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Ancient Fish Fossil Could Help Explain How Our Skulls Evolved

Fish Fossil
Image Source: MP cz@Shutterstock

Back in the day, I’m talkin’ hundreds of millions of years ago, the oceans of this ol’ Earth were playgrounds for jawless fishes. These critters had brains that were wrapped up like a birthday present, armored on the outside and cushioned on the inside with cartilage plates. Now, hold onto your hats, ’cause scientists have been chasin’ the trail of how these ancient fish ancestors paved the way for the skulls we sport today, us modern vertebrates with backbones. And let me tell ya, they’ve stumbled upon a real gem of a fossil that’s fillin’ in some gaps.

This here fossil, folks, ain’t your run-of-the-mill discovery. It’s a cranium, an articulated one at that, and it’s been kickin’ around for 455 million years. We’re talkin’ about Eriptychius americanus, a jawless fish that’s been hangin’ out in the Harding Sandstone formation over in Colorado. This critter’s cranial anatomy, preserved in glorious 3D, is like a blast from the past, and it’s the oldest one we’ve got, bar none.

Now, before we get all giddy, let’s dive into the nitty-gritty. You see, our modern-day kinfolk of those jawless fishes can be divided into two camps: the ones with jaws and the jawless wonders like hagfish and lampreys. But E. americanus? Well, its skull setup is somethin’ straight outta left field, nothin’ like what we see today. It’s got cartilage sections, some playin’ nice and symmetrical, others just doin’ their own thing, right up at the front of the noggin, wrappin’ ’round the mouth, the smelly bits, and them peepers.

Dr. Richard Dearden, the fella leadin’ this show, he’s as excited as a kid on Christmas morning. He’s sayin’, “You don’t find these oddball sets of cartilages anywhere else, folks!” And I gotta say, I’m inclined to agree.

Now, let’s talk about the backstory. Back in ’49, a smart feller named Robert Denison dug up this fossil treasure trove. He was a paleontologist, a real fossil fish enthusiast workin’ over at Chicago’s Field Museum of Natural History. Denison had a real knack for sniffin’ out unique stuff, and he knew he had somethin’ special. But back then, they couldn’t just crack open this fossil like a nut; it woulda ruined the whole shebang.

Fast forward a few decades, and we got ourselves some fancy CT scans in the mix. Dearden and his gang managed to peek into the fossil’s secrets without layin’ a finger on it. They built a digital replica of that fish’s head in three dimensions, a real modern-day miracle, I tell ya.

Now, why’d it take so darn long to scan this bad boy? Well, as Dearden put it, not many folks are into these Ordovician fishes, and you gotta be a real specialist to see the gold in ’em. It’s like tryin’ to spot a needle in a haystack, partner.

Let’s talk history, shall we? These jawless fishes from the Ordovician era, they’re called ostracoderms. It’s a fancy name, but it’s all about their armored skin. Most of what we know ’bout ’em comes from the armor they left behind. It’s like tryin’ to figure out a jigsaw puzzle with most of the pieces missin’. You see eye holes in that armor, and you guess where the eyes might’ve been, but it’s all guesswork.

Now, here’s the juicy part: Dearden and the gang, they found ten pieces of skull cartilage in that ol’ fossil. Some in the epoxy, some stuck in the rock. It’s like findin’ buried treasure, ain’t it? Scales were wrappin’ around ’em, and there were canals that might’ve held all sorts of secrets – could be sensors, could be blood vessels, who knows?

But here’s the twist in the tale. We still got questions, partner. What’s the deal with them canals? Why’s all the cartilage sittin’ up at the front of the head? Maybe there was more cartilage in the back, but it didn’t make the fossil cut, who’s to say?

And let’s not forget the big mystery: when did jaws make their debut in the fish world? That’s still up in the air.

But despite all them mysteries, this fossil’s a game-changer, no doubt about it. Paleobiologist Lauren Sallan, she says it fills a gap in our knowledge ’bout how vertebrate heads came to be. It’s like findin’ the missin’ puzzle piece under the couch, a real leap forward in our understandin’.

So there ya have it, folks. Ancient fish, CT scans, and a dash of curiosity, all mixin’ up into a story that’s got us holdin’ our breath for what comes next in the wild world of science. Yeehaw!

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