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Go to Brilliant.org/SciShow to learn more. [ ♪ Intro ]. If I ask you to picture a hyena, you would probably picture it wading through the long grass of a savanna or trotting across the dry sands of a desert.

But new research published in the journal Open Quaternary reports the first fossil evidence of hyenas in the Arctic, during an ice age. Today, there are four species in the hyena family found in Africa and Asia. But hyenas were once some of the most widespread carnivores on the planet.

Paleontologists have described dozens of hyena species from Africa, Asia, Europe, and even the southern parts of North America. And researchers have long suspected that they made it to that last continent by crossing the Bering Land Bridge, a patch of land north of the Pacific Ocean that connects North America to Asia. It's submerged under the ocean today, but was exposed at various times in the past when sea levels were lower.

And lots of species crossed it to make their way into the Americas, including bison, mammoths, and humans. But no fossil evidence could place hyenas north of Kansas, until now. Well, technically, until several decades ago, because the two teeth described in the new study were actually discovered separately in the Yukon Territory of northwest Canada in 1973 and 1977.

They were safely stored in the collections of the Canadian Museum of Nature until a researcher from the University at Buffalo rediscovered some old notes about them and decided to take a closer look. The teeth are estimated to be between 1.4 and 0.85 million years old, which would put them in the middle of the Pleistocene Epoch, the time period most people are talking about when they say the ice age. While that makes sense for a land bridge crossing, the earliest hyena fossils in North America date all the way back to about five million years ago, which means there should be even earlier Arctic hyenas waiting to be discovered.

By comparing these teeth with other fossils from around the world, the researchers were able to identify them as belonging to the extinct hyena genus Chasmaporthetes. From other, more complete remains, we know these extinct hyenas were a bit less hunched than their living cousins, and were probably better adapted for chasing down prey, so scientists sometimes call them the running hyenas. And they likely played a key role in the Arctic ecosystem of the time because of their rare ability to eat and digest bone.

We don't know why they disappeared from North America, though. They were gone long before people arrived. Despite being widespread, fossils are not common, so they might never have gotten much of a foothold.

The continent already had dog species with bone-crunching abilities, though, those disappeared about 2 million years ago, so they probably didn't drive hyenas to extinction directly. The authors of this new paper think competition with an even more powerful hunter and scavenger might have done them in. You see, the ginormous short-faced bear appeared in the Americas around the same time those dogs went extinct, and it almost certainly would have been capable of kicking hyenas off their hard-won kills much like lions do today.

To know what really happened, though, scientists will need to get a better idea of when North America's hyenas arrived and went extinct, and what else was happening on the continent at the time, like, how the distributions of other animals and plants were changing. Which brings me to another bit of fossil news: research published this week in the Journal of Vertebrate Paleontology suggests that ancient crocodiles and alligators could provide valuable insights into past climates. The crocodyliforms are the group of reptiles that includes living crocodiles and alligators as well as their ancient kin.

For decades, it's been thought that the presence of these fossils in an area can tell researchers a lot about climates of the past. But the authors of this new paper point out that crocodyliforms exhibited a lot of ecological variety over time, including how they responded to changing climates. And that means they can tell us a lot about what was going on where they lived, but we have to be more careful in how we interpret their fossil record.

The new study looked at a particularly challenging time in Earth history: the transition between the Eocene and Oligocene Epochs around 34 million years ago. At that time, global temperatures and sea levels dropped dramatically, and many species of plants and animals went extinct, including a number of crocodyliforms, which at this point roamed as far north as England. This was a major event that set the stage for the cooler world that we live in today, and we have detailed records of what happened climatically during this period thanks to other lines of evidence like deep sea sediment cores.

So it's a great opportunity to see if different lineages of crocodyliforms reacted to temperature and sea level changes similarly. Now, it might seem like a no-brainer that crocs would struggle in a cooling world because they are poikilothermic animals: their internal temperature relies on the temperature of their environment. And previous research does indicate that crocodyliforms declined in general.

But this new study found that they didn't all weather the crisis the same way. By analyzing the crocodyliform fossil record, including some newly described fossils, the researchers found that some crocodyliforms did go extinct. Some were clearly impacted by the lower temperatures, while others were more affected by changing sea levels.

Other species survived by migrating to new areas, and still others were actually able to tough it out and survive in chilly northern regions, so the distributions of those species don't tell researchers as much about temperature fluctuations as previously thought. This doesn't invalidate using these animals to figure out climate and ecosystem changes, the authors say, actually quite the opposite. A better understanding of how different crocodyliforms respond to changes to temperature and sea level means that what we infer from their distributions will be more precise.

And that kind of information not only helps scientists understand how the world came to be as it is now, but can also allow them to make predictions about how today's ecosystems might react in the intense climate change happening to our modern world. Thanks for watching this episode of SciShow News! If you enjoy learning new things, and I assume that you do because you watched this video, then you might want to check out Brilliant.org.

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