Good morning, John!

Welcome back to Bizarre

Beasts: Season Zero. Hank and I are trading off hosting duties on  our year-long journey to remaster the original   Bizarre Beasts episodes from vlogbrothers  with corrections, updates, and new facts. Around a hundred million years ago,   the continent that is currently North  America was two or three large islands. And slicing through the space  between these islands was a massive,   shallow ocean called the Western Interior Seaway.

It stretched all the way from the  Gulf of Mexico to the Arctic Ocean. And at its deepest, this giant  sea was just 900 meters deep. For comparison, the deepest  point in the Mediterranean Sea  is 5,000 meters deep.

It was warm, it was shallow,  there were rivers from all   over the place dumping nutrients into this thing. And today, all over the interior of America,  you can still see the remnants of that time. There are these little cylinders,  they look like maybe crystals or   fossilized plant parts.

But, really,  they are the remains of crinoids. These tree-like filter feeders blanketed that sea. But they were not plants.

They were animals. Beautiful animals. And if you've ever wanted to see a fossil  come to life, I've got good news for you. [♪INTRO♪] One, crinoids are still common on Earth,  as they have been for nearly half a billion years.

And, two, they do not disappoint  in their beauty and oddity. Crinoids come in two main flavors  today: the stalked kind, which we   call sea lilies, and the un-stalked  kinds, which we call feather stars. And I wanted to pause here just to give you  a little more background info on these guys.

There are more than 660 species of crinoids alive  today, only about 80 of which are sea lilies. Most of the sea lilies live in water that’s  deeper than 200 meters, so, relatively deep. The feather stars, on the other hand,   tend to live in reef ecosystems, which  are found in water shallower than that.

And sea lilies used to be much more common,  but they nearly got wiped out during the mass   extinction at the end of the Permian  Period, around 252 million years ago. After that, feather stars evolved  and took over shallow water habitats. Now, they look more like a kind  of coral than anything else.

Like, that they would just sit,  anchored to one spot in the ocean,   filtering plankton out of  the water and chillin' out. But corals are collections of tiny organisms,  and corals are very much stuck to one place. Crinoids are animals.

They are macro organisms like us and  they can, though they don't often, move. Oh, yeah. I mean, I maybe forgot to mention the main  thing about feather stars, which is this.

Like, you've probably seen  viral videos of this movement,   but it isn't the kind of thing  that, like, it hurts to watch again. Crinoids spend almost all of  their time sitting in one spot, but they spend almost all of their  viral video time engaging in this   amazing, mesmerizing locomotion. Like other echinoderms, like starfish,  sea urchins, sea cucumbers, etc.,   feather stars are pentaradially symmetrical.

They have five-sided symmetry. This is harder to see in  crinoids, but it is a thing. They might have any number of legs, but  that number should be divisible by five,   except that they often get their  legs chewed off or knocked off.

They are pretty delicate but  they could just grow them back. And while feather stars move around looking like  the most unearthly gorgeous thing that has yet   happened, sea lilies, which are essentially the  same thing--like, they're different species,   but very similar--when they move around...  yeah, they just drag their stalk behind them. Just trudging across the ocean floor!

And I actually just learned this  bonus fact that might explain why   otherwise sedentary sea lilies sometimes do this! In a study from 2010, researchers  put crinoids and pencil urchins   together in a tank to see if the  urchins would eat the crinoids. And...yeah, they did.

Which is maybe a little weird, because there’s  not much on a crinoid that looks edible to me,   but an urchin’s gotta do  what an urchin’s gotta do. The researchers then studied the marks  left behind on the crinoid parts by the   urchin’s beak-like mouth and went looking  for those same marks on crinoid fossils   from around 230 million years ago,  in the middle of the Triassic Period. And they found them!

So, based on this and on when crinoids that  can swim and drag themselves around originated,   the researchers think that predation by  ancient urchins might’ve been one of the   evolutionary pressures driving  crinoids to need to get away. Check this out: Their blood--they have a  vascular system--their blood is just water. It transports oxygen and nutrients and waste.

It does the whole vascular system  thing, but it's just seawater. We're talking about an organism that figured out   how to do its thing before blood  existed and is still doing that. But crinoids have continued to adapt.

Like their locomotion--that wasn't  happening 500 million years ago. That's relatively recent. I mean like 200 million years ago, but still.

Crinoids, y'all did it. Good work. Just keep swimming, I guess, is what this is.

If you missed this critter the first time  around, our Season Zero pin sets are now available! This set includes all 12 of the animals  we began this Bizarre Beasts journey   with on Vlogbrothers, including the Feather Star! And this one really glows in the dark!

To get the Season Zero Pin set,  visit bizarrebeastsshow.com! [♪OUTRO♪]