certainly Baryonyx can not be assigned. All previous English finds date from the Wealden Group, a major fossil site in southern England, and have been dated to the time of the Hauterivian to Aptian.
Further, undoubtedly derived from Baryonyx finds were discovered, especially in Spain: In 1995, paleontologists skull fragments of Baryonyx from the Barremian of Encisco Group in the Spanish province of La Rioja, 2001 was reported from a partially preserved skull from the Hauterivian of the province of Burgos. Portuguese artifacts from the 19th century, originally interpreted as remnants of a crocodile named Suchosaurus, 2007 Baryonyx were attributed. They come from Barremiumschichten around Lisbon.
Paleobiology
Nutrition
The skull of Baryonyx and other Spinosauriden shows a number of features that can Piscivorie (nutrition of fish ) suggest. The crocodile -like snout was long, flat and narrow, they would therefore have less resistance when immersed in water had. The narrow snout, and a bony palate reduced torsional loads as they go out of wriggling fish. The general mechanics of Baryonyx skull is more similar to that of the piscivorous Gavial crocodile than that of normal theropod. A bone comb the Spinosauriden, the dorsal extends over the entire skull, is also an indication of a strong neck muscles that is necessary to pull the muzzle against the water resistance through the water and withdraw the head quickly. The elongated conical teeth that have very fine sawn edges, suitable mainly for grab and hold the total prey and thus differ from the teeth of carnivores who must tear down or cut parts of the prey after the grab. Widely used is the idea of a Baryonyx which a heron on the shore or in shallow water lurked like to fish. Perhaps he took with his 30 -centimeter-long claws also fish. The unusually large forelimbs also showed bony crests on the approach to muscles; Baryonyx arms were probably immensely strong. Perhaps her strength was used in conjunction with the claw when hunting larger, land-dwelling animals. Likewise, they might serve to tear the prey.
In the nearly complete skeleton of England received in the abdomen fossil stomach contents: the impugned gastric acid scales and teeth of a fish ( Lepidotes ), and the bones of a young Iguanodon ( a frequently found in Europe, herbivorous dinosaurs). The finding confirms the assumption that Baryonyx has nurtured piscivor - the thesis of pure Piscivorie is contradicted by the discovery of Iguanodon as stomach contents. Pterosaur ( Pterosauria ) are also considered prey of Spinosauriden, it is concluded from bite marks in pterosaur bones. Most paleontologists suggest a mixed, opportunistic diet that includes fish and land vertebrates, similar to today's crocodiles. A number of Spanish paleontologists speculated about a far less fish -heavy diet of; they rely on the findings of teeth baryonychiner theropod from the Spanish province of Teruel: Fossil water fleas in a stage for persistence of drought in this region show that there were no major permanent waters. This also explains the absence of larger fish. Thus, Baryonyx or a close relative nourished not fish in the Lower Cretaceous of Teruel.
In the abdomen of Baryonyx gastroliths ( stones swallowed in the stomach ) were found. In some animal groups they meet various purposes in Baryonyx going from accidental swallowing of.
Semi-aquatic lifestyle?
One recent study estimates that Spinosauriden were semi -aquatic, so partially water- inhabiting. Researchers led by Romain Amiot studied the mineral apatite from the teeth of Spinosauriden on the ratio between two isotopes of oxygen, oxygen -16 and oxygen - 18th The analysis shows a ratio of two isotopes, as typically found it of aquatic animals. The isotope ratio is different for land and water animals, as the body of land animals lose water by evaporation, with the heavier oxygen - 18 isotope accumulates in the body. A semi- aquatic lifestyle appeared to the researchers as a plausible explanation for the ratio of the isotopes. An indication of floating locomotion provide a theropod tracks from La Rioja: They show that a bipeder theropod swam in about three meters high water; there is scratch marks of the hind legs in the sediment received.
However, the Body of Baryonyx shows no adaptation to a semi- aquatic behavior, therefore deny paleontologists usually a too strongly bound to the water of life. His physique is that of a terrestrial runner. Further research is needed to substantiate the thesis of Romain Amiot and colleagues.
Paleoecology
The fossils from the UK were found in the deposits of the Wealden Group, which in the Cretaceous mostly a large wetland with rivers and a large freshwater lake, the Wealden Lake figured. The climate was subtropical by today's standards. The Spanish artifacts lay in areas which were covered in the Cretaceous Period of lakes, the Portuguese fossils probably come from one of the lagoon. In such an environment Piscivorie would have been quite possible. One of the common European dinosaur was at this time Iguanodon, which demonstrably part of the food spectrum of Baryonyx. He also lived with a number of other, about the same large theropods, such as Neovenator and Eotyrannus. One can assume that he compete with these typical theropods avoided by its possibly semiaquatic lifestyle and piscivorous diet and a particular ecological niche occupied. An example from today's time is the coexistence of the mainly piscivorous Australia crocodile and the more specialized to mammals and birds strips crocodile in Australian rivers.
System
In the first description we proposed a separate family ( Baryonychidae ) for the genus Baryonyx, today you updates them to the Spinosauridae family. The Spinosauridae defined by synapomorphies ( common ) in the construction of the skull and in the number and size of teeth. Baryonyx is allocated since 1998 the subfamily Baryonychinae which faces the Spinosaurinae with Irritator and Spinosaurus. The Baryonychinae split before probably more than 130 million years of the Spinosaurinae from. Your synapomorphies are a greater number of teeth and strongly keeled dorsal vertebra. 1998 Suchomimus was first described from Africa; it is similar to Baryonyx very strong and is filed together with this within the Baryonychinae. Some paleontologists keep Baryonyx and Suchomimus for one and the same genus, the majority also using confirmed by other scientists separation of Suchomimus and Baryonyx within the Baryonychinae. Recent studies also see the Megaraptora as Baryonyx very close: Fossils of Megaraptora were found in Australia and South America, and show a number of characteristics that suggest a relationship with Baryonyx and Suchomimus; among others also had the Megaraptora a strongly elongated claw on the thumb of the forelimb.
A possible cladogram:
Spinosaurus
Irritator
Baryonyx
Suchomimus
The only recognized species of the genus Baryonyx Baryonyx walkeri is, however, suggest a number of finds of isolated teeth in various ways towards. They resemble the teeth of BMNH 9951 very strong, but show slight differences. It is not clear whether these differences are due to different species or individual differences, so far has been for ambiguous findings being classified as Baryonyx sp. ( unspecified type of Baryonyx ) or baryonychine remains preferred.
After the paleontologist Eric Buffetaut described 1841 species Suchosaurus girardi recognized as a synonym of Baryonyx in 2007, the genus Baryonyx in accordance with the rules of the ICZN would henceforth Suchosaurus hot (priority rule). However, since the holotype of Suchosaurus is an isolated tooth only by Baryonyx, however, a nearly complete skeleton, the genus name Baryonyx is still used. Dubious remains the assignment of the second Suchosaurus type; English Suchosaurus cultridens is probably a Spinosauride, but can not be clearly assigned to Baryonyx.
Palaeobiogeography
The evolution of Baryonyx is often explained by allopatric speciation. At present, the Lower Cretaceous of the former North Continent Laurasia (Europe, Asia, North America ) and the southern continent of Gondwana (Africa, South America, India, Australia, Antarctica ) by the Tethys Ocean were separated. It seems certain that the developed Baryonychinae and her oldest known representative of Baryonyx in Europe. Basal ( primitive ) Spinosauriden migrated from Africa therefore face the separation of the two continents to Europe and developed due to geographic isolation for Baryonychinae. This is supported by findings of baryonychinen teeth from the Hauterivian of Spain and England, which are older than all African remains of Baryonychinen. The remaining in Gondwana, basal Spinosauriden developed for Spinosaurinae with Irritator and Spinosaurus. The geologically younger Suchomimus seems to descend or to share a common ancestor with this due to some synapomorphies of Baryonyx, but lived in Gondwana. It is thought that passed through an unspecified incident ancestors of Suchomimus by Gondwana, or that the Iberian Peninsula (Spain & Portugal ) formed a land bridge through the Tethys. Due to insufficient fossil record, the evolution of Spinosauridae remains unclear.
In popular culture
Baryonyx excited after its discovery in 1983 large public attention; initially it was assumed the extended claw was a normal claw of the foot, and a press release was assumed a gigantic tyrannosaurids. For the first time the public got the news on 19 July 1983 and the Dinosaur subsequently received nicknames like " Claws ", " Big Claws " or " Superclaws ". The newspaper The Guardian about the headline with " Dinosaur find of the century " ( "Dinosaur find of the century " ), the well-known newspaper The Times published on July 20, 1983 article " Fossil -hunter unearths Surrey dinosaur " ( " fossil hunters discovered Surrey Dinosaur New chapter for Dinosaur " (" "), the following day the headline appeared " New chapter for dinosaurs "). Even later Baryonyx appeared in the British press: On November 27, 1986 The Guardian headlined after the first description " Claypit dinosaur claws takes on plumber 's name" ( "Dinosaur given the name of a plumber ", walkeri allusion to the epithet and Style the occupation of William J. Walker).
Likewise, Baryonyx is a popular dinosaurs in exhibitions, Skelettreplikate and live reconstructions can be found in numerous museums and dinosaur park.