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Hard Parts
A skeletal view of trilobites and other objets d’art
By David Quammen
Let me pose an intrusive but well-meant question: When you pass from this life, what will you leave behind? And don’t try to tell me you haven’t thought about it.
Will you leave children, each of whom carries a random half-share of your genes and remembers you (if you’ve been loving and lucky) with a nonrandom, full share of devotion? Will you leave a house with two BMWs in the garage, all paid for, gas tanks full? Will you leave your name on a marble headstone and on a couple of bitter ex-wives? Each of us yearns to generate some sort
of notable entity, an extension or token of our selfhood, that will hold its shape on the planet long after we’ve checked out. But differences of inclination and talent dictate a variety of forms. Will you leave your eyes to a blind person, your brain to science (assuming science wants it), the rest of your carcass to the local worm fauna, and your money to a church? Will you
leave curiosity and zeal in the minds of a handful of students? Will you leave a three-foot shelf of ponderous books with your authorial name on the spines — or, better yet, one perfect poem? Will you leave a towering granite building that you’ve designed, an honest wooden boat that you’ve built with your hands, a single delicate watercolor that you’ve painted? Will you leave
four minutes of happy saxophone solo on a cassette? Will you leave your baby shoes in bronze and your softball trophies in plastic? Whatever you leave, will it partake somehow of both beauty and permanence?
Then again, maybe we shouldn’t dwell on this issue. The trilobites of the Cambrian period never did, and look how well things worked out for them. They left only themselves — transmogrified into configurations of stone and still beautiful after 500 million years.
The comeliness of the average trilobite, I admit, is an arcane felicity that most of us rarely see. You wouldn’t notice it in the austere pen diagrams of a paleontology text, designed to show only the basics of trilobitic anatomy — the horseshoe head, the multisegmented thorax, the tail, and the three longitudinal lobes (one axial, two pleural, like a caterpillar with fancy
flanges) that give these extinct arthropods their name. But you can’t miss the aesthetic dimension if you browse through a certain book, simply called Trilobites, by an unusual man named Riccardo Levi-Setti.
Levi-Setti is a distinguished physicist at the University of Chicago. Whereas his day job includes the directorship of the Enrico Fermi Institute, his after-hours energies are devoted in large part to the collection, study, and photographing of trilobite fossils. His Trilobites is a coffee-table volume for people with odd tastes in coffee. It
includes a modest bit of scientific commentary and some taxonomic annotation, but mostly it’s a gallery of photos — adoringly large black-and-white portraits of Olenoides superbus, Elrathia kingii, Calymene celebra, and other species. Here is Paradoxides davidis, from a middle Cambrian deposit in Newfoundland, a
magnificent lanky thing with 20 thoracic segments, resembling the breastplate of a Mycenaean warrior-king. Here is Isotelus maximus, from the Ordovician period, smooth and symmetrical as a polished mahogany bowl. Here is Phacops rana, from the Devonian, with its rolled-up body and its gaping compound eyes. And here is
Dicranurus monstrosus, also Devonian, a fierce-looking little beast consisting of long wiry spines, so spooky that you’ll flinch when you turn the page. Although the shapes from the later periods are more elaborate, the oldest forms, from the Cambrian, have a special gravity. It’s amazing to contemplate that, 300 million years before the first
dinosaur evolved, the same Olenoides superbus portrayed on Levi-Setti’s page was scuttering along the bottom of a sea in what is now Utah.
Despite my own impulse to chatter about them, the bizarre variousness and the collective force of these photographs just can’t be put into words. So I ask you to take it on hearsay that, if trilobites can have their own Richard Avedon, their own Annie Leibowitz, their own Diane Arbus, Riccardo Levi-Setti is the guy. He has seen them so lovingly and photographed them so
knowingly as to turn arthropods into art.
No, that isn’t quite right. He has simply seen and photographed, artfully, what was there — what the trilobites themselves left behind. It’s no diminishment of Levi-Setti’s work to recall that, after all the eons of struggle and adaptation that the trilobites underwent, and then all the further eons of their adamantine endurance as fossils, taking these images was the easy
part.
Trilobites hold a special position in the history of life. They are the first great success story embodying (literally) an ingenious innovation in zoological anatomy, whose importance can hardly be overstated: the skeleton.
Fifteen hundred genera of the class Trilobita, encompassing about 10,000 species, are represented in the fossil record. Their survival spanned 350 million years, from near the start of the Cambrian period (almost 600 million years ago) until the end of the Permian. By these standards, they did well — and at their height, in the later Cambrian, they were a dominant ecological
presence in shallow marine environments. Levi-Setti makes no claim in Trilobites to encyclopedic coverage of the subject. He has concerned himself more, he says, with the pure visual appeal of his selection.
Part of what attracts him, as a photographer, to trilobites is that they “provide an endless source of form and composition.” By now he has been a serious trilobite amateur for more than 30 years. To some degree he has mixed his avocation, applying a touch of the physicist’s expertise as he coauthored such technical papers as “Trilobite Eyes and the Optics of Descartes and
Huygens.” But mostly his trilobite work has been a mode of “time travel,” his phrase, to eras far earlier and stranger than the seventeenth century of Huygens and Descartes. One of his goals, he confides, has been to demonstrate that “dinosaurs were not the only prehistoric animals that inspire awe and fascination. Trilobites tell us of an earlier world, perhaps less threatening,
when life on earth could still explode into a myriad of new, unseen, uncounted forms discovering their own way to survive.”
That last sentence is loaded with scientific content. The explosion to which he’s alluding was the “Cambrian explosion,” in paleontological parlance, and it didn’t involve only trilobites. It was the greatest episode of large-scale biological diversification that ever occurred — or as Levi-Setti writes, “the most revolutionary and far reaching single event in the history of
life.” The new way to survive included that ingenious anatomical innovation I’ve already mentioned, allowing animals of many different kinds to increase their mobility, their efficiency, their strength, their security against predators, and in consequence their evolutionary success. After the invention of the skeleton, life on Earth was never the same again.
Before the Cambrian explosion, back in Precambrian time, all animals were soft and gooey, like jellyfish. None of them possessed skeletons — neither the intricate external sort (exoskeletons) as later evolved by arthropods, nor the simpler external sort (shells) as in snails and clams, nor the internal sort (endoskeletons) as in vertebrates like us and in a few anomalous
invertebrates such as squid. Closely linked to the absence of skeletons (maybe as cause, maybe also as consequence) was the fact that animal evolution hadn’t progressed far. There did exist, by about 630 million years ago, an interesting assemblage of soft-bodied animals, flat creatures showing quilted or leaflike anatomy. But the Ediacaran fauna, as these creatures are now
collectively known, was nowhere near as diverse or successful as later phases of animal evolution, and it doesn’t seem to have led to the major faunal lineages that have prevailed throughout the past half-billion years. One estimable authority, Stephen Jay Gould, suspects that the Ediacaran animals “may represent a failed, independent experiment in multicellular life, not a set of
simpler ancestors for later creatures with hard parts.” We can’t confidently attribute that failure to the absence of skeletons, but it’s a plausible guess.
The age of hard parts began about 600 million years ago, and even the experts are still asking themselves why. Richard Fortey of the British Museum puts it this way: “The acquisition of shells and skeletons is one of the great milestones in the history of the biosphere, and the difficulty of finding a single neat explanation only adds to its fascination.” George Gaylord
Simpson, an eminent American paleontologist, has called it “a mystery to speculate about: Why and how did many animals begin to have hard parts — skeletons of sorts — with apparent suddenness around the beginning of the Cambrian?” The earliest skeleton-bearing animals seem to have been tiny things that lived unassumingly on the bottom of the sea, equipped with mineralized little
widgets that functioned nobody-knows-how. Formally these creatures are assigned the label Tommotian; less formally they’re called the small shelly fauna. Gould suggests that the Tommotian creatures might represent ancestors of more familiar animal lineages that “had not yet developed full skeletons, but only laid down bits of mineralized matter in small and separate places all
over their bodies.” On the other hand, he adds, they might be another failed experiment, ancestral to nothing we’ve ever seen.
Relatively soon after the Tommotian fauna, maybe 570 million years ago, the trilobites made their first appearance in the fossil record. By that time they had already carried the skeleton principle to a rather advanced stage — their carapaces were elaborately segmented, integrally articulated, and (except in a few species) hardened with calcium carbonate. With these
advantages, the trilobites would achieve what the Ediacaran and the Tommotian faunas hadn’t: vast success, as measured in their abundance, their diversity, their breadth of geographical distribution, their duration as a class, and — the measure of those other measures — their conspicuous representation as fossils in sedimentary rocks. Still another measure of their success, I
suppose, is popular appeal. No one has published a coffee-table book titled The Tommotian Fauna as Revealed in Their Itty Bits of Shell.
But trilobites weren’t the only group to turn hard-bodied during the early Cambrian. Various lineages of mollusks, brachiopods, and corallike animals were doing it too. The roughly simultaneous development of hard parts in those disparate lineages, and the rapid evolutionary diversification that hard parts made possible, figured importantly in the Cambrian explosion — which
was more of a building boom than an actual detonation, after all. To return to the mystery mentioned by Simpson: Why then? What triggered this revolution in skeletal engineering at the start of the Cambrian?
Although a single neat explanation is impossible, as Richard Fortey warned, one school of thought points to environmental changes. Those changes include the episodes of glaciation and thaw that alternately lowered and raised sea levels, the transgressions and regressions of seawater across continental shelves that attended each glaciation and thaw, the losses and gains of
shallow marine habitat that resulted from the transgressions and regressions, and — most suggestively — the increase in atmospheric oxygen, which may have been a biochemical prerequisite for building mineralized skeletons. “There is some evidence,” according to Fortey, “that it was not possible for calcium carbonate (or perhaps other skeletal minerals) to be deposited by living
tissues until the pressure of oxygen in the atmosphere had reached a critical level.” Increased availability of calcium carbonate was a boon to later paleontologists as well as to early sea creatures, because the stuff makes for nice fossils.
Whatever combination of factors did trigger the skeletal revolution, that revolution was immeasurably consequential. Without the appearance of hard parts in the early Cambrian, to be followed by vertebrate skeletons in the Ordovician, there would have been no fish, no amphibians, no reptiles, no birds, no mammals, no us, no paleontology, no fine art, no photography, and no
major-league baseball. As it is, we have everything but the baseball.
About eight years ago I paid a visit to a small private museum in a village in southern Germany, not far from a series of quarries renowned for their high-quality Jurassic shales. The village was Holzmaden. The shales were famed in paleontological circles as die Posidonienschiefer, named for a little shell-bearing marine creature that constituted
their predominant fossil, Posidonia bronni, which in turn had been named for the Greek god of the sea. Those shales, formed of fine-grain sediments that had settled onto a sludgy sea bottom about 170 million years ago, were smooth slabs of darkish-gray rock. In addition to their larding with Posidonia bronni, they
contained some spectacularly detailed fossils of other Jurassic sea creatures — ichthyosaurs and plesiosaurs (two groups of marine reptiles, both distinct from the dinosaurs), ammonites (spiral-shelled mollusks, like a chambered nautilus but now extinct), sea lilies (plantlike animals related to starfish), and many more. The little museum and its workshop, run by a family named
Hauff, were devoted to the extraction and display of these fossils. The Hauffs were perfectionists, sensitive to the sheer visual beauty as well as the scientific significance of the fossils they processed. Because the rock was so fine, because the conditions of preservation on that sea bottom had been so ideally gentle, and because the fossil preparations done in the Hauff
workshop were so painstaking, the results were extraordinary. Some of the ichthyosaurs contained what appeared to be embryos, delicate little skeletons within the skeleton of the mother’s abdomen. Others showed not just the hard parts, the reptilian skeleton modified for swimming, but also the faint impression of soft tissue, resembling the silhouette of a dolphin. Besides
adorning the walls of this little museum, Hauff preparations hang like Pre-Raphaelite paintings in some of the major public museums of the world.
I had been sent over by a little-known but very solvent magazine — it was a car magazine, actually, with a special reverence for German workmanship in any mode — to write an article about Museum Hauff. I spent one day there, gawking at the great dark slabs and visiting with a bright, likable man named Rolf Bernhard Hauff, third-generation purveyor of ichthyosaurs. He showed
me the workshop. We shared lunch and some excellent pilsner. He talked about his great-grandfather, who had come to Holzmaden as an industrial chemist; about his grandfather, who began the fossil-processing enterprise; about his father, who ran the museum until recently; and he mentioned his own abandonment of a doctoral program in geology to come home to the family business. He
also spoke with some passion about the extinction of species — not just of ichthyosaurs, not just of ammonites, but also the countless extinctions that humans have caused within recent centuries. He made a point with which I didn’t disagree: Humanity is presently perpetrating a mass-extinction event surpassing any such catastrophe since the death of the last dinosaurs. But that’s
another story — not the one I was chasing for the car magazine and not precisely the one I’m telling now.
I flew home, taking two souvenirs from the museum’s shop: a small slab of Jurassic shale and a book. The shale contained an ammonite fossil. The book, titled Das Holzmadenbuch, included many large black-and-white photographs of the Hauff ichthyosaurs, plesiosaurs, and sea lilies in exquisite detail.
Das Holzmadenbuch is in German. I can’t read a sentence of it but that doesn’t matter. It’s one of the most beautiful things I own.
The ammonite was a gift for the biologist whose husband I am. She keeps it now with her collection of other biological treasures. They all reside, carefully arranged over a swatch of red velvet, inside a dry aquarium that fills one bookshelf in our dining room. There’s the skull of a gray fox, the skull of a beaver, the shell of a nautilus, the lower jaw of a piranha from the
Amazon headwaters, the skull of a coyote from suburban Los Angeles, a three-point antler, a flake of beige rock containing a fossil fish, a vertebra from an Asian buffalo, a sand dollar, a few cowries, a few cone shells, the breastbone of what seems to have been a Canada goose, and a number of other skulls, jawbones, vertebrae, shells, and fossils. All of the animals in question
died natural deaths, so far as we know, except for the piranha, which I ate. The softest and most perishable item on display is the shed skin of a rattlesnake.
She has gathered and saved these things for two reasons: because she loves wild creatures and because she loves graceful shapes. Like Levi-Setti, she finds aesthetic delight in the forms by which evolution has met functional demands. Her collection consists almost entirely of hard parts, not just because an aquarium full of little carcasses in formaldehyde would stink up our
dining room, but because hard parts convey a structural certitude and a permanence that no flesh (not even beef jerky) can match.
This biologist whose husband I am happens also to be a graphic artist. At times she has worked as a scientific illustrator. During one of those times, she collaborated with the paleontologist Jack Horner on a monograph he was writing about hadrosaurs from the late Cretaceous. Her role, among others, was to create dozens of precise, richly textured drawings of cranial fragments
— drawings meant to serve other paleontologists in place of having the fossils themselves in their hands. The monograph was published as Cranial Morphology of Prosaurolophus (Ornithischia: Hadrosauridae), with Descriptions of Two New Hadrosaurid Species and an Evaluation of Hadrosaurid Phylogenic Relationships, a handsome volume not available at
Waldenbooks. Although the work had been exhausting and she was glad to finish, she remained mildly amazed that someone would pay her for drawing pictures of bones. On her own time, over a span of years, she had been doing the same thing for the sheer love of it.
She was invited to hang some of those drawings as part of a fine-art show at a good gallery in Butte, Montana. She put them up in a grid pattern, 24 organic shapes without explanation, and let people make of it all what they would.
Likewise I invite you to make of these facts and anecdotes what you will.
My own inclination is to take them at face value. It’s intriguing — and it really doesn’t need to be more than intriguing — that, for the past 570 million years, animal evolution has been creating skeletal structures in which can be seen, at least by some human observers, the qualities for which we normally turn to art: grace, harmony, beauty,
majesty, surprise, truth. The proof lies here on my desk: Das Holzmadenbuch, Cranial Morphology of Prosaurolophus, and Trilobites. To the same shelf of images I would add Ernst Haeckel’s classic book of lithographs, Art Forms in Nature, and a stunning volume of scanning electron microscope
photos recently published by Harvard University Press under the winsome title Identification Guide to the Ant Genera of the World. These are books to be seen, to be savored visually, not to be read. They express more about our planet’s half-billion-year saga of zoological diversification than could be packed into a thousand pages of purple prose. And
they do it largely by displaying the hard parts that various (I mean really various) creatures have left behind.
Look past their face value, though, and these images challenge us to address another question: What will we as a species leave behind?
Rolf Bernhard Hauff had an opinion. I recorded it in my notebook at the time, but found it unsuitable for my car-magazine story. For eight years I’d forgotten about it, until I pulled out the notebook last week. Having voiced his concern about human-caused extinctions, Herr Hauff wondered aloud how the era of modern civilization — in his caustic phrase, “our Coca-Cola culture”
— would appear to paleontological observers in the distant future. Inglorious, he thought. “They will know us by our Coca-Cola cans.” His eyes showed a glint of irony, then, as he remembered my assigned task for the Mercedes-Benz company. Accommodatingly, he added: “And perhaps a few automobiles.”
Herr Hauff’s comment carried an echo, probably unintentional, of a famous passage from T. S. Eliot. The lines appear in a poem titled “The Rock,” written 60 years ago with a certain late-modern gloom: “And the wind shall say: ‘Here were decent godless people: / Their only monument the asphalt road / And a thousand lost golf balls.'”
Me, I’m slightly more of an optimist. I’m hoping we might also leave a few libraries, full of poetry and science and the great art forms, including life.
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