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Thunder Birds, Australia’s big ugly ducklings

Harry Pettit, March 25, 2021 7:00PM The Sun

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Artist’s impression of giant flightless birds that roamed the plains of Australia until about 50,000 years ago. Picture: Brian Choo media_cameraArtist’s impression of giant flightless birds that roamed the plains of Australia until about 50,000 years ago. Picture: Brian Choo

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The world’s biggest-ever bird weighed as much as a cow and lived in Australia until 50,000 years ago.

The flightless Dromornis stirtoni plodded along on two hind legs like an emu. It was the largest member of an extinct group of creatures called the mihirungs – based on an Aboriginal word for giant bird.

In new research published in the journal Diversity this week, scientists described how they analysed the ancient skulls of mihirungs to get a better idea of their brains.

They discovered that the animals’ enormous heads left little room for brains, giving rise to some oddly shaped skulls.

“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 depth perception* and fed on a diet of soft leaves and fruit,” said study lead author and Flinders University researcher Dr Warren Handley.

“The shape of their brains and nerves have told us a lot about their sensory capabilities*, and something about their possible lifestyle which enabled these remarkable birds to live in the forests around river channels and lakes across Australia for an extremely long time.”

Nicknamed “Thunder Birds”, mihirungs lived across Australia for millions of years.

The largest species – Dromornis stirtoni – could grow to 3m tall and weigh about 600kg.

The research team studied four fossilised skulls from four species of mihirungs found across Australia.

These included a 7-million-year-old Dromornis stirtoni cranium*, as well as a 24-million-year-old Dromornis murrayi and 12-million-year-old Dromornis planei and Ilbandornis woodburnei skulls.

The researchers discovered that mihirung brains and nerves were most like those of modern day 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,” said study author Dr 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.”

The team used CT scans of the skulls to create casts of the creatures’ brains.

M041248 Dromornis stirtoni, Reconstruction of Central Australian Miocene.   

This reconstruction depicts a scene in times past, 8 million years before the present. Then Dromornis stirtoni, the largest species of "Mihirung", roamed the Central Australia landscape, browsing on leaves, fruit, flowers, petioles and twigs growing three or four metres above the ground. (Credit: Artist Peter Trusler) media_cameraArtist’s impression of Dromornis stirtoni, the largest species of mihirung, roamed the Central Australian landscape, browsing on leaves, fruit, flowers and twigs. Picture: Peter Trusler

The largest and last species Dromornis stirtoni, which died out 50,000 years ago, was an “extreme evolutionary experiment”, Dr Worthy said.

“This bird had the largest skull but behind the massive bill was a weird cranium,” he explained.

“To accommodate the muscles to wield this massive bill, the cranium had become taller and wider than it was long, and so the brain within was squeezed and flattened to fit.”

This story was first published on The Sun and is republished with permission.

Palaeontology researcher Associate Professor Trevor Worthy with the Dromoni femur bone at Flinders University. media_cameraThe Dromoni birds were very big. Palaeontologist Trevor Worthy with a Dromoni femur bone during earlier research at Flinders University.

GLOSSARY

  • perception: ability to become aware of something through the senses
  • capabilities: abilities
  • cranium: skull
  • ratities: group of flightless, long-legged birds

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QUICK QUIZ

  1. What is the main point of this story?
  2. Where did these birds live?
  3. Are they still alive today?
  4. List three things we know about them.
  5. What are ratities?

LISTEN TO THIS STORY

CLASSROOM ACTIVITIES
1. Think About It
What do you think caused the mihirungs to become extinct? Think about the information in today’s story and look for clues in the story to help you write down some ideas.

Time: allow 20 minutes to complete this activity
Curriculum Links: English, Science, Critical and Creative Thinking

2. Extension
The scientists have been studying the skulls of the mihirungs, but how do you think they know what they rest of their bodies looked like?

List all of the evidence, or types of information, or things that the scientists might have looked at or done that you think would have helped them to understand what the ancient birds would have looked like.

Time: allow 20 minutes to complete this activity
Curriculum Links: English, Science, Critical and Creative Thinking

VCOP ACTIVITY
I Spy Nouns
Nouns are places, names (of people and objects), and time (months or days of the week).

How many nouns can you find in the article?

Can you sort them into places, names and time?

Pick 3 nouns and add an adjective (describing word) to the nouns.

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