Are Pademelons Related To Dinosaurs?

If the title of this article made you stop for a second and wonder what on earth I’m talking about, stick with me. There is actually a perfectly reasonable explanation for how we ended up here.

This whole article started with a fairly random observation about a Tasmanian pademelon. More specifically, those ridiculously little arms they hold in front of themselves when they sit upright.

They look like tiny Tyrannosaurus Rex arms.

At first glance, it is probably difficult to imagine much connecting one of Tasmania’s small, round forest potatoes with one of the largest terrestrial predators ever to walk the Earth.

And those arms have always left me with one fairly ridiculous question. Is there any chance a pademelon and Tyrannosaurus Rex are actually related?

Are Pademelons Actually Related to Tyrannosaurus Rex?

Strangely enough, yes.

But before anyone starts imagining tiny dinosaurs slowly evolving into pademelons, we need to put an enormous amount of evolutionary history between the two.

Pademelons are mammals. More specifically, the Tasmanian pademelon (Thylogale billardierii) is a marsupial and a member of the macropod family, alongside kangaroos and wallabies. Tyrannosaurus Rex, meanwhile, was a theropod dinosaur. On the evolutionary family tree, those two lineages sit a very long way apart.

Follow both branches far enough backwards, however, and eventually they meet.

Both mammals and dinosaurs belong to a much older group of vertebrates called amniotes. Hundreds of millions of years ago, early amniotes diverged into two great evolutionary branches. One, the synapsid lineage, would eventually give rise to mammals and, much later, our Tasmanian pademelon. The other, the sauropsid lineage, would eventually give rise to reptiles, dinosaurs and birds.

Exactly when that split occurred is still being refined. For years, estimates generally placed the origin of crown amniotes somewhere around 320 million years ago. Remarkable fossil footprints described from Victoria in 2025 may push that history much further back. Interpreted as the tracks of an early crown-group amniote, most probably a primitive sauropsid, they suggest those two great amniote branches had already separated by around 355 million years ago.

To put that into perspective, Tyrannosaurus Rex did not appear until roughly 68 million years ago. Whatever the distant common ancestor connecting its lineage with ours looked like, it was neither a dinosaur nor a mammal and lived an almost incomprehensibly long time before either existed.

So yes, a Tasmanian pademelon really is a distant relative of Tyrannosaurus Rex.

Then again, so are we.

Humans and pademelons remained on the mammalian side of that ancient split for a very long time before our respective placental and marsupial lineages eventually went their separate ways.

And if you really want to meet one of Tyrannosaurus Rex’s considerably closer living relatives, don’t look at the pademelon with the tiny arms. Look at the birds.

Birds are living dinosaurs, descended from within the theropod dinosaur lineage itself. Every magpie, raven, kookaburra and chicken you see today shares a far more recent evolutionary connection with Tyrannosaurus Rex than any pademelon ever did.

And here in Tasmania, that includes the turbo chook.

The Tasmanian native hen (Tribonyx mortierii) tearing across a paddock at full speed is not just vaguely dinosaur like. It is, quite literally, a living dinosaur.

Which brings us back to those little arms.

Because if the pademelon’s tiny forelimbs aren’t some bizarre little evolutionary souvenir from its dinosaur relatives, why does it have them?

What Is Going On With Those Tiny Arms?

Here is where my original theory starts to fall apart a little.

Those ridiculously little Tyrannosaurus Rex arms that started this entire rabbit hole are not actually as ridiculously little as they look.

Compared with larger members of the macropod family, Tasmanian pademelons have relatively long forelimbs. Males in particular can have quite muscular chests and forearms. It is the rest of the pademelon, and the way it carries those forelimbs, that helps create the illusion.

The Tasmanian pademelon is also much more compact than the larger kangaroos and wallabies we tend to picture when we think of macropods. It has a squat body and a thick, relatively short tail, giving the whole animal a very different set of proportions.

Then there is the way they move.

When a Tasmanian pademelon hops, it holds its forelimbs close against its chest and leans its body forward. At higher speeds, its body can become almost horizontal to the ground as it moves rapidly through the vegetation.

And there it is.

The Tyrannosaurus Rex pose.

But those little forelimbs are certainly not useless.

Pademelons can use their forepaws while feeding, including grasping vegetation and pulling branches towards themselves. Observations of captive Tasmanian pademelons have also recorded them holding and manipulating food with their forepaws.

At slower speeds, things become even more interesting. Pademelons do not simply spend their entire lives bouncing around Tasmania with their arms tucked against their chests. They can use a much slower form of movement while feeding and travelling short distances, bringing the forelimbs back into the business of getting around.

This is also where the Tasmanian pademelon differs in an important way from some of its much larger macropod relatives.

Kangaroos are famous for using their enormous tails almost like a fifth limb during slow movement, supporting the body as they move forward. Tasmanian pademelons do things somewhat differently. Their tail is relatively short and does not provide the same substantial support during slow movement and grazing.

So those forelimbs are not evolutionary leftovers, nor are they miniature appendages waiting patiently for millions of years to disappear.

They are perfectly functional pademelon arms.

They only happen to look particularly hilarious when their owner sits upright, holds them against its chest and gives us its best impression of a Cretaceous theropod.

Which raises another question.

If we have been unfairly accusing the pademelon of having useless little Tyrannosaurus Rex arms, have we also been unfair to Tyrannosaurus Rex?

Were Tyrannosaurus Rex Arms Actually Useless?

Apparently, I owe Tyrannosaurus Rex an apology too.

Its famously tiny arms have been the butt of jokes for decades. Stick a pair of ridiculously short arms onto almost anything and we immediately know what they are supposed to represent. But just like the Tasmanian pademelon, having small arms did not necessarily mean they were useless.

In fact, Tyrannosaurus Rex forelimbs were surprisingly robust. Each arm ended in two clawed fingers, and studies of the bones and reconstructed muscles have suggested they were capable of producing considerable force. What exactly Tyrannosaurus Rex was doing with them, however, is still one of those wonderfully frustrating questions that palaeontologists cannot simply go back 66 million years and watch.

Holding struggling prey has been proposed. So has helping the enormous animal rise from the ground, assisting during mating, display, and even slashing at prey. Other researchers have questioned whether some of those ideas are mechanically realistic at all.

In other words, we know Tyrannosaurus Rex had arms.

We know they were small.

We know they were not simply two floppy little decorations hanging from its chest.

Beyond that, the argument gets considerably more interesting.

There is, however, another question we can ask. Instead of wondering what Tyrannosaurus Rex did with its tiny arms, why did its evolutionary lineage end up with such short arms in the first place?

And remarkably, some very recent research may have brought us closer to an answer.

A study published in 2026 examined 82 species of theropod dinosaur and found that reduced forelimbs evolved independently in several different groups of large meat eating dinosaurs. More importantly, shorter arms were more strongly associated with the development of robust, powerful skulls than they were with simply having a gigantic body.

In very simple terms, as the head became an increasingly formidable weapon, the arms may have become less important for attacking and subduing prey.

Tyrannosaurus Rex was perhaps the ultimate example. It had an enormous, powerfully built skull and devastating jaws, while its forelimbs had become proportionately tiny. Rather than its arms simply failing to keep pace as the rest of the animal became enormous, the research suggests there may have been a genuine evolutionary shift in how these predators were doing the business of being predators.

The head was taking over.

That does not mean Tyrannosaurus Rex stopped using its arms altogether. Evolution does not require a body part to have one single purpose, and an arm can become less important for one job while remaining perfectly useful for others. It simply means that whatever Tyrannosaurus Rex was doing with those little forelimbs, bringing down prey may increasingly have become a job for the enormous set of jaws sitting above them.

So perhaps we owe Tyrannosaurus Rex an apology after all.

Its arms were certainly tiny. They just weren’t necessarily useless.

Which still leaves us with the strange resemblance that started this whole post.

Why Do They Look Weirdly Similar?

After all of that, there is still one fairly obvious problem.

They really do look a little bit alike.

Put a Tasmanian pademelon upright with its forelimbs tucked against its chest and there is something undeniably dinosaurish about the silhouette. Add those powerful hind legs, a tail behind it and the little arms out front, and you can perhaps forgive me for starting this entire research project.

But evolution has a habit of producing similarities that can be misleading.

Sometimes, distantly related animals independently evolve similar features because they face similar problems. This is known as convergent evolution. Dolphins and sharks both evolved streamlined bodies for moving through water, for example, despite one being a mammal and the other a fish.

That does not mean we can simply declare the pademelon and Tyrannosaurus Rex arms another example of convergent evolution.

In fact, the more closely we look at them, the more the resemblance starts to disappear.

The Tasmanian pademelon does not actually have unusually tiny forelimbs. Much of the Tyrannosaurus Rex illusion comes from its compact proportions and the way it holds those forelimbs close to its chest.

Tyrannosaurus Rex really did have extraordinarily reduced forelimbs relative to the enormous size of the rest of its body.

So what looked like an intriguing anatomical connection turns out to be something much simpler.

To our eyes, two very different animals happen to strike a remarkably similar pose.

So, Is a Pademelon a Distant Relative of Tyrannosaurus Rex?

After taking a question about tiny arms considerably further than any reasonable person probably should, we have our answer.

Yes.

A Tasmanian pademelon and Tyrannosaurus Rex really are very distant relatives. Follow their evolutionary family trees backwards for hundreds of millions of years and eventually those two branches meet near the beginning of the amniote family tree, long before there were pademelons, dinosaurs or even mammals as we know them today.

But those tiny Tyrannosaurus Rex arms that started this whole thing?

They have absolutely nothing to do with it.

The pademelon’s forelimbs are functional parts of a compact macropod body, while the famously reduced arms of Tyrannosaurus Rex evolved along an entirely different path. What looks like an unlikely family resemblance is really just two very different animals striking a pose that happens to look remarkably similar to us.

And somehow, I think that makes the answer even better.

A completely random thought about a pademelon sitting upright with its little arms tucked against its chest led us back hundreds of millions of years, through the origins of mammals and dinosaurs, into some very recent Australian fossil discoveries, and eventually back to where two extraordinary evolutionary stories began to separate.

So the next time you see a Tasmanian pademelon sitting quietly at the edge of the bush and those tiny forelimbs make you think there is something vaguely dinosaurish about it, you are not entirely wrong.

Just remember that the little forest potato is much more closely related to you.