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.

Why did the dinosaur cross the river? Because it wasn’t a stampede.

One of Australia’s best known dinosaur sites, the Dinosaur Stampede National Monument at Lark Quarry, near Winton, Queensland has just been dramatically reinterpreted in a new paper published in the Journal of Vertebrate Paleontology.  The site, which was covered by a purpose built building in 2002 and placed on the Australian National Heritage List in 2004 preserves over 3000 individual tracks that, until recently, were believed to demonstrate evidence of a ‘jumanji-esque’ dinosaur stampede.

Where these tracks made by fleeing dinosaurs of were they trying to cross a river? Image from environment.gov.au
Were these tracks made by fleeing dinosaurs or were they trying to cross a river? Image from environment.gov.au

The new paper, by Anthony Romilio (University of Queensland), Ryan Tucker (James Cook University) and Steven Salisbury (University of Queensland) puts forward a rather different hypothesis: the tracks represent a river of varying depth that dinosaurs often had to cross.

The orthodox spin on the story identifies two ichnotaxa (taxa known only from their tracks) as the track makers. Wintonopus, a small ornithopod and Skartopus, a small theropod. This was actually used as evidence of ‘mixed herding’ where small herbivores and carnivores hung around together as protection against larger predators Thulborn and Wade (1979, 1984, 1989).

Romilio et al. disagree with this interpretation. they claim that there is in fact only a single track maker present, which would be named as Wintonopus as it was named first, with Skartopus becoming a junior synonym. They also failed to find any evidence of a single mass of running individuals leaving them with their own opinion on what was going on here. “The presence of swim traces, long stride lengths, and preferred trackway orientation indicates that the majority of Lark Quarry trackmakers moved downstream and were current assisted. The paleo-water depth would have had to vary in order to allow different-sized buoyed trackmakers to contact the substrate, indicating that animals passed through the area at different time intervals. In the absence of evidence for the single mass of running terrestrial trackmakers, we consider that Lark Quarry is not representative of a ‘dinosaurian stampede.'”

A more accurate picture? Image by Anthony Romilio.
A more accurate picture? Image by Anthony Romilio.

So, which view is more accurate? Only time, and further research will tell. But as there appears to be some friction between the authors of the new paper and Richard Thulborn (one of the authors of most of the earlier work on the trackways), one thing is for sure; this isn’t the last we’ve heard about the Lark Quarry trackway.

The paper is discussed in a little more detail by Brian Switek (@Laelaps) on his excellent blog Laelaps (one of the best palaeo blogs going).

References

Romilio A, Tucker, R. T. and S. W. Salisbury (2013): Reevaluation of the Lark Quarry dinosaur Tracksite (late Albian–Cenomanian Winton Formation, central-western Queensland, Australia): no longer a stampede?, Journal of Vertebrate Paleontology, 33:1, 102-120

Thulborn, R. A., and M. Wade. 1979. Dinosaur stampede in the Cretaceous of Queensland. Lethaia 12:275–279.

Thulborn, R. A., and M. Wade. 1984. Dinosaur trackways in the Winton
Formation (mid-Cretaceous) of Queensland. Memoirs Queensland
Museum 21:413–517.

Thulborn, R. A., and M. Wade. 1989. A footprint as a history of movement; pp. 51–56 in D. D. Gillette andM.G. Lockley (eds.),Dinosaur Tracks and Traces. Cambridge University Press, Cambridge, U.K.

Australian fossil penguins – the story so far…

Everybody loves penguins. From Happy Feet to the plethora of nature documentaries on the breeding cycle of the Emperor penguin, who can resist that awkward shuffle on land and the effortless grace in water? One facet of the penguin story that most people won’t be as familiar with is penguin palaeontology. This field has seen a renaissance since the early 1990’s with New Zealand and South America and Antarctica leading the way and South Africa also having their fair share of attention. One region that has been left out of this flurry of penguin research is Australia.

The published fossil record of penguins in Australia, although limited compared to that of Antarctica, New Zealand and South America, spans some 40 million years from the late Eocene to Recent (Ksepka and Ando, 2011). The majority of previous work has been produced by one author, none other than George Gaylord Simpson (Simpson, 1957, 1959, 1965, 1970), with the first publication released in 1938 (Finlayson, 1938) and the last primary research conducted by Van Tets and O’Connor (1983) a 30 year lull! A total of ten different localities are known from South Australia and Victoria (Park and Fitzgerald, 2012). In addition to numerous unidentifiable fragments, a total of five species have been named from the Australian material: Pachydyptes simpsoni (Eocene); Anthropodyptes gilli (Miocene); Pseudaptenodytes macraei (Miocene); Pseudaptenodytes minor (Miocene) and Tasidyptes hunteri (Holocene). Only two of these (A. gilli and P. macraei) are at present considered taxonomically distinct and only one species (P. simpsoni) is known from associated remains. All other species are based on individual and/or partial specimens, with the majority of specimens being too fragmentary for identification below the family level.

Holotype of Pachydyptes simpsoni. Unfortunately this is the most complete fossil penguin yet found in Australia, perhaps a reason for the lack of research! From Park & Fitzgerald, 2012. Photo taken E. M. G. Fitzgerald.
Holotype of Pachydyptes simpsoni. Unfortunately this is the most complete fossil penguin yet found in Australia, perhaps a reason for the lack of research! From Park & Fitzgerald, 2012. Photo taken by E. M. G. Fitzgerald.

A new paper co-authored by myself and Dr. Erich Fitzgerald (senior curator of vertebrate palaeontology at Museum Victoria) reviews the fossil record of penguins in Australia. Whilst the record is undoubtedly fragmentary, material is known from every epoch since the Eocene and virtually every find up until now has been by chance. So the potential is there for new discoveries to be made, should actually someone go and specifically look for fossil penguins. Furthermore, material has continued to accumulate in museum collections over the past 30 years despite the lack of research, some of it worthy of further study (keep your eyes peeled later in the year for that). So consider this an unfinished story, the fossil penguins of Australia have a few more tales to tell.

Link to the paper: http://museumvictoria.com.au/pages/41623/momv-2012-vol-69-pp309-325.pdf

References

Finlayson, H. H. 1938. On the occurrence of a fossil penguin in Miocene beds in South Australia. Transactions of the Royal Society of South Australia 62:14–17.

Ksepka, D. T., and T. Ando. 2011. Penguins Past, Present, and Future: Trends in the Evolution of the Sphenisciformes; pp. 155–186 in G. Dyke, and G. Kaiser (eds.), Living Dinosaurs. The Evolutionary History of Modern Birds. Wiley-Blackwell, West Sussex.

Park, T., and E. M. G. Fitzgerald. 2012. A review of Australian fossil penguins (Aves: Sphenisciformes). Memoirs of Museum Victoria 69: 309–325

Simpson, G. G. 1957. Australian fossil penguins, with remarks on penguin evolution and distribution. Records of the South Australian Museum 13:51–70.

Simpson, G. G. 1959. A new fossil penguin from Australia. Proceedings of the Royal Society of Victoria 71:113–119.

Simpson, G. G. 1965. New record of a fossil penguin in Australia. Proceedings of the Royal Society of Victoria 79:91–93.

Simpson, G. G. 1970. Miocene penguins from Victoria, Australia, Chubut, Argentina. Memoirs of the National Museum, Victoria 31:17–24.

Van Tets, G. F., and S. O’Connor. 1983. The Hunter Island penguin, an extinct new genus and species from a Tasmanian midden. Records of the Queen Victoria Museum 81:1–13.