Slow Worms at Wormsloe

Every time I visit the Georgia coast, traces that have been there all along make themselves apparent to me for the first time. One would think these personal discoveries would stop happening after more than fifteen years (on and off) of going to that coast and studying its traces, especially after writing a 700-page book about them (Life Traces of the Georgia Coast). Nevertheless, they happen, and when they do, these insights underscore the importance of doing regular field work in the same places. However familiar it might seem, there’s always something different you missed previously while there. So before each trip to the Georgia coast, I make sure to become wide-eyed and expectant, rather than jaded and bored.

Intersecting-Worm-Trails-Wormsloe-1Mysterious trails in a sandy road, crossing and re-crossing paths. What could have made them? And why so many? If curious, read on. If not, I’ve heard there are some Web sites with pictures of cats that require your viewing. (Photo by Anthony Martin, taken at Wormsloe Historic Site, Georgia.)

The latest example of this exercise in place-based humility happened just a little more than a week ago during a short time at Wormsloe Historic Site, south of Savannah, Georgia. Sarah Ross, the President and Director of the Wormsloe Institute for Environmental History, invited me there to give a nature walk and talk to guests at a private event on the evening of Saturday, October 11. After the walk and talk (which was a big success), we all watched lovely and enlightening story-telling by a local Gullah/Saltwater Geechee performance group (The Saltwata Players), had a delicious dinner, partook in great conversations fueled by nice wine, and I got to sell and sign copies of the book I mentioned earlier. In short, the proverbial good time was had by all.

My wife Ruth and I stayed in a guest cabin on the grounds of the former plantation that night; in morning, I got up just before dawn to start tracking and otherwise looking for traces. In the dimness, only a few raccoon and deer tracks stood out on the sandy roads, as well as a pile of scat that had been inside a feral hog only a few hours before. A nearby salt marsh beckoned, and because the low tide had exposed its banks, I walked out onto a nearby dock for better views of its exposed surfaces. The dark mud was pockmarked by thousands of holes, most belonging to mud-fiddler crabs and other burrowing invertebrates that call this place home.

Salt-Marsh-WormsloeA small part of the salt marsh at Wormsloe Historic site where it abuts the maritime forest, and during low tide. See all of those holes in the foreground? I wonder what those might be?

Salt-Marsh-Wormsloe-BurrowsEach and every one of these holes is the burrow of a small marine-adapted animal – fiddler crabs, polychaete worms, and more. In other words, an ichnologist’s dream come true. (Photos by Anthony Martin.)

Less than a hundred meters from this dock is the home of Craig and Diana Barrow. Mr. Barrow is the ninth-generation heir of Wormsloe, but donated its grounds to the state of Georgia so that it could become a natural laboratory for researchers studying its environmental history. Ruth and I were acquainted with the Barrows from two previous visits to Wormsloe, and Craig – a great outdoors enthusiast – had eagerly given us personal tours of the woods, fields, and marshes on the property.

Having hunted for most of his life, Craig is a good tracker, and we’ve had in-depth discussions on animal-track forms, trackway patterns, aging of tracks, scat, and related topics. I find these conversations refreshing. Academic hierarchies, journal articles, impact factors, grant amounts, and other dull concerns become meaningless when you’re in the field with experienced naturalists. Here are some traces. Let’s learn.

Thus as the dawn light started to illuminate the maritime forest, I was not surprised to see Craig already outside his home, and to have him enthusiastically invite me to hop onto a golf cart with him to go look for tracks. He had already been out earlier on one of the sandy roads near his house and spotted three red foxes, so he wanted to check on whether their tracks were there, too. Within minutes, we arrived at the spot where he saw the foxes, and we quickly confirmed his sighting by identifying their fresh tracks in the loose sand on the road.

That was also about when Craig asked me a question that I answered wrong at first, then corrected once I gathered more data. You know, like any good scientist should. His question was “What’s this?”, and he was referring to a thin, shallow, and meandering groove in the sand. “Beetle trackway,” I answered instantly, without looking too closely. Then I squatted to show him the tiny tracks that would be on each side of the groove, where I imagined the beetle had dragged its abdomen.

Worm-Trail-Wormsloe-4Oh look, a beetle trackway, and right next to the tracks of a red fox (Vulpes vulpes)! How exciting! Gee whiz, I gosh-darn love science! Isn’t it neat? Wait a minute: what’s that earthworm doing at the end of a beetle trackway? (Photo by Anthony Martin, taken at Wormsloe Historic Site.)

That’s when I realized there were no tracks on either side of the groove. This was a trail made by a legless animal. “Wait a minute, this isn’t from a beetle,” I said. “Maybe a worm?” And by “worm,” I meant earthworm, but my small amount of experience with identifying earthworm traces made me a little uncomfortable with elaborating further on that idea. After all, I didn’t want to appear too ignorant about such common animals, and ones I had written about in both my book and on this blog (Of Darwin, Earthworms, and Backyard Science and Darwin, Worm Grunters, and Menacing Moles).

Fortunately, an earthworm saved me from further embarrassment by having the decency to be at the end of one of these trails, moving and otherwise actively demonstrating how these traces had been made. With our eyes and brains properly (and instantly) trained by this association between trace and tracemaker, Craig and I glanced around us. We were rewarded for looking, and promptly became astonished. The road was criss-crossed with hundreds of earthworm trails for as far as we could see, and most of them had living worms at their ends.

Even better, a few of these trails connected to open, small-diameter vertical burrows. My second insect-biased mistake of the morning was to initially identify these burrows as the shafts of halictid bee burrows. However, too many earthworm trails connected directly to these holes. Again, like any good scientist should in the face of contradictory evidence, I changed my mind. These traces were also from earthworms, and showed where the earthworms exited their subterranean homes.

Vertical-Burrow-Worm-WormsloeEarthworm burrow marking exactly where it left its home for the surface world, and intersecting a trail. (Photo by Anthony Martin, taken at Wormsloe Historic Site.)

What really surprised me, though, was the length and complexity of the trails. These were not simple meandering paths, but complicated records of earthworm decision making. These worms may have been slow, but their traces certainly weren’t dull.

Worm-Trail-Wormsloe-2This trail was made by one earthworm that moved from right to left. The pointed grooves on either side of the main trail are from where its “head” and “tail” ends probed the sand.

Worm-Turning-Wormsloe-1Here’s an earthworm in action, moving from right to left. Compare this to the next photo to see how movement of both its forward and rear ends changes the trail, putting newer traces on top of the previously made ones.

Worm-Turning-Wormsloe-2See what I mean? Small but multiple movements from both ends of a worm – as well as its middle – make this much, much more than just a “worm trail.” So don’t be calling it that. (Photos by Anthony Martin, taken at Wormsloe Historic Site.)

Yes, I know, there’s a bigger question that looms over all of this ichnological minutiae: Why were so many worms on top of the ground, instead of in it? What could have caused hundreds of them to leave their homes and risk the perils of dehydration and predation at the surface?

I speculated aloud that their mass stranding might have been related to vibrations imparted to the road. After all, Charles Darwin had noted how earthworms reacted like this to subsurface vibrations, associating these with their mortal enemies, burrowing moles. This was independently verified by “worm grunters” of the Appalachians, who took advantage of earthworm-mole co-evolution to get bait for their fishing. Craig backed up my idea by saying that he had grated the road the previous day. So perhaps the vibrations from his vehicle and activities had persuaded the earthworms to come up and out of the ground.

Later, though, I wondered whether another much larger stimulus had invoked such aversive reactions in the earthworms, one that persisted for more than a day after the road had been grated. What else could have done this, impelling these earthworms to flee, much like urban hipsters sensing the first few notes of a nearby Justin Bieber concert, and leaving spilled PBR’s in their wake?

Then it came to me. A full moon that weekend had caused higher tides than normal in the area, ranging from 2.6 to 2.9 m (8.5-9.6 ft). As a result, saltwater probably crept high enough in the soil profile to trigger a collective reaction in the earthworms, which do not fare well once salty water starts filling their homes. Yes, that would do it.

Salt-Marsh-WormsloeHi, terrestrial earthworms. Remember me? I’m a salt marsh with 2.5-3 m high tides, right next to where you live.

Assuming this hypothesis is correct, what we saw there on that sandy road of Wormsloe Historic site was a great example of a marine ecosystem forcing animals living in a terrestrial ecosystem to drastically change their behaviors. Best of all, these animals made a suite of traces that reflected this sudden change in their behaviors. If preserved in the fossil record, such trails and burrows might even be recognizable to geologists and paleontologists, some of whom are quite fond of calling every invertebrate trace fossil a “worm burrow” anyway.

All in all, this field experience at Wormsloe taught me a lesson about keeping my senses open to noticing and wondering about traces wherever I go, as should you, gentle readers. Look for those moments when the worm has turned: they will teach you something new.


Fossil Visions in the Two Medicine

(This post is the third in a series of three about my field work on the trace fossils of the Late Cretaceous (75 million-year-old) Two Medicine Formation, which I just completed a week ago. My previous two posts, which mostly explain the scientific importance of this field work, are Tracing the Two Medicine and Burrowing Wasps and Baby Dinosaurs.)

Looking back on three weeks of field work in the Late Cretaceous Two Medicine Formation, one of the realizations I had was how long it took before I could see more of what was there. The most frustrating part of this realization, though, is also knowing that I still missed plenty. This mix of satisfaction and unease is the duality that often accompanies the birthing and honing of search images, a visual training that enables paleontologists to find the fossils we want to find whenever we walk around a field site and look.

Tony-Martin-Searching-Fossils-Two-MedicineThis outcrop of the Late Cretaceous (75 mya) Two Medicine Formation in central Montana is chock-full of fossils, but you might not know that from just looking at this picture. That means you have to get out onto the rocks and look closely for them, but first make sure you have the right search images for finding them. (Photograph by Ruth Schowalter.)

The Two Medicine Formation in particular presents a major challenge for cultivating search images because of the variety of fossils in it. Moreover, most of these fossils require very different search images. For example, over my three weeks of prospecting, I looked for the following fossils:

  • Plant root traces
  • Invertebrate burrows and tracks
  • Insect cocoons and pupal chambers
  • Dinosaur tracks
  • Dinosaur nests
  • Dinosaur eggshells
  • Dinosaur coprolites
  • Dinosaur bones
  • Dinosaur toothmarks (on dinosaur bones)

I also found a few other fossils I didn’t expect to find, but there they were. This happenstance served as a good reminder that simply going out into the field with a bullet-point checklist of what you think you’ll find (like what you just read) isn’t good enough. In other words, you also need to see what’s there, rather than just what you expect to be there.

On top of looking for these fossils, I’m a geologist, too. This means I also paid close attention to the rock types in the Two Medicine Formation – sandstones, mudstones, conglomerates, limestones – and their physical sedimentary structures – such as cross-bedding or graded bedding. Moreover, Two Medicine strata in the field area are not necessarily in their original horizontal positions, but instead are bent, tilted, and faulted in places. This is where training I had in structural geology – the study of how rocks were deformed – came in handy.

Geologic-Anticline-Two-MedicineOriginally horizontal sedimentary strata were bent upward into a fold, which we geologists normally call an anticline. In such folds, the fossils in the center of the fold are geologically older, whereas the fossils on the outside of the fold are younger. That is, unless the strata were overturned, in which case we’d call it antiformal syncline, then the fossils would have the opposite age relations. Thank you for teaching this, structural geology professors! (Photograph by Anthony Martin.)

Geologic-Fault-Two-MedicineIt’s not my fault, so we’ll blame the Two Medicine Formation for this breakage of sedimentary rocks. Based on how it looks like the fault block on the right moved up relative to the one on the left, I think this is a reverse fault, which – like the anticline and almost everything else on earth – was caused by plate tectonics. (Photograph by Anthony Martin.)

Thus whenever I stepped into the field each day, I had to rapidly switch, combine, or otherwise tap into different types of vision. I’ve often jokingly referred to my ability to spot traces and trace fossils in the field as “ichnovision” (my most likely comic-book hero superpower), and my geological training means I’m using “geovision.” Yet in the Two Medicine Formation – a rock unit world-famous for its dinosaur bones and eggs – I also had to use “osteovision” (seeing fossil bones) and “oovision” (seeing fossil eggshells). These forms of fossil vision are tough for me, as I never see dinosaur bones or eggshells in the southeastern U.S., which is where I spend most of my time in the field.

So just to give you an appreciation of what it was like during my three weeks of looking for fossils in the Two Medicine Formation, here are a few photos and brief descriptions of some fossils I found. To be sure, there was much more than this, but at least I can share these for now so you can begin to see through my eyes.

Fossil-Plant-Root-Traces-Two-MedicineThese odd-looking structures weathering out of an outcrop in the Two Medicine Formation had variable diameters, central cores filled with calcite, and branched in places. I’m fairly sure these are fossil plant root traces, but they were the only ones I saw like them during three weeks of field work. So I remain a little skeptical of my identification, and remain open to their being some geological features I’ve just never seen before then. (Photograph by Anthony Martin.)

Horizontal-Burrows-Two-MedicineThese are longitudinal sections of horizontal burrows in a sandstone, showing off their beautifully expressed internal structures called meniscae. Meniscae are formed by burrowing invertebrates – such as beetle larvae or cicada nymphs – that pack their burrow with sediment behind them as they move. This means the convex side of the meniscae points in the direction the animal was moving. Go ahead, apply that principal and see what you figure out for yourself. (Photograph by Anthony Martin.)

Vertical-Burrows-Two-MedicineThese are more invertebrate burrows, but they’re vertically oriented, meaning you only see their circular cross-sections when you look at the top bedding-plane surface of this sandstone. Notice how some of them are open but others are filled with sandstone. The open ones were filled with mud originally, but that softer sediment has since weathered out, leaving them hollow. (Photograph by Anthony Martin.)

Limulid-Tracks-Two-MedicineThese are invertebrate tracks, and they form a distinctive enough pattern that I recognized them as a trackway, where the trackmaker (probably a freshwater horseshoe crab) turned. But they’re also preserved in positive relief (“sticking out”) because the original traces were filled with sand, which made a natural cast of the tracks. Think about how you have to reverse your concept of tracks to recognize these. (Photograph by Anthony Martin.)

Fossil-Cocoons-Two-MedicineOne of my main research interests in the Two Medicine Formation is its insect trace fossils, which include some of the best-preserved fossil insect cocoons I’ve ever seen in the geologic record. See where the patterns of their original weaves? These cocoons were likely made by wasps – or something acting very much like wasps – 75 million years ago. I usually prospected for these cocoons by looking for their distinctive oval shapes on the ground, then looked more closely for the weave pattern. (Photograph by Anthony Martin.)

Fossil-Cocoon-in-situ-Two-MedicineThis is what a fossil insect cocoon looks like in an outcrop. Sometimes a burrow would be connected to the cocoon, showing where the original mother insect dug a brooding chamber for its intended offspring. (Photograph by Anthony Martin.)

Dinosaur-Bone-Two-MedicineA rare piece of dinosaur bone that actually looks like a bone, even to an untrained eye. Although this one is white, the dinosaur bones in the Two Medicine Formation varied wildly in their colors. So spotting these fossils was more a matter of looking for both a shape and texture that translate into “bone.” (Photograph by Anthony Martin.)

Fragmented-Dinosaur-Bone-Two-MedicineThis is more what most dinosaur bones looked like when I found them in the field area. You probably spotted the big chunk right away, but how about the smaller ones that tend to blend in with the non-dinosaur-bone rocks around them? (Photograph by Anthony Martin.)

Adult-Hadrosaur-Track-Two-MedicineHere’s another example of how fossil tracks are not like modern ones in size, shape, and how it’s preserved. This is a three-toed dinosaur track (probably made by a hadrosaur), but it was originally made in mud, then sand filled in the track-sized hole to make a natural cast, which 75 million years later weathered out so that it’s sitting by itself on the eroded surface of a mudstone. What’s the scale? My boot’s a size 8 1/2 (men’s). Yes, I felt a little inadequate.  (Photograph by Anthony Martin.)

Hadrosaur-Track-in-situ-Two-MedicineWhat does a natural sandstone cast of a dinosaur track look like when it’s still in outcrop? Look for a lump on the bottom of a sandstone bed. From a side view, you might then see a couple of “toes” pointing in one direction, like in this one: the central toe is to the left and one of the outer toes is on the side, clser to you. Note how the sandstone bed also has a few open invertebrate burrows in it, too. Ichnobonus! (Photograph by Anthony Martin.)

Hadrosaur-Coprolite-Two-MedicineCheck out this big piece of, well, dinosaur coprolite. These trace fossils contained blackened (carbonized) wood fragments that originally passed through the gut of a dinosaur (probably a hadrosaur), and were later cemented by calcite. But you had to look at them doubly, because some of these trace fossils included their own trace fossils made by insects, namely dung beetle burrows. (Photograph by Anthony Martin.)

Field-of-Feces-Two-MedicineYou’ve heard of ‘Field of Dreams’? This is a ‘Field of Feces.’ The ground here is adorned with dinosaur coprolites, which are weathering out of the mudstone and breaking apart on the surface. This serves as a good example of how once you know what the dinosaur coprolites look like in this area, you’re less likely to just walk by them, singing “Where Have All the Coprolites Gone?”. (Photograph by Anthony Martin.)

Eggshell-Fragments-Two-MedicineThe Two Medicine Formation is famous for its dinosaur eggs and babies, but even more common than those are bits and pieces of dinosaur eggshells. These show up as black flakes on ground surfaces and sometimes in a rock, which you then must distinguish from all other black flakes that are not dinosaur eggshells. (Photograph by Anthony Martin.)

Find-Dinosaur-Eggshell-Two-MedicineCan you find the dinosaur eggshell in this photo? I’ll bet the answer was “yes,” but I made it a little easier for you by cropping the photo, placing the eggshell near the center of the image, and oh yea, showing you what typical eggshells look like in the previous photo. Now think about detecting this bit of eggshell from a standing height and while walking. (Photograph by Anthony Martin.)

After viewing the photos and reading the descriptions, do you think you could recognize each of these fossils if you were somehow magically transported to the Two Medicine Formation in Montana?

The likely answer to that question is, maybe, maybe not. For instance, despite all of my previous paleontological and geological field experience, it took me about two weeks of being in the field before I started accurately identifying dinosaur bones and eggshells. This humbling situation gave me a renewed appreciation for the people who regularly work in the Two Medicine Formation, but also imparted a lesson about taking the time to learn from misidentified burrows, cocoons, coprolites, bones, and eggshells in it. Most things I saw in the Two Medicine were not these fossils, meaning my ways of seeing had to become more discriminating over time.

Thus given enough practice and “dirt time” seeking fossil in the field and correcting your mistakes – preferably with an expert peer-reviewing your finds beside you – the fossil visions will come to you. Then, next thing you know, you start noticing more of what you didn’t see before, expanding your consciousness of the lives that preceded your own.

* * *

Many thanks to Dr. David Varricchio for inviting me to be part of his NSF-sponsored research project in the Two Medicine Formation this summer, and by extension, my deep appreciation to Montana State University and Museum of the Rockies for their logistical support at Camp Makela. May it have many more successful field seasons.

Seven-Samurai-PaleontologyThe Seven Samurai of paleontology at Camp Makela, ready for action in the Two Medicine Formation of central Montana. These ruffians/malcontents/Guardians of the Cretaceous Galaxy are otherwise known as (left to right): Ulf, Jared, me, Ashley, Emmy, Paul, and Eric. (Photograph and choreography by Ruth Schowalter.)

For more about these people and other human connections between the paleontological research that took place in the Two Medicine Formation – and told from a non-paleontological perspective – go to Cretaceous Summer 2014, which had links to four blog posts done on site by my wife Ruth Schowalter. Also be sure to check out Brad Brown’s blog post from the Burpee Museum of Natural History about his experiences at the field site, Just What the Doctor Ordered: Two Medicine Delivers High Biodiversity in a Low Profile Area.

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

(This is the third of a three-part series honoring the memory of paleontologist-ichnologist-teacher-artist Dolf Seilacher, who died on April 26, 2014. Part I of the series is here and Part II is here.)

After Dolf’s only trip to Georgia in 1997, I saw and talked with him a few more times, conversations that sometimes involved rocks and trace fossils in the field, but sometimes not. These times and places were in 2003 (Switzerland), 2004 (Argentina), 2006 (the far-off land of Philadelphia), and 2008 (Krakow, Poland).

Plenty of other ichnologists from around the world attended these meetings, too. Many of them I now consider as long-time friends, in which we get back for regular reunions to talk and argue about trace fossils, discussions that are normally accompanied by ritualistic consumption of significant volumes of libations. Almost always in such conversations, though, someone mentions the name “Dolf.” This then leads to animated discussions of his articles, remembrances of personal encounters with him (which usually involve some sort of strongly worded disagreement about a scientific idea), or telling stories about field trips, where Dolf noticed something extraordinary that everyone else had missed. In other words, even when Dolf wasn’t there, he was still present.

Seilacher-Ichnia-ArgentinaIf invited to speak at a gathering of ichnologists, Dolf Seilacher was never shy about saying “yes.” Here he addresses participants of the 1st International Ichnological Congress (Ichnia), held in Trelew, Argentina in 2004. (Photograph by Anthony Martin.)

As opposed to his trip to Georgia in 1997, the 2003 meeting in Switzerland was more-or-less in Dolf’s backyard, a short trip from his home in Tübingen, Germany. This was the International Ichnofabric Workshop, a biannual meeting of ichnologists that’s been taking place since the 1990s in various trace-fossil-rich places throughout the world. I love these meetings because of their balance between time spent blabbing in conference rooms and time spent in the field, looking at trace fossils: typically three days inside, three days outside. Now that’s what I call “fair and balanced.”

Dolf-Roland-IIW-BaselHow would you like to have your “Dolfing“? Inside or…

Dolf-Field-Switzerland…outside? (Both photographs taken by Anthony Martin in July 2003, Switzerland.)

Many of the trace fossils we encountered on the field-trip portion of the workshop were originally from deep-marine environments, made 30-50 million years ago by invertebrate animals that lived in on ocean-floor sediments hundreds or perhaps thousands of meters below the surface. Later, when the Alps were uplifted by colliding plates, this oceanic-continental mashing transported the trace fossils, resulting in seemingly anomalous signs of life from a deep seafloor, but in alpine settings. Dolf was one of the world’s experts on deep-sea traces, and among the few ichnologists to have taken a submersible ride (DSV Alvin) to more than 3,500 m (11,500 ft) down, highlighted in the IMAX film Volcanoes of the Deep Sea (2003). So it was no surprise when our first encounters with these trace fossils in the field prompted him to share his considerable knowledge about them.

Although Volcanoes of the Deep Sea is a fine documentary film in its entirety, for now just watch the first three minutes here to see Dolf in the field, looking for deep-sea trace fossils and talking about his mistress, who he met on his honeymoon. (Spoiler alert: His “mistress” is a trace fossil, and a complicated one, named Paleodictyon.)

Seilacher-SpirorapheDolf was clearly excited about sharing what he knew about the deep-sea trace fossils during our Ichnofabric Workshop in Switzerland. And he knew a lot. (Photograph taken by Anthony Martin in July 2003, Switzerland.)

The 2004 meeting in Argentina was a big deal for ichnologists, as this marked the first International Ichnological Congress, more briefly called Ichnia. More than a hundred ichnologists of varied interests, backgrounds, and nationalities gathered in Patagonia, Argentina, first for a glorious four-day field trip based out of Comodora Rivadavia, then for the congress itself in Trelew. Dolf joined us for the latter, and people who delivered talks in the sessions soon realized they were not going to leave the stage until Dolf asked them a question or made a comment about their work. At the time, he was 79 years old, but clearly was not ready to slow down teaching all of us.

Bromley-Pemberton-Seilacher-IchniaA rare circumstance: three of the most significant ichnologists in the world leaving fresh and contemporaneous footprints in the same habitat. From left to right is Richard Bromley (Denmark), George Pemberton (Canada), and Dolf, who was accepting an award from the organizers of this Ichnia. Jorge Genise’s hands (left) for scale. (Photograph by Anthony Martin, taken in Trelew, Argentina in April 2004).

The 2006 meeting in Philadelphia was significant, as this was for a symposium in honor of Dolf’s long and successful career. Organized as a session within the Geological Society of America meeting, it attracted so many ichnologists that the symposium lasted the entire day. In our talk, Andy Rindsberg (mentioned in my last post) and I decided we would cover one of Dolf’s favorite topics, the traces made by animals when they stop, nicknamed “resting traces.” In planning our talk, we knew Dolf would appreciate some good-natured poking fun at his expense. So we decided to lampoon both his authority in our field and his penchant for smoking good cigars through the following two slides (shown here side-by-side).

Freud-Seilacher-CigarTwo slides shown in succession at the Seilacher symposium, held in the 2006 Geological Society of America meeting in Philadelphia, Pennsylvania. Translation on the right is “Sometimes a resting trace is just a resting trace,” and I think you can figure out the one on the left now. I don’t know the photo credit for Dr. Freud, but the one on the right was taken by Andy Rindsberg at the Seilachers’ home in Tubingen, Germany in 2006.

It was a success. Dolf was sitting in the front row while I gave my talk, and I’ll never forget his delighted smile when he saw the image of Sigmund Freud dissolve into his, with an almost perfectly mirrored pose.

The last time I saw Dolf was in Krakow, Poland, and at the second Ichnia meeting in 2008. His presence was doubly appreciated by all of us, as Jagiellonian University was also hosting – at the same time – Dolf’s pride and joy, the Fossil Art exhibit.

Fossil-Art-Sign-KrakowIt’s a sign! Advertising the exhibit Fossil Art, that is. In this instance, the venue was at Jagiellonian University in Krakow, Poland, and in 2008. (Photograph by Anthony Martin.)

However, it was at this meeting where Dolf showed us a side we had almost never seen, but one that was completely appropriate for where we were. Alfred Uchman, the meeting organizer (and one of the world’s experts on deep-sea trace fossils), had asked Dolf to speak at the opening of the meeting on an ichnologically themed topic of his choosing. I don’t remember the main topic of his presentation, and the reason why for my faulty memory is because of what happened first.

Dolf began his talk with a deeply heartfelt and remorseful apology. In an awareness of both history and place, he told us how the grand room in which we were seated was where, in 1939, Jagiellonian University officials had handed over control of this esteemed institution – one of the oldest universities in the world and the intellectual home of Copernicus – to invading forces of Nazi Germany. Dolf, as a German citizen, a World-War II veteran who fought on the side of the Nazis, and who shared a first name with a certain genocidal dictator from Germany, expressed his shame and regret about what had happened in that place and then. I looked around the room and recall sensing the surprise we all felt at his  expression of regret, but also its poignancy and sense of redemption. He then went on and delivered his scientific talk, but it had become one overshadowed by our realization of how horrific histories and inquisitive inquiries are shared facets of our humanity.

Then there was Fossil Art. I remember seeing the first iteration of this traveling display in Germany in 1994, then elsewhere. This exhibit consists of life-sized reproductions (epoxy resin casts) of rock slabs, most of which held gorgeously intricate and intriguing trace fossils, but some with body fossils and physical sedimentary structures, such as ripples and mudcracks. At this meeting, we were privileged enough to get a guided tour of the exhibit by Dolf himself, who gave an introduction to its purpose as a way of engaging our minds and senses with beautiful patterns in rocks, many of which were made by animals from millions of years ago.

Seilacher-Fossil-Art-2Seilacher-Fossil-Art-1Dolf Seialcher introducing Fossil Art to a gathering of ichnologists at Ichnia 2008 in Krakow, Poland. (Photographs by Anthony Martin.)

Many of these reproductions received fanciful titles, such as The Trilobite Circus of Penha Garcia and Witch Broomings, and are mounted like works of art, with carefully arranged lighting accentuating their features. These “slabs” also have Dolf’s written explanations in placards next to them, describing and interpreting their geological significance, but also marveling at their beauty. Is it art, or is it science? Yes. Anyway, I’ll just let these images speak for this masterful blending of natural, aesthetic beauty and scientific information.

Cambrian-Beach-Party-Fossil-ArtCambrian Beach Party II, representing trace fossils made by large slug-like animals on a beach about 500 million years ago. (Photograph by Anthony Martin, taken in Krakow, Poland in 2008.)

Trilobite-Circus-Fossil-ArtThe Trilobite Circus of Penha Garcia, a collection of exquisitely preserved trilobite burrows from Portugal, preserved as natural casts. (Photograph by Anthony Martin, taken in Krakow, Poland in 2008.)

Trilobite-Pirouettes-Fossil-ArtTrilobite Pirouettes, more natural casts of trilobite burrows, but showing looping and stopping (“resting”) behaviors. (Photograph by Anthony Martin, taken in Krakow, Poland in 2008.)

More ichnology meetings took place since then: the third Ichnia meeting in Newfoundland, Canada (2012), and the most recent International Ichnofabric Workshop in Çannakale, Turkey (2013). Dolf did not physically attend either meeting, which did not surprise anyone, as he was in his late 80s, and we were starting to hear stories about his failing health. Nevertheless, a day never passed without his name coming up in conversation. So although most of us had not seen him since 2008, his ideas, personality, and methods seemed permanently attached to us, akin to some of the fossils he had studied.

Now that Dolf is gone and we are left with his considerable life traces, what would be  the best way for all of us to remember him? I suggest we do it through the flattery of imitation.

We are living in a time when science is very popular, even in the U.S., evident from TV shows like Cosmos and Your Inner Fish, as well as many clear and wonderfully written  science books. A few people have even declared that we’ve entered a “golden age” of science communication. Yet basic scientific research is also under assault from anti-science political forces, ones that insist on alternative realities where opinions are given equal (or superior) weight when compared to factual evidence. Moreover, mainstream academia is currently undergoing an administratively led collapse from within, as U.S. universities move more toward a corporate model that places higher profits over discoveries, knowledge, and teaching.

Still, through Dolf Seilacher’s life and accomplishments as a scientist, teacher, and artist, he showed a way to side-step the current chaos. Through his practices, he demonstrated how nearly all of us can do science and make discoveries every day by simply using our senses, pencils, paper, and intellects. Just to be clear, this is not a call to Neo-Luddism, in which we abandon our precious iPads and laser scanners while chanting incantations honoring our pre-technological ancestors. Instead, it is one that asks us to rediscover these basic skills – observing, drawing, and imagination – for conducting science, discovering, learning, and passing on new-found insights to future generations. In short: be more like Dolf.

Danke und Auf Wiedersehen, Dolf, for the gifts you gave us, traces that will continue long after you have become part of the earth and life you so loved studying.


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

Seilacher, A. 1997, 2008. Fossil Art. (Two versions of this book were published, one through the Royal Tyrell Museum of Palaeontology in 1997, which was 64 page long; the other was through CBM Publishing in Laasby, Denmark, and was 101 pages long. The latter book can be purchased here.)

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

(This is the second in a three-part series honoring the memory of ichnologist-paleontologist-educator-artist Dolf Seilacher (1925-2014). For Part I, please go here.)

Dolf Seilacher and I crossed trails again in the fall of 1997, but through my initiative and in my backyard, here in Georgia. After the Evolutionary Biology Study Group at Emory University hosted a series of prominent biologists on the Emory University campus – such as George C. Williams, Richard Lewontin, and the Grants (Rosemary and Peter) – its director asked me which paleontologist we might bring to campus. Having invited theoreticians and lab-based or field biologists as our main guests, he wanted to give the members of our group more of a “deep time” perspective on evolutionary processes. So I immediately said, “Dolf Seilacher.”

Seilacher-Coca-Cola-EmoryDolf Seilacher in Melton’s App & Tap, a neighborhood pub near the Emory University campus that served both Coca-Cola (which has economic connections to Emory) and proper adult beverages, the latter necessary for fueling meaningful paleontological conversations. (Photograph by Anthony Martin, taken in Atlanta, Georgia 1997.)

I recall a few snobbish members of the group doubted that any paleontologist could be a real evolutionary scientist: after all, paleontologists don’t do “experimental work.” (Yes, I’ve actually heard this smug, self-important drivel emit from the mouths of proudly lab-bound neontologists, making Sheldon Cooper look downright open-minded by comparison.) I was also at a university that had jettisoned its Department of Geology only eight years previously, meaning I had little support in my on-campus academic community for hosting an earth scientist. However, Dolf had won the Royal Swedish Academy of Sciences Crafoord Prize just five years before, thus he qualified as prestigious enough for most of the doubters. (Needless to say – but it bears saying anyway – none of his prejudiced skeptics had similar honors.)

Fortunately, Dolf did not disappoint, and hosting him at Emory University was among the most intellectually exhilarating three days I’ve experienced in the past 24 years at my institution. I had him mostly to myself on his first day in Atlanta, but we were joined by fellow ichnologist and friend Andrew (Andy) Rindsberg for dinner, with both of us feeling as if we had the world’s best private tutor in ichnology for that brief time. The next day, Dolf did a lunchtime seminar for the Evolutionary Biology Study Group, then later that afternoon delivered a talk in a big room open to the entire university and the general public. For his last full day in Georgia, he insisted we take him out in the field to see some of the Ordovician-Silurian rocks in the northwest corner of the state. (Other than transferring planes in Atlanta’s airport, Dolf had never been to Georgia and wanted to see our trace fossils.)

His second day in Atlanta, he began his engagement with the Evolutionary Biology Study Group, which was composed mostly of biologists, anthropologists, and psychologists; Andy and I were the lone paleontologists there. The lunchtime seminar was held in a cramped room, and most people there were awkwardly holding flimsy paper plates weighed down by slices of cheap pizza. The overall mood was one of curiosity, as Dolf was a complete unknown to most people there. (Remember, this was 1997: “Googling” was still a year away from being anything, let alone a verb.)

His seminar topic was on fossil tracks, and he started with the classic historical example of how some Early Triassic tracks from Germany (named Chirotherium) had been badly misinterpreted by some of the greatest scientists of their time, such as Alexander von Humboldt, Richard Owen, and Charles Lyell. Later, with more scrutiny and the application of a few key ichnological principles, other scientists revealed what animals made them and how, which Dolf explained in his book Trace Fossil Analysis (2007, p. 6-7).

Seilacher-Chirotherium-AnalysisDolf Seilacher’s visual explanation for how the anatomy and dimensions of a tracemaker, its behavior, and the original substrate (a firm mud) all contributed to making a fossil trackway from the Early Triassic Period (about 245 million years old). He also included  explanations of previous interpretations for these tracks and when they were proposed (middle right), neatly summarizing the progression of the science done on these tracks. (Figure from: Seilacher, A., 2007, Trace Fossil Analysis, Springer, p. 7.)

Wrong-Way-Hands-Fossil-ArtA reproduction of the Early Triassic (about 245 million-year-old) rock slab with mudcracks and Chirotherium tracks, both preserved in convex relief as natural casts. I said “reproduction” because this is a epoxy resin cast made from a latex mold that was also colored to mimic the original rock. Does this sound like a work of art? Well, as a matter of fact, this was one piece in a show Seilacher conceived called Fossil Art. (Photograph by Anthony Martin, taken in Krakow, Poland in 2008.)

Once introduced, Dolf took off, and his audience went with him. In a lively, mesmerizing presentation, Dolf deftly interwove history of science with detective-like applications of ichnology, anatomy, sedimentology, and evolution, all delivered with his trademark enthusiasm, humor, and charisma.

In one memorable instant, he used his hands and arms to play-act the wrongly interpreted gait of the Chirotherium maker, in which this wretched imaginary animal had to cross its limbs as it walked. (Later, paleontologists figured out its so-called “thumb” was actually its outermost digit, thus erasing any need for the animal to cross-step.) He then pantomimed the more correct gait, again bringing across his points far more effectively than if he had used, say, a computer-animated reconstruction of the tracemaker. The audience was enthralled, enchanted, engaged, or whatever words science communicators use to describe what happens when a speaker is rhetorically kicking butt.

How did I know Dolf’s talk was a success? About five minutes into it, one of the most egotistical and pedantic curmudgeons in the Evolutionary Biology Study Group (who may or may not have been an anthropologist) turned to me and said with genuine delight, “This guy is terrific!” Yes, he was.

Later that afternoon, Dolf gave a lecture in a, well, lecture hall, with about a hundred people attending. For me, this was less exciting than his noontime talk because trace fossils and ichnology only figured briefly in its message. Instead, it was more about the “big picture” of evolution as reflected by the fossil record, with emphases on constructional morphology and biological structuralism, and connecting these to the evolution of animal behaviors. Some of these concepts – which I won’t even try to explain here – represented expansions on research by Dolf’s Ph.D. advisor, Otto Schindewolf. Nonetheless, he delivered a thought-provoking lecture, and enthusiastically answered a variety of questions when the time came.

Dinner at a Lebanese restaurant after the lecture was an opportunity to see yet another side of Dolf. For instance, soon after our party had been seated, he and the restaurant owner exchanged pleasantries (and jokes) in Arabic. I had forgotten that Dolf taught at the University of Baghdad early in his career and did much field work in Libya and other parts of the Middle East. The dinner – which included many field stories Dolf had experienced around the world – went well into the night, but did not hinder Dolf’s observation skills at the end of it.

As we exited the restaurant, he pointed to the cement on the doorstep and said, “Look, evidence of a former biomat, helping to preserve this footprint.” We looked down and saw where a shoe-clad human had stepped into the originally wet cement. But wrinkle marks around its edges – as Dolf explained – showed where plastic sheeting had been placed over the cement in a vain attempt to prevent people from stepping on it. It was a moment when we felt like Watson to his Sherlock.

Following his triumphant visit to the Emory campus in Atlanta, Dolf was then ready to experience something that really mattered, like trace fossils. The next day, we took him to northwestern Georgia to look at trace fossils in the Ordovician-Silurian rocks there, a mere 2.5 hour drive from Atlanta.

We had a varied group, composed of a few paleontologists – Andy Rindsberg, Sally Walker, and me – along with the director of the Evolutionary Biology Study Group (Michael Zeiler), a couple of evolutionary biologists and biology graduate students, and a few undergraduate students from one of my geology classes. Our only goal for the day was to see the I-75 Ringgold roadcut, which through its height, breadth, and gently tilted strata afforded an opportunity to stroll along its length, find many trace fossils, and put them into the context of changing environments from more than 440-430 million years ago.

Dolf-Seilacher-Ringgold-Georgia-1The start of the field trip with Dolf Seilacher to see Ordovician-Silurian rocks near Ringgold, Georgia. This photo was taken about 10 minutes before he took over the field trip, which immediately followed Andy Rindsberg and me getting “Dolfed.” (Photograph taken by Anthony Martin in November 1997.)

Andy and I were thrilled to have Dolf at this outcrop with us because we had done a lot of work there, and we wanted to show off what we had found. Andy studied the Ordovician and Silurian trace fossils there in an M.S. thesis done at the University of Georgia, and I completed a bed-by-bed analysis of its Upper Ordovician rocks as part of my Ph.D. dissertation, also at the University of Georgia. Because we worked for the same graduate advisor (Robert “Bob” Frey), Andy and I communicated well with one another, and we mostly agreed on what trace fossils were there and what they meant. Moreover, Frey had published a paper with Dolf in 1980 (well before he died in 1992). Thus Andy and I felt as if we were fulfilling an ichnological legacy by taking Dolf to see trace fossils that Frey had studied here in Georgia.

Dolf-Seilacher-Ringgold-Georgia-2A first sign that Andy and I were not leading this field trip: within minutes of arriving at the site, the group gathered around Dolf to listen to what he had to say about the Late Ordovician rocks under our feet and around us. Did I mention this was his first time there? (Photograph by Anthony Martin, taken near Ringgold, Georgia in November, 1997.)

Dolf-Seilacher-Ringgold-Georgia-3Probably my favorite photograph of Dolf, showing him in full lecture mode while surrounded by Late Ordovician rocks in northwest Georgia. His synapses also might have been firing double time because of the caffeinated beverage he picked up at a Golden Gallon convenience store just beforehand. (Photograph by Anthony Martin, taken near Ringgold, Georgia in November, 1997.)

When we got to our destination, we parked and walked a short ways to our first stop. Rather than going directly to the road cut, we first looked at big slabs of sandstone in a former quarry site. These sandstones were from the Late Ordovician Sequatchie Formation, and they made for wonderful teaching specimens, containing many fossil burrows, mudcracks, and reddish clay, all indicating formerly intertidal environments. However, Andy and I didn’t know what made the burrows. Little did we know (but we should have), we were about to find out.

After Andy and I gave a brief introduction to this site and a preview of what to expect at the outcrop, Dolf strolled over to a large slab of sandstone, and nonchalantly placed his hand over a bump on its surface. “This trilobite resting trace shows how they were well adapted to living in intertidal environments at this time…” he began.

Andy and I exchanged startled looks. “Trilobite resting traces?” we both said. In all of our years of field work at this site, we had found very little evidence of a trilobite presence. We also had never recognized a trace fossil showing where a trilobite dug into mud or sand in one place and left an outline of its body, a so-called “resting trace,” sometimes called Rusophycus.

That’s when we realized it. We’d been Dolfed. And on our own field trip.

Fortunately, we didn’t care. Dolf then went on to propose that the more common burrows in these rocks were also made by trilobites, but smaller ones. I’ve written previously about this trilobite-themed revelation and how Andy and I tried later to disprove it, only to find that Dolf was probably right. This served as yet another example of why experience matters in ichnology, and why we ichnologists should always listen to those who have it.

Dolf-Seilacher-Ringgold-Georgia-4Dolf in action, as he started to put together the story of how trilobites were burrowing on and into tidal flats more than 400 million years ago in a place we now call Georgia. Notice how Dolf was using pencil and paper to assist in his explanations of what was in front of us, no doubt drawing out his conclusions. (Photograph by Anthony Martin, taken near Ringgold, Georgia in November, 1997.)

Dolf-Seilacher-Ringgold-Georgia-5Dr. Sally Walker, getting a close look at the bedding-plane surface of the sandstone, which is loaded with natural casts of mudcracks. But wait: what’s that blurry, whitish bump in the lower left corner?

Dolf-Seilacher-Ringgold-Georgia-6Why, that’s a trilobite resting trace, the first ever found in this formation and locality. Thanks for the Dolfing, Dolf. (Both photographs by Anthony Martin, taken near Ringgold, Georgia in November, 1997.)

Seilacher-Trilobite-Resting-Trace-DrawingDon’t quite see the trilobite resting trace fossil, and you think it’s a just a random bump on that rock surface? Here’s an illustration by Dolf that should help to enlighten. Take a look at the left-hand side of this figure with his depictions of trilobite resting traces, then look again at the photograph of the “random bump.” Yes, that’s right: you’re wrong. And you know what? It’s perfectly fine to be wrong in science. Just make sure you learn from your mistakes. (Figure from: Seilacher, A., 2007, Trace Fossil Analysis, Springer, p. 39.)

The rest of the field trip seemed almost anti-climatic after Dolf’s discovery, but it was still quite enjoyable. We left the quarry site and walked along the roadcut itself for the next few hours, stopping to look at whatever caught our attention. Its titled strata meant were were going forward in geologic time, from oldest to youngest (Middle Ordovician –> Early Silurian). This provided a nice lesson for the geological novices in our group in how to interpret changing environments through time. We found more trace fossils, and even a few body fossils, giving everyone plenty of paleontological stimulation to get them through that day and beyond.

Dolf-Seilacher-Ringgold-Georgia-7Dolf Seilacher, master ichnologist and consumate teacher. We will greatly miss his pointing out the obvious to the oblivious. (Photograph by Anthony Martin, taken near Ringgold, Georgia in November, 1997.)

When it came time to leave, we walked out with Dolf, feeling exceedingly grateful for his requesting this trip. Later, we joked with him about the success of his “first visit to Georgia.” Alas, we did not know then that it would also his last. Nonetheless, what remains are the provocative thoughts and methods he imparted on so many of us during his brief time here, no doubt inspiring future generations of paleontologists, ichnologists, and all others interested in learning about the wondrous history of the earth.

Seilacher-Ringgold-14A group picture following our field trip with Dolf Seilacher to northwest Georgia in November 1997 (and much gratitude to whoever suggested it and took it). For me (far right, big hat), the road behind us seems to symbolize a trail he blazed for us to follow. Thanks for all of the cognitive traces, Dolf: may they continue to reach into the fossil record.


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


A Sneak Peek at a Book Jacket (with Traces)

After returning from a two-week vacation in California with my wife Ruth, we noticed a cardboard tube awaiting us at home. Intriguingly, the mystery package, which was only about 60 cm (24 in) long and 8 cm (3 in) wide, had been sent by Indiana University Press, the publisher of my new book, Life Traces of the Georgia Coast. We were a little puzzled by it, considering that it couldn’t possibly contain complimentary copies of the book. (As of this writing, I still have not held a corporeal representation of the book, hence my continuing skepticism that it is really published.) What was in this mystery tube?

Front cover and spine of my new book, Life Traces of the Georgia Coast: Revealing the Unseen Lives of Plants and Animals (Indiana University Press). The book, newly released this month, is not yet in stores, but supposedly on its way to those places and to people who were kind enough to pre-order it. But if you didn’t pre-order it, that’s OK: you can get it right here, right now.

Upon opening it, we were delighted to find that it held ten life-sized prints of the book jacket: front cover, spine, back cover, and front-back inside flaps. The cover art, done by Georgia artist Alan Campbell, looked gorgeous, and had reduced well to the 16 X 25 cm (6 X 9″) format, retaining details of traces and tracemakers, but also conveying a nice aesthetic sense. I was also amused to see the spine had the title (of course) but also said “Martin” and “Indiana.” Although I’ve lived in Georgia for more than 27 years, I was born and raised in Indiana, so it somehow seemed fitting in a circle-of-life sort of way to see this put so simply on the book.

Back cover of Life Traces of the Georgia Coast, highlighting a few of the tracemakers mentioned in the book – sea oats, sandhill crane, sand fiddler crab, and sea star – while also providing a pretty sunset view of primary dunes, beach, and subtidal environments on Sapelo Island. (P.S. I love that it says “Science” and “Nature” at the top, too.)

I had no idea what the back cover might be like until seeing these prints, but I thought it was well designed, bearing a fair representative sample of tracemakers of the Georgia barrier islands: sea oats (Uniola paniculata), a sandhill crane (Grus canadensis), sand fiddler crab (Uca pugilator), and lined sea star (Luidia clathrata), as well as a scenic view of some coastal environments. I had taken all of these photos, so it was exciting to see these arranged in such a pleasing way. My only scientifically based objection is that I would have like to see it include photos of insects, worms, amphibians, reptiles, or mammals (these and much more are covered in the book), as well as a few more tracks, trails, or burrows. Granted, I suppose they only had so much room for that 6 X 9″ space, and thus I understood how they couldn’t use this space to better represent the biodiversity of Georgia-coast tracemakers and their traces. (Oh well: guess you’ll have to read the book to learn about all that.)

Inside front and back flap material for Life Traces of the Georgia Coast, which also includes a summary of the book (written by me) and a rare photo of me (taken by Ruth Schowalter) in my natural habitat, which in this instance was on St. Catherines Island, Georgia.

I had written the summary of the book on the inside flap nearly a year ago, so it was fun to look at it with fresh eyes, almost as if someone else had written it for me. Fortunately, I banished my inner critic while reading it, and just enjoyed the sense that it likely achieved its goal, which was to tell people about the book and provoke their interest in it.

In short, this cover jacket symbolizes a next-to-last step toward the book being real in my mind. Now, like any good scientist, all I need is some independently verifiable evidence in the form of tactile data, such as a physical book in my hands. Stay tuned for that update, which I’ll be sure to share once it happens. In the meantime, many thanks to all of the staff at Indiana University Press – who I’ll mention by name next time – for their essential role in making the book happen and promoting it in this new year.

Information about the Book, from Indiana University Press

Life Traces of the Georgia Coast: Revealing the Unseen Lives of Plants and Animals, Anthony J. Martin

Have you ever wondered what left behind those prints and tracks on the seashore, or what made those marks or dug those holes in the dunes? Life Traces of the Georgia Coast is an up-close look at these traces of life and the animals and plants that made them. It tells about the how the tracemakers lived and how they interacted with their environments. This is a book about ichnology (the study of such traces), a wonderful way to learn about the behavior of organisms, living and long extinct. Life Traces presents an overview of the traces left by modern animals and plants in this biologically rich region; shows how life traces relate to the environments, natural history, and behaviors of their tracemakers; and applies that knowledge toward a better understanding of the fossilized traces that ancient life left in the geologic record. Augmented by numerous illustrations of traces made by both ancient and modern organisms, the book shows how ancient trace fossils directly relate to modern traces and tracemakers, among them, insects, grasses, crabs, shorebirds, alligators, and sea turtles. The result is an aesthetically appealing and scientifically accurate book that will serve as both a source book for scientists and for anyone interested in the natural history of the Georgia coast.

Life of the Past – Science/Paleontology

692 pp., 34 color illus., 137 b&w illus.
cloth 978-0-253-00602-8 $60.00
ebook 978-0-253-00609-7 $51.99

More information at: ]

The Traces We Leave Behind: A Tribute to Jordi Maria de Gibert

Paleontologists have an odd relationship with death. We often joke about how our livelihoods depend on what has died before us, or we experience great delight when we find an exquisite fossil, which probably was buried alive for it to be so well preserved. We also blithely talk about “death assemblages” and happily explain this gruesome term to non-paleontologically inclined students, friends, spouses, and partners without much thought about how it sounds to people outside of our field.

For ichnologists, who mostly study the tracks, burrows, and other vestiges of these lives that preceded us, our perspectives become even more skewed. Once-live animals, through their behavior, made trace fossils. Yet we almost never see what made them. Hence we also spend much of our time among the living, watching them make traces that we can use as analogs for those trace fossils left by their ancestors. Sometimes we find ourselves identifying with modern animals, developing empathy for what they experience as they form traces, a sensitivity that can extend to their trace-fossil equivalents. Hence for ichnologists, these parts of the fossil record become just a bit less removed from death, and we end up feeling for our tracemakers, both long gone and extant.

Jordi Maria de Gibert, contemplating and lamenting the loss of dinosaurian tracemakers from mass extinctions. The window display was in Basel, Switzerland, one of many places visited by Jordi in his quest to learn all things ichnological. (Photograph by Anthony Martin, who is also pictured in the reflection, along with ichnologists Luis Buatois and Gabriela Mángano, taken in 2003.)

In this sense, our small and close-knit international community of ichnologists was shocked to learn about the sudden loss of one of our own “tracemakers” this past weekend, Jordi Maria de Gibert. His death was unexpected and its impact accentuated because he and the rest of us had just gathered together only last month for the International Congress of Ichnology (Ichnia) in St. Johns, Newfoundland. We also anticipated seeing him again in his home city of Barcelona in 2016, where he died on Sunday. None of us had prepared ourselves to reflect on his legacy, let alone contemplate the possibility that his cognitive traces would cease any time soon.

The aftermath of the first Ichnia football match (sometimes known as “soccer” to you Yanks) between ichnologists of Team Gondwana and Team Laurasia, which took place on a pitch near Trelew, Argentina. Jordi, in the middle of the back row, is either signaling “Peace,” “Victory,” or, most likely, ordering two beers: one for him, and one for you so he can sit down to argue about trace fossils with you. (Photograph by Anthony Martin, taken in 2004.)

Most of our dismay about Jordi’s departure is because we loved him as a person, but it is also surely connected to our witnessing an ascendancy cut short. For instance, at the end of the meeting in St. Johns, Jordi addressed all of us as the newly elected president of the International Ichnological Association, and he had volunteered to serve as the main organizer for the next Ichnia meeting four years from now. His larger-than-life personality was on full display during his informal and impromptu speech: enthusiastic, cheerful, witty, earnest. In the days before then, he delivered multiple presentations on ongoing research projects, most of which revolved around his continuing interests in crustaceans and their traces, as well as those of marine bioeroders, animals that make a living by boring into rocks. Jordi was a prolific publisher of peer-reviewed papers on these topics, and was well known for his cooperative spirit, coauthoring with many ichnologists and other types of paleontologists on these papers.

Jordi (right, seated), in his preferred life habit, talking about fossils with colleagues (and friends) at an outcrop. And this wasn’t just any outcrop, but was at Mistaken Point, Newfoundland, which has one of the most spectacular Ediacaran fossil assemblages in the world. This had to have been a dream come true for him, as it was for many of us.

Jordi showing off his “Bama booties,” required footwear for the sacred ground of Mistaken Point, as some other ichnologist vainly attempts to “photobomb” him with his own blue-footed bootie. (Photograph by Ruth Schowalter.)

I had known Jordi since 1995, having first met in Bornholm, Denmark at a small ichnological meeting there. He and I were still new to our discipline (we were about the same age) and quite green, but eager to learn from our elders. As is typical with many academic friendships, over the next 17 years we would see each other at various meetings, and by my count we saw trace fossils and toasted one another in six countries (Denmark, U.S., U.K., Switzerland, Poland, Canada). Each time together, I grew more impressed with his intense and tenacious will to seek out more knowledge, digest it, and pass it on to others. He was a fierce intellectual who relished the debating of ideas, and was never satisfied with a conversation if he did not leave it wiser. This, of course, benefited all who were brave enough (and lucky enough) to enter into such discussions with him.

A happy time at the Ichnia 2004 banquet in Trelew, Argentina, with (from left to right) Renata Guimarães Netto, Jordi, and Ludvig Loewemark, where the exchange of ideas and good cheer flowed nearly as fast as the wine.

Jordi was young as far as ichnologists go, and as I argued in my previous post, the best ichnologists are the most experienced ones. So he knew as well as any of us that gaining more experience in the field was essential, and traveled to many places and studied traces of all ages – from the Ediacaran to the present – and traces of all kinds, from plant roots to dinosaur tracks. Accordingly, because of his dedication and broad interests, he had already become one of our best. In this vein, one of the metaphorical jokes ichnologists tell is how our academic success can be measured by how deeply we can burrow: shallow tiers are the least successful, whereas the deepst tiers are the most successful. Jordi was assuredly well on his way to the deepest tier, but we are all saddened about his unexpectedly reaching the historical layer before so many of us.

Los quatros amigos, posing happily toward the end of an ichnology field trip in Switzerland in 2003: from left to right, ichnologists Noelia Carmona, Gabriela Mángano, Luis Buatois, and Jordi, sporting some distinctive headgear and proudly flouting conformity. (Photograph by Anthony Martin.)

I learned about Jordi’s death on Sunday through our mutual ichnologist friend, Renata Guimarães Netto, who had likewise known Jordi for more nearly 20 years. Quickly the word spread through social media, e-mails, and phone calls, our sadness multiplying and magnifying worldwide. Only last month, we had celebrated with him, and now we mourned him, and expressed our sorrow to his family members, and close friends.

To ease some of this pain and enjoy an otherwise beautiful Sunday in Decatur, Georgia, my wife Ruth and I went for a walk. Without thinking, I suggested that we meander in one of the largest, quietest green spaces in Decatur, which turned out to be its cemetery. (Yes, I know. All I can say is that the subconscious is more powerful than we know.) While we strolled, I thought about times spent with Jordi on field trips and in conferences, while also recalling papers he had written and discoveries he had made. As mentioned earlier,  Jordi’s interests were varied, but perhaps his favorite research topic was crustacean burrows, especially the burrows of crabs, shrimp, lobsters, and other 10-legged crustaceans. Too bad we were nowhere near the Georgia coast, I thought, as it would have been a fitting and comforting homage for Ruth and I to take in the many decapod burrows of the Georgia beaches and salt marshes, which Jordi had never seen in person.

That’s when an eerie coincidence happened. During our walk, we spotted a former pond on the cemetery grounds, now drained for dredging. There’s something about a big pit of mud that appeals to every ichnologist, so I excitedly suggested that we go take a look to see what traces were there. We expected to find lots of tracks, such as those of birds, raccoons, squirrels, and coyotes, and maybe a few other urban fauna. Instead, though, the muddy surface was perforated by decapod tracks and burrows.

Need to see some crustacean traces, but you live in the landlocked part of Georgia? Just go to a dried pond and look for tracks like these.

These were the traces of crayfish, decapods that diverged from a common ancestor to modern lobsters more than 250 million years ago to live in freshwater environments as their brethren dispersed throughout the seas. A few years back, I studied Cretaceous crayfish and their burrows in Australia, but had never seen a live crayfish in its burrow here in Georgia, let alone seen so many of their tracks in one place. We even saw some crayfish (probably a species of Procambarus) poking their heads and claws out of their burrows, or walking around on the mudflat. So it turned out we did not need to go to the Georgia coast after all to see traces reminding us of Jordi: they had been right here with us the whole time.

A crayfish at its burrow entrance in the mudpit now in Decatur Cemetery, either defending its territory, or waving goodbye to people who study its kind and their traces. Your choice, but I know which one I’m picking.

In April, Jordi began writing about ichnology and invertebrate zoology for a more public audience through his cleverly titled blog, Infaunal Epiphany. His first entry was titled First Post, Hope Not Last!, in which he expressed a growing aspiration to connect with more than just his academic colleagues:

We scientists produce science. We scientists consume science. Most of us do that. We do our research, we publish it and other scientists read it. We are keeping all the fun for ourselves!!! It is true that there are scientists, journalists and writers who devote an effort to popularize science results. They are the ones building a bridge to society and I think it is fair to do that as many of us are investigating on public money.

Jordi wanted to share the fun of science, and in that respect, field trips with him were always a delight. These are probably what I will miss most about him, a pang that becomes particularly acute when I realize that one of our last conversations was about his some day visiting the Georgia coast to see its modern traces with me and our like-minded friends.

Lastly, in the light of his most recent life departing us, perhaps Jordi’s most poignant post on his nascent blog was Seven Reasons to Reincarnate as a Cephalopod. I won’t spoil it for anyone who hasn’t read this wonderful piece, but will just say that this post alone showcases how Jordi’s fine sense of humor blended readily with his science.

We will never know whether Jordi’s wish came true, let alone which cephalopod he might have become, or whether some element of his considerable spirit is now somehow connected to one of his beloved crustacean tracemakers or bioeroders in the past or present. But we can be assured that he will continue to live with us through his works and our memories of him. When our ichnological community meets again in his home town of Barcelona four years from now, his traces will all around us, continuing to inspire us to learn and live more.

Salud y un abrazo grande, mi amigo Jordi. Vaya con las trazas.

Correction: Someone pointed out to me that the newly elected International Ichnological Association (IIA) president is actually Alfred Uchman, not Jord. Jordi only seemed presidential to me because of his inspiring report given at Ichnia 2012 as outgoing secretary of the IIA and his agreement to host Ichnia 2016. (I am pleased to report that Alfred likewise gave an excellent speech to those gathered.) Apologies for the mistake, and thanks (as always) to anyone who points them out to me.

Out of One’s Depth in the Ediacaran

In my previous post, which followed a field trip to see a spectacular assemblage of 565-million-year-old Ediacaran body and trace fossils at Mistaken Point in Newfoundland, I made an awkward confession. This admission was that the stock phrase “the present is the key to the past,” used by geologists and paleontologists to describe actualism (also known as uniformitarianism) really depends on which past you’re talking about. As it turns out, when it comes to earth history, there are a lot of pasts.

Looking from afar onto the world standard for rocks recording the transition from life that lived superficially to life that, well, went a little deeper. (Photograph by Ruth Schowalter, taken at Fortune Head, Newfoundland (Canada).)

For instance, if you mean to apply that aphorism while referring to the last 12% of earth history, then for the most part you’ll be OK, although some of it will fall completely flat (more on that later).

But if you think it can be said blithely when referring to a time when all of the lifeforms looked like aliens from a bad Star Trek episode (TOS, of course), or when global oxygen levels were significantly lower than today, or the ozone layer protecting us from UV radiation was mostly absent, or deep-burrowing predators were completely unknown from every ecosystem, or the geochemistry of bottom sediments in the world oceans were radically different, then that’s not going to work so well for you. The world was vastly different at the Precambrian-Cambrian transition about 550 million years ago, and no amount of studying modern geological and biological processes or, say, modern traces of the Georgia barrier islands, is going to close that factual gap.

Underneath the intertidal sandflats of the Georgia barrier islands lurks the common moon snail (Neverita duplicata), detected through its burrow (left); and it radiates malevolence once exhumed from the burrow end (right, arrow). It is the top predator, the lion of the tidal flat, one might say, burrowing under sandflat surfaces to stalk its prey (other mollusks, including its own species), enveloping them with its muscular foot, and drilling into their shells to eat them alive. Simple, effective, and deadly. Was there anything like this moon snail in the Ediacaran Period, 635-542 million years ago? Nope. (Photographs by Anthony Martin, taken on Jekyll Island, Georgia.)

So let’s say you took a common moon snail from the Georgia coast and sent it back to the Ediacaran. You would think its evolutionarily advanced status, placed among such primitives, means that it would suddenly become the gastropod equivalent of a Terminator (the Summer Glau version, of course), wiping out every Ediacaran challenger in its mucus-lined path. Instead, it would die and quick and messy death from a combination of low oxygen levels, excessive biomats getting in its way, a lack of desirable prey, and excessive UV radiation. So you can stop building that gastropod-sized Tardis, and just face up to two realities: (1) the present is not always the key to the past; and (2) there is no such thing as time travel.

Oh yeah, back to the field trip. During the same excursion that included a stop at Mistaken Point, we also went to Fortune Head. Fortune Head is the place where the International Commission on Stratigraphy established the standard stratigraphic boundary for the switch from the Precambrian to the Cambrian. Called a Global Boundary Stratotype Section and Point (GSSP), or simply “stratotype,” this is a section of rock with the most nearly complete transition of rock units representing one time unit to the next.

A plaque at Fortune Head Ecological Reserve, informing visitors about the scientific importance of this site to geologists and paleontologists.

For example, the outcrop at Fortune Head is the stratotype for the transition from the Ediacaran Period (635-542 mya) to the Cambrian Period (542-488 mya). Sometimes geologists nickname this system of picking an exact boundary “the golden spike,” invoking images of a geologist hammering such a gaudy implement into the outcrop to imperiously announce its precise location. Lacking such geo-bling, though, we settled for one of the field trip leaders simply pointing with his walking stick to the boundary.

While we stayed safely on the hillside, the graduate students risked their lives to climb down onto the section and point at the Ediacaran-Cambrian boundary at Fortune Head, Newfoundland. For me, this brought back fond memories of Marlin Perkins, Jim Fowler, and Wild Kingdom. (Spoiler: the graduate students made it back OK.) (Photograph by Anthony Martin.)

So how would you know for yourself where, er, when you are – geologically speaking – in a section that has the youngest rocks of the Ediacaran Period and the oldest rocks of the Cambrian Period? That’s where the awesome power of ichnology comes into play, and it’s really simple to wield. If you look at the rocks and see the following trace fossil – Treptichnus pedum – you’re in the Cambrian Period. But if you don’t, you’re in the Ediacaran.

Whoa, check out that beautiful trace fossil! It’s Treptichnus pedum, a burrow made by a deposit-feeding animal, which was probably a worm-like animal, but also could have been an arthropod. Regardless of who made it, it’s a burrow reflecting a new behavior that evidently didn’t exist only a few million years before it was made. And that, boys and girls, makes this trace fossil a distinctive one. Scale in centimeters. (Photograph by Anthony Martin, taken at Grand Bank, Newfoundland.)

This trace fossil, a feeding burrow made by an invertebrate animal living in the seafloor 542 mya, is one of the few trace fossils used as an index fossil. Index fossils (also called guide fossils) tell you the age of the rocks you’re viewing. A good index fossil should have the following traits:

  • Abundant
  • Easily identifiable
  • Stratigraphically restricted
  • Geographically widespread

Treptichnus pedum indicates a behavior very different from every other trace fossil seen in Ediacaran rocks. It shows that the burrowing animal – probably a type of worm or arthropod – systematically probed into the sediment to ingest some of it, withdrew back into the main part of its burrow, then moved forward to probe again. Furthermore, over the course of making its burrow, its pathway may make loops, which increased the likelihood of it getting lots of goodies (organics) from the sediment. This behavior was totally different, and if it had been allowed to happen in the Ediacaran, no doubt would have led to laughter and ostracizing by other epifaunal and infaunal invertebrates. That is, if they could laugh or ostracize. (Hey, like I said, it was really different back then.)

But here’s the really strange dimension of the Ediacaran Period: as far as burrowers were concerned, it was mostly two-dimensional. Animal movement seemed restricted to horizontal planes, in which animals (worm-like or otherwise) squirmed, crawled, anchored and pulled, or whatever they did to get around, but stayed mainly in the plane.

Vertical movement, such as daring to burrow up or down in the sediment, was forbidden by either the rules of the marine ecosystems at that time, or by the bodies of the animals themselves. What kept animals from digging a little deeper? Part of the problem was that the seafloor was ruled by microbial mats, which covered sediment surfaces like plastic coverings on furniture at your grandma’s home.

This wrinkled surface on a Lower Cambrian sandstone just above the Ediacaran-Cambrian boundary at Fortune Head, Newfoundland is evidence of a probable microbial mat, or “biomat” These biomats were really common in the Ediacaran, became less common in the Cambrian, then after the Cambrian became more rare than a modest politician in an election year. Scale in centimeters. (Photograph by Anthony Martin.)

So if you were an animal then, you had no choice: you could adapt to being under these mats or on top of them. To make matters worse, all animal life apparently lacked the right hard parts, limbs, or other anatomical traits that could have pierced those mats or excavated the sediment underneath them. So no amount of rugged individualism in those invertebrates was going to change their horizontal movement to vertical.

A horizontal trail, probably made by an invertebrate animal, preserved on a 565-million-year-old bedding plane at Mistaken Point, Newfoundland. So you thought you could burrow vertically? Forget it, Jake – it’s Ediacaratown!

Of course, eventually the earth changed, the tyranny of the microbial mats was overcome by new evolutionary innovations in animals, and other adaptive paths took life into a third dimension. Consequently, the animals living on the seafloor started acting more like the ones we see today: not just living on or just underneath that seafloor, but also going down into it. This change was huge in an ecological sense, sometimes dubbed by paleontologists as the agronomic revolution, which accompanied the Cambrian explosion. This is not to say that revolutions must involve explosions, though. On the contrary, this was a quiet and slow sort of revolt, in which as earth environments changed, natural selection favored the burrowers, and the burrowers changed their environment. ¡Viva la revolución!

Here’s a little musical lesson about the increased biodiversity of the Cambrian Period. Professors, assign it to your students. Students, tell you professors about it, so they can look like they’re almost hip when they assign it. And for American viewers: the song has some sort of subversive subliminal message toward the end, praising some country other than the U.S. You’ve been warned.

In this respect, what was most meaningful about our visit to Fortune Head was seeing evidence of this ecological shift at the very same outcrop holding the stratotype for the Ediacaran-Cambrian boundary. Small, thin burrows preserved in the rocks from the earliest part of the Cambrian Period, spoke of this difference in the way life related to the seafloor. Vertically oriented they were, having gone into the sediment at a depth only the width of my fingernail. Nonetheless, it was a start, and an important one, heralding the evolution of ecosystems that more closely approach those of today.

See that little U-shaped burrow just below that thin sandstone? It only goes about a centimeter down, but that’s deeper than nearly any other burrow you would see in rocks from the Ediacaran Period. This sort of simple U-shaped burrow is given the ichnogenus name Arenicolites by ichnologists. Canadian-themed scale is in centimeters. (Photograph by Anthony Martin, taken at Fortune Head, Newfoundland.)

Same goes for this burrow, which is a spiral – cut on its side – and named Gyrolithes. Scale bar = 1 cm (0.4 in). (Photograph by Anthony Martin, taken at Fortune Head, Newfoundland.)

Life has moved further downward since, from worms to arthropods in marine environments, then later from millipedes to dinosaurs to gopher tortoises in continental environments, looking to places well below the surface that they could call home. So it was a awe-inspiring privilege to see a sample from the geologic record of when this first started, one centimeter at a time.

What was next stage for burrowing animals in the world’s oceans during the next 100 million years or so? To answer that question, we’ll jump ahead to the Ordovician Period, shuttling between rocks and trace fossils of that age in both Newfoundland and Georgia (USA, y’all). But while doing this, we’ll also look for glimpses of how these Ordovician trace fossils get just a little bit closer to the traces we being made in the modern sediments of the Georgia coast, and thus more like the actualism we all know and love.

Further Reading

Bottjer,D.J., Hagadorn, J.W., and Dornbos, S.Q. 2000. The Cambrian substrate revolution. GSA Today, 10(9): 1-7.

Canfield, D.E., and Farquhar, J. 2009. Animal evolution, bioturbation, and the sulfate concentration of the oceans. Proceedings of the National Academy of Sciences, 106: 8123-8127.

Gingras, M., et al. 2011. Possible evolution of mobile animals in association with microbial mats. Nature Geoscience, 4: 372-375.

Seilacher, A. 1999.Biomat-related lifestyles in the Precambrian. Palaios, 14: 86-93.

Vickers-Rich, P., and Komarower, P. (editors). 2007 The Rise and Fall of the Ediacaran Biota. Geological Society of London, Special Publication 286: 448 p.

Mistaken Point and the Limits of Actualism

Sometimes we paleontologists, especially those who also study modern organisms and their behaviors, get a little too sure of ourselves, thinking we have a clear vision of life during the pre-human past. So it’s good to have that confidence shaken a little, made uneasy by a glimpse at a much deeper past, one that preceded the bulk of fossils that shape our accepted norms and basic expectations in paleontology.

Welcome to the Ediacaran Period, the span of earth history from 635-542 million years ago, and a time when actualism – the precept that the present is the key to the past – becomes a naïve, idealistic dream, a glib summary of a world that has only existed for a mere 12% of earth history.

What are these? They’re fossils, but otherwise I’m not sure what else to tell you: guess I’ve been spending too much time in the present. But for for those people who have studied them and know better than me, they’re called Charniodiscus, and they’re frond-like fossils with holdfasts (those circular parts connected to their stems) that kept them attached to the seafloor about 565 million years ago. All you have to do to see these fossils is go to Newfoundland, Mistaken Point Ecological Reserve in Newfoundland, Canada, get permission from the Reserve to visit them, have a guide accompany you, and walk 40-45 minutes to the site from a car park. Incidentally, there will be absolutely no cafes or toilets on the way there. You know, just like how it was in the Precambrian. (Photograph by Anthony Martin; scale in centimeters.)

These discomforting realizations started a little less than two weeks ago, inspired by a field trip to the Ediacaran-Cambrian rocks of eastern Newfoundland, Canada. Why was I in cool, temperate Newfoundland, instead of sweating it out on the summertime Georgia coast? The occasion was a pre-meeting trip associated with the International Congress on Ichnology, simply known among ichnologists as Ichnia. This was the third such meeting, a once-every-four-years event (coinciding with years of the summer Olympics). The previous two were in Krakow, Poland (2008) and Trelew, Argentina (2004), and thus far these meetings also include fabulous field trips.

For Ichnia 2012, upon seeing an announcement of a field trip to Mistaken Point and other localities associated with the Precambrian-Cambrian boundary, I eagerly signed up for it. You see, Mistaken Point is world famous for its extraordinary preservation of more than 1,000 body fossils of those weird and wonderful fossils known as the Ediacaran fauna, Ediacaran biota, Vendian fauna, or Vendobionts (take your pick). This was the main reason why my fellow ichnologists on the field trip – 16 of us from 9 countries – were along for the ride, despite the trip’s clear emphasis on body fossils.

A rare photo of ichnologists getting really excited about seeing body fossils, which is totally understandable when we’re talking about the Ediacaran fossils at Mistaken Point, Newfoundland. Eventually, though, they later became unruly and started demanding, “Show me your trace fossils!” Fortunately for the sake of international ichnological relations, the field-trip leaders happily obliged that same day. (Photograph by Ruth Schowalter.)

These rare fossils, which are strange enough to even cause paleontologists to question whether or not they are animals (hence the cautious use of the more inclusive term “biota” instead of “fauna”), are abundantly exposed on broad bedding planes in Mistaken Point Ecological Reserve on the southeastern coast of Newfoundland. Discovered in 1967, these fossils have since proved to be one of the best examples of easily visible body fossils from more than 542 million years ago, and the Newfoundland fossils comprise the only such assemblage that originally lived in deep-marine environments. They evidently died in place when suffocated by a layer of volcanic ash that settled onto the seafloor, hence the fossils reflect a probable sample of their original ecosystem. This ash layer neatly preserved the fossils, and its minerals provided a means to calculate absolute age dates for the assemblage, which is from 565 +/- 3 mya (million years ago).

Bedding-plane exposure at Mistaken Point with many frond-like fossils, broadly referred to as rangeomorphs. (Photograph by Anthony Martin, Canadian-themed scale is in centimeters.)

A close-up of one of the more exquisitely preserved rangeomorphs, which I think is Fractofusus misrai. But you really shouldn’t trust this ichnologist with that identification, so it’d be wise to double-check that with a real expert. (Photograph by Anthony Martin.)

Just a few years ago, though, Mistaken Point became paleontologically famous again, and this time for its trace fossils. Researchers from Memorial University in Newfoundland and Oxford University looked at bedding planes near those holding the the body fossils, and were surprised to find a few trails there. At that time, it was the oldest evidence of animal movement from the fossil record, and although these finds have been disputed and others have tried to stake this claim for trace fossils elsewhere, it is still holding up fairly well.

A surface trail, probably made by a < 1 cm wide animal moving along the seafloor about 565 mya. The animal moved from left to right, which is indicated by the crescentic ridges inside the trail, which open in the direction of movement. (Photograph by Anthony Martin, taken at Mistaken Point, Newfoundland.)

Another surface trail, but this one without the internal structure of the other one, and with levees on either side of the central furrow. (Photograph by Anthony Martin, taken at Mistaken Point, Newfoundland.)What’s this? Don’t have a clue. It looks like a series of overlapping trails, some looping, but would have taken me several hours to unravel. Anyway, it generated some good discussion at the outcrop, and they’re probably trace fossils, which made us ichnologists both happy and perplexed. (Photograph by Anthony Martin, taken at Mistaken Point, Newfoundland; scale in centimeters.)

What made these trace fossils? It’s hard to say, and that’s a humbling statement for me to make. In public talks I’ve given about my upcoming book, and in a presentation I gave the following week at Ichnia on the Memorial University campus, I’ve assured how the actualism of the Georgia barrier islands and its traces can reliably serve as models for interpreting many trace fossils formed in different environments, and trace fossils of various geologic ages from around the world. But in this instance, I didn’t have a inkling of what made the Mistaken Point trace fossils. These trace fossils were also made in deep-marine environments, which are lacking from the Georgia coast, and I haven’t learned much about deep-marine trace fossils from elsewhere.

In short, my ignorance was showing, and these trace fossils were completely out of my realm of experience. The only feeble hypothesis I could conjure on the basis of what I’ve seen in modern sediments of the Georgia barrier islands are small marine gastropod trails. Sorry, that’s all I got.

Oooo, look, it’s snail! Making a trail! Isn’t that neat? And if you squint really hard and have a couple of beers, you might agree that it almost resembles one of the fossil trails from Mistaken Point. Don’t see it yet? Here, have another beer. (Photograph by Anthony Martin, taken at Sapelo Island, Georgia; scale in millimeters. )

But if ignorance loves company, I can feel good in knowing that others have grasped at the same straw of actualism and found it far too short. I could tell a few of my ichnological colleagues were likewise a little challenged by what they saw at Mistaken Point, and I knew that for some of them – like me – they normally deal with trace fossils in much younger rocks. But hey, that’s what geology field trips are supposed to do: challenge us with what’s really there in the rock record, right there in front of us, rather than what we wish were there.

Fortunately, a little more information provided during the meeting after the field trip helped my understanding of the trace fossils we saw at Mistaken Point, and actually connected to modern tracemakers. Alexander Liu, the primary author of the paper that first reported the trace fossils, gave a talk that reviewed the evidence for Precambrian trace fossils, including those from Mistaken Point. In experiments he and his coauthors did with living anemones in a laboratory setting, they were able to reproduce trails similar to the Mistaken Point trace fossil with the internal structure. Thus these researchers were able to use actualism to assist in their interpretation, which also meant that neoichnology was not so useless after all when applied to the Ediacaran. That made me feel a little better.

Let’s take a look at that first surface trail again, but this time with the help of my trustworthy colleague Paleontologist Barbie, who was along for the field trip. The crecentic ridges in the interior of the trail may represent marks where the basal disc of a anemone-like animal pushed against the surface as it moved. Even more interesting, the arrow points to an oval impression, which may be a resting trace that shows the approximate basal diameter of the tracemaker. What was the tracemaker? It’s currently identified as a small anemone, which is based on modern traces. Neoichnology rules! (Photograph by Anthony Martin.)

Ediacaran trace fossils still engender debate, though, and especially with people who don’t necessarily accept that animals made trails during the Ediacaran. For instance, about four years ago, some scuba-diving researchers observed a giant protozoan making a trail on a sediment surface in the Bahamas. Accordingly, they proposed that one-celled organisms – not animals – could have made similar trails during the Ediacaran Period. Interestingly, this shows how actualism can produce conflicting results when applied to Ediacaran fossils. After all, it’s still a big world out there, and we humans haven’t really observed everything in it yet.

So I’ll make one last point about Ediacaran fossils here, then will move on to more recent times. If you think that at the very least we paleontologists should be able to tell the difference between trace fossils and body fossils in Ediacaran rocks, you’re also in for some confusion. In the only research article I have ever attempted on Ediacaran fossils, which were much closer to Georgia – coming from the Carolina Slate Belt of North Carolina – my coauthors and I struggled with exactly that question with some fossils found in that area. In the end, we said they were body fossils, not trace fossils. And as everyone knows, I love trace fossils, and I really wanted these to be trace fossils. But they were not. That’s science for you: denying your deepest desires in the face of reality.

So surely the Cambrian would be easier to interpret, right? I meanl, after 542 mya, animals started burrowing merrily, to and fro, hither and tither, with uninhibited and orgiastic abandon, and, well, you get the idea. But, not really. Another part of the field trip involved looking at what happened with the departure of the relatively unbioturbated alien world of the Ediacaran, pre-542 mya, to the more familiar sediment mixing of the Cambrian and Ordovician Periods, post-542 mya. Yet even these rocks and their trace fossils were still not quite like what we see today.

This will be the subject of my next post, which will again explore the theme of how we should approach strict actualism like any scientifically based idea: with a mixture of astonished wonder, but also with a hard-edged look at what is really there.

As we bid adieu to Mistaken Point and began our walk back to the car park, we could swear we saw lifeforms emerging from the mist-covered rocks, resurrected from the deep time and deep water of the Avalonian Precambrian. Then we realized those were just some of our group behind us. Oh well. Maybe next time. (Photograph by Anthony Martin.)

(Acknowledgements: Much appreciation is extended to the field trip leaders – Liam Herringshaw, Jack Matthews, and Duncan McIlroy – for their organization and execution of a fantastic three-day field trip; to Valerie and Richard of the Mistaken Point Ecological Reserve for guiding us to the site; to my ichnological colleagues for their cheery and knowledge-broadening company; and my wife Ruth for being with me and providing an artist’s perspective about her experiences with us crazy ichnologists, shared here and here.)

Further Reading

Fedonkin, M., Vickers-Rich, P. Grey, K., and Narbonne, G. 2007.The Rise of Animals: Evolution and Diversification of the Animalia. Johns Hopkins Press, Washington: 320 p.

Liu, A.G., McIlroy, D., and Brasier, M.D. 2010. First evidence for locomotion in the Ediacaran biota from the 565Ma Mistaken Point Formation, Newfoundland. Geology, 38: 123-126.

Matz, M.V., Frank. T.M., Marshall, N.J., Widder, E.A., and Johnsen, S. 2008. Giant deep-sea protest produces bilaterian-like traces. Current Biology, 18: 1-6

Tacker, R.C., Martin, A.J., Weaver, P.G., and Lawver, D.R. 2010. Trace vs. body fossil: Oldhamia recta revisited. Precambrian Research, 178: 43-50.

Vickers-Rich, P., and Komarower, P. (editors). 2007 The Rise and Fall of the Ediacaran Biota. Geological Society of London, Special Publication 286: 448 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.