Baryonyx

Baryonyx (/ˌbæriˈɒnᵻks/) is a genus of theropod dinosaur which lived in the Barremian stage of the early Cretaceous Period, about 130–125 million years ago. The holotype specimen was discovered in 1983 in Surrey, England, and the animal was named Baryonyx walkeri in 1986. The genus 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 hunter William J. Walker. Fragmentary specimens were later discovered in other parts of the United Kingdom and Iberia. The holotype specimen is one of the most complete theropod skeletons from the UK, and its discovery attracted media attention.

The skull of Baryonyx is incompletely known, and much of the middle and hind portions are not preserved. The full length of the skull has been estimated to be 950 mm (37.4 in), based on comparison with that of the related genus Suchomimus (which is 20% larger). It was elongated, and the front 170 mm (6.6 in) of the premaxillae formed a long, low snout (rostrum) with a rounded upper surface. The nostrils, far back from the tip, passed horizontally from one side of the skull to the other. The front 130 mm (5.1 in) of the snout expanded into a spatulate (flared outwards to the sides), "terminal rosette" shape similar to the modern gharial, and the front 70 mm (2.7 in) of the lower margin was downturned. The snout was very narrow just behind the rosette. The creature's maxilla and premaxilla fit together in a complex articulation, resulting in a strongly curved tooth row. The gap in the row is comparable to that of Dilophosaurus. The front 140 mm (5.5 in) of the dentary in the mandible curved upwards towards this area, and the gap between the upper and lower jaw is known as the subrostral notch. The snout had extensive pits (which would have been exits for blood vessels and nerves), and the maxilla appears to have housed sinuses.^[2][6]

Most of the teeth found with the holotype specimen were not attached to the skull; a few remained in the upper jaw, and only small replacement teeth were in the lower jaw. The teeth had the shape of recurved cones, flattened somewhat sideways. The larger teeth were less recurved than the smaller ones, but were otherwise uniform. The roots were very long, and the teeth slender. The carinae (edges) of the teeth were finely serrated with denticles on the front and back. There were seven narrow, uniform denticles per millimetre (0.039 in), more than in most theropods. Some of the teeth were fluted, with six to eight ridges along the length of their inner sides and fine-grained enamel.