Multiple occurrences of pathologies suggesting a common and severe bone infection in a population of the Australian Pleistocene giant, Genyornis newtoni (Aves, Dromornithidae)

Abstract

Vertebrate fossils showing pathological lesions are incredibly rare, and even more so is the identification of an ailment affecting multiple individuals in a population. However, the unique Lake Callabonna fossil deposit of South Australia has produced several such fossils from a single species of giant bird. Examination of the Lake Callabonna fossils of Genyornis newtoni, an extinct Pleistocene dromornithid, representing at least 34 individuals, has resulted in the identification of six osseous pathologies. These lesions are typical of the bone infection osteomyelitis, and affect a sternum, a tarsometatarsus and four phalanges across four individuals. The identification and description of osteomyelitis in these bones is the first of its kind for extinct galloanseres. Optically stimulated luminescence dating of host deposits shows that these animals were mired in lakebed sediments ranging from 54.2 to 50.4 kyr in age, probably becoming entrapped during a protracted drought phase previously identified as beginning at c. 48 ka and which would have resulted in the lakebed becoming exposed. Additional pathologies are recognized in phalanges of two other dromornithids, Dromornis stirtoni and Ilbandornis woodburnei, from the Miocene Alcoota deposit of the Northern Territory that are also interpreted as drought associated. It is possible that drought‐driven stress and consequent immunosuppressive effects may have contributed to the high frequency of lesions observed in the sampled birds.

Osteohistology of Dromornis stirtoni (Aves: Dromornithidae) and the biological implications of the bone histology of the Australian mihirung birds

“…As such, it took several years to reach adult body size and took only a few more years for skeletal maturation. This contrasts with G. newtoni , that lived in what may have been turbulent, stochastic times with unpredictability in terms of rainfall, available browse‐forage, and so forth (e.g., Martin, 2006; McInerney et al, 2022), and these birds may have been under strong selection pressure to grow more rapidly to adult body size, after which skeletal maturity could occur more at a more leisurely pace (hence several more LAGs in the OCL). It is interesting to note that four bones of the modern emu studied by Canoville et al (2022) have a faster growth trajectory than G. newtoni , in that, emu appear to grow rapidly until the deposition of an OCL, that is, without any periodic interruptions in their rapid phase of growth.…”

“…While G. newtoni had less of the markedly K‐selected strategy than seen in D. stirtoni , it did not approach the rapid‐breeding reproductive potential of emus (Chinsamy & Worthy, 2021), and this was probably a key factor as to why G. newtoni became extinct and the extant emu did not. Genyornis newtoni became extinct in the latest Pleistocene: it was common in the lacustrine deposits at Lake Callabonna where their skeletons were deposited during a major drought period about 48 ka (McInerney et al, 2022) and they may have survived a few more thousand years at most (reviewed in Johnson et al, 2021). Humans arrived in Australia by about 55 ka (Johnson et al, 2021; Saltré et al, 2016) and were present in the Flinders Ranges, in sight of Lake Callabonna, at 49 ka (Hamm et al, 2016) so overlapped temporally and spatially with G. newtoni .…”

“…They come from the late Miocene Alcoota localities in the Northern Territory of Australia (22 52 0 S 134 25 0 E; Woodburne, 1967aWoodburne, , 1967b; P. Murray & Megirian, 1992) and together with the Madagascan aepyornithid, Vorombe titan (Andrews, 1894) are the largest birds to have ever lived (Handley & Worthy, 2021;Hansford & Turvey, 2018). Genyornis newtoni Stirling & Zietz, 1896, which stood about 2.5 m tall and probably weighed about 240 kg (Grellet-Tinner et al, 2017), is the last member of the dromornithid lineage and went extinct about 40-50,000 years ago (ka) (e.g., Johnson et al, 2021;McInerney et al, 2022;Saltré et al, 2016).…”

Systematics and palaeobiology of kangaroos of the late Cenozoic genus Protemnodon (Marsupialia, Macropodidae)

“…SIAM Site 5, 29.7832°S, 140.1164°E, Lake Callabonna Fossil Reserve, northeastern South Australia. Lacustrine late Pleistocene fossil deposits (deposited during a drought phase commencing about 48 ka in sediments 54.2-50.4 ka) (McInerney et al 2022). Worthy and Camens et al in 2013 and 2019 led joint Flinders University-University of Adelaide expeditions to the lake, recovering a wealth of fossil material including all the type material listed for this species.…”