Fossil Frontier

Scrimble 0:05
Hello everybody. I'm Scrimble and welcome to the eighth episode of my podcast, fossil frontier, a paleontology podcast brought to you by wknc 88.1

this show will be dedicated to talking about my favorite fossils and prehistoric phenomena, we're going to explore some of Earth's ancient treasures and uncover the stories that they have to tell. So if that's something you're into, you better lock in, because this week, we're talking about the ichthyosaur. This dinosaur survived over 150 million years and sparked a revolution that we can still see the effects of today.

Okay, So picture this. It's the Triassic period about 200 million years ago, and you're an ammonite, a shelled cephalopod in the open ocean searching for food. So far, evolution has treated you well. You've survived a mass extinction event, and you even grew a new, stronger shell for protection. Surely, nothing can hurt you now, or so you thought, because a new predator has just entered the scene.

It's the tholodus, a type of ichthyosaur with specialized teeth to crush the shells of any shellfish in its way, it easily makes lunch out of you with its low, densely packed, convex teeth. But unfortunately, that's not the end of this story, because as the tholodus swims on, it encounters an even larger foe, a bigger ichthyosaur has its sights set on the predator. It quickly attacks the tholodus and eats it, leaving almost no remains, just another exercise in the ancient oceanic food web.

As you can see, the many species of ichthyosaur were very successful, filling in many niches in their ecosystem. But how did they end up this way, and how did their evolution cause the ocean to completely change the way it operated forever?

So the story of the ichthyosaur starts right after the Permian-Triassic extinction, or the great dying about 252 million years ago. This extinction event killed many sea creatures, including over 80% of the crinoids and brachiopods and all of the trilobites. While the great dying was devastating for ocean ecosystems, it left a lot of space to be filled by new creatures, like the ichthyosaur, which evolved from the cartorhynchus, a land dwelling reptile who began to hunt in the sea for food. It then adapted to living in the ocean full time and became the first ichthyosaurus. This species quickly branched off and began evolving for different abilities, like the tholodus Crushing shells. In fact, the tholodus would cause the shellfish that it hunted to begin developing harder shells in response, creating an evolutionary arms race. Furthermore, there was the phalarodon, who looked more like sharks or dolphins and used its nimble body and incredible speed to chase after prey. These species evolved during the very important Mesozoic marine revolution, which greatly increased the complexity of ocean species and food webs by creating more prey and predators, as well as apex predators like the temnodontosaurus, another ichthyosaur, which grew up to 10 meters long and preyed on other predators, including other ichthyosaurs. In fact, ichthyosaur were so diversified that while some maintained their reptilian looks, others almost fully resembled fish, even though they weren't related to them at all.

So there they were, the ichthyosaur living all over the world, taking over the marine ecosystem and creating their own niches, because it's important to remember that before these guys came along, many of their adaptations were never heard of before, so they were the true revolutionaries of their era. But unfortunately, it wouldn't last for long.

This is because of the Triassic-Jurassic mass extinction, which wiped out many species of ichthyosaur, save for the more fish or porpoise like species. This event greatly reduced their diversity, setting up the conditions for their swift extinction. But if you think they went out that easily, then you don't know the ichthyosaur, because with an extinction event fresh on their heels and new competition from the Plesiosaurus and crocodiles, they still survived and even thrived for millions of years into the Cretaceous period. During this time, it was mostly the generalist species, the ones that ate a little bit of everything and the apex.

Predators that survived. New species popped up here and there, but they never quite reached the level of diversity that they once had in the Triassic Period. Eventually, after their over 150 million year run, they slowly began to die off until their final extinction around 93 million years ago,

but the question remains, how did they go extinct when they were once the most successful predators in the world?

Well, there are a few theories as to their extinction, from competition to climate change, but ultimately, it was their inability to diversify that caused their demise. As the world changed around them, with new ocean predators and climate patterns, they just couldn't keep up, and that's what led to the end of the ichthyosaur

but when these guys died out, other marine animals took their place in the niches that they created, and when those died out, new ones came in and took their place too. Even to this day, the complex behaviors and relationships between predator and prey that were started by the ichthyosaur can be seen in modern ocean animals.

Ultimately, the ichthyosaur was a force to be reckoned with for millions of years, creating their own niches and patterns that are still being replicated today. But in the end, it was the thing they were so good at diversifying that they ultimately failed to do when they needed it most, which caused their extinction. But these guys were a key part in the Mesozoic marine revolution, even if they didn't see the actual Mesozoic Era to its end, their lineages rise and fall highlight the complex interplay of evolutionary innovation and environmental pressures on Earth, and even if they didn't stick around the revolution and legacy lives on.

Thank you for listening to the eighth episode of fossil frontier. This has been a wknc podcast. Good night, and I love you.

The audio used in this podcast was Song Thrush, nature, field recording garden atma recorded by Garuda 1982 under Creative Commons license.

Transcribed by https://otter.ai