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| Genyornis newtoni Stirling & Zietz, 1896 in McInerney, Blokland & Worthy, 2024. Illustration by Jacob C. Blokland. |
ABSTRACT
The presence of Dromornithidae in the Australian Cenozoic fossil record was first reported in 1872, yet although eight species and hundreds of specimens are known, key information on their morphology remains elusive. This is especially so for their skulls, which contributes to a lack of resolution regarding their relationships within Galloanserae. The skull of the Pleistocene dromornithid, Genyornis newtoni, was initially described in 1913. Additional fossils of this species have since been discovered and understanding of avian skull osteology, arthrology, and myological correlates has greatly advanced. Here we present a complete redescription of the skull of Genyornis newtoni, updating knowledge on its morphology, soft-tissue correlates, and palaeobiology. We explore the diversity within Dromornithidae and make comprehensive comparisons to fossil and extant galloanserans. Furthermore, we expand on the homologies of skull muscles, especially regarding the jaw adductors and address the conflicting and unstable placement of dromornithids within Galloanserae. Findings support generic distinction of Genyornis newtoni, and do not support the close association of Dromornithidae and Gastornithidae. We thus recommend removal of the dromornithids from the Gastornithiformes. Considering character polarities, the results of our phylogenetic analyses, and palaeogeography, our findings instead support the alternative hypotheses, of dromornithids within, or close to, the Suborder Anhimae with Anseriformes.
KEYWORDS: Skull morphology, Homology, Galloanserae, Musculus adductor mandibulae externus, Functional morphology
Systematic palaeontology
AVES Linnaeus, 1758
NEORNITHES Gadow,1892
NEOGNATHAE Pycraft, 1900
GALLOANSERAE Sibley, Ahlquist and Monroe, 1988
DROMORNITHIDAE Fürbringer, 1888
GENYORNIS Stirling and Zietz, 1896
GENYORNIS NEWTONI Stirling and Zietz, 1896
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| An artistic reconstruction of the skull of Genyornis newtoni, based on all available fossil material, left lateral view. Scale bar is equal to 50 mm. Illustration by Jacob C. Blokland. |
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| An artistic reconstruction of the skull of Genyornis newtoni, based on all available fossil material, left lateral view. Illustration by Jacob C. Blokland. |
Conclusion:
The discovery of new skull fossils of the Pleistocene dromornithid Genyornis newtoni, and their description and phylogenetic analysis in this study, have considerably furthered the current understanding of this taxon, as well as the Dromornithidae. Their morphology, based on their osteology and inferred syndesmological and myological structures, likely facilitated a wide gape, fine and independent control over movement of the upper and lower bills, and adaptations for water-associated habitats, potentially retained from the early divergence of the anseriform lineage from stem Galloanserae. We support a varied soft-browse, folivorous and frugivorous diet, as previously proposed for dromornithids, although variation between Genyornis newtoni and species of Dromornis, suggest differences in niche occupation and beak functionality.
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Phoebe L. McInerney, Jacob C. Blokland and Trevor H. Worthy. 2024. Skull Morphology of the enigmatic Genyornis newtoni Stirling and Zeitz, 1896 (Aves, Dromornithidae), with Implications for Functional Morphology, Ecology, and Evolution in the Context of Galloanserae. Historical Biology: An International Journal of Paleobiology. 36(6); 1093-1165. DOI: 10.1080/08912963.2024.2308212
