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Australian Megafauna A-Z: B is for Barawertornis

Just over a month ago I started a new series here on Blogozoic, the Australian megafauna A-Z, in order to show people the weird and wonderful products of the evolutionary and geographic isolation of Australia. In the first post of the series I wrote about Alkwertatherium, a large marsupial that roamed the Northern Territory in the Late Miocene. Now we move onto the letter B and this time the animal, somewhat appropriately, is a bird.

The group to which this bird belongs is the Dromornithids. Those of you with very good memories may remember I wrote a post giving an introduction to these giant, extinct, flightless birds back in February (click here to read it). This time however I will focus on one species of dromornithid in particular, the species in question is Barawertornis tedfordi.

A reconstruction of Dromornis stirtoni by the fantastic palaeo-artist Peter Trusler.

A reconstruction of the dromornithid Dromornis stirtoni by the fantastic palaeo-artist Peter Trusler.

Barawertornis tedfordi isamong the oldest known dromornithids, dating to the Late Oligocene to Early Miocene. Its generic name means ‘ground bird’ and it specific name is in honour of the vertebrate palaentologist Richard Tedford, who was one of the first people to collect dromornithid remains in Australia. The holotype, a partial left femur, was described along with other partial hind limb fragments and a dorsal vertebra by Vickers-Rich (1979). Little more was discovered of the taxon until 2010, when Nguyen and colleagues described multiple partial femora, tibiotarsi and tarsometatarsi from the Riversleigh World Heritage Area in north-western Queensland. This new material allowed the researchers to better understand the relationship of B. tedfordi to other dromornithids as well as make some inferences about how this animal may have lived.

Some of the new material described in 2010 by Nguyen and colleagues. You can see the fragmentary nature of the material, one of the joys of palaeo in Australia! Image from Nguyen et al. 2010.

Some of the new material described in 2010 by Nguyen and colleagues. You can see the fragmentary nature of the material, one of the joys of palaeo in Australia! Image from Nguyen et al. 2010.

As well as being one of the oldest dromornithid species, B. tedfordi is also the smallest known species of dromornithid and would have been similar in size to the extant southern cassowary (Casuarius casuarius), with an estimated mass of around 45 – 65 kg (Nguyen et al. 2010). Furthermore, the relative proportions of the hind limb bones in are also most similar to that of the southern cassowary, suggesting that it may have been capable of similar cursorial (walking and running) abilities. With Australia being mainly covered by forest during the Early Miocene it makes sense that B. tedfordi would have converged upon a similar physique to the cassowary that today still roams the forests of north-eastern Australia and Papua New Guinea.

Anyone who thinks birds aren't related to dinosaurs need to look at the cassowary. Barawertornis is thought to have lived in a similar manner to this modern day forest-dweller. Image from www.flickr.com.

Anyone who thinks birds aren’t dinosaurs need to look at the cassowary. Barawertornis is thought to have lived in a similar manner to this modern day forest-dweller. Image from http://www.flickr.com.

The phylogenetic position of B. tedfordi is also still not certain. Previous analyses (e.g. Murray & Vickers-Rich 2004) and the strict consensus of the analysis by Nguyen et al. (2010) found that B. tedfordi was the sister taxon to all other dromornithids. However, Nguyen et al. (2010) also found weak support for B. tedfordi forming a clade with Ilbandornis sp., I. woodburnei, Dromornis planei, and D. stirtoni. The fragmentary nature of most dromornithid material however prevents more definitive statements being made about their phylogenetic relationships at present.

The phylogeny on the left shows the currently accepted position of B. tedfordi. The phylogeny on the right shows the position that Nguyen et al. 2010 found weak support for. Images modified from Nguyen et al. 2010.

The phylogeny on the left shows the currently accepted position of B. tedfordi. The phylogeny on the right shows the position that Nguyen et al. 2010 found weak support for. Images modified from Nguyen et al. 2010.

So that’s B done, I’ll leave it up to you clever people to figure out what letter is coming next. Stay tuned…

References

MURRAY, P.F. & VICKERS-RICH, P., 2004. Magnificent Mihirungs: the Colossal Flightless Birds of the Australian Dreamtime. Indiana University Press, Bloomington, 410 pp.

NGUYEN, J.M.T., BOLES, W.E. & HAND, S.J., 2010. New material of Barawertornis tedfordi, a dromornithid bird from the Oligo- Miocene of Australia, and its phylogenetic implications. Records of the Australian Museum 62, 45–60.

Other posts in the Australian Megafauna A-Z series:

A is for Alkwertatherium

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The Dromornithids: An Introduction

Australia has been separated from the rest of the world for the majority of the last 65 million years, with complete separation occurring around 30 million years ago. This has given the various forms of life on the continent plenty of time to evolve into their own unique groups. One particularly fascinating and enigmatic group is the family of extinct, giant flightless birds known as the dromornithids.

A reconstruction of Dromornis stirtoni by the fantastic palaeo-artist Peter Trusler. In this image they have been reconstructed as herbivores.

A reconstruction of Dromornis stirtoni by the fantastic palaeo-artist Peter Trusler. In this image they have been reconstructed as herbivores.

Australia today is famous for a group of flightless birds known as the emus; and for a long time the dromornithids were believed to be members of the same group of birds (the ratites). However, in 1998 a study by Murray and Megirian demonstrated that dromornithids are in fact neognathous birds in the Anseriformes. Nonetheless, it remains debatable as to which anseriform group is sister to the dromornithids (Murray & Vickers-Rich 2004, Olson 2005, Agnolin 2007). With a fossil record spanning around 25 million years, dromornithids are known from the late Oligocene through to the late Pleistocene (Field & Boles 1998, Nguyen et al. 2010). An ancient origin for the group is implied by a possible dromornithid foot impression from the early Eocene (approx. 50 million years ago) of Queensland (Vickers-Rich and Molnar 1996). Following an overdue taxonomic revision of the Dromornithidae (Nguyen et al. 2010), the family includes seven accepted species in four genera, with a geographic distribution including every state in Australia. The largest species, Dromornis stirtoni, is estimated to have stood at 3 m tall and weighed up to 500 kg, potentially even larger than the famous elephant bird of Madagascar.

A skeletal reconstruction of Dromornis stirtoni with human for scale showing just how big these animals could have been. Image from www.carnivoraforum.com.

A skeletal reconstruction of Dromornis stirtoni with human for scale showing just how big these animals could have been. Image from http://www.carnivoraforum.com.

There has been some debate as to whether the dromornithids were herbivorous or carnivorous, with features of the skull hinting at the potential for either way of life. Skull material is not known from every species however, and all members of the group may not have shared the same feeding ecology. Gizzard stones have been found in association with dromornithid remains, suggesting they needed the stones to help process plant material, although carnivores such as crocodiles are also known to possess them.

The dromornithids went extinct in the late Pleistocene and it is still unclear what combination of human hunting, landscape changing or climate change was the ultimate cause of their demise.

This is another Peter Trusler reconstruction, this time of the late Pleistocene species Genyornis newtoni. This species could well have encountered the first humans to arrive in Australia, but were they the cause of their extinction?

This is another Peter Trusler reconstruction, this time of the late Pleistocene species Genyornis newtoni. This species could well have encountered the first humans to arrive in Australia, but were they the cause of their extinction? Image from Museum Victoria.

I have also had a personal interest in the dromornithids as myself and Dr. Erich Fitzgerald published a short paper on the Dromornithids last year (Park and Fitzgerald, 2012). In it we detailed the oldest known occurrence of the dromornithids in Victoria, a poorly preserved partial tarsometatarsus (one of the bones in the legs of birds). This bone appeared to represent a new species as it could not be referred to any of the known taxa elsewhere in Australia. Previously, the earliest known dromornithids in Victoria were from the late Pleistocene ( approx. 30,000 years ago) Lancefield Swamp locality, so this find pushes their presence in Victoria back in time considerably. It also cautions against deriving evolutionary patterns solely on the basis of fossils from northern Australia.

The dromornithids as a group still retain a lot of mystery and unanswered questions, and are long overdue for a thorough reanalysis. In fact, one of my colleagues plans to do exactly that over the next few years and I for one look forward to seeing what new details he can reveal about these ‘magnificent Mihirungs’.

References

AGNOLIN, F.L., 2007. Brontornis burmeisteri Moreno & Mercerat, un Anseriformes (Aves) gigante del Mioceno medio de
Patagonia, Argentina. Revista del Museo Argentino de Ciencias Naturales 9, 15–25.

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.

MURRAY, P.F. & MEGIRIAN, D., 1998. The skull of dromornithid birds: anatomical evidence for their relationship to Anseriformes. Records of the South Australian Museum 31, 51–97.

MURRAY, P.F. & VICKERS-RICH, P., 2004. Magnificent Mihirungs: the Colossal Flightless Birds of the Australian Dreamtime. Indiana University Press, Bloomington, 410 pp.

NGUYEN, J.M.T., BOLES, W.E. & HAND, S.J., 2010. New material of Barawertornis tedfordi, a dromornithid bird from the Oligo- Miocene of Australia, and its phylogenetic implications. Records of the Australian Museum 62, 45–60.

OLSON, S.L., 2005. Review of Magnificent Mihirungs: the Colossal Flightless Birds of the Australian Dreamtime. The Auk 122, 367–371.

Travis Park & Erich M. G. Fitzgerald (2012): A late Miocene–early Pliocene Mihirung bird (Aves: Dromornithidae) from Victoria, southeast Australia, Alcheringa: An Australasian Journal of Palaeontology, 36:3, 419-422.

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.

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