FDromornithidae

These flightless birds are a characteristic element of the Cenozoic avifauna of Australia. Our state of knowledge about them was summarized by Murray and Vickers-Rich (2004), on whose book the following notes are based. Dromornithids have a comparatively abundant Neogene fossil record, but few remains were described from Paleogene deposits. The earliest named species is the Southern Cassowary (Casuarius casuarius) sized Barawertornis tedfordi Rich, 1979 from the late Oligocene/early Miocene of the Riversleigh Formation, which is also the smallest known dromornithid. A tentative record consisting of impressions of pedal phalanges comes from the early Eocene of Queensland, and putative dromornithid trackways were also reported from the late Oligocene of Tasmania (Vickers-Rich 1991). Dromornithids were graviportal birds and in some osteological features are superficially similar to gastornithids. As in the latter, there are well-developed Galloanseres-like articulation facets for basipterygoid processes, and the mandible bears long retroarticular processes. In several other features, however, dromornithids are clearly distinguished from gastornithids, including the presence of a marked ventral crest on the palatine bone, the absence of a hallux, and the fact that the fourth toe consists of only four phalanges.

As detailed by Murray and Vickers-Rich (2004), there exists convincing evidence for a herbivorous diet of dromornithids. Not only are some specimens preserved with gastroliths, but analyses of stable isotopes from the eggshells of a Pleistocene species also point at plant matter as food components.

Although anseriform affinities of dromornithids are well based, their position within waterfowl and their affinities to the Gastornithidae have not yet been conclusively resolved. Murray and Vickers-Rich (2004) considered them to be the sister taxon of the Anhimidae, i.e., to be within crown group Anseriformes, whereas they assumed that gastornithids are outside crown group Anseriformes. However, the two characters listed by the authors as supporting evidence for a sister group relationship between the Dromornithidae and Anhimidae, i.e., absence of uncinate processes and presence of a tubercle on the deltopectoral crest of the humerus (see p. 156 in Murray and Vickers-Rich 2004), are also present in the Gastornithidae.

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