Paleopathology in a nearly complete skeleton of Majungasaurus crenatissimus (Theropoda: Abelisauridae)

Abstract

Research in the Upper Cretaceous (Maastrichtian) Maevarano Formation of northwestern Madagascar has yielded numerous individuals of the abelisaurid theropod Majungasaurus crenatissimus. The number of individuals and quality of preservation allow for a detailed assessment of pathology in this species. A previous survey of Majungasaurus material collected prior to 2005 indicated assorted types of potential infectious and traumatic etiologies. Ongoing research on materials recovered since 2005 provide many additional opportunities to better characterize the anatomy and paleopathology in Majungasaurus. In particular, an almost complete skeleton of a single individual (FMNH PR 2836) preserves evidence of pre-mortem pathologies on multiple bones, including elements of the face and lower jaw, vertebrae, forelimb, ribs and gastralia. Analyses of the pathologies suggest infection of the jugal and quadratojugal, healed fractures and hypertrophic bone growth on several dorsal ribs and a gastralium, septic arthritis in the left forelimb, and evidence of healed/partially healed tooth marks on one cervical vertebra. The injuries appear to be the result of multiple non-fatal events experienced during the life of the individual, rather than a single traumatic incident. Our survey of Majungasaurus indicates most well preserved individuals lack observable pathology, whereas select individuals possess multiple pathologies, a general pattern also noted in other large, nonavian theropods. Such a pattern may result from a snowball effect wherein one injury or infection increases the likelihood of additional maladies due to functional impairment or a compromised immune system in an individual once an initial injury has occurred.