EVALUATION AND INTERPRETATION OF SURFACE BONE ABNORMALITIES AND DEFORMITIES IN A NEW TRICERATOPS SPECIMEN

Skeletal elements recovered from a Triceratops excavation site in the Grand River National Grasslands of South Dakota have been prepared and are currently being evaluated for bone surface deformation and abnormalities. Several bones from a disarticulated skeleton of Triceratops (specimen GRNG-20) have exhibited a variety of deformed and atypical surface textures. This study investigates possible explanations for such surficial defects and has divided them into two broad categories: 1) surface depressions and 2) surface irregularities. Surface depressions include deep irregular fractures, conical-shaped puncture marks, and shallow linear grooves. Some deep fractures propagate through only a portion of the skeletal element. A CT scan of the radius shows a deep fracture that penetrates the surface at the distal anterior side and propagates proximally into the central axis of the bone. This fracture has been interpreted as happening post-mortem and shows no signs of bone regeneration. The conical-shaped punctures and shallow linear grooves are hypothesized to be crocodile and theropod bite marks, respectively. This study is currently quantifying the shapes of surface depressions and teeth of fossil crocodile and theropods using a 3-D scanner. All surface depressions being referred to as bite marks do not show bone regeneration and suggest post-mortem damage. Surface irregularities have been observed at the proximal extremity of a dorsal rib as well as on the central medial side of a second. Texturally, the irregular surfaces of the two ribs are different and may represent possible pathological sites. If pathological, we assume that irregular surfaces of bone close to articulations may be associated with osteoarthritis or osteochondritis. The irregular surface in the middle portions of the rib bone may be associated with infections such as osteomyelitis or osteosarcoma. Both rib bones possessing irregular surfaces will be compared to modern and fossil specimens with known pathological evidence. Furthermore, invertebrates like insects or molluscs will be considered as possible agents responsible for surface bone degradation. With the use of CT and high resolution 3-D scans, as well as comparative studies, we hope to provide a better understanding of the life and post-mortem history of specimen GRNG-20.