You wanna know a word that bugs me?

At least one that bugs me when people use it to talk about natural history.

Monster You see it all the time, like in blog posts that describes some awesome mosasaur fossil as a sea monster or articles that try to get more clicks by calling a pterosaur a flying monster.

Now don't get me wrong.

In the right context, monsters are awesome.

The Harry Potter books, Stranger Things, the collected works of JJ Abrams.

They'd all be basically meaningless if they didn't have monsters.

But the problem with referring to actual organisms that lived on this earth as monsters is that monsters are by definition IMAGINARY.

They're made-up creatures that are so terrifying and so threatening to our sanity that they can't possibly be real.

And yet there are animals in the fossil record that challenge some of the most basic ideas about what animals are supposed to look like.

If there ever was a monster on this planet that was ready of the name, it might have been this: the Tully Monster.

It lived in the Inland Seas of North America 300 million years ago at the very end of the carboniferous period.

Back then rainforest covered much of the land and the seas teemed with life ranging from sharks to tiny shell covered protozoans.

The Tully Monster wasn't, like, monstrously large for its time.

It was maybe a foot long.

What makes it strange to modern eyes is that it just looks imaginary.

It doesn't look remotely like anything that's alive today, or maybe it looks more like a bunch of other things put together.

Which is just as creepy.

I mean things like Mosasaurs at least bear some resemblance to reptiles we know, like crocodiles or snakes or Komodo dragons.

But the Tully Monster?

I mean if George Lucas ate a pepperoni pizza, and then drank a whole thing of chocolate yoohoo before going to bed, this is what he'd dream up.

Its body was long and tapered, built for life in the water.

Like a giant worm crossed with a small squid.

It also apparently had eyes that flopped around on the sides of its body attached to these fleshy stalks.

And out of its head came this long skinny appendage with a claw at the end, which may or may not have been a mouth.

But that's just one interpretation of it, because what exactly this thing looked like depends on what exactly it was, and scientists have been fighting about that since Tullys were first discovered in Illinois in the 1950s.

To paleontologists, if anything is creepy about the Tully monster, is that it's missing the one thing that biologists value very highly.

Phylogeny.

Phylogeny is evolutionary relationship that every organism has to its ancestors and its descendants.

But the Tully Monster doesn't have a permanent place in the evolutionary scheme of things that we call the Tree of Life.

Not yet anyway.

In 2015 some paleontologists at Yale thought they had found a home for it.

After analyzing more than 1,200 fossils of the Tully Monster they determined that the creature was a vertebrate, probably an ancestor of Jawless fish like lampreys.

They came to this conclusion in part because of a telltale mark that they found in some of the fossils.

A white line that ran down the middle much like a backbone.

But instead of being made out of bone that spine was probably made of something like cartilage.

Forming a notochord like those still found in some of today's jawless fish.

So, that was as close to an answer as paleontologists could get.

The Tully Monster was a member of team vertebrate.

But then, in 2017, another team of researchers gave the fossils another pass and came to the exact opposite conclusion.

They determined that they actually don't know what it is... still.

But they said Tully definitely was not a vertebrate.

For one thing, the white lines found on some of those fossils go past the eyestalks where true notochord would end.

And other fossils of vertebrates found from the same period, like fossils of lampreys, didn't have those white lines at all.

Even Tully's bizarre dangling eyes don't seem to have been true complex eyes like other vertebrates have.

Instead, they might have been so-called cup eyes, much more simple light-sensing organs that are found in things like worms and mollusks.

So we're left with a mystery.

We don't know this thing was a worm or a fish or a mollusk.

And we don't know how it's related to us or to anything else.

But guess what?

In the fossil record, there's a lot more where that came from.

There are animals like Banffia, a sea creature that look basically like a swimming hot water bottle; and Opabinia, a Cambrian animal with five eyes.

There are many organisms out there whose phylogeny is a total mystery to us.

So many, in fact, that scientists have a special category for fossils that defy classification.

They call them problematica.

But if we can find a home for creatures like these in the Tree of Life, we'll have a much better understanding of what the rules of life are on our planet.

So, animals like Tully Monster are weird, definitely.

And for scientists, they're frustrating.

Absolutely.

But a monster?

I prefer to think of it as problematic.