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Osteopathy in Hadrosauridae from Alberta, Canada.

The Late Cretaceous rocks of Alberta record a diverse array of well-preserved examples of hadrosaur osteopathy which occur mostly on isolated bones. In sheer numbers of specimens and quality of preservation for research (i.e., gross inspection, histology, X-ray, MRI and CT scanning), they represent the best known examples of dinosaur osteopathy globally. Healing fractures predominate the sample. Curiously, nearly all the fractures are well healed but not completely healed- suggesting the afflicted animal survived for an extended period of time, but succumbed before the fracture repair was completed. Pathology of the teeth (deformations) are rare and skull pathology seldom recognized. Several examples of dentaries with healing fractures and/or massive infection have been observed. Dorsal vertebrae osteopathy consist of fused neural spines, wedge-shaped “hemivertebrae”, and excessive centrum unilateral growth. Rib fractures with well-aligned healing are well represented. Forelimb injuries include severe fracture of a humerus with massive infection, simultaneous fracture with healing of a radius and ulna (which fused together mid-shaft), and few metacarpal and manal phalanges with minor fractures or infection. The most serious example of hadrosaur osteopathy in Royal Tyrrell Museum (TMP) collections is an unspeciated lambeosaurine with bilateral fracture of the proximal ischia with extensive healing and without infection. It is remarkable this individual survived such a deep-body pelvic fracture, especially so near to the acetabulum. Pathology of the major hind limb bones is rare, as they were likely incompatible with survival; though a tibia with massive osteomyelitis is known. Despite a large sample size of metatarsals and pedal phalanges, traumatic or infectious osteopathy is infrequent, however osteochondrosis of the latter are well documented (Rothschild and Tanke, 2007). The most common hadrosaur injuries affected caudal vertebrae, with so many specimens known that a demonstrable pattern of types and distribution of injuries is well understood. Only adult-sized animals are affected. Caudals demonstrate differing patterns of osteopathy that appear related to their anatomical position. Injuries of a serious nature occur throughout the tail, but are more severe as one moves distally. Injuries consist of fractured and healing neural spines with trauma typically occurring near the distal end; some with pseudoarthrosis formation above and below the pre- and postzygapophyses. Centra sometimes have deep cracks on one or both (typically) endplates; CT scans show similarly aligned disruptive trabecular bone, suggesting the centrum was split in two (or more) pieces resulting from a burst fracture and then healed back together. Centra fusions affect up to five (but usually two) adjoining centra, the mid and distal caudals being affected. Affected distal centra often demonstrate a swollen condition, anteriorly-placed neural arch (suggesting post-traumatic posterior elongation of the centrum), abnormal “diseased” bone texture, longitudinal keel on ventral midline, and other malformations. These vertebrae are sometimes fused together at angles indicating the tail healed with the tip kinked up or off to one side. Some specimens suggest extreme distal tail infection and amputations or sloughing. Rare tumors are reported in caudal vertebrae (Rothschild et al., 2003) but none affect Albertan specimens. Albertan hadrosaur material offer great potential for future multidisciplinary studies in paleopathology. The Royal Tyrrell Museum is the World’s largest repository of these and other pathologic dinosaur specimens.

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