Seeing Through The Trilobite's Eyes: Strategies of History's Most Successful Animal
For the most part, fossils entirely consist of hard body parts- bones, shells, teeth, that sort of thing. On rare occasions we find preserved soft tissue, but those are few and far between, and even then we seldom find eyes. On trilobites, however, eyes are a dime a dozen. Or, more accurately, a dime a hundred.
The reason we've found so many trilobite eyes? Because they're not actually soft parts. They actually are better preserved in the fossil record than the legs, which were unarmored, since their legs were protected underneath their armored bodies. Trilobite eyes are formed of calcite (calcium carbonate) crystals. They were actually an extension of the trilobite's exoskeleton, so in many species they were likely hardly even a weak point. The use of calcite crystals for eyes is an interesting one- due to the optical properties of calcite crystals (ones exploited to this day by geologists for mineral identification purposes), trilobites likely would have seen doubled images of everything. It still seemed to work just fine, though- trilobites with eyes started showing up everywhere, and fast.
A schizochroal trilobite eye from Erbenochile erbenii. Note the rim overhanging the compound eyes- this was to shield them from the sun. The positioning of the two eye turrets also likely allowed in 360 degree vision. [Image source]
Like so many other biological innovations, trilobite eyes are the earliest examples of complex vision systems. Trilobites were the first animals to be able to see clearly. Their eyes occurred in vast variety, too: One pair of eyes offers 360 degree vision. Another pair are on stalks, allowing the trilobite to see above the mud it burrowed in. Another lived deep enough in the gloomy depths of the ocean that its eyes atrophied almost completely.
As the 300 million year history of the trilobites advanced, their adaptations grew more and more elaborate, and more and more species appeared. Trilobites could be found scattered throughout the food chain all across the world. Any biological niche that could possibly be filled by one of these crawling little critters was filled by them.
They were around, in the end, for twice as long as the dinosaurs, though they never existed alongside one another. The trilobites were around from the beginning of the Cambrian explosion. It took two mass extinctions to kill them- the Devonian mass extinction to drop their biodiversity into a single order, then the Permian mass extinction, the greatest of all the mass extinctions, to finish them off. Nothing we have accomplished comes close to this feat of survival, and if we end up even making it to a small fraction of their age, we can count ourselves champions of evolution.
Bibliography
Life: A Natural History of the First Four Billion Years of Life on Earth, by Richard Fortey
http://www.trilobites.us/trilobite-eyes.htm
https://io9.gizmodo.com/5145786/trilobites-the-greatest-survivors-in-earths-history
https://whyevolutionistrue.wordpress.com/2009/09/26/this-eye-saw-400-million-years-ago/
https://depositsmag.com/2016/11/01/unravelling-the-wonders-of-trilobite-eyes/
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Interesting stuff. But how would they taste in a stew? That is what I am wondering.
Good question! My first guess is that they'd fit somewhere in the spectrum of modern day crustaceans- somewhere along the shrimp-crab-lobster spectrum. Odds are, though, that most trilobites wouldn't be especially tasty- we definitely only eat some of the crab species out there for instance. Also, most trilobites were tiny, so there'd be essentially no meat on them.
That was all just my first thought, though. After a bit more thought, I recalled that they're more closely related to horseshoe crabs than proper crabs, and horseshoe crabs are essentially inedible, except for their roe, so there's a good chance they would have been inedible.
Very interesting. You seem to know a lot of interesting facts about them. That is very cool! I will follow you . Since you have some interesting content! have a good day.
Thanks, I'm glad you liked it!
ALWAYS SO INTERESTING! I always think they look dam cool as a kid.
Yeah, I love trilobites! My youngest brother was actually afraid of them as a little kid, though.
Haha, these things got me liking dinosaurs. I'm afraid of the huge crocodile like dinosaur though. The ones that lives underwater.
Icthyosaurus? Those things are pretty scary.
Yeeeeaaa.... Imagine ur plane crashed and ur stuck in the middle of the ocean. Deep blue sea scares me
These are such amazing creatures! My son bought a box in a toystore a couple of months ago. There was this case where we put water in, some food and the eggs... These pre-historic creatures suddenly appeared after a few days, as if there was a flashback to age of the dinosaurs. Incredible!
Sea monkeys, or the other critters you do that with?
Oh, you're right, these are indeed different, they're called triops, but still look pretty prehistoric to me..
Still really cool!
Thanks for teaching me something about trilobites I din't know.
Do we know if their blood was cuprous, like horseshoe crabs?
It's certainly possible- the use of hemocyanin instead of hemoglobin is common enough amongst crustaceans. There have been several studies of trace elements in lagerstatten preserved fossils that indicate it is likely they did. We don't know for sure, though.
Those eyes are scary...
The actual creature was only a couple inches long, usually!
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