Life Traces of a Master: A Tribute to Dolf Seilacher (Part I)

Every paleontologist has a Dolf story. Or at least it seems that way, especially for the past couple of weeks. One-by-one, like feather-duster worms poking their heads out of burrows, these stories have all emerged since the paleontological community heard the sad news that Adolf (Dolf) Seilacher died on April 26, 2014.

This manifestation of Dolf connecting with so many paleontologists over multiple generations symbolizes his ultimate and most lasting trace as a scientist and teacher. During his 89 years with us, he observed, discovered, pondered, argued, and argued more over the evidence that life left in the rocks of the past 600 million years or so. Much of this evidence is preserved as trace fossils, the vestiges of animal behavior that imparted their former presence as burrows, trails, tracks, feces, or other signs of life that almost never connect to their undoubted makers. Although Dolf was no slouch when pontificating on the bodily remains of ancient animals, either, it was with trace fossils where he truly excelled.

Seilacher-Ringgold-Georgia-TeachingAdolf (“Dolf”) Seilacher in his natural habitat, teaching students and professors alike when in the field. Notice how he was using paper and pencil as tools, which were instrinsic to his teaching methods. (Photo taken by Anthony Martin at Ringgold, Georgia in November 1997; Dr. Sally Walker (right) for scale.)

Dolf is often acknowledged as the founder of modern ichnology, the study of traces and trace fossils. Through this science, he could divine the original intents and purposes of trilobites, worms, clams, snails, shrimp, fish, pelycosaurs, dinosaurs, and many other former denizens of the earth. He accomplished this Sherlockian feat through the careful examination of ancient animals’ signatures, or the jots and tittles in those signatures: miniscule clues he reconstructed as entire manuscripts or symphonies that spill their secrets to those who pay heed. Dolf’s marvelous ability to spin fossil gold from carbonized straw is most of what inspired the many stories we paleontologists tell about him, although his personality was intrinsically linked to this, too (more on that later).

Nonetheless, what was truly remarkable about how Dolf worked his ichnological magic was his use of such old-fashioned methods. What were his primary tools for observing? His eyes, brain, pencil, paper, and drawing: no laser scanners (let alone “laser cowboys”), CT imaging, digital photogrammetry, rotating 3-D visualizations, or other modern technological tools were necessary for what he did. If someone had a time machine, they could have inserted Dolf into the late 19th century among the naturalists of those days, and he would have blended. Paradoxically, though, we 21st century paleontologists remember him as someone who surpassed all of us with his observational and intuitive skills. In this sense, he was a reminder of the readily available and valuable means we already possess that allow us to make sense of our planet and its vast history.


The Hand of Dolf, drawing onto a Middle Jurassic trace fossil (Zoophycos) to teach me and others how it was made by worm-like animal on a deep seafloor about 170 million years ago. (Photograph taken by Anthony Martin in Switzerland, 2003.)

Field-Notebook-Dolf-DrawingA composite trace (drawings plus writings) made by Dolf and me. The central figure is a visual explanation he drew for me, showing how one could figure out whether the Zoophycos-making animal was moving down below the sediment surface (protrusive) or moving up (retrusive) as it burrowed. Under his watchful eye, I then parceled out the details below. Field notes and drawings done on July 16, 2003, at the outcrop indicated in Switzerland.

Still, Dolf vigorously disagreed whenever anyone praised him as an “artist,” insisting he was a mere illustrator. With all due respect to his memory, he was wrong on this, and most of the paleontological community likewise rejected such statements. He was a fine artist and scientist, inseparably partnered in one person.

Trilobite-Grazing-SeilacherOne of many examples of how Dolf Seilacher was both a scientist and an artist, in which through drawing he interpreted a series of movements made by a trilobite along an Early Cambrian seafloor, more than 500 million years ago. (Figure from Seilacher, A., 2007, Trace Fossil Analysis, Springer: p. 27. If you support the unification of science and art, then you must get this book.)

Like all students of paleontology who took their first toddling steps in the 1970s-80s, I first learned of Seilacher through his papers. In those readings, I also soon realized the most effective way to discern the key points of his papers was to skip straight to his exquisite illustrations. Following a long tradition of German artist-scientists, such as Albrecht Dürer, he could accurately reproduce what might have been evident from a photograph of a trace fossil, or the specimen itself. Yet the salient qualities of a trace fossil were somehow more deeply understood – and thus better communicated – through his drawing of that specimen. His illustrations often impelled a viewer to take a second, third, or fourth look at a trace fossil, prompting more learning and often provoking marvel at what he perceived.

In some instances, he “cheated” in his drawing by using a camera lucida. This is a clever device that, through a prism, projects the image of a subject onto paper, where its proportions and details can be traced and thus captured accurately by the person drawing it. However, in Dolf’s drawings, his tracings were often fortified and embellished with dramatic black-and-white contrast rendered by pen and ink. Even better, these so-called “illustrations” were used as launching points for interpretive drawings that presented provocative explanations for how a trace fossil was made. Sometimes he even added a whimsical touch to these figures, such as placing a little windmill next to the cross-section of a marine-invertebrate burrow. Was this science, or was this art? Yes.

When did I first meet Dr. Adolf Seilacher, a person many other paleontologists and I would later casually call “Dolf”? It was on a Geological Society of America field trip in Cincinnati, Ohio, in the fall of 1992. In retrospect, I was extremely lucky with that first meeting to watch him perform his expertise – and it was always a performance – in the field, rather than the sterile confines of a convention hall or conference room.

On this field trip, we paleontologists were looking at outcrops in the Cincinnati area, which bear some of the best Late Ordovician fossils (about 445 million years old) in the world. Among these fossils are brachiopods, bryozoans, snails, clams, crinoids, and other animals – such as trilobites – that have no living relatives today. You can walk up to most of these outcrops, close your eyes, and scoop up a handful of these fossils. I had also done my M.S. thesis in this area, so it was a trip back to familiar territory, and some of the fossils felt like old friends: I mean, really old friends.

Yet thanks to Dolf, these body fossils were not the stars of the field trip that day. When we went to an outcrop with numerous U-shaped burrows preserved in its limestones – trace fossils the field-trip leaders called Rhizocorallium – I witnessed his scientific process at work. After we had all listened to the field-trip leaders give their interpretation of the burrows, he sat down next to one of these trace fossils, and for about 10 minutes, he quietly drew in his field notebook. Gradually, some of us gathered around to see what had attracted his attention and we watched him draw. Once he had a critical mass for what he considered an adequate audience, he began sharing his thoughts, a didactic lecture accompanied by more drawing as he explained his conception of how the burrows were made by small animals living in a shallow sea hundreds of millions of years before that moment.


A field-trip memory expressed through drawing: my recollection of what Dolf Seilacher illustrated in his field notebook in October 1992 while explaining a 445-million-year-old burrow and how it was made. The burrow is the main U-shaped structure, and the lines in between are spreite, showing where the former location of the animal’s burrow. In my illustration here, the animal – either a small arthropod or worm – adjusted its burrow downward into the sediment, then to the right. The behaviors recorded here may have been from the animal feeding, reacting to changes in the surrounding sediment, or a combination of ecological cues.

“You see, this so-called ‘Rhizocorallium’ is just the beginning of a Zoophycos,” he said with his patented Teutonic confidence mixed with professorial charm. He then drew more in his field notebook to show what he meant, a slow-motion visualization that delivered his lesson unambiguously. In his estimation, the U-shaped burrow, which had curved lines showing where the animal had moved it, was only the start of a more complex feeding probe. In Dolf’s assessment, one trace fossil (what ichnologists would call Rhizocorallium) could have thus easily merged into another form, one we would then assign another name (Zoophycos). This was a clarifying moment for me as a young scientist and educator about the communicative power of drawing. As a result, I have tried to use drawing in my research articles, books, and teaching ever since.

Based on this sample of one, I did not know then that Dolf’s “hijacking” of field trips was a time-honored tradition for him. Moreover, I did not know then that nearly every paleontologist who had ever disagreed with him, or presented a hypothesis he somehow found lacking, was running the risk of being subjected to an intense and aggressive interrogation that over the years was nicknamed “Dolfing.”

Dolf-Roland-IIW-Basel-2“Dolfing” in action, in which Dolf Seilacher would ask a series of penetrating questions as a follow-up to a helpful statement informing the “Dolfee” that she/he is completely wrong about everything ever. And just to show how no one was excused from potential “Dolfing,” regardless of their accomplishments and seniority, here he is subjecting Dr. Roland Goldring (1928-2005) to this treatment, just like he would have done to a well-meaning but woefully misguided graduate student. (Photograph by Anthony Martin, taken in Basel, Switzerland in July 2003.)

This harrowing critique was equal opportunity, in that he applied it to graduate students, senior professors, and everyone in between. For Dolf, getting the science right was far more important than honoring silly academic hierarchies. Although “Dolfing” occasionally caused discomfort in those getting “Dolfed,” these lopsided personal lectures often resulted in more details emerging, clearer explanations, and deeper understanding about a paleontological problem, meaning both the “Dolfer” and “Dolfee” learned more in the process. “Dolfing” became such a badge of honor, graduate students even wished for it to happen (“I’ve been Dolfed!”, they would say excitedly after surviving such an encounter.) One paleontologist friend of mine – after a colleague and I described “Dolfing” to her – said wistfully, “Oh…I want to be Dolfed!”

It was with much pleasure, then, that I got to watch “Dolfing” happen again during a field trip to the Cretaceous-Paleogene stratigraphic boundary in Recife, Brazil in 1994. This was when the “end-Cretaceous meteorite” hypothesis was still debated fiercely at professional meetings, with both proponents and skeptics fighting over the evidence. Preceding the field trip was a morning symposium on this contentious topic, much of which dealt with the 65-million-year-old boundary exposed at a nearby outcrop we would see later that afternoon.

In this session, one of the geologist speakers referred to a “massive” deposit of limestone as a tsunamite (a deposit formed by a meteorite-induced tsunami), which we were all supposed to see on the field trip. As soon as this speaker finished and the question-answer period began, Dolf sprang to his feet and declared, “You realize, of course, that if we find one burrow, it will completely negate your hypothesis.” Very simply, an animal would not have continued burrowing blithely on and in the ocean sediments while a gigantic sea wave washed over it. The speaker, taken aback by Dolf’s confident pronouncement, simply repeated that the deposit was “massive,” meaning it lacked any defined layering (bedding), and had no burrows. Ichnologists know better, though, as we sometimes translate “massive” as “There’s no bedding because it’s been completely burrowed, you ichnologically ignorant geologist!”

Dolf’s statement turned out to be a prophetic one. Later that afternoon, we field trip participants walked along the outcrop, looking at the layer of limestone interpreted as a meteorite-induced “tsunamite.” Sure enough, within ten minutes of inspecting, I found a burrow. Acting as a field-trip troll, I called out, “Oh Dolf, look what I found!” He came over and confirmed that yes indeed, it was a burrow, he quickly spotted dozens more, and the rest of the field trip was his for the taking. Many of the participants on the trip sat back and watched the fireworks, enjoyed the show, and we very nearly applauded at the end. Although I felt a little sorry for the field-trip leaders, it served as a good reminder that all you need is one burrow (or its factual equivalent) to upset a hypothetical apple cart.


Dolf Seilacher (left) delivering the intellectual equivalent of a bolide impact while standing in front of an outcrop containing evidence from the Cretaceous-Paleogene boundary. (Photograph by Anthony Martin, taken in 1994 near Recife, Brazil.)

After such a memorable conference and field trip, when would Dolf and I cross trails again? Not until 1997, and through my initiative and in my backyard, here in Georgia. But that story is worth its own post, one I promise to tell next time.

(To Be Continued)

Reference (Which is Also Quite Likely the Best Book Ever Done on Trace Fossils That Also Includes Some Incredible Artwork):

Seilacher, A. 2007. Trace Fossil Analysis. Springer, Berlin: 226 p.

Deep in the Dinosaur Tracks of Texas

Given the continuing public mania over dinosaurs, and recent important discoveries of yet more exquisite specimens of feathered theropod dinosaurs discovered in countries far away from the U.S. (here and here), it is sometimes easy to forget what has long been known about these animals, and right here in my own “backyard” (globally speaking).

Need to see some of the best dinosaur tracks in the world, and you live in the southeastern U.S.? Guess what: you can seen them in Glen Rose, Texas. Not China, Mongolia, Canada, Utah, or some other far-off land inhabited by strange people with unusual customs, but Texas. Saddle up! (Photograph by Michael Blair, taken in Dinosaur Valley State Park, Texas.)

So on July 22, just to jog my memory a bit, I flew from Atlanta, Georgia to the Dallas-Ft. Worth (Texas) airport, and only a few hours later was gazing upon dinosaur tracks accompanied by the burrows of invertebrate animals, both trace fossils having been made more than 100 million years ago. It was a fitting welcome to Glen Rose, Texas, a place famous for its dinosaur trace fossils since the 1930s, and where dinosaurs were an integral part of its culture long before it was cool, hip, and contemporary elsewhere.

In Glen Rose, Texas, the dinosaur tracks are so abundant, you can choose whether to see these just outside of your hotel room, or go to the hotel jacuzzi and pool. Naturally, I chose both. (Photograph by Anthony Martin, taken in Glen Rose, Texas.)

So just how did I end up in Glen Rose, Texas, looking at Cretaceous dinosaur tracks and invertebrate burrows? I was lucky enough to be there as an invited participant in an expedition sponsored by the National Geographic Society. I say “lucky” because luck was certainly a part of it, a fortuitous connection made through my writing a book about the modern traces of the Georgia coast. James (Jim) Farlow, a paleontologist at Indiana-Purdue University Fort Wayne (IPFW) and an associate editor with Indiana University Press, reviewed the first draft of my book, but he was also in charge of this dinosaur-track expedition to Glen Rose. Evidently he was impressed enough about what I knew about invertebrate burrows (or at least what I wrote about them) that he considered me as a possible member for his team of scientists, field assistants, and teachers on this expedition.

Dr. Jim Farlow, the world expert on the Glen Rose dinosaur tracks, having a reflective moment at Dinosaur Valley State Park near Glen Rose, Texas. What’s with the broom? He and other people in the expedition used these to sweep river sediment out of dinosaur tracks submerged in the river. In 100° F (38° C) temperatures. On the other hand, I just described invertebrate trace fossils, which was more of a job, not work. (Photograph by Anthony Martin, taken in Dinosaur Valley State Park, Texas.)

Thus when Jim asked me last fall if I would be interested in joining them to describe and interpret the Cretaceous invertebrate burrows that occur with the dinosaur tracks there, I jumped at the opportunity. The Glen Rose dinosaur tracksites, most of which crop out in the Paluxy River bed in Dinosaur Valley State Park, are world famous for their quantity and quality, and they connect with an important part of the history of dinosaur studies. Going there, experiencing these tracks for myself, and better understanding their paleoecological and geological context would be of great benefit to me, my students, and of course, you, gentle readers.

Just to back up a bit, and clarify for anyone who doesn’t know why these tracks are so darned important, here’s a brief background. In November 1938, Roland T. Bird, an employee of the American Museum of Natural History and a field assistant to flamboyant paleontologist Barnum Brown (the guy who named Tyrannosaurus rex), saw large, isolated limestone slabs with theropod dinosaur tracks in a Native American trading post in Gallup, New Mexico. Upon inquiring about the origin of these tracks, Bird was told they came from Glen Rose, Texas. So he set out in his Buick for Glen Rose to see for himself whether these tracks were real or not, and whether there were any more to see in the rocks around Glen Rose. The theropod track set in the town bandstand – pictured below – was one of the first sites that greeted him, and Glen Rose locals told him about the tracks in the Paluxy River.

Glen Rose, Texas, the only place in the world where the town bandstand has an Early Cretaceous theropod dinosaur track on display. Wish I could also tell you about all of those little holes in the rock with that track, but I can’t right now. Nonetheless, rumor has it they are burrows made by small, marine invertebrates that lived at the same time as the dinosaurs. (Photograph by Anthony Martin, taken in Glen Rose, Texas.)

Bird had hit the jackpot, the motherlode, the bonanza, the surfeit, the, well, you get the point. Not only did the Paluxy River outcrops contain hundreds of theropod dinosaur tracks – many as continuous trackways – but also the first known evidence of sauropod dinosaur tracks.

A couple of beautifully preserved theropod tracks under shallow water in the Paluxy River. Note that the track at the bottom also has a partial metatarsal (“heel”) impression, and look closely for the digit I (“thumb”) imprint on the right. Scale is about 20 cm (8 in) long. (Photograph by Anthony Martin, taken in Dinosaur Valley State Park, Texas.)

Funny how those “potholes” in the limestone bedrock of the Paluxy River have oblong outlines and form regular alternating patterns, isn’t it? Well, them ain’t no potholes, y’all. They’re sauropod tracks, and were among the hundreds recognized as the first know =n such tracks from the geologic record. (Photograph by Anthony Martin, taken in Dinosaur Valley State Park, Texas.)

The discovery of sauropod tracks was as huge as the tracks. Up until then, sauropods were assumed to have been so large that they could not support their weights on land and spent most of their time in water bodies. These tracks said otherwise, that these sauropods were walking along mudflats along with the theropods. In short, the trace fossil evidence contradicted the assumed story about how these massive animals moved. After all, trace fossils are direct records of animal behavior, and if interpreted correctly, can tell paleontologists more about what an animal was doing on a given day than any amount of shells, bones, and yes, even feathers.

Sauropod tracks from the main tracksite in Dinosaur Valley State Park, Texas. The sauropod was moving away in this view, and the trackway pattern is a typical diagonal-walking one, right-left-right. In parts of this trackway, both the manus (front foot) and pes) rear foot registered, something Bird noticed in 1938, his observation accompanied by more than a little bit of excitement. (Photograph by Anthony Martin, taken in Dinosaur Valley State Park, Texas.)

The details preserved in these sauropod tracks are also astounding. Most sauropod tracks I have seen elsewhere, in Jurassic and Cretaceous rocks of the American West, Europe, and Western Australia, are only evident as large, rounded depressions that you would only know are tracks because they form diagonal-walking patterns. In contrast, the Glen Rose tracks include all five toe and claw impressions on the rear feet (pes) and full outlines of the front feet (manus). The original calcium-carbonate mud in the shoreline environments where the sauropods walked, similar to mudflats I’ve seen in the modern-day Bahamas, is what made this exquisite preservation possible. The mud had to be firm enough to preserve these specific details of the sauropods’ feet, but not so soft that the mud would collapse into the tracks after the sauropods extracted their feet.

Beautifully preserved tracks, manus (top) and pes (bottom). Note the five toe impressions in the pes, which along with its size confirms that these were made by a large sauropod. Meter stick for scale. (Photograph by Anthony Martin, taken in Dinosaur Valley State Park, Texas.)

One sauropod trackway, preserved with a theropod trackway paralleling and intersecting it, was actually quarried out of the river and taken to the American Museum. Once there, its pieces stay disassembled for years, before Bird helped with putting the puzzle pieces back together so that it could be used as part of a display there.

Archival video footage of Roland Bird and his field crew working on the dinosaur tracks in the Paluxy River near Glen Rose, Texas. More about this tracksite and its role in the history of dinosaur paleontology is ably conveyed by Brian Switek here.

Photos at the visitor’s center at Dinosaur Valley State Park, showing the sequence of clearing (left) and extraction (right) of the limestone bed containing the theropod and sauropod dinosaur tracks. (Photographs taken of the photographs, then enhanced, cropped, and placed side-by-side by Anthony Martin.)

A lasting trace today of Roland Bird and his field helpers from the 1940s, in which they took out a sauropod and theropod trackway from this place and transported it to New York City. (Photograph by Anthony Martin, taken in Dinosaur Valley State Park, Texas.)

Other than some of the best-preserved Early Cretaceous dinosaur tracks in the world, one other claim to fame for the Glen Rose area, and not such a proud one, is its attraction to evolution deniers, a few charlatans who used the tracks to promote what might be mildly termed as cockamamie ideas. You see, Glen Rose is also the site of the infamous “man tracks.” These tracks are preservational variants of theropod tracks that – through a combination of the theropods sinking into mud more than 100 million years ago and present-day erosion of the tracks in the Paluxy River – prompted some people to claim these were the tracks of biblical giants who were also contemporaries of the dinosaurs. (Perhaps this is as good of a time as any to start humming the theme music for The Flintstones.)

Rare documentary footage of humans and dinosaurs interacting with one another during the Early Cretaceous Period, or the Late Jurassic Period. Whatever. Note the inclusion of other seemingly anachronistic mammals, too, such as the saber-toothed felid Smilodon. Perhaps this footage could be included in the curriculum of some U.S. public schools, providing a formidable counter to the views of 75 Nobel laureate scientists. Then we’ll let the kids decide which is right.

I will not waste any further electrons or other forms of energy by continuing to flog this already thoroughly discredited notion, but instead will direct anyone interested to a thorough accounting of this debacle to some actual scholarship here, summarizing original research by Glen Kuban and others in the 1980s through now that have laid to rest such spurious notions. Speaking of Mr. Kuban, I was delighted to meet him for the first time during while in Glen Rose (we had corresponded a few times years ago). I was even more gratified to spend a few hours in the field with him, discussing the genuinely spectacular trace fossils there in Dinosaur Valley State Park with these directly in front of us. Again, I’m a lucky guy.

The expedition was scheduled in Glen Rose for three weeks during late July through early August, but with so many commitments for this summer, I could only carve out a week for myself there, from July 22-29. Fortunately, this was enough time for me to accomplish what was needed to do, while also having fun getting to know the rest of the expedition crew – teachers, artists, videographers, laborers – and enjoying wonderful discussions (and debates) with colleagues in the field. The people of Glen Rose were also exceedingly welcoming and accommodating to us: we felt like rock stars (get it – “rock”?), and were feted by local folks three nights in a row during the week I was there. Many thanks to these Glen Rose for the the exceptional hospitality they extended to our merry band of paleontologists, geologists, river sweepers, or what have you.

You can’t see it, but I’m standing in a sauropod dinosaur track, which is a little deeper than the rest of the river bed. You also can’t see the invertebrate burrows that are in the limestone bedrock, which is fine, because I can’t show them to you yet anyway. But be patient: you’ll learn about them some day. (Photograph by Martha Goings, taken in Dinosaur Valley State Park, Texas.)

I can’t yet say much more about what I did during that week, as all participants signed an agreement that National Geographic has exclusive rights to research-related information, photos, and video unless approved by them. But if you’re a little curious about the daily happenings of the expedition (which just ended last week), Ray Gildner maintained a blog that succinctly touched on all of the highlights, Glen Rose Dinosaur Track Expedition 2012.

Still, I can say, with great satisfaction, that I did successfully describe and interpret invertebrate trace fossils that were in the same rocks as the dinosaur tracks. Hopefully my colleagues and I will have figured out how these burrows related to environments inhabited by the dinosaurs that walked through what we now call Texas.

All in all, my lone week in the Lone Star State was a marvelously edifying and educational experience, one I’ll be happy to share with many future generations of students and all those interested in learning about the not-so-distant geologic past of the southeastern U.S.

Group photo from the Glen Rose Dinosaur Track Expedition 2012. Names of all participants can be found here, but in the meantime, just sit back and admire those Dinosaur World t-shirts everyone is wearing. (Photograph by James Whitcraft or Ray Gildner: they can fight over who actually took it. Although, the automatic timer on his camera took the photo, so maybe it should get credit instead.)

Further Reading

Bird, R.T. 1985. Bones for Barnum Brown: Adventures of a Dinosaur Hunter. Texas Christian University Ft. Worth, Texas: 225 p.

Farlow, J.O. 1993. The Dinosaurs of Dinosaur Valley State Park. Texas Parks and Wildlife Department, Austin, Texas: 30 p.

Jasinski, L.E. 2008. Dinosaur Highway: A History of Dinosaur Valley State Park. Texas Christian University, Ft. Worth, Texas: 212 p.

Kuban, G.J. 1989. Elongate Dinosaur Tracks. In Gillette, David D., and Martin G. Lockley (editors), Dinosaur Tracks and Traces, Cambridge University Press, Cambridge, U.K.: 57-72.

Pemberton, S.G., Gingras, M.K., and MacEachern, J.A. 2007. Edward Hitchcock and Roland Bird: Titans of Vertebrate Ichnology in North America. In Miller, William, III (editor), Trace Fossils: Concepts, Problems, Prospects. Elsevier, Amsterdam: 32-51.