[♪ INTRO] Discovering a fossil is always pretty exciting.

Each little piece gives us a little more insight into the history of life on our little green planet. The fact that we have fossils /at all/ is pretty remarkable; the odds of a living thing dying in just the right place to fossilize are extremely slim.

So when we find fossils that change our understanding of whole groups of organisms, it's extra special. And we’re regularly uncovering a range of relics left behind from our planet’s past. The more fossil specimens we find, the more we can learn about different groups of organisms that came before us, over millions of years.

So here are five of our favorite fossil discoveries announced in 2022 that not only teach us about the world that was, but can help us better understand life on Earth today, as well. Our first fossil is a two-for-one special that gives us a gnarly look into ancient food chains. We’re talking about crocodilians, some of Earth’s most formidable flesh-eaters for hundreds of millions of years.

And while their toothy grin may seem like an obvious giveaway of their dietary preference, it’s hard to know for certain what exactly these prehistoric crocs were chowing down on. Previously, paleontologists had to piece together the details of their diet from fossilized bite marks on their prey that got away, and fossilized croc poop. And although the evidence suggested that early crocodilians were feeding on dinosaurs, at least some of the time, we were missing more direct evidence this was the case.

Until now! A recently discovered croc fossil from Australia is very likely a new kind of mid-Cretaceous crocodilian group dating to around 93 million years ago. Not only that, but it was also found with preserved stomach contents!

This croc kicked the bucket very soon after finishing a meal, so it didn’t have time for its digestive enzymes to do their thing. And it turns out its final meal was a juvenile ornithopod, the group of dinosaurs that includes duck-billed hadrosaurs. Studying the crocs' fossilized gut contents also confirmed that they chewed, dismembered, and crushed the bones of their prey in the same way their modern relatives do.

And looking at the vertebrae of the croc, its strong neck indicated that this ancient predator likely ambushed its prey, much like most modern crocodilians. It’s yet to be confirmed, but the researchers think this young ornithopod may be a completely new dinosaur discovery too, since this is the first full body of an ornithopod that they’ve found from this particular location of Australia. Talk about a BOGO deal!

When it comes to dinosaurs, the obvious fan favorite dinosaur is the formidable Tyrannosaurus rex. Its massive size, huge teeth, and terrifying jaws made the T. rex the ultimate predator, despite their comically small arms. But even as one of the most famous dinosaurs of all time, we still don’t fully understand why its arms are so tiny.

It’s not the only ferocious dinosaur with teeny arms either. Other large, predatory dinos have shorter front limbs as well, like Carnotaurus. which is a member of a family called abelisaurids. And, these guys didn’t inherit those tiny limbs from their common ancestor; they both shrank their arms independently.

And it turns out, little limbs showed up independently in a third group of dinosaurs as well. And this recent discovery has shed some light on the possible evolutionary pressures that resulted in this puzzling adaptation to appear in distantly related dinos. A new and massive meat-eating dinosaur was discovered in Patagonia in 2012, Meraxes gigas.

And after years spent carefully extracting, preparing, and studying the fossil, a team of researchers have finally released some exciting conclusions around their find. Not only was this specimen an impressive beast, at almost 11 meters snout-to-tail and estimated to weigh over 4000 kilograms. It’s also the most complete fossil of its family, which means it gives us a lot of insight into this group.

Its skull, hips, and all four limbs were intact. Which is key, because before this discovery, fossils from this group of dinosaurs left a lot of holes in our understanding of them. And we weren’t really sure what their head and forelimbs even looked like!

This dino’s huge skull and tiny front limbs revealed that it was really similar in body form to tyrannosaurs. Which is a little bit odd because they’re actually pretty distantly related! Not only that, but the tyrannosaurs’ closer relations aren’t as physically similar as Meraxes, meaning this isn’t something that they just inherited from their earlier ancestors.

So it turns out that tiny arms evolved at least three times, in three different families of dinosaurs. Which raises the question: Why do they need such tiny arms? Well, these researchers think that they didn’t.

They argue that tiny limbs themselves didn’t evolve to fill a specific purpose, but that their limbs shrinking allowed their skulls to become massive. Basically, their body was being optimized for catching large prey thanks to a massive jaw, so their forearms just weren’t as important. Why bother to grow big ones that will just get in the way?

So while their little arms look a bit goofy to us, they’re all part of the apparatus that made these predatory dinos so powerful back in their day. Now while the dinosaurs were certainly the most famed reptiles of their time, the other major reptile groups were already around too - like the humble lizard. Lizards and their relatives make up a group known as squamates, which have been around since the Jurassic period, although new evidence suggests there may have been a few dating even further back into the Triassic.

We’re already pretty confident that squamates split from their closest living relatives, the tuataras, about 240 million years ago. However, because these lizards are so small, their bones don’t fossilize nearly as often, so there’s not as much that we know about squamates’ early evolutionary history. The big question on researchers’ minds has been which of the main few squamate groups broke away from the pack first.

Genetic data on modern animals conflicts with the pattern we see in their anatomy, so researchers have been stumped; though the iguana group is often thought to be the first group to have branched off.. But in 2022, a study was published on a near-perfect, itty bitty fossilized lizard ancestor found in Scotland called Bellairsia gracilis, that may help us answer this question. This miniature fossil was special in a few key ways.

For one, it’s really rare that researchers get to study a fossil that’s this complete. The largest missing pieces were from the tail and snout, but otherwise the body was about 70% accounted for, which is pretty impressive for a 168 million year old fossil. On top of that, this little guy helps fill in a 100 million year long gap in the fossil record for this particular group.

It lived about 168 million years ago, which puts it right in the middle of a major hole in the lizard lineage. And by comparing the traits of this lizard-like ancestor to living squamates, the researchers were able to reconstruct which of those modern groups split from the rest before all the others. It turns out the traits this fossil shared with modern lizards were closest to geckos.

So this discovery supports the hypothesis that geckos were actually one of the early splits in the modern squamate timeline, and not the iguanas after all. So this fossil has shed light on some pretty big secrets of its family tree, despite its miniature size. But there’s a lot more than just reptile fossils out there to be discovered.

It turns out, animals don’t need to have bones for them to show up in the fossil record. Modern vampire squid are mollusks that live in the deep dark sea, and look like an octopus dressed as a Dracula dog for Halloween. Their eight arms are connected to each other with webbing, and they have little fins that look like floppy ears.

Basically, they’re adorable. Their name is pretty misleading though. Not only do they not drink blood, they aren’t even true squids!

Their closest living relatives are actually octopuses, which you might guess based on their eight-legged similarities. These two major orders are clumped together in a bigger clade called Vampyropods. The other soft-bodied relatives, like squids and cuttlefish, have eight arms and two tentacles, but researchers weren’t completely sure whether that difference is due to octopuses and vampire squids losing two limbs, or squids and cuttlefish gaining them..

And in 2022, researchers published their work on the oldest known relative of the Vampyropods that sheds a little light on this tentacle question. They published their brand-new fossil species, named Syllipsimopodi bideni after current US president Joe Biden. And it turns out the researchers didn’t have to go very far to find this species.

The fossil in question had been donated to the Royal Ontario Museum in 1988, but hadn’t been closely studied until now! At 328 million years old, this vampire squid is not only the oldest fossil record for this group, but it pushes back previously estimated timelines of the group’s origin by nearly 82 million years! This ancestor vampire squid also sports fins much like the modern vampire squid, and it’s the only known vampyropod with 10 suckered arms.

This fossil shows that the ancestors of vampire squids and octopuses did start with ten arms, much like their current living relatives, the squid and cuttlefish. But the vampyropods lost a couple limbs somewhere along the way . This discovery has revealed a significant amount of info about these amazing animals’ evolutionary past, providing a bit more insight into the distant split between modern ten-armed mollusks and the vampyropods.

But the jury’s still out on which group gives better hugs. Studying the form and function of organs is an important part of evolutionary research, as it helps us compare changes over time and between species. Unfortunately, paleontologists don’t usually have the luxury of studying these key features, since they’re too soft and squishy to fossilize.

Most of the time. But in rare cases, ancient organs do become fossilized, as in the case of the oldest heart ever found, described in 2022. This ancient heart is about 380 million years old and belonged to a jawed fish, the group of fishes most closely related to the land-dwelling vertebrates, like us.

And the heart wasn’t the only organ that was preserved from these fish fossils. Researchers also found the fish’s stomach, intestines, and liver, all of which is especially surprising given how rare it is for soft tissue to preserve at all. And much like with the lizard discovery, modern scanning technology was able to give us 3D images of these organs, including what the interior of these organs would have looked like, without having to break into the fossil itself.

As it turns out, these two-chambered hearts were pretty advanced, and their distinct S-shape helps tell the story of how and when the heads and necks of our fishy ancestors began evolving. Their organs were laid out similarly to those of modern sharks, with the heart situated near the mouth, just behind the gills, which may bring new meaning to having your heart in your throat. This is completely different from the hearts of jawless fishes, which are found way further back in the body.

But when some fishes began to evolve jaws, they developed more complex body forms to accommodate their changing mouths, including shifting their hearts forward. And this heart fossil shows us that this repositioning happened very early on! These types of discoveries really help us unravel some of the remaining evolutionary mysteries along the incredible transition from jawless fish all the way to modern jawed vertebrates, including us!

It’s clear that fossils have so much to teach us. And the more of these incredible preserved specimens we uncover, the more mysteries we can solve. From ten-armed vampire squids to Scottish lizards, 2022 was pretty stellar for the world of paleontology.

So let’s see what else we can find in 2023! We’ll keep bringing you more scientific discoveries in the next year thanks in part to your support. SciShow viewers like you help keep us around to share the latest, greatest, and weirdest research by becoming patrons of the channel.

As a SciShow Patron, you get more than the satisfaction that you’re supporting a show you enjoy. You get all sorts of perks as well! You could join the discord community, ask us your science questions in our Quick Question inbox, read our monthly newsletter, wear a shiny new pin every month, and even get your name on a SciShow video.

Those perks can all be yours with a click of the link down below in the description. Patrons can support this SciShow channel at patreon.com/SciShow, the SciShow Space channel at patreon.com/SciShowSpace, and the SciShow Kids channel at patreon.com/SciShowKids. You can support whichever SciShow channels speak to you.

And we’re so grateful to have your support for another awesome year. [♪ OUTRO]