Mad About Science: Leedsichthys

By Brenden Bobby
Reader Columnist
Sponsored by the Sandpoint Library

Try saying that one ten times fast: “Leeds-ICK-thiss”

A weird name for a truly weird fish. Leedsichthys was a colossal filter-feeding fish that swam the seas from the mid-to-late Jurassic to Cretaceous period, a time spanning roughly 100,000,000 years.

So much weird to cover in such a short span of time.

The Leedsichthys, with a human scuba diver to show scale.

Let’s start with that name. Like many archaeological firsts, the beast was named after its discoverer: Alfred Nicholson Leeds. This is pretty cool, because Leeds was an amateur paleontologist. How many people can claim they discovered a new species and had it named after them? Now how many of them just did that as a hobby?

So that’s where Leeds comes from. Ichthys is Greek for fish, and is actually the source for the Jesus Fish symbol. The next time you see one on someone’s bumper, you can proudly exclaim “ICHTHYS!” and pretend you’re Aristotle for a second.

So, for our etymology lesson for today, this giant fish is literally called “Leeds’ Fish.”

Pretty sure paleontologists are just trying to be cool and edgy when it comes to scientific names. Kind of like teenagers speaking pig Latin.

In the realm of weird, Leeds’ Fish doesn’t stop with its name. This thing was huge. Initial estimates put it at around 100 feet, about the length of a blue whale. While possible, in the century since its discovery, scientists think it was more likely around 50 to 60 feet long, but it’s still very hard to tell. Why?

The ocean isn’t incredibly kind when it comes to fossilizing things. For one thing, most creatures that evolve to live in the ocean have large amounts of cartilage; I imagine this helps keep their weight down and aids in buoyancy. For another, the ocean is water, and water is filled with bacteria that like to eat everything that doesn’t fight back. Preserving marine fossils is tricky, and finding them is often even trickier.

Luckily, when it comes to Leedsichthys, we’ve found enough fossils to approximately know what it looked like, and who it was related to.

Weird thing #3 (Note: not a hashtag…Unless you want it to be.): Despite my former comment about cartilage, Leedsichthys was actually a bony fish. It had large bony plates on its skull, and most of the head fossils that we’ve found are pretty bony. We believe it’s actually related to modern Gars, though the two look nothing alike. Leeds’ Fish was believed to have a large, rounded head while Gars are… Well, alligator fish.

Looking at a comparison of the two, you can see some similar anatomy (divided by an evolutionary gulf of 165 million years), yet it’s completely confounding how different they are. I mean, one is freakin’ huge!

Weird thing quatro: It was a giant animal that, like whales, was a filter feeder. It would take in huge amounts of microscopic plankton as it swam through the oceans. We aren’t sure if it spit the water back out or if it had some other mechanism, but given the filter we know it didn’t swim around eating other fish or aquatic dinosaurs.

That’s pretty amazing when you think about it, how microscopic organisms can feed some of the biggest creatures the world has ever seen for millions of years, and continues to do so to this day. How much of that do you figure one of these things would have to eat per day in order to grow?

Humpback whales eat anywhere from 4,000 to 6,000 pounds of plankton and small fish per day.

That’s just one whale!

I feel stuffed after a royale with cheese.

Leedsichthys probably had very few predators. Humans wouldn’t be around for a looooooong time, and based on the fossil record, we’ve only seen evidence of one creature committing an act of predation upon Leeds’ Fish, and that was the Liopleurodon (which means smooth-sided teeth). These things looked like giant terrifying alligators with fins and got up to around 20 feet long. That thing was bigger than my SUV.

Despite being an oceanic predator and having fins, the Liopleurodon was a reptile, unlike the Leedsichthys, which was a fish. There’s your summer action movie: “Giant Aquatic Reptile Vs. Giant Aquatic Fish, Boats Beware.”

There is evidence on the fossil record of an attack by another species, a form of strictly aquatic crocodilian, but the damage to the bone never healed at all, which led paleontologists to believe that it was made in an act of scavenging, rather than attack.

Crazy that people can infer that from bones older than our species.

We’re going to end the article with the end of Leeds’ Fish. It went somewhere, and it certainly wasn’t to our current oceans. We’d definitely notice, harvest and eat a fish that big.

Leedsichthys was ultimately undone by a changing climate. The largest members of their kind likely started dying off when they couldn’t sustain their massive size as water temperatures changed. They must have, over countless generations bred themselves to be smaller and smaller, split and diverged in their huge family tree until eventually their descendants would end up at the end of our fishing rods, floating around our aquariums and wowing us on TV. They would change form to become completely unrecognizable, far adrift from the ocean-ruling titans that dominated the seas for over 100 million years.

Now I don’t know about you, but this article has really given me a hankerin’ for a fish taco.

‘Til next week!