Geologically oldest evidence of ‘lumpy jaw’ (Macropod Progressive Periodontal Disease) in kangaroos of Australia: implications for conservation management

Abstract At a time of widespread concern over the prevalence of viruses and infectious diseases in global ecosystems, it is helpful to consider the history of afflictions in the geological record. Amongst captive species of Australian kangaroos, one of the most common pathological conditions observed is the occurrence of ‘lumpy jaw’, or Macropod Progressive Periodontal Disease (MPPD). Macropods (including both kangaroos and wallabies) affected by the disease commonly exhibit osteological swellings in either the mandible or maxilla, or both, including in areas surrounding the cheek teeth. Diseased individuals struggle to eat, often resulting in death. The specific cause of MPPD is unclear, although it may be multifactorial. When present in wild populations, the condition is more likely to occur in situations that result in the mass-gathering of individuals around critical resources such as drying waterholes. Here we report a case of MPPD in a Pliocene (ca 3 Ma) kangaroo, the geologically oldest record of this condition within macropods. The fossil is identified as Osphranter ?pan and was excavated from a deposit in the Chinchilla Sand, southeast Queensland. The osteomyelitis is expressed by a noticeable lateral mandibular swelling on the horizontal ramus; this is clearly pathological and has not been observed in any other member of the species. The specific circumstance that led to the development of MPPD in this individual likely reflects palaeoenvironmental stress, principally drought, in the Pliocene ecosystem. Lumpy jaw is evidently a geologically young disease, with its higher incidence through the late Cenozoic closely tied to long-term shifts towards progressively drier and more arid conditions. Given predictions that future climate change will follow such trajectories across many regions of Australia, MPPD is expected to become an increasingly important pathology for management in extant populations. This includes conservation projects that may lead to resource-limited settings such as fenced (including re-wilding) and translocated island populations. Gilbert J. Price [g.price1@uq.edu.au], School of Earth and Environmental Sciences, The University of Queensland, Brisbane, Queensland 4072, Australia; Julien Louys [j.louys@griffith.edu.au], Australian Research Centre for Human Evolution, Griffith University, Brisbane, Queensland 4101, Australia; Joanne E. Wilkinson [joanne.wilkinson@qm.qld.gov.au], Queensland Museum Geosciences, 122 Gerler Road, Hendra, Queensland 4011 Australia.