A Trilobite With a Hyper-Compound Eye

Posted on October 16, 2021 by Brian H. Gill

It’s barely over two weeks since scientists at the University of Cologne published what they’d learned about a trilobite’s unique eye.

Their research vindicated an amateur paleontologist’s observations, and very likely will raise more questions than it answers.

That’s par for the course.

Answering a few questions and raising many more, I mean.

So is discovering something new. New to us, that is. This trilobite’s ‘hyper-compound’ eye last saw the light of day — or dark of the ocean floor — 390,000,000 years ago.

I had fun writing this, and hope you enjoy reading it. Who knew trilobite eyes could be so entrancing?

Welcome to the Devonian Period

Map of Earth in the Early Devonian, 390,000,000 years ago, from Christopher R. Scotese's PALEOMAP Project at scotese.com
(From Christopher R. Scotese, used w/o permission.)
(Earth, 390,000,000 years ago: early or middle Devonian, depending on who’s talking)

Dragons flight's 500 million years of climate change, via Wikimedia Commons, used w/o permission. (2004)Most of Earth’s land was in the southern hemisphere 390,000,000 years ago.

The climate was nice, if you like it warm.

We’re pretty sure that water near tropical beaches was around 86 °F, 30 °C, and didn’t get much cooler near the poles.

Wattieza forests were home to insects that flew and tetrapods that did well to galumph from one bit of water to the next.

Wattieza weren’t ferns, exactly, but they were much like today’s ferns and horsetails.

Don’t bother trying to remember all those names. There won’t, as I’ve said before, be a test on this.

We started calling this era the Devonian about two centuries back, after Roderick Murchison, Adam Sedgwick, Henry De la Beche and George Bellas Greenough didn’t agree about how old a bunch of rocks were.

What matters, sort of, is that Murchison and Sedgwick’s name for a particular slice of Earth’s history has been used ever since: Devonian. They named the era after Devon, British real estate between Cornwall and Somerset.1 Again, don’t bother with those names.

And never mind the plants that aren’t ferns and galumphing tetrapods.

This week I’ll be mostly talking trilobites. Mostly.

Good Times for Trilobites

Major trilobite clades summarized. Figure 6, 'The Evolution of Trilobite Body Patterning,' Nigel C. Hughes, Annual Review of Earth and Planetary Sciences (2007)
(From Nigel C. Hughes, used w/o permission.)
(Trilobite diversity: the trilobite family tree, from the Cambrian to the Permian.)

The Ordovican, Silurian and Devonian eras were good times for trilobites. Judging from how diverse the critters were, at any rate.

Agnostida, Asaphida and Ptychopariida trilobites had gone the way of Nineveh and Tyr by the early(ish) Devonian, 390,000,000 years ago. Although those two cities wouldn’t exist until after the most recent glacial melt, and I’m drifting off-topic.

Agnostida may or may not nave been trilobites. There’s ongoing discussion of that, partly because they look funny.

That’s how I see it, at any rate. They look like they’ve got two front ends. Most agnostid species didn’t have eyes.

Which reminds me. Trilobite eyes, in species with eyes, had calcite lenses.2

I’m not sure whether the main question is why trilobite eyes had calcite lenses, or why only Ophiomastix wendtii have calcite lenses today. O. w. is a sort of brittle star.

The Trilobite With a Hyper-Eye

Phacops geesops. The trilobite's eyes have 200 single 'outside' lenses each. Behind each 'outside' lens is a six-facet compound eye.
(From University of Cologne, used w/o permission.)
(Phacops geesops: Devonian trilobite with unique eyes.)

“Primordial ‘hyper-eye’ discovered”
PD Dr. Brigitte Schoenemann, Press release, University of Cologne (September 30, 2021)

“Trilobites of the suborder Phacopina had a unique eye in which about 200 large lenses in each eye spanned at least six individual facets, each of which in turn formed its own small compound eye / 40-year-old X-ray photographs by amateur paleontologist Wilhelm Stürmer show fossilized eye nerves.

“An international research team has found an eye system in trilobites of the suborder Phacopina from the Devonian (390 million years B.P.) that is unique in the animal kingdom: each of the about 200 lenses of a hyper-facet eye spans a group of six normal compound-eye-facets, forming a compound eye itself. In addition to the hyper-facetted eyes, the researchers, led by zoologist Dr. Brigitte Schoenemann at the University of Cologne’s Institute for Didactics of Biology, identified a structure that they believe to be a local neural network which directly processed the information from this special eye, and an optic nerve that carried information from the eye to the brain. The article, ‘A 390 million-year-old hyper-compound eye in Devonian phacopid trilobites,’ has been published in Scientific Reports….”

This trilobite’s eyes are “hyper” because a compound eye lay behind each outer lens. The inner compound eyes had at least six facets, in one or two rings. These eyes were exactly like nothing else we’ve discovered.

I think Wilhelm Stürmer’s trilobite was a Geesops sparsinodosus, but haven’t confirmed it. That’s one of five species in the Geesops genus.

Like all trilobites, the critters in the Geesops genus had clacite lenses in their eyes. The ones that had eyes, at any rate.3

Look at That!

From 'A 390 million-year-old hyper-compound eye in Devonian phacopid trilobites,' B. Schoenemann et al., figure 4. Structure of the visual unit of phacopid trilobites. Scientific Reports (September 30, 2021)
(From Schoenemann et al., via Scientific Reports, used w/o permission.)
(Trilobite eyes.)

You’re looking at:

  • (o) Schematic drawing of Ampelisca’s eye
  • (p) Schematic drawing of Geesops schlotheimi’s eye.

There’s more at “A 390 million-year-old hyper-compound eye in Devonian phacopid trilobites,” Science Reports. (September 30, 2021)

More than you may need, or want, to know.

Now, back to Wilhelm Stürmer and X-rays.

X-Rays and an Amateur Paleontologist

From 'A 390 million-year-old hyper-compound eye in Devonian phacopid trilobites,' B. Schoenemann et al., figure 3. Structure of the hyper-compound eye of phacopid trilobites. Scientific Reports (September 30, 2021)
(From Schoenemann et al., via Scientific Reports, used w/o permission.)
(More trilobite eyes.)

Stürmer’s day job was running the Siemens X-ray department. Off the clock, he was a paleontologist; doing field work and making x-rays of fossils.

“…To facilitate his palaeontological research, he bought a minibus, installed an X-ray machine within it, and between 1960 and 1986, travelled from quarry to quarry in the Hunsrück, part of the Central German uplands, and visited numerous collectors to investigate the faunas of dark-coloured slates, originally intended to be roofing tiles…”
(“A 390 million-year-old hyper-compound eye in Devonian phacopid trilobites,” B. Schoenemann et al., Scientific Reports (September 30, 2021))

At any rate, Stürmer had spotted and marked fossilized soft tissue in and near trilobite eyes. He said the filaments were probably optic nerves. Or maybe light guides, optical fibers.

But this was the 1970s.

Many professional paleontologists assumed that soft tissue doesn’t fossilize. Just teeth and bones and hard stuff like that. And they assumed that visual systems of animals don’t have optical fibers.

At the time, given the data they had, those were reasonable assumptions.

And, as it turns out, they were wrong.

Then, in the 1980s, scientists found deep-sea crab eyes with optical fibers. Recently, by my standards, scientists have been finding fossilized soft tissues. Sometimes with traces of the original organic matter.

Fossilized soft tissue is very rare, but it does exist.

Anyway, one of Stürmer’s heirs gave zoologist Dr. Brigitte Schoenemann his marked-up x-rays. She found that he’d marked structures that almost certainly include optic nerves.4

A Little History: Geissler Tubes, Lenard Windows and the Royal Society

From 'A 390 million-year-old hyper-compound eye in Devonian phacopid trilobites,' B. Schoenemann et al., figure 3. Structure of the hyper-compound eye of phacopid trilobites; detail highlighting Stürmer's red arrow. Scientific Reports (September 30, 2021)X-rays aren’t new.

No, that’s not quite what I meant.

X-rays have been part of this universe from the start.

An X-ray is electromagnetic radiation with a wavelengths that’s shorter than ultraviolet and longer than a gamma ray. We’ve known about X-rays since about 1895.

That’s when Wilhelm Conrad Röntgen noticed, measured and defined that particular sort of radiation. He had been experimenting with cathode rays from a tube designed by Philipp Lenard.

Lenard had been studying cathode rays, high-speed electrons from a the cathode in a vacuum tube, since 1888.

Scientists had been experimenting with cathode rays since 1857, when Heinrich Geissler invented the Geissler tube.

Assorted researchers tweaked the Geissler tube design between 1869 and 1875. We call one version the Crookes tube, maybe because William Crookes invented it. He’s English.

At any rate, Philipp Lenard invented Lenard Windows, thin metal surfaces that kept air out of cathode ray tubes but let radiation out. That let scientists measure cathode rays outside the not-quite-vacuum tubes.

Lenard also denounced Einstein’s work as “Jewish physics.” I’ll get back to that, briefly.

Röntgen analyzed, defined — and so “discovered” — X-rays in 1895 or thereabouts.

But Geissler and company had noticed them the 1850s.

Then again, William Morgan and Joseph Priestley arguably did the same in the 1780s. The Royal Society got a paper describing Morgan’s research in 1785.5

Now, about Lenard, Einstein and attitudes.

Seeking Truth and Other Options

From NASA/ESA: Galaxy UGC 9391.As I said before, Philipp Lenard denounced Einstein’s work as “Jewish physics.”

Back in 1905, when Lenard got his Nobel Prize and Einstein published his theory of special relativity, physicists had legitimate reasons for testing Einstein’s new ideas.

Testing, not denouncing.

By the 1930s, when Lenard published his “Deutsche Physik,” physicists had decided that general relativity made sense. Although it wasn’t until around the 1960s that they saw it as more than a sort of footnote to Newtonian physics.

Meanwhile, Lenard had asserted that relativity was a “Jewish fraud” and became Chief of Aryan Physics. I am not making that up.

I’m a Christian. And I’ve been talking about scientific stuff.

So, how come I’m not supporting “creation science”6 and condemning paleontology as a Satanic snare?

Basically, it’s because I’m a Catholic and think truth is important.

Even if I hadn’t decided to become a Catholic, I’d value truth. If I had my head on straight, that is. (Catechism of the Catholic Church, 2467)

And because I’m a Catholic, I must respect folks who have other faiths; recognizing that, like pretty much everyone else, they’re seeking truth. (Catechism, 839-843)

Then there’s the whole ‘faith and reason, science and religion, don’t mix’ viewpoint.

Again, I’m a Catholic: so I must recognize that although faith isn’t reason, faith and reason get a long fine, or should. And that seeking truth is a good idea. (Catechism, 31-35, 159; “Fides et Ratio;” “Gaudium et Spes,” 36)

Another point, also an important one. Being a Catholic means I must think that being anti-Semitic is a bad idea. Or being anti-anyone, for that matter.

On the other hand, it also means I must be against actions and beliefs that aren’t right. Like genocide, and that’s another topic. (Catechism, 2313)

Next Step: Educated Guesses

Dwergenpaartje's photo of trilobite Phacops rana's schizochroal eye. (October 2011) via Wikimedia Commons, used w/o permission.Figuring out why Phacopina trilobites had ‘hyper-eyes’ would be easier if we could study living Phacopina trilobites.

The last of those critters died about 360,000,000 years ago, give or take a bit; and the last trilobite of any sort that we know of died some 352,000,000 years back.

So studying hyper-eyed trilobites in their natural habitat isn’t an option. Or in laboratories, for that matter.

But scientists can make educated guesses about why they had such complex eyes.

“…The trilobite’s ‘hyper-eye’ may have been an evolutionary adaptation to life in low light conditions, Schoenemann believes. With its highly complex visual apparatus, it may have have been much more sensitive to light than a normal trilobite eye. ‘It is also possible that the individual components of the eye performed different functions, enabling, for example, contrast enhancement or the perception of different colours,’ the biologist said. So far, such an eye has only been found in the trilobite suborder Phacopinae: ‘This is unique in the animal kingdom,’ she concluded. In the course of evolution, this eye system was not continued, since the trilobites of the suborder Phacopinae died out at the end of the Devonian period 360 million years ago.”
(“Primordial ‘hyper-eye’ discovered,” PD Dr. Brigitte Schoenemann, Press release, University of Cologne (September 30, 2021))

The trick will be figuring out how to test those educated guesses. The good news there is that we’ve been learning a great deal about how vision and visual processing works.7

At least, I see that as good news; and I talked about truth and making sense earlier.

We may even learn why these ‘hyper-eyes’ are unique to that one suborder of trilobites.

Finally, the usual link list of stuff I’ve said before:

1 Plants, animals and names:

2 Trilobites, mostly:

3 More trilobites and crystal eyes:

4 Vindicating Stürmer:

5 A radiographical ramble:

6 Science and attitudes:

7 Miscellany:

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About Brian H. Gill

I was born in 1951. I'm a husband, father and grandfather. One of the kids graduated from college in December, 2008, and is helping her husband run businesses and raise my granddaughter; another is a cartoonist and artist; #3 daughter is a writer; my son is developing a digital game with #3 and #1 daughters. I'm also a writer and artist.
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2 Responses to A Trilobite With a Hyper-Compound Eye

  1. irishbrigid says:
    May 17, 2023 at 21:43

    Um, what? “And that animals don’t have optical fibers.”

    The Friendly Neighborhood Proofreader

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