What period did Ammonite live in?

Ammonites: A Wild Ride Through Time (and What Their Shells Tell Us)

Ever stumble upon a perfectly coiled fossil and wonder about its story? Chances are, you’ve met an ammonite. These incredible creatures, related to modern squid and octopuses, aren’t around anymore, but their fossilized shells are like little time capsules, giving us a peek into ancient oceans.

So, when exactly did these guys live? Buckle up, because it’s a long story – a story that stretches back over hundreds of millions of years!

From Ancient Seas to a Rocky End: Ammonite Time Travelers

Ammonites first popped up way back in the Early Devonian period, around 410 million years ago. Imagine that! They evolved from these straight-shelled ancestors, kind of like how your quirky uncle might be related to royalty way back when. Over eons, they spread throughout the seas, becoming incredibly diverse and surviving quite a few bumps in the road – those extinction events that thinned the ranks of life on Earth. They really hit their stride during the Mesozoic Era, which included the Jurassic and Cretaceous periods. Think dinosaurs roaming the land, and ammonites ruling the waves!

The Jurassic and Cretaceous? That’s roughly a 140-million-year sweet spot for ammonites. We’re talking from about 201 million years ago to 66 million years ago. During this time, they went wild with different shapes and sizes. Some were smooth, some were spiky, some were even… well, we’ll get to the weird ones later.

The Big One: How the Ammonites Checked Out

Sadly, the ammonite party had to end. About 66 million years ago, at the Cretaceous–Paleogene (K-Pg) extinction event – you might know it as the asteroid that took out the dinosaurs – the ammonites also bit the dust. It was a bad day for almost everyone.

That asteroid impact? Total chaos. Darkness, freezing temperatures, and a complete disruption of the food chain in the oceans. Imagine trying to survive that! The ammonites, like many other marine creatures, just couldn’t hack it. There’s a tiny bit of debate about whether a few stragglers hung on for a little longer, but the fossil record basically says “game over” at that point.

Ammonites: Nature’s Dating Service

Here’s where things get really cool. Because ammonites were so abundant and evolved so quickly, they’re super useful for geologists. They’re what we call “index fossils.” Basically, if you find a specific type of ammonite in a rock layer, you know roughly how old that rock is. It’s like finding a vintage record and knowing exactly what year it came out – except we’re talking millions of years, not just a few decades!

Shell Shocked: Diversity and…Ammonite Romance?

Ammonites weren’t just all the same boring coil. Some went totally off the rails with their shell designs. These are the “heteromorph” ammonites I mentioned earlier. Straight shells, corkscrew shells, shells that look like they tied themselves in a knot – you name it, they probably tried it!

And get this: some ammonites were seriously into gender differences. The males (microconchs) were way smaller than the females (macroconchs). I mean, seriously tiny in comparison. So different, in fact, that scientists used to think they were different species! Turns out, the ladies needed that extra size for, well, lady stuff – like making baby ammonites.

From Tiny Terrors to Giant Sea Monsters

Ammonites came in all shapes and sizes, literally. Some were tiny, just a few millimeters across. Others? Absolutely gigantic. Most Jurassic ammonites were on the smaller side, but later on, things got supersized. The biggest ammonite ever found, Parapuzosia seppenradensis, could reach up to 3.5 meters in diameter! That’s bigger than a Smart car! And heavy, too – one of these bad boys weighed in at around 3500 kg.

Ammonites: More Than Just Pretty Shells

Even though they’re long gone, ammonites still fascinate us. Their shells are beautiful, sure, but they also tell us so much about the history of life on Earth. They’re a reminder that even the most successful creatures can disappear, and that the planet is always changing. Plus, they’re just plain cool. So, next time you see an ammonite fossil, take a moment to appreciate the incredible journey these creatures took through time. It’s a story written in stone, just waiting to be read.