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 'Thunder Birds' - The Family Dromornithidae Page contents
The so-called 'thunder birds' belonged to the family Dromornithidae, a group of large, flightless birds. 'Thunder birds' is one of several names that have been used for this group. Because they were long thought to be related to emus, they were called 'giant emus'; another term was 'giant runners'. The western Victorian Aboriginal term, 'mihirung', has been applied to these birds; it comes from a legend about 'giant emus' that once lived in the area. The name used here, 'dromornithids', is taken from the family name.
So far, 5 genera and 7 species have been described, although at least one new genus is currently under study. The smallest species was Barawertornis tedfordi. It was about the size of the living cassowary, with a mass of 80-95 kg. The two species of Ilbandornis (I. lawsoni, I. woodburnei) were larger birds, but had more slender legs than the other dromornithids. They were similar to Ostriches in their build and size. Bullockornis planei and Genyornis newtoni were more heavily built. They stood about 2-2.5 tall and probably reached 220-240 kg. The largest dromornithids were Dromornis australis and the massive D. stirtoni. The latter may have been the heaviest bird to have existed. It was about 3 m tall and some estimates place it at 500 kg.
These birds are known only from Australia. Most of the records of dromornithids come from the eastern half of the continent, although evidence of these birds is also known from Tasmania and Western Australia. At some Northern Territory sites they are very common, sometimes comprising 60-70% of the fossil material. There is a fragment of dromornithid-sized foot bone from Antarctica, but whether it represents these birds is uncertain and awaits further study.
The earliest bones identified for this family come from Late Oligocene deposits (about 25 million years ago) of Riversleigh, northwest Queensland. There are foot impressions from the Early Eocene (about 50 mya) in southeast Queensland that may be referable to this group. The most recent species, Genyornis newtoni, has been found at Cuddie Springs, north central New South Wales, dated at 31,000 years ago. The greatest diversity was in the Late Miocene, when three species have been found occurring together.
The most recent species, Genyornis newtoni, was certainly known to Aborigines during the Late Pleistocene. Cave paintings thought to be this bird are known, as are carved footprints larger than those considered to represent emus. At Cuddie Springs, its bones have been excavated in association with human artefacts. The impact that humans had on dromornithids and other large animals of the time is unresolved but much debated. While dromornithids were certainly known to the Aborigines, the first Europeans to encounter the bones of dromornithids may have been Thomas Mitchell and his team. While exploring the Wellington Caves for the first time, one of his men tied his rope to a projecting object. As he descended, this broke. After he climbed back up, it was found that the projecting object was the fossilised long bone of a large bird. The first species to be named was Dromornis australis. The specimen was found in a 55 m deep well at Peak Downs, Queensland, and subsequently described by Richard Owen in 1872. Extensive collections of any dromornithid fossils were first made at Lake Callabonna, South Australia. In 1892, E.C. Stirling & A.H. Zietz of the South Australian Museum received reports of large bones in a dry lake bed in the northwest of the state. Over the next years, they made several trips to the site by buggy and camel, collecting nearly complete skeletons of several individuals. They named this species Genyornis newtoni in 1896. Additional remains of Genyornis have been found in other parts of South Australia and in New South Wales and Victoria. Other dromornithids fossils were discovered at other sites in subsequent years. Of major importance were Bullock Creek and Alcoota, both in the Northern Territory. These remained unstudied and unnamed until 1979, when Patricia Rich described five new species and four new genera. Another new genus and species is currently under study at the Australian Museum.
The best represented bones of dromornithids are vertebrae, long bones of the hindlimb and toe bones. Ribs and wing bones are uncommonly preserved.
A cervical (neck) vertebrae The rarest part of the skeleton is the skull. For many years, the only skull known was a damaged specimen of Genyornis. Reconstructions of dromornithids initially made it appear like an oversized emu. Peter Murray and Dirk Megirian, of the Northern Territory Museum, recovered enough skull material of Bullockornis to give a good idea of what that bird's head looked like.
It is now known that this was very large, with the enormous bill making up about two-thirds of it. The bill was deep, but rather narrow. At the front, the jaws had cutting edges and at the back, crushing surfaces. There were attachments for large muscles, indicating that Bullockornis had a powerful bite. More fragmentary remains of the skull of Dromornis suggest that it, too, had an oversized skull.
Bones are not the only remains of dromornithids that have been found.
It has been generally thought that the dromornithids were plant eaters. This is based on:
Amino acid analysis of Genyornis eggshells also indicates that this species was herbivorous. The very large skull and deep bill of Bullockornis, however, are very unlike those found in large herbivorous birds such as the moas. If this dromornithid ate plants, it was equipped to process very robust material and nothing requiring such power has thus far been identified. Growing and maintaining such a large head would be detrimental unless it provided a strong benefit of some sort. It has been suggested that, despite the indications of herbivory in some dromornithids, Bullockornis may have been a carnivore or possibly a scavenger. The jaws could easily cut meat and their robust structure could have resisted damage if it bit into bones. With this armament, the bird could easily have fed on the carcasses of large animals. It is, of course, not necessary that all dromornithids had the same diet. There is good evidence that Genyornis, at least, was a plant eater, while Bullockornis and Dromornis, with larger heads, may have had different diets.
Because of their size, dromornithids have been considered to be slow, lumbering birds. Their legs are not long and slender like those of emus, which are specialised for running. Biomechanical analyses of the attachments and presumed sizes of the muscles suggest that dromornithids would have been able to run much faster than originally thought. The legs would have been powered by brute strength to generate speed. Some of the medium-sized species may have run faster than an emu.
What the nearest relatives of this group are is a controversial issue. For many years it was thought that dromornithids were related to other large flightless birds, such as emus, cassowaries and ostriches. It is now considered that the similarities between these groups are the result of similar responses to the loss of flight. The latest idea on dromornithid relationships, based on details of the skull, is that they evolved early in the lineage that includes waterfowl. Because of this combination of its large skull and possible carnivorous habits and its probable waterfowl relationships, Bullockornis was nicknamed 'The Demon Duck of Doom'!!
The reasons for the extinction of this entire group by the end of the Pleistocene are still debated. Several factors have been proposed, including predation by early humans, human modification of the environment by fire and natural climate change. It is likely that there was some combination of these, but there is disagreement about the relative importance of each.
Archer, M. (1999). Brain of the demon duck of doom. Nature Australia 26 (7): 70-71. Pain, S. (2000). The demon duck of doom. New Scientist 166 (no. 2240): 36-39. Wroe, S. (1999). The bird from hell? Nature Australia 26 (7): 56-63.
Clarke, W.B. (1877). On Dromornis Australis (Owen), a new fossil bird of Australia. Journal of the Proceedings of the Royal Society of New South Wales 11: 41-49. Field, J.H. & Boles, W.E. (1998). Genyornis newtoni and Dromaius novaehollandiae at 30,000 b.p. in central northern New South Wales. Alcheringa 22: 177-188. Jennings, S.F. (1990). The musculoskeletal anantomy [sic], locomotion and posture of the dromornithid Dromornis stirtoni from the Late Miocene Alcoota Local Fauna. Unpublished Honours Thesis, School of Biological Sciences, Flinders University of South Australia. Miller, G.H., Magee, J.W., Johnson, B.J., Fogel, M.L., Spooner, N.A., McCulloch, M.T. & Ayliffe, L.K. (1999). Pleistocene extinction of Genyornis newtoni: human impact on Australian megafauna. Science 283: 205-208. Murray, P.F. & Megirian, D. (1998). The skull of dromornithid birds: anatomical evidence for their relationship to Anseriformes (Dromornithidae, Anseriformes). Records of the South Australian Museum 31: 51-97. Owen, R. (1872). [Untitled]. Proceedings of the Zoological Society of London 1872: 682-683. Rich, P.V. (1979). The Dromornithidae, an extinct family of large ground birds endemic to Australia. Bulletin of the Bureau of Mineral Resources, Geology and Geophysics 184: 1-190. Rich, P.V. (1980). The Australian Dromornithidae: a group of extinct large ratites. Contributions to Science, Natural History Museum of Los Angeles County 330: 93-103. Rich, P.V. (1985). Genyornis newtoni Stirling and Zietz, 1896. A mihirung. Pp. 188-194 in Rich, P.V. & van Tets, G.F. (eds). Kadimakara: Extinct Vertebrates of Australia. Pioneer Design Studios, Lilydale, Victoria. Rich, P.V. & Gill, E. (1976). Possible dromornithid footprints from Pleistocene dune sands of southern Victoria, Australia. The Emu 76: 221-223. Rich, P.V. & Green, R.H. (1974). Footprints of birds at South Mt Cameron, Tasmania. The Emu 74: 245-248. Stirling, E.C. (1913). Fossil remains of Lake Callabonna. Part IV. 1. Description of some further remains of Genyornis newtoni, Stirling and Zietz. Memoirs of the Royal Society of South Australia 1: 111-126. Stirling, E.C. & Zietz, A.H.C. (1896). Preliminary notes on Genyornis newtoni: a new genus and species of fossil struthious bird found at Lake Callabonna, South Australia. Transactions of the Royal Society of South Australia 20: 171?190. Stirling, E.C. & Zietz, A.H.C. (1900). Fossil remains of Lake Callabonna. I. Genyornis newtoni. A new genus and species of fossil struthious bird. Memoirs of the Royal Society of South Australia 1: 41-80. Stirling, E.C. & Zietz, A.H.C. (1905). Fossil remains of Lake Callabonna. Part III. Description of the vertebrae of Genyornis newtoni. Memoirs of the Royal Society of South Australia 1: 81-110. Vickers-Rich, P. & Molnar, R.E. (1996). The foot of a bird from the Eocene Redbank Plains Formation of Queensland, Australia. Alcheringa 20: 21-29. Williams, D.L.G. (1981). Genyornis eggshell (Dromornithidae; Aves) from the Late Pleistocene of South Australia. Alcheringa 5: 133-140. Williams, D.L.G. & Vickers-Rich, P. (1992). Giant fossil egg fragment from the Tertiary of Australia. Contributions to Science, Natural History Museum of Los Angeles County 36: 375-378.
The named species of dromornithids, their ages and the localities from which they have been found are given below.
Dromornithidae indeterminate Early Eocene (Redbank Plains Formation). QLD: Redbank Plains [foot impression] Mid-Tertiary. TAS: Endurance Tin Mine pit, 5 miles north of Pioneer [trackway] Late Oligocene/Early Miocene. SA: Muloorina Station: Snake Dam Locality [eggshell] Pleistocene. WA: Mammoth Cave
Barawertornis tedfordi Rich, 1979
Undescribed new genus and species
Bullockornis planei
Dromornis australis Owen, 1872
Dromornis stirtoni Rich, 1979
Ilbandornis woodburnei Rich, 1979
Ilbandornis lawsoni Rich, 1979
Genyornis newtoni Stirling & Zietz, 1896
Walter Boles
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Dromornithids were superficially like very large emus. Most were heavy-bodied. The legs were powerfully developed, whereas the wings were greatly reduced. Interestingly, the last bones of the toes resembled small hooves, rather than claws, as in most birds Like emus and other flightless birds, dromornithids lost the keel on the sternum, or breastbone, that served as the attachment for the large flight muscles. The skull, however, was quite different from that of emus. These birds ranged from about the size of a cassowary up to possible the largest bird to have lived.
