Baryonyx

Baryonyx (/ˌbæriˈɒnɪks/) is a genus of theropod dinosaur which lived in the Barremian stage of the Early Cretaceous period, about 130–125 million years ago. The first skeleton was discovered in 1983 in the Smokejack Clay Pit, of Surrey, England, in sediments of the Weald Clay Formation, and became the holotype specimen of Baryonyx walkeri, named by palaeontologists Alan J. Charig and Angela C. Milner in 1986. The genus name Baryonyx comes from Ancient Greek βαρύς (barús), meaning "heavy" or "strong", and ὄνυξ (ónux), meaning "claw", alluding to the animal's very large claw on the first finger; the specific name, walkeri, refers to its discoverer, amateur fossil collector William J. Walker. The holotype specimen is one of the most complete theropod skeletons from the UK (and remains the most complete spinosaurid), and its discovery attracted media attention. Specimens later discovered in other parts of the United Kingdom and Iberia have also been assigned to the genus, though many have since been moved to new genera.

The holotype specimen, which may not have been fully grown, was estimated to have been between 7.5 and 10 metres (25 and 33 feet) long and to have weighed between 1.2 and 2 metric tons (1.3 and 2.2 short tons; 1.2 and 2.0 long tons). Baryonyx had a long, low, and narrow snout, which has been compared to that of a gharial. The tip of the snout expanded to the sides in the shape of a rosette. Behind this, the upper jaw had a notch which fitted into the lower jaw (which curved upwards in the same area). It had a triangular crest on the top of its nasal bones. Baryonyx had a large number of finely serrated, conical teeth, with the largest teeth in front. The neck formed an S-shape, and the neural spines of its dorsal vertebrae increased in height from front to back. One elongated neural spine indicates it may have had a hump or ridge along the centre of its back. It had robust forelimbs, with the eponymous first-finger claw measuring about 31 centimetres (12 inches) long.

Now recognised as a member of the family Spinosauridae, Baryonyx's affinities were obscure when it was discovered. Some researchers have suggested that Suchosaurus cultridens is a senior synonym (being an older name), and that Suchomimus tenerensis belongs in the same genus; subsequent authors have kept them separate. Baryonyx was the first theropod dinosaur demonstrated to have been piscivorous (fish-eating), as evidenced by fish scales in the stomach region of the holotype specimen. It may also have been an active predator of larger prey and a scavenger, since it also contained bones of a juvenile iguanodontid. The creature would have caught and processed its prey primarily with its forelimbs and large claws. Baryonyx may have had semi-aquatic habits, and coexisted with other theropod, ornithopod, and sauropod dinosaurs, as well as pterosaurs, crocodiles, turtles and fishes, in a fluvial environment.

In January 1983, the plumber and amateur fossil collector William J. Walker explored the Smokejack Clay Pit, a clay pit in the Weald Clay Formation near Ockley in Surrey, England. He found a rock wherein he discovered a large claw, but after piecing it together at home, he realised the tip of the claw was missing. Walker returned to the same spot in the pit some weeks later, and found the missing part after searching for an hour. He also found a phalanx bone and part of a rib. Walker's son-in-law later brought the claw to the Natural History Museum of London, where it was examined by the palaeontologists Alan J. Charig and Angela C. Milner, who identified it as belonging to a theropod dinosaur. The palaeontologists found more bone fragments at the site in February, but the entire skeleton could not be collected until May and June due to weather conditions at the pit. A team of eight museum staff members and several volunteers excavated 2 metric tons (2.2 short tons; 2.0 long tons) of rock matrix in 54 blocks over a three-week period. Walker donated the claw to the museum, and the Ockley Brick Company (owners of the pit) donated the rest of the skeleton and provided equipment. The area had been explored for 200 years, but no similar remains had been found before.

Most of the bones collected were encased in siltstone nodules surrounded by fine sand and silt, with the rest lying in clay. The bones were disarticulated and scattered over a 5-by-2-metre (16.4-by-6.6-foot) area, but most were not far from their natural positions. The position of some bones was disturbed by a bulldozer, and some were broken by mechanical equipment before they were collected. Preparing the specimen was difficult, due to the hardness of the siltstone matrix and the presence of siderite; acid preparation was attempted, but most of the matrix was removed mechanically. It took six years of almost constant preparation to get all the bones out of the rock, and by the end, dental tools and air mallets had to be used under a microscope. The specimen represents about 65 per cent of the skeleton, and consists of partial skull bones, including premaxillae (first bones of the upper jaw); the left maxillae (second bone of the upper jaw); both nasal bones; the left lacrimal; the left prefrontal; the left postorbital; the braincase including the occiput; both dentaries (the front bones of the lower jaw); various bones from the back of the lower jaw; teeth; cervical (neck), dorsal (back), and caudal (tail) vertebrae; ribs; a sternum; both scapulae (shoulder blades); both coracoids; both humeri (upper arm bones); the left radius and ulna (lower arm bones); finger bones and unguals (claw bones); hip bones; the upper end of the left femur (thigh bone) and lower end of the right; right fibula (of the lower leg); and foot bones including an ungual. The original specimen number was BMNH R9951, but it was later re-catalogued as NHMUK PV R9951.

In 1986, Charig and Milner named a new genus and species with the skeleton as holotype specimen: Baryonyx walkeri. The genus name derives from Ancient Greek βαρύς (barús), meaning "heavy" or "strong", and ὄνυξ (ónux), meaning "claw". The specific name honours Walker, for discovering the specimen. At that time, the authors did not know if the large claw belonged to the hand or the foot (as in dromaeosaurs, which it was then assumed to be). The dinosaur had been presented earlier the same year during a lecture at a conference about dinosaur systematics in Drumheller, Canada. Due to ongoing work on the bones (70 per cent had been prepared at the time), they called their article preliminary and promised a more detailed description at a later date. Baryonyx was the first large Early Cretaceous theropod found anywhere in the world by that time. Before the discovery of Baryonyx the last significant theropod find in the United Kingdom was Eustreptospondylus in 1871, and in a 1986 interview Charig called Baryonyx "the best find of the century" in Europe. Baryonyx was widely featured in international media, and was nicknamed "Claws" by journalists punning on the title of the film Jaws. Its discovery was the subject of a 1987 BBC documentary, and a cast of the skeleton is mounted at the Natural History Museum in London. In 1997, Charig and Milner published a monograph describing the holotype skeleton in detail. The holotype specimen remains the most completely known spinosaurid skeleton.

Fossils from other parts of the UK and Iberia, mostly isolated teeth, have subsequently been attributed to Baryonyx or similar animals. Isolated teeth and bones from the Isle of Wight, including hand bones reported in 1998 and a vertebra reported by the palaeontologists Steve Hutt and Penny Newbery in 2004, have been attributed to this genus. A maxilla fragment from La Rioja, Spain, was attributed to Baryonyx by the palaeontologists Luis I. Viera and José Angel Torres in 1995 (although the palaeontologist Thomas R. Holtz and colleagues raised the possibility that it could have belonged to Suchomimus in 2004). In 1999, a postorbital, squamosal, tooth, vertebral remains, metacarpals (hand bones), and a phalanx from the Salas de los Infantes deposit in Burgos Province, Spain, were attributed to an immature Baryonyx (though some of these elements are unknown in the holotype) by the palaeontologist Carolina Fuentes Vidarte and colleagues. Dinosaur tracks near Burgos have also been suggested to belong to Baryonyx or a similar theropod.

In 2011, a specimen (catalogued as ML1190 in Museu da Lourinhã) from the Papo Seco Formation in Boca do Chapim, Portugal, with a fragmentary dentary, teeth, vertebrae, ribs, hip bones, a scapula, and a phalanx bone, was attributed to Baryonyx by the palaeontologist Octávio Mateus and colleagues, the most complete Iberian remains of the animal. The skeletal elements of this specimen are also represented in the more complete holotype (which was of similar size), except for the mid-neck vertebrae. In 2019, the palaeontologist Thomas M. S. Arden and colleagues found that the Portuguese skeleton did not belong to Baryonyx, since the front of its dentary bone was not strongly upturned. This specimen was made the basis of the new genus Iberospinus by Mateus and Darío Estraviz-López in 2022. Multiple studies found that additional spinosaurid remains from Iberia may belong to taxa other than Baryonyx, such as Vallibonavenatrix and Protathlitis, or may be indeterminate. A 2024 article by the palaeontologist Erik Isasmendi and colleagues reviewed the spinosaurid fossil record of Iberia and concluded that no specimens from there could be assigned to Baryonyx. They moved a specimen formerly assigned to Baryonyx from La Rioja to the new genus Riojavenatrix.