Baryonyx was about 28 ft long and weighed in the region of 1,700 kg. 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 about 9.8 in in a straight line from tip to base. Its long neck was not as strongly S-curved as in many other theropods.