page_title: Baryonyx
section_title: Classification
hierarchical_section_title: Baryonyx / Classification
caption_attribution_description: English: Skeletal reconstruction of Suchomimus tenerensis and Baryonyx walkeri to scale.
context_page_description: Baryonyx 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 Weald Clay Formation of Surrey, England, and became the holotype specimen of Baryonyx walkeri, named by palaeontologists Alan J. Charig and Angela C. Milner in 1986. The generic name, Baryonyx, means "heavy claw" and alludes 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 its discovery attracted media attention. Specimens later discovered in other parts of the United Kingdom and Iberia have also been assigned to the genus.
  The holotype specimen, which may not have been fully grown, was estimated to have been between 7.5 and 10 metres long and to have weighed between 1.2 and 1.7 metric 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.
context_section_description: In their original description, Charig and Milner found Baryonyx unique enough to warrant a new family of theropod dinosaurs: Baryonychidae. They found Baryonyx to be unlike any other theropod group, and considered the possibility that it was a thecodont (a grouping of early archosaurs now considered unnatural), due to having apparently primitive features, but noted that the articulation of the maxilla and premaxilla was similar to that in Dilophosaurus. They also noted that the two snouts from Niger (which later became the basis of Cristatusaurus), assigned to the family Spinosauridae by Taquet in 1984, appeared almost identical to that of Baryonyx and they referred them to Baryonychidae instead. In 1988, the American palaeontologist Gregory S. Paul agreed with Taquet that Spinosaurus, described in 1915 based on fragmentary remains from Egypt that were destroyed in World War II, and Baryonyx were similar and (due to their kinked snouts) possibly late-surviving dilophosaurs. Buffetaut also supported this relationship in 1989. In 1990, Charig and Milner dismissed the spinosaurid affinities of Baryonyx, since they did not find their remains similar enough. In 1997, they agreed that Baryonychidae and Spinosauridae were related, but disagreed that the former name should become a synonym of the latter, because the completeness of Baryonyx compared to Spinosaurus made it a better type genus for a family, and because they did not find the similarities between the two significant enough. Holtz and colleagues listed Baryonychidae as a synonym of Spinosauridae in 2004.
  Discoveries in the 1990s shed more light on the relationships of Baryonyx and its relatives. In 1996, a snout from Morocco was referred to Spinosaurus, and Irritator and Angaturama from Brazil (the two are possible synonyms) were named. Cristatusaurus and Suchomimus were named based on fossils from Niger in 1998. In their description of Suchomimus, Sereno and colleagues placed it and Baryonyx in the new subfamily Baryonychinae within Spinosauridae; Spinosaurus and Irritator were placed in the subfamily Spinosaurinae. Baryonychinae was distinguished by the small size and larger number of teeth in the dentary behind the terminal rosette, the deeply keeled front dorsal vertebrae, and by having serrated teeth. Spinosaurinae was distinguished by their straight tooth crowns without serrations, small first tooth in the premaxilla, increased spacing of teeth in the jaws, and possibly by having their nostrils placed further back and the presence of a deep neural spine sail. They also united the spinosaurids and their closest relatives in the superfamily Spinosauroidea, but in 2010, the British palaeontologist Roger Benson considered this a junior synonym of Megalosauroidea (an older name). In a 2007 conference abstract, the American palaeontologist Denver W. Fowler suggested that since Suchosaurus is the first named genus in its group, the clade names Spinosauroidea, Spinosauridae, and Baryonychinae should be replaced by Suchosauroidea, Suchosauridae, and Suchosaurinae, regardless of whether or not the name Baryonyx is retained. A 2017 study by the Brazilian palaeontologists Marcos A. F. Sales and Cesar L. Schultz found that the clade Baryonychinae was not well supported, since serrated teeth may be an ancestral trait among spinosaurids.
  The following cladogram shows the position of Baryonyx within Spinosauridae, according to a 2018 study by the British palaeontologist Thomas M. S. Arden and colleagues:
caption: Skeletal diagram of the holotype specimen (below) compared with the closely related genus Suchomimus
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