First diagnosis of septic arthritis in a dinosaur

Abstract

Identification and interpretation of pathologies in the fossil record allows for unique insights into the life histories of extinct organisms. However, the rarity of such finds limits not only the sample size for palaeopathologic studies, but also the types of analyses that may be performed. In this study, we present the first occurrence of a palaeopathology in a vertebrate from the Mesozoic of the East Coast of North America (Appalachia), a pathologic ulna and radius of an indeterminate hadrosaur from the Navesink Formation (New Jersey). X-ray microtomography allowed for both detailed and more accurate diagnosis of the pathologic condition as well as virtual conservation of the specimen. Based on extant archosaurian comparisons, the hadrosaur was diagnosed with severe septic arthritis affecting the proximal ulna and radius. Diagnosis was based on erosion of the joint and highly reactive periosteal bone growth and fusion of the elements. To the best of our knowledge, this is the first recorded account of septic arthritis in dinosaurs. The severity of the pathology suggests the animal suffered with this condition for some time before death. Unfortunately, only the ulna and radius were found. Thus, the extent to which the condition spread to other parts of the body is unknown.

Keywords: X-ray microtomography; hadrosaur; palaeopathology.

Figure 1.

Pathological ulna from a hadrosaur (NJSM GP11961) with severe bone remodelling along the proximal articulation with the radius surface (PRU). The reactive bone has a ‘cauliflower-like’ appearance. The olecranon process has been highly degraded by the pathological condition. Large lesions can be seen on the proximal surface (red circle). The red box marks the area scanned using XMT in figure 2.

Figure 2.

XMT scans of the NJSM GP11961 ulna in longitudinal and transverse (a–d) views. The area scanned is indicated on the gross picture insert. Locations for the transverse sections are marked by red lines on the longitudinal section. Well-developed enthesiophytes are seen in two different locations (a,c; red arrows). Necrosis is seen along the proximal articulation surface (b; circled in red). Reactive bone growth is present throughout the first proximal half of the element, tapering out distally (lateral, c,d circled in red). Scale bar, 10 mm.

Figure 3.

Pathological radius from a hadrosaur (NJSM GP11961) showing heavy reactive bone growth on the proximal articulation surfaces. The proximal articulation surface with the ulna (PRU) shows extensive pathological bone growth, giving the element a ‘cauliflower-like’ appearance. The distal articular surface with the ulna has mostly eroded away due to taphonomic effects. The red box marks the area scanned using XMT in figure 4.

Figure 4.

XMT scans of the NJSM GP11961 radius in longitudinal and transverse (a–d) views. The area scanned is indicated on the gross picture insert. Locations for the transverse sections are marked by red lines on the longitudinal section. The original outline of the bone is completely unrecognizable on the proximal end, with severe, radial bone growth (a,b; red arrow). There is a large gap between the pathological growth and the original cortex of the radius (a,b; red arrows). The outline of the radius becomes clear with the appearance of the normal cortical bone structure moving distally (c,d; original radius outline circled in red). Scale bar, 10 mm.