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New meat eater Meraxes gigas had tiny arms and giant head like T-rex

AFP, July 20, 2022 7:00PM Kids News

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An artist's impression of the Meraxes gigas with its small forearms and large head. Fossils of this carnivorous dinosaur were found in the Patagonia region of Argentina. Picture: Carlos Papolio media_cameraAn artist's impression of the Meraxes gigas with its small forearms and large head. Fossils of this carnivorous dinosaur were found in the Patagonia region of Argentina. Picture: Carlos Papolio

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Palaeontologists have discovered a new giant carnivorous* dinosaur species that had a massive head and tiny arms, just like Tyrannosaurus rex.

The researchers’ findings, published in the journal Current Biology, suggest that small forelimbs* were no evolutionary* accident, but rather gave apex predators* of the time certain survival advantages.

Meraxes gigas – named after a fictional dragon in the Game of Thrones book series – was dug up over four years during field expeditions in the northern Patagonia region of Argentina, starting with the skull which was found in 2012.

“We won the lottery and found it literally on the first morning,” said palaeontologist Peter Makovicky, from the University of Minnesota.

Excavation site. Picture: Juan I Canale media_cameraThe excavation site in the northern Patagonia region of Argentina where the Meraxes gigas fossil was found. Picture: Juan I Canale

The fossilised remains were remarkably well preserved. The skull is just over 1.27m, while the entire animal would have been about 11m long and weighed 4000kg or 4 tonnes.

Its arms were only about 61cm long, “so it’s literally half the length of the skull and the animal would not have been able to reach its mouth”, Prof Makovicky said.

But T-rex didn’t get its tiny arms from Meraxes gigas, which went extinct 20 million years before the T-rex roamed. The two species were also far apart on the evolutionary tree*, Prof Makovicky said.

Instead, the researchers believe these dinosaurs evolved* tiny arms for certain reasons, including mating and to help them stand up after a fall.

“I’m convinced that those proportionally* tiny arms had some sort of function,” said fellow researcher Juan Canale, from the Ernesto Bachmann Palaeontological Museum in Argentina.

“The skeleton shows large muscle insertions* and fully developed pectoral girdles*, so the arm had strong muscles.”

Artist's impression of the Meraxes gigas. Picture: Jorge A Gonzalez media_cameraAn artist’s impression of the Meraxes gigas shows the crests, furrows, bumps and small horns on its head. Picture: Jorge A Gonzalez

Prof Makovicky believes that Meraxes’ large head became its dominant* weapon, taking on the function that forelimbs would have had in smaller species.

Meraxes roamed the Earth between 90 to 100 million years ago during the Cretaceous period, at a time when the region was wetter, had more forests and was much closer to the sea, Prof Makovicky said.

They would have preyed on a range of sauropods*, some of which were discovered at the same site.

The Meraxes found by the team is thought to have lived to about 40 years – a ripe old age for dinosaurs – and its skull had crests*, furrows, bumps and small horns.

“It certainly would have looked very imposing* and gargoyle* like,” Prof Makovicky said.

GLOSSARY

  • carnivorous: meat-eating
  • forelimbs: front limbs, in this case arms
  • apex predators: animals at the top of the food chain and which are not preyed upon by other animals
  • evolutionary: gradual process of change or development
  • evolutionary tree: a diagram that shows how species are related
  • evolved: developed over time in response to a need
  • proportionally: comparing the size of one thing to another
  • muscle insertions: the sites where the bone and muscle would have attached
  • pectoral girdles: the sets of bones that connect the arms on each side of the body
  • dominant: most powerful, important
  • sauropods: plant eating dinosaurs that walked on four legs and had a long neck and tail
  • crests: tufts of feathers, fur or skin on the head
  • furrows: long, narrow folds in the skin
  • imposing: grand and impressive in appearance
  • gargoyle: stone carving of a strange and ugly creature that is attached to the roof of a building

EXTRA READING

Dino set to fetch millions of dollars at auction

T-rex may be three different species

Dinosaurs’ ferocious fight to the death

QUICK QUIZ

  1. What was Meraxes gigas named after?
  2. Where was the fossil found?
  3. How big was its skull?
  4. How long were its arms?
  5. How long ago to Meraxes gigas roam the Earth?

LISTEN TO THIS STORY

CLASSROOM ACTIVITIES
1. What were they for?
Prof Makovicky said that the skull of Meraxes gigas had crests, furrows, bumps and small horns. Why do you think Meraxes’ skull would have these? What would they be used for? Use information in the story to help you to create a diagram or drawing with labels. The purpose of your diagram is to show how the different features of Meraxes’ skull would have helped him.

Time: allow 25 minutes to complete this activity
Curriculum Links: English, Science

2. Extension
Why did it take four years to dig up Meraxes gigas? Write a step-by-step guide that shows how you think palaeontologists would go about searching for a fossil like Meraxes. Think about how they would need to protect the skeleton and make sure that they find as much of the skeleton as possible.

Time: allow 25 minutes to complete this activity
Curriculum Links: English, Science

VCOP ACTIVITY
Wow word recycle
There are plenty of wow words (ambitious pieces of vocabulary) being used in the article. Some are in the glossary, but there might be extra ones from the article that you think are exceptional as well.

Identify all the words in the article that you think are not common words, and particularly good choices for the writer to have chosen.

Select three words you have highlighted to recycle into your own sentences.

If any of the words you identified are not in the glossary, write up your own glossary for them.

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