The huge mihirung Dromornis stirtoni, by artist Peter Trusler. Credit: Peter Trusler
The biggest flightless bird ever to live weighed in approximately 600kg and had a tremendous head about half a meter long — however its brain was squeezed for area.
Dromornis stirtoni, the biggest of the ‘mihirungs’ (an Aboriginal word for ‘giant bird’), withstood 3m high and had a cranium larger and greater than it was long due to an effective huge beak, leading Australian paleontologists to look inside its brain area to see how it worked.
The brand-new research study, simply released in the journal Diversity, took a look at the brains of the extinct huge mihirungs or dromornithid birds that were an unique part of the Australian animals for lots of countless years, prior to going extinct around 50,000 years earlier.
The last mihirung Genyornis newtoni, by artist Peter Trusler. Credit: Peter Trusler
“Together with their large, forward-facing eyes and very large bills, the shape of their brains and nerves suggested these birds likely had well-developed stereoscopic vision, or depth perception, and fed on a diet of soft leaves and fruit,” states lead author Flinders University scientist Dr. Warren Handley.
“The shape of their brains and nerves have actually informed us a lot about their sensory abilities, and something about their possible way of life which made it possible for these exceptional birds to reside in the forests around river channels and lakes throughout Australia for a very very long time.
“It’s exciting when we can apply modern imaging methods to reveal features of dromornithid morphology that were previously completely unknown,” Dr. Handley states.
The brand-new research study, based upon fossil stays varying from about 24 million years ago to the last in the line (Dromornis stirtoni), suggests mihirung brains and nerves are most like those of contemporary chickens and Australian mallee fowl.
“The unlikely truth is these birds were related to fowl — chickens and ducks — but their closest cousin and much of their biology still remains a mystery,” states vertebrate paleontologist and senior author Associate Professor Trevor Worthy.
“While the brains of dromornithids were very different to any bird living today, it also appears they shared a similar reliance on good vision for survival with living ratities such as ostrich and emu.”
While the bones of these huge flightless birds are reasonably typical in the fossil record, their skulls are incredibly uncommon. The most total skull understood, from Dromornis planei, was found in the late 1980s filled with strong limestone. Neutron CT scanning innovation made it possible for the Flinders scientists to ‘see’ inside the skull to expose the shape of the brain for the very first time because the skull was found. Credit: Flinders University
The scientists compared the brain structures of 4 mihirungs — from the earliest Dromornis murrayi at about 24 million years earlier (Ma) to Dromornis planei and Ilbandornis woodburnei from 12 Ma and Dromornis stirtoni, at 7 Ma.
Ranging from cassowary in size to what’s called the world’s biggest bird, Flinders vertebrate paleontologist Associate Professor Worthy states the biggest and last types Dromornis stirtoni was an “extreme evolutionary experiment.”
“This bird had the biggest skull however behind the huge expense was a strange cranium. To accommodate the muscles to wield this huge expense, the cranium had actually ended up being taller and larger than it was long, therefore the brain within was squeezed and flattened to fit.
“It would appear these giant birds were probably what evolution produced when it gave chickens free rein in Australian environmental conditions and so they became very different to their relatives the megapodes — or chicken-like landfowls which still exist in the Australasian region,” Associate Professor Worthy states.
The big, flightless birds Dromornithidae — likewise called satanic force ducks of doom or thunder birds — existed from the Oligocene to Pleistocene Epochs.
During prehistory, the body sizes of 8 types of dromornithids ended up being bigger and smaller sized depending environment and offered feed.
The Flinders scientists utilized the skulls of fossil birds to draw out endocasts of the brains to explain how these associated to modern-day birds such as megapodes and waterfowl. Brain designs were likewise made from CT scans of 5 other dromornithid skulls from fossil websites in Queensland and the Northern Territory. The earliest 25 Ma Dromornis murrayi specimen was discovered in the famous Riversleigh World Heritage Area in Queensland.
Reference: “Endocranial Anatomy of the Giant Extinct Australian Mihirung Birds (Aves, Dromornithidae)” by Warren D. Handley and Trevor H. Worthy, 15 March 2021, Diversity.
DOI: 10.3390/d13030124
