Modern Australian

how do we know if a dinosaur skeleton is from a child dinosaur or an adult dinosaur?

  • Written by Caitlin Syme, PhD in Vertebrate Palaeontology, The University of Queensland

When you find dinosaur skeletons, how can you tell how old the dinosaur was? Like, if the skeleton is from a child dinosaur or an adult dinosaur? – Henry, aged 8.

how do we know if a dinosaur skeleton is from a child dinosaur or an adult dinosaur?

Hi Henry, that’s a good but tricky question.

There are a couple of ways we can try to tell how old a dinosaur was when it died.

If you cut open a fossil dinosaur bone, you can see lines, just like if you were looking at rings in a tree. Trees rings happen when a tree grows slowly in a tough season like an icy cold winter. You can count the rings to see how many winters that tree has lived through. And because there is only one winter each year, then you know how many years old the tree is. Easy!

Animals, like dinosaurs, formed similar lines in their bones whenever they slowed down their growing. But there’s a catch: this might not happen once each year like in a tree.

Read more: Curious Kids: why did the dinosaurs die?

Why would a dinosaur slow down its growing? A dinosaur might not grow very fast if there is not enough food to eat. This might happen if there hasn’t been much rain and so there are not as many plants around to eat. Or there might be loads of food around, but the dinosaur is using all its energy to fight other dinosaurs, rather than using it to grow.

There might be lots of times each year when the dinosaur stopped growing, and each time would make a growth line in its bones. So if you find a fossil with lots of growth lines, you might not be looking at the bones of a really old dinosaur, but a very busy, stressed-out dinosaur! So this is quite a complicated way to try and guess its age.

Another way to try to guess the age of a dinosaur is to look at how its skull bones connect to each other. Lots of baby animals don’t have a solid skull. Instead, their skull is made up of different bits that gradually stick together into one piece as it grows.

We’re not sure whether baby dinosaurs had skulls that grew like this. Some scientists have tried to find out by looking at skulls from baby emus and alligators, both of which are a bit similar to dinosaurs. They discovered that emu chicks have skull bones that stick together as they grow, but baby alligators don’t! So that doesn’t really give us a clear answer either.

how do we know if a dinosaur skeleton is from a child dinosaur or an adult dinosaur? The growth of a dinosaur called Protoceratops, from newborn baby (on the left) to grown-up (on the right). Harry Nguyen/Wikimedia Commons

Sometimes it’s really easy to tell how old a dinosaur was. If you find a dinosaur egg, you can use something called X-rays to look inside it and see if there is a baby dinosaur fossil inside. If there is, you know that dinosaur was 0 years old!

Then, if you find a bigger fossil from the same kind of dinosaur nearby, there is a chance that dinosaur was the baby dinosaur’s grown-up parent.

If you find a baby and a grown-up together, you can learn lots more things by looking at the differences between the two. It might tell you how the dinosaur changes size and shape as it gets older.

You might find a dinosaur that looks like a mixture between the two. That might be a “big kid” dinosaur that is well on its way to becoming a grown-up.

It’s still hard to tell exactly how old each dinosaur was. But scientists are like detectives, and they have lots of clever ideas that are helping them get better at it all the time.

Read more: Curious Kids: did the velociraptors have feathers?

Hello, curious kids! Have you got a question you’d like an expert to answer? Ask an adult to send your question to

Authors: Caitlin Syme, PhD in Vertebrate Palaeontology, The University of Queensland

Read more


Before we rush to rebuild after fires, we need to think about where and how

A primary school in East Gippsland was burnt down in the current bushfire crisis. While Premier Daniel Andrews immediately committed to rebuilding the school as it was, media reported the...

Australian sea lions are declining. Using drones to check their health can help us understand why

Australian sea lions (Neophoca cinerea) are one of the rarest pinnipeds in the world and they are declining.Jarrod Hodgson, CC BY-NDAustralian sea lions are in trouble. Their population has never...

With costs approaching $100 billion, the fires are Australia's costliest natural disaster

It’s hard to estimate the eventual economic cost of Australia’s 2019-20 megafires, partly because they are still underway, and partly because it is hard to know the cost to attribute...

In cases of cardiac arrest, time is everything. Community responders can save lives

Cardiac arrest can occur with little or no warning in people who were previously healthy, including young people.From shutterstock.comEach year more than 24,000 Australians experience a sudden cardiac arrest. This...

So the government gave sports grants to marginal seats. What happens now?

When Australians pay their income tax, they assume the money is going to areas of the community that need it, rather than being used by the government to shore up...

The Olympics have always been a platform for protest. Banning hand gestures and kneeling ignores their history

It is the year of the Tokyo Olympics, and the International Olympic Committee was quickly out of the blocks with new guidelines regarding athlete protests. The IOC is worried...

Catherine Hay Thomson, the Australian undercover journalist who went inside asylums and hospitals

Catherine Hay Thomson went undercover as an assistant nurse for her series on conditions at Melbourne Hospital. A. J. Campbell Collection/National Library of AustraliaIn this series, we look at under-acknowledged...

how fraudsters take advantage of those in need

Australians were also cheated out of A$400,000 last year in charity scams.Dean Lewins/AAPThere’s been an overwhelming outpouring of love and support around the world for those impacted by the bushfires...

To improve firefighters' mental health, we can't wait for them to reach out – we need to 'reach in'

Many firefighters will by now be exhausted, having been on the front line of Australia’s bushfire crisis for weeks or months. This bushfire season has been unrelenting, and the hottest...

'What subjects do I choose for my last years of school?'

Locking yourself into one career path too early may be risky.from shutterstock.comWe are being asked to do work experience this year, in a field we might like to work in...

the end of the checkout signals a dire future for those without the right skills

Shops checkouts are predicted to disappear this decade. Customers will be able to take what they want and walk out, with payment done automatically.www.shutterstock.comThere has already been a fair...

Take care when examining the economic impact of fires. GDP doesn't tell the full story

It is possible to calculate the impact impact of fires, but not using GDP.Shutterstock/Andrew Brownbilll/AAPEstimates of the economic damage caused by the bushfires are rolling in, some of them big...

Popular articles from Modern Australian

Embarrassed of your teeth? Here's what you can doWant to become a ballerina? Here's what you should know10 Signs You Are Obsessed with ShoppingArchitects and interior designers reveal what will shape the homes of a new decadeTips To Transform Your Bedroom With An Ecstatic ViewFive things to take when traveling to New ZealandBenefits of Cosmetic Surgery10 signs you're obsessed with cleaning5 Healthy Snacks To Bring To The OfficeExperts Think We Should Repair Items MoreIs Dental Floss Really That Useful? Dentists Weight InThings to keep out of your children reachTips To Maintain Your High-Quality CookwareTips for planning perfect picnic for new yearsBenefits of hiring a car for your vacation