Victorian Dinosaur Tracks of the ’80s

Posted on August 17, 2016 by TMartin

The first time Tom Rich and Patricia (Pat) Vickers-Rich visited Knowledge Creek was also their last. Their sojourn that day – December 18, 1980 – had been motivated by a renewed sense of exploration and scientific discovery on the coast of Victoria, Australia. But they also had no idea that a little footprint left by a dinosaur 105 million years before them there would soon become a part of their paleontological legacy.

Two of the first known dinosaur tracks, found in Victoria, Australia in the 1980s, but described for the first time this year. (Scale in centimeters; photo by Anthony Martin.)

Just two years before Tom and Pat’s trip to Knowledge Creek, a couple of students of theirs at the time, John Long and Tim Flannery, along with geologist Rob Glennie, discovered bits and pieces of dinosaur bones in rocks from the Early Cretaceous (120-105 million years ago) of coastal Victoria, Australia. Because these were the first dinosaur remains found in that region of Australia since 1903, the husband-wife paleontologist team decided they might prospect for more bones in other places with Early Cretaceous rocks. This was a daunting task, considering the lengthy and imposing coastal outcrops both west and east of the big city of Melbourne, Victoria, but they were up for the challenge.

A rare portrait of these two Australian paleontologists – Tom Rich and Pat Vickers-Rich – in which they are not a blur of discovering, publishing, and educating. (Photo by Anthony Martin, taken in 2010.)

Knowledge Creek was one of many spots on their map of coastal outcrops that had not been properly vetted for their fossils. It was named after a modest drainage that cut across the Cretaceous rocks in the Otway Ranges and located about 2.5 hours drive west of where Tom and Pat lived in Melbourne. So off they went to assess it, a decision they soon regretted.

Need to find the way to the outcrop at Knowledge Creek? Just take a wallaby trail partway down, look for the somewhat-human trail, take a right, then a left, and keep going downhill until you find the creek with the leeches. How do you get back up? No bloody idea, mate. (Photo by Anthony Martin.)

The terrain is what prompted them to soon question their sanity. To access the outcrops then (and still) required driving along an unmarked dirt road high above the cliffs, finding a wallaby trail or other such clearing through the coastal scrub forest, bushwhacking your way down a steep, muddy slope, crossing leech-infested Knowledge Creek, and then – once on the rocky marine platform, eyes down looking for fossils – not slipping on the algae-covered rocks and getting pummeled by waves. While there, they also tried not to think about the trip back up. One challenge at a time.

Here they found Victoria’s first known dinosaur track, and the first discovered in all of southern Australia. The track was exposed on the marine platform about 200 meters (660 feet) east of where Knowledge Creek flowed out and onto the rocks. It stood out clearly as a single, raised, dark-brown three-toed entity on a flat sandstone surface, with no matching companion tracks nearby.

Discovery site of the first known dinosaur track in Victoria, Australia, found by Tom Rich and Pat Vickers-Rich on December 18, 1980. The spot where they saw the track on the marine platform would have been about 100 meters to the left, where the big wave in this photo is about to smash. (Photo by Anthony Martin.)

Luckily, Tom and Pat had brought hammers and chisels with them. so where a dinosaur foot once pressed into soft sand, they added their own traces to its hardened periphery. Into a backpack the little slab went and they carried it out, their feet leaving longer and deeper prints than before as they slogged back up the slope.

The first known dinosaur track from Victoria, Australia. It’s only about 10 cm (4 in) wide and long, and it’s all by its lonesome self, but it’s a pretty track. Also, check out those chisel traces around it, made by Tom and/or Pat Vickers-Rich. (Photo by Anthony Martin.)

They took the track to Museum Victoria, where it was assigned a specimen number and label, then put in a drawer in the paleontological collections in the basement of the old Exhibition Hall for the museum. As Victoria’s only known dinosaur track – and such a neatly defined one – it became iconic through the rest of the 1980s and afterwards. Because its shape so clearly said “dinosaur track!”, it was frequently displayed in the museum, and photos of it showed up in books and articles on the paleontology of the area. As a sign of Pat’s passion for science education and outreach, she had reproductions made of it and gave these away to local schools so Australian students could learn about Victoria’s only dinosaur track by proxy.

The old Exhibition Hall of Museum Victoria in downtown Melbourne, Australia, which houses the extensive fossil collections for the museum, including its dinosaur tracks. (Photo by Anthony Martin.)

Oddly, more than thirty years passed, and this dinosaur footprint was neither described nor diagnosed. Despite its importance, it was overshadowed by far more abundant and seemingly more exciting dinosaur bones in outcrops near Knowledge Creek. This place and its fossils were discovered by Tim Flannery, Michael Archer, and Tom Rich on December 13, 1980, and only five days before Tom and Pat descended into Knowledge Creek. Tom called it Dinosaur Cove, and thanks to its fossils and total coolness as a place name, it stuck. Here’s what he said about its origin story:

That night, needing a name for this then unnamed cove, I scribbled in my notes ‘Dinosaur Cove,’ not thinking then that it would ever have any particular significance.

Dinosaur Cove, one of the most important fossil sites in Australia and for polar dinosaurs in the Southern Hemisphere. (Photo by Anthony Martin.)

Tom Rich next to the sealed tunnel at Dinosaur Cove, where he, Pat Vickers-Rich, and many volunteers extracted many fossils during the 1980s and early 1990s. (Photo by Anthony Martin.)

Here was where this part of Australia became justifiably famous for its dinosaur fossils in the 1980s and 1990s, as Tom and Pat, along with dedicated field crews, extracted hundreds of skeletal bits and pieces of dinosaurs and many other animals that lived there. What made these remains even more important, though, was how their former owners lived near the Cretaceous South Pole, when Australia was still connected to Antarctica. This meant Tom, Pat, and their colleagues were documenting what was then one of the few known polar-dinosaur assemblages in the world. For about ten years, they and their teams also performed some of the hardest labor any dinosaur-recovery effort should ever have to endure, described in their book Dinosaurs of Darkness (2000).

The cover of Dinosaurs of Darkness (2000), coauthored by Tom Rich and Pat Vickers-Rich, with cover art by famed paleoartist Peter Trusler.

Nearly nine years went by after the discovery of the track at Knowledge Creek, as it remained the only one in Victoria. That changed in early 1989, when geologist Helmut Tracksdorf found two more. While out for a walk along the genteel seashore near the small coastal community of Skenes Creek (Victoria), he spotted the tracks on a marine platform only 50 meters (~160 feet) south of The Great Ocean Road. Although these footprints were about 35 kilometers (18+ miles) east of Knowledge Creek, they were also in Early Cretaceous rocks, from a little more than 100 million years old. One of the tracks had three clearly defined toes, whereas the other was not so obviously a track. (Spoiler alert: But it was.)

Helmut next did the right thing, and reported the tracks and their location to Tom Rich at Museum Victoria. On March 18, 1989, a field crew from the museum stopped by the marine platform, found the tracks, used a portable rock saw to cut each out into manageable sizes, and loaded the two slabs into a vehicle for the drive back to Melbourne. Again, these two tracks received a Museum Victoria specimen number and were placed in a drawer, sharing the same Exhibition Hall basement with the Knowledge Creek track. And there they stayed, also unstudied until just recently.

The better-defined of the two Skenes Creek dinosaur tracks discovered by Helmut Tracksdorf in 1989. The scale bar is 5 cm (2.5 in), so this track is also about 10 cm (4 in) wide, has three toes, and raised, just like the Knowledge Creek track. You can also tell it was on a marine platform because of the little crustacean (barnacle) on its lower right edge. (Photo by Anthony Martin.)

The not-so-well-defined of the two Skenes Creek dinosaur tracks discovered by Helmut Tracksdorf in 1989. Yeah, I know, it’s blobby and you have to squint and maybe have a few beers before it starts looking like a three-toed dinosaur track, but it’s a track. Just like bones, tracks aren’t always perfectly preserved, either. (Scale in centimeters; photo by Anthony Martin.)

Oddly, Helmut did not receive any confirmation that the tracks had been collected. He only learned of their acquisition indirectly later in 1989 when he saw rectangular holes in the marine platform marking where the tracks used to reside. Also, whoever wrote the specimen label in 1989 did not record that he was the person who discovered the tracks. Years later, I asked Tom, Pat, and others at the museum then, and no one could recall who found it. Only in October 2013 did I and everyone else finally find out it was Helmut, who wrote to me to confess his role after reading a blog post of mine. For that, I thank him most sincerely for his long-time non-credited contribution to the dinosaur ichnology of Victoria.

Helmut Tracksdorf, who in 1989 discovered Victoria’s second and third dinosaur tracks, as well as Victoria’s first dinosaur trackway. Here he is more recently taking a rest from bushwalking by sitting on Cretaceous rocks of the Victoria coast. Also, he either lost his boots or was busy making his own distinctive tracks for future generations to discover. (Photo courtesy of Helmut Tracksdorf.)

In February 2006, about 17 years after Helmut’s find, I was in Australia on a rare sabbatical from my university (very rare, too rare, as in, the only one ever). I was there primarily to work on a science-education project with Pat, who I had long admired as both a scientist and science educator. Yet within my first week there, Tom Rich invited me to go with him to the Dinosaur Dreaming dig site near Inverloch, Victoria. Tom, Pat, and the other dinosaur hunters of Museum Victoria and Monash University had abandoned Dinosaur Cove since the early 1990s, and Dinosaur Dreaming was their “new” polar-dinosaur dig site. Again, it was relatively close to Melbourne (only a little more than a two-hours drive away), and although it had its own set of logistical challenges, it was was much easier to access than Dinosaur Cove.

On the morning of February 26, 2006, Tom drove just him and me from Melbourne to the Dinosaur Dreaming site, and I was soon walking on the Cretaceous rocks of Victoria for the first time. That same day, I found two large theropod dinosaur tracks, the first ever found in Victoria, but which Tom instantly rejected as real when I showed them to him. Later that day, he drove off with my field boots on the top of his Land Rover. But both of those are stories that can be told another time.

My first view of the Dinosaur Dreaming site (near Inverloch, Victoria) on February 24, 2006. The photo was taken from a car park just above, with wooden steps leading below, lending to a bit more civilized journey for volunteers compared to Knowledge Creek or Dinosaur Cove. (Photo by Anthony Martin.)

Since that day in 2006, I’ve worked with Pat, Tom, and others there on-and-off for the past ten years, during which I have found and/or documented a few other trace fossils in that part of the world. Some of these turned out to be paleontologically significant (such as this one, this one, this one, and oh yeah, this one), and more are on the way. It’s been a really good journey for all of us, and my working with Pat and Tom changed my life and career for the better. I am extremely and unreservedly grateful to them for their mentorship and friendship.

Yet probably the most important gesture of support for my ichnological work in Victoria came from Tom in 2010. He decided to apply unused Museum Victoria research funds to fly me round-trip from Atlanta, Georgia to Melbourne, Victoria, and paid for a month of our doing field work together along the Victoria coast. It was an unforgettable experience in many ways, which I partially documented in my first blog (The Great Cretaceous Walk, dormant since 2011). We walked together for probably a few hundred kilometers on the rugged Victoria coast, him looking for bones, and me looking for dinosaur tracks, insect and crustacean burrows, and other trace fossils. You could say it was a bit of an adventure.

Yours Truly in May 2010 with Cretaceous sandstones to the left and the ocean to the right, near the start of what I called “The Great Cretaceous Walk.” (Photograph by Tom Rich.)

Three weeks into that excursion along the Victoria coast with Tom, I’m happy to say I finally helped end the drought of dinosaur-track discoveries in Victoria, which had seemingly been in limbo since the 1980s. While walking along Milanesia Beach, west of Knowledge Creek and Dinosaur Cove, I spotted a motherlode of small dinosaur tracks on a rock slab there. Tom and Greg Denney – a long-time friend of Tom’s from Dinosaur Cove – were with me at the time, and Greg soon found another slab with more dinosaur tracks next to mine. The detailed story of this day and the discovery of these tracks is in a chapter titled The Great Cretaceous Walk in my book Dinosaurs Without Bones (2014).

Although the two slabs together only held twenty tracks, it still constitutes the best assemblage of polar-dinosaur tracks in the Southern Hemisphere. Would someone have eventually found these or other dinosaur tracks at Milanesia Beach? Probably. But thanks to Tom’s support and Greg’s help, we found them a lot sooner.

Most of the video footage shown here, along with thousands of photographs (and many more footsteps) were taken at Milanesia Beach by my wife Ruth Schowalter. We shared many adventures on the Victoria coast and elsewhere in Australia.

Thus in 2013, when paleontologist Erich Fitzgerald of Museum Victoria sent out a request for former and current colleagues of Tom Rich to contribute research papers for a special volume in his honor, I readily accepted. But what topic could I address that would be scientifically meaningful, while also linking it to Tom and Pat? That’s when I decided to dust off my detailed notes, measurements, and photos taken of Victoria’s first dinosaur tracks during previous visits to the museum. There were just three footprints to study: the one Tom and Pat found in 1980, and the two Helmut found in 1989.

The two best-preserved of the Victoria dinosaur tracks of the 1980s. The one on the left is from the marine platform near Skene’s Creek and the one on the right is from Knowledge Creek. Even though they look almost identical, they were separated by more than 30 km (18 miles). (Photo by Anthony Martin.)

With only three tracks to examine, this was a manageable study, and I did it in an old-fashioned way, using a ruler, calipers, pencils, notebook, my eyes, and occasionally my brain as the main instruments for scrutinizing the tracks. No lasers, CT scanners, 3-D printing, virtual reality, aerial drones, avatars, self-aware AI devices, or other forms of technology were necessary for doing this science. All I needed was for one of the collections managers – David Pickering – to retrieve the tracks from Museum Victoria collections for me, a table to support them, and I was in business.

Because drawing is one of the best ways for me to observe, I started with making scaled sketches of the tracks, which helped me to pick up details missed in times before when just glancing at the tracks. This is an example of practicing what I preach, as I often require my students to make labeled drawings as part of their scientific process.

Scaled drawings (“maps”) of the two tracks, drawn on May 25, 2010, which helped me to compare their relative dimensions and forms. These and other sketches, descriptions, and measurements are in a field notebook, which I prefer using even when in a museum.

I also measured the tracks so that they were thoroughly quantified. Ideally, this meant I would have recorded track width, track length, widths and lengths of individual toes, and angles between the toes. However, two of the three tracks (from Skenes Creek) were not preserved well enough to measure everything I wanted, although one of those was good enough I could compare its measurements to those of the Knowledge Creek track. These numbers, when combined with my qualitative descriptions, later helped me to identify “who” (which dinosaurs) made the tracks.

Diagram showing what was measured in the Victoria dinosaur tracks: TW = total width, TL = total length, L1-3 = digit lengths, W1-3 = digit widths, and IA1-2 = interdigital angles. Figure from Martin (2016).

Based on my perusal, these three-toed tracks were made by small ornithopod dinosaurs, often informally called “hypsilophodontids.” Although such dinosaurs do not belong an evolutionarily united group (clade), dinosaur paleontologists still use this term informally when talking about small ornithopods that lived during the Late Jurassic through the Cretaceous Period in different parts of the world. Among the Victorian dinosaurs found and documented by Tom, Pat, and others, hypsilophontids are the most common dinosaurs, abundantly represented by bones and teeth.

What’s significant about my interpretation is that these are the first known small ornithopod tracks from Victoria, and by default, all of southern Australia. (All other dinosaur tracks found in Victoria since the 1980s are from theropods, both bird and non-bird.) This is important because it officially connects the body-fossil record of small ornithopods with their probable trace fossils for the first time. Another meaningful facet of this connection is how the tracks scientifically affirm details of Peter Trusler’s remarkable 1992 painting, Early Cretaceous in Southeastern Australia – Spring Scene. In this artwork, he used the Knowledge Creek track as a template for depicting tracks made by small hysilophodontids on a sandy riverbank following spring thaws (and flooding) of that formerly polar region. So I was most pleased to have my science finally connect with his predictive (and gorgeous) artwork.

Peter Trusler’s extraordinary painting Early Cretaceous in Southeastern Australia – Spring Scene (1992), visualizing then-fresh three-toed tracks left by hysilophontid dinosaurs on a sandy riverbank after spring-thaw floodwaters had waned. Let me emphasize that this is a painting and he made it in 1992, meaning there is nothing digital about it. When I show it projected on a screen in my talks, people gasp because they at first think it is a photograph, but also because of its beautiful, evocative composition. No wonder I wanted it to be on the cover of my book Dinosaurs Without Bones.

One remarkable point about the two well-preserved tracks from Knowledge Creek and Skenes Creek, though, is their strikingly similar size and form. Despite being separated by more than 30 kilometers (18 miles) they could have been made by not just the same species of dinosaur, but the same dinosaur. They were even preserved the same, protruding from the top of the bed, instead of as depressions or natural casts on the bottom of a bed. This odd preservation likely was caused by the tracks filling with a different sediment holding the track, which then cemented more firmly, leaving the track behind when modern-day ocean waves eroded the top surface.

Yet another insight that came out of the study, and a totally unexpected one, resulted from correspondences with Helmut and ace Victoria-fossil-finder Mike Cleeland. After exchanging a few messages with one another, Mike decided that he and his wife Pip would try to re-locate the original discovery site for the tracks by looking for the 1989 saw marks in the rocky marine platform. And re-locate them they did. Even better, the rock-saw traces lined up, indicating that the two tracks were aligned, and likely from a trackway made by the same individual dinosaur. This means Helmut found Victoria’s first dinosaur trackway – consisting of two or more tracks made by the same dinosaur – in 1989. This was 21 years before I found what I thought was the “first” dinosaur trackway at Milanesia Beach, so I need to stop bragging about that. In my face!

The site of the first known dinosaur trackway discovered in Victoria (Australia), originally found in 1989 and marked today by rock-saw marks. (Pip Cleeland for scale; photo by Mike Cleeland.)

The sequential steps of a small ornithopod dinosaur represented by rock-saw cuts. (Photo by Mike Cleeland.)

Given such intriguing results, it was time to write the article and have it reviewed. However, it took a while. I wrote the main text of the article in a few months, then picked out and labeled photos of the tracks, made a few illustrations, put them all together into one coherent manuscript, and submitted the article for peer review in June 2014. A few months later I received the reviews, which were mostly positive and helpful. (Thanks, reviewers!) I changed the article accordingly, then resubmitted it a few months later. However, I didn’t see page proofs of the corrected article until July of 2015, and the final galley proofs until just a few months ago. So you could say I was most pleased when it was published last month, although probably not as much as the editor of the volume.

Because the article was one of many in a special volume honoring Tom, all authors were told to keep quiet about it so that it would be a big surprise for Tom and Pat once published. Somehow we did it, and on July 19, 2016, Tom received his bound copy of the volume and at Museum Victoria, flanked by former students Tim Flannery and Erich Fitzgerald. It must have been quite a special moment, and I smiled when I saw the following photo posted on Twitter the next day.

The Tom Rich special volume was complete once the secret was unveiled, which happened on July 19, 2016 at Museum Victoria. Here Tom is accompanied by his former students Tim Flannery (left) and Erich Fitzgerald, the latter of whom did a ripper of a job on editing the volume. (Photo by Alastair Evans.)

Other than everything else I said before, are there two takeaway messages from this study? Yes. One is that amateur contributions have been and always will be important for paleontology. Helmut Trackdorf’s discovery of the first dinosaur trackway in Victoria in 1989 and his contacting me about it in 2013 may seem small when compared to other discoveries in that area of the world. Yet it is a puzzle piece that now fits better in our picture of Cretaceous life in that area of the world: every little bit helps. Also, now that we’ve relocated the original discovery spot, we might find more dinosaur tracks near there. We’ll see.

The second message is that well-curated museum collections are damned important for doing a lot of good science in paleontology. For instance, I have been to Knowledge Creek three times, and on all three of those visits I looked for the chiseled hole in the marine platform where Tom Rich and Pat Vickers-Rich found that first dinosaur track in 1980. Alas, I did not find it. So if they had not collected the track and put it in Museum Victoria, it may never have been found and studied by me or anyone else. The same goes for the Skenes Creek tracks found my Helmut Tracksdorf in 1989: If these hadn’t gone to the museum, no study of those, either.

Those tracks belonged in a museum, and so did I. But if the museum wasn’t there to act as a repository for the specimens, or it didn’t have collections to study, then I wouldn’t have been there either. What’s the moral of the story? Support museums.

In summary, this is a little article about a few fossil tracks made by two small dinosaurs a long time ago in a cold place very far away from when and where I am right now in Atlanta, Georgia. Yet I am very proud of it as a way for me to give something back to my mentors and other discovers out there, as well as all of the good people in Victoria who helped make it happen. Good on ya, mates!

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The citation for the original research article is:

Martin, A.J. 2016 A close look at Victoria’s first dinosaur tracks. Memoirs of Museum Victoria, 74: 63-71.

The article is also open access and free to download at the following link:

A Close Look at Victoria’s First Dinosaur Tracks

Blog Posts Reporting on the Article:

Dinosaur Tracks Lead Paleontologist through Museum to Mentor’s Discovery: Carol Clark, eScienceCommons (Emory University), July 29, 2016.

Tracking Australia’s Dinosaur Past: Jon Tennant, PLoS One Paleo Community, August 8, 2016.

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Afterthought: The main reason why I published this article with Memoirs of Museum Victoria rather than another journal was to honor Tom Rich. But what sealed the deal for me was learning that the article would also be freely available to the people of Victoria – or anyone else, for that matter – with an Internet connection. Some things in life are more important than journal impact factors. So there.

Of Sacred Mules and Sauropod Tracks

Posted on May 25, 2016 by TMartin

Legends and storytelling are an intrinsic part of being human. Given this statement, you might then also think of myths and other stories you’ve heard throughout your life. Which were the most memorable, and why? With such remembrances, your next step may be to do something else that is very much a part of being human, which is to wonder whether that myth or story holds some lesson applicable to real life. Whether a story is an accurate account of reality is beside the point, as its imparted teachings are sometimes more important than factual accuracy.

Modern scientists say these depressions in a tilted rock surface near Sesimbra, Portugal were made by sauropod dinosaurs in soft sediments during the Jurassic Period more than 150 million years ago. But what if you lived in this area during the 14^th century? How would you explain these depressions? While you’re thinking about that, here’s another question: If I hadn’t told you these were dinosaur tracks, would you even know they were tracks? (Photograph by Anthony Martin.)

Yet, what if reality and scientific reasoning – with the latter thriving on a spirit of disproof – rudely intrudes on a good story, disrupting its original intent? In such instances, a legend previously regarded as literal truth may lose its narrative power, as we begin to doubt not just its details, but also its intent. Can anything useful be salvaged from a myth when skepticism assaults faith? Should we completely reject parables once we know foxes do not talk about grapes, sour or otherwise?

Less than two weeks ago I visited a place where the basic facts of a long-held legend had been disproved, yet a lesson from it remains. The place is Cabo Espichel, marked by a lighthouse, church, and small chapel on a plateau high above rocky cliffs along the southwest coast of Portugal. Cabo Espichel is about a 90-minute drive from the modern metropolis of Lisbon, yet it felt far more remote, and very much connected to a medieval past.

A view of Lagosteiros Bay from the top of Cabo Espichel. Also check out those gorgeous outcrops of tilted Jurassic and Cretaceous rocks! Gee, I wonder what trace fossils might be in them? (Photograph by Anthony Martin.)

The legend associated with that place concerns a 14^th century visitation there by someone named Mary, who is also known by many other names: Saint Mary, Mary of Nazareth, Blessed Virgin Mary, Our Lady, The Madonna, or very simply the Mother of Jesus. Given the Catholic culture that is very much still a part of the Iberian Peninsula, her purported arrival to Portugal there was (and still is) considered a blessing and a ringing endorsement of Christianity there. Accordingly, the church complex is called the Santuário de Nossa Senhora do Cabo Espichel (“Sanctuary of Our Lady of Cape Espichel”).

Ichnologists approaching the Santuário de Nossa Senhora do Cabo Espichel, Portugal, not on the way to confess their sins (that would have taken way too long), but to see the small chapel behind it, as well as some great coastal outcrops of Mesozoic rocks. So you might say they were there for a different type of worship. (Photograph by Anthony Martin.)

How did Mary get to Portugal from the Middle East? Given the absence of airlines then, she and the Baby Jesus traveled by boat. Once the Mother and Child reached the shore of Lagosteiros Bay below Capo Espichel, a giant mule carried them up the steep rock faces of Cabo Espichel. This scene came in a vision to two men in the area, who shared the same dream of her arrival on the same night. In a splendid example of confirmation bias, their testimony was taken quite seriously by the local populace and beyond, and has endured since.

Cliff face below the present-day chapel and church at Cabo Espichel, with well-exposed and tilted bedding planes of sedimentary rock. This would have been the most likely route for a mule (giant or otherwise) to have accessed the top from Lagosteiros Bay. Photo is a still taken from an online edited drone video titled “Cabo Espichel – Dinosaur Trackway Adventure.” Related to the question asked in the previous caption: Huh, I wonder what those depressions on the rock face might be, how they relate to the legend, and the title of that video?

In commemoration of this momentous event, the church and chapel – the latter called Ermida da Memória (Chapel of Memory) – were built near the precipice. Portuguese royalty hosted annual feasts there, and many pilgrims put it on their spiritual “bucket list” as a must-visit place. Today, it is still visited by devout Catholics, who may be imagining themselves walking on the same holy ground trodden by Mary and her miraculous mule.

The Ermida do Memória seen from afar on Capo Espichel. Imagine it in the darkness of night, when suddenly a glow comes from the bay below. Inside this light, the head of a giant mule appears, and as more of its body emerges from the cliff edge, you see Mother Mary astride it carrying the Baby Jesus, accompanied by an aerial escort of angels and the most beautiful music you’re ever heard in your life. OK, Guillermo de Toro, I just wrote the scene for your next movie: the rest is up to you. (Photograph by Anthony Martin.)

So where did this legend come from: crazed fishermen who had spent one day too many at sea, villagers imbibing enthusiastically on local vinho verde, or clergymen overcome by ecclesiastic visions? No, this story actually had evidence backing it up. All one had to do is get in a boat just offshore, and you could see for yourself enormous footprints in the rocks leading from the sea to the top of the cliff at Cabo Espichel.

They’re a little tough to see from this far out, but the big white arrows help. The “mule tracks” are on tilted strata just above the bay, and compose diagonal-walking patterns. (Photo taken as still from video Cabo Espichel – Dinosaur Track Adventure. I would have prefaced that information with “Spoiler Alert,” but you did read the title of this post, right?)

A closer view of a rock surface with the diagonal-walking pattern clearly defined, accentuated by vegetation growing in the depressions. Don’t believe me that these are from the same site? Look up “Cabo Espichel, Portugal” on Google Earth™, scan the rock surfaces just north of the chapel, and see them for yourself. (Photo again is still taken from video Cabo Espichel – Dinosaur Trackway Adventure.)

These tracks, people said, marked where the weight of the mule pressed into the rocks. Even better, some of these tracks formed patterns clearly made by four-legged animals, and individual tracks were crescent-shaped, resembling the feet of mules or other horse-like animals. As a result, one name applied to this place is Pedras de Mula, which translates as “Rocks of the Mule,” although Pegadas de Mula (“Tracks of the Mule”) is also applied.

Every good story also needs images, and this one has a particularly noteworthy visual aid. The building of a chapel on the site in the 16^th century contains tile artwork commemorating this divine calling; however, the tile was probably made later, in the 18^th century. Although the chapel interior is closed to the public, a open slot in its door afforded a glimpse of this depiction, aided by the zoom lens on my camera. Like any good illustration, the story is neatly encapsulated in the tiles: Mother Mary and The Baby Jesus riding on a mule, with angels in tow and stunned onlookers properly prostrating.

18^th century tiled artwork inside the Ermida do Memória depicting the legend of Mary’s visitation of Cabo Espichel. To all artists out there (and I’m one of you), the original creator of this work is unknown, hence image credit cannot be assigned here. (Photograph by Anthony Martin.)

Centuries later, ichnology happened. Beginning in the mid-1970s, geologists and paleontologists realized that the Mesozoic rocks of Portugal, including those at and near Cabo Espichel, held dinosaur tracks. This consciousness has been affirmed many times since, with discoveries of tracks belonging to a wide variety of Jurassic and Cretaceous dinosaurs: theropods, ornithopods, stegosaurs, and sauropods among them. Portugal is now rightly renown as one of the best places in the world to see thousands of well-preserved dinosaur tracks, all within just a few hours drive of one another.

A close-up of a dinosaur trackway – probably from a sauropod – on one of the rock surfaces at Cabo Espichel. As folks would say in my part of the U.S., “Those ain’t from no mule.” (Photo is still from video Cabo Espichel – Dinosaur Trackway Adventure.)

Dr. Vanda Faria dos Santos, Portugal’s premier dinosaur tracker, telling us about the sauropod tracks at the Avelino tracksite, just south of Cabo Espichel. Notice the abundant depressions on a tilted rock face, very similar to those at Cabo Espichel. (Photograph by Anthony Martin.)

Of these tracks, those of sauropods were the most relevant to the tale of Cabo Espichel. The majority of sauropod tracks in Portugal are very large, especially those of the rear-foot (pes), which can be about a meter long and nearly as wide. The front-foot (manus) impressions are smaller, but still approach a half-meter wide, and are crescent-shaped. You know, like those of a horse, or mule.

Front-foot (manus) track made by a Late Jurassic sauropod preserved as a cresent-shaped depression at the Avelino tracksite near Sesimbra, Portugal. (Photograph by Anthony Martin.)

A detailed field study of the tracks at Cabo Epischel, done by Martin Lockley, Christian Meyer, and Vanda Santos in 1993 and published in 1994, confirmed that the “mule tracks” at Cabo Epsichel were indeed those of sauropods. The original surfaces were of soft sediment and horizontal; only later did a combination of cementation and plate tectonics harden and tilt these rocks, with coastal erosion finally rendering their current appearance. Moreover, ten sauropod trackways on one of the bedding-plane surfaces there recorded the herding movements of seven smaller sauropods (juveniles) and three larger ones (adults), all of them walking in more-or-less the same direction. These results thus made the site scientifically famous, as it was one of the first convincing examples of family herding behavior in sauropods demonstrated from their footprints.

Trackway map of bedding plane at Cabo Espichel in article by Lockley, Meyer, and Santos (1994). The map shows parallel smaller (juvenile) sauropod trackways (numbers 1-7), followed by two larger (adult) sauropod trackways (numbers 8-9); another adult trackway is not on this figure, but was below the other two.

Here’s the full edited aerial-drone video linked previously, Cabo Espichel – Dinosaur Trackway Adventure. The video credit only says “rlage3,” so if the person/people who produced this would just let me know who you are, I’m more than glad to give full attribution. In the meantime, thanks much for providing such a nice overview of this beautiful and ichnologically rich area!

This situation with competing stories is where ichnology excels, as it is also a science based on storytelling. Granted, the story told by ichnologists is radically different from the one first accepted by the 14^th century people of Portugal, or those since who have accepted the faith-based explanation for the tracks. On a personal note, I’m ex-Catholic; hell, I was an altar boy, went to a Catholic college for my undergraduate studies, and my mother was a more devout Catholic than most pontiffs. Thus I have much empathy for how people of faith (especially Catholics) feel about such things. So if pilgrims still chose to believe the tracks of Cabo Espichel were made by a giant mule bearing Mary and Jesus, and this fills them with joy, I’m cool with that. Just don’t tell me our science is wrong.

So now I will leave you with two provocative thoughts. The first is that the tile artwork in the chapel is the first known illustration of dinosaur tracks. Is it a scientifically accurate, to-scale, 3-D rotating digital model of a dinosaur trackway? No, but it’s still an illustration, and even though its interpretation does not qualify as science, it clearly shows a large, diagonal-walking trackway pattern on an inclined cliffside at Cabo Espichel. Let that sink in for a second: an 18^th century artist must have seen dinosaur tracks on a bedding plane somewhere in that area, and faithfully reproduced them in a recognizable pattern.

Close-up of tile artwork in the Ermida da Memória, connecting the trackway pattern to a mule, but which we now can be sure was inspired by the trackway of a Late Jurassic sauropod dinosaur. (Photograph by Anthony Martin.)

The second thought is that although the interpretations of this trackway might differ radically, what they share is true: These impressions in the rock were made by enormous, walking, four-legged animals. How many modern people today, their eyes no-doubt glued to their 21^st-century devices, would stumble in such tracks, possibly never recognizing their connection to animal life? So rather than make fun of the people of Portuguese past, or whoever else must have observed the tracks preserved in the rocks of Cabo Espichel, we should celebrate those who recognized these depressions as traces of life. In this sense, then, the faith-filled people of the past were doing their own form of ichnology in Portugal, centuries before we modern ichnologists walked in the same place.

Afterword: Many other paleontologists and science historians have written about the discovery of the first known sauropod tracks in Portugal, so I will not repeat nor summarize their contributions here. Instead, I’ve included the following bibliography. Many thanks to Drs. Vanda Santos, Paulo Caetano, Carlos Neto de Carvahlo, and Joana Rodrigues for teaching other ichnologists and me about the long ichnological history of Cabo Espichel.

Further Reading

Atunes, M.T. 1976. Dinossáurios Eocretácios de Lagosteiros. Ciéncias da Terra (UNL), 1: 1-35.

Atunes, M.T. 1990. Dinossáurios em Sesimbra e Zambujal – Episódios de há cerca de 140 milhões de anos. Sesimbra Cultural: 12-14.

Chure, D. 2012. Sacred birds, lucky rhinos, and The Virgin and the sauropod. Land of the Dead (blog), January 7, 2012.

Lockley, M.G., Meyer, C.A., and Santos, V.F. 1994. Trackway evidence for a herd of juvenile sauropods from the Late Jurassic of Portugal. Gaia, 10: 29-40.

Lockley, M.G., Novikov, V., Santos, V.F., Nessov, L.A., and Forney, G. 1994. “Pegadas de mula”: an explanation for the occurrence of Mesozoic traces that resemble mule tracks. Ichnos, 3: 125-133.

Santos, V.F. 2008. Pegadas de dinossáurios de Portugal. Museo Nacional de História Natural da Universidade de Lisbõa, Lisbõa, 123.

The Ichnology of Pacific Rim

Posted on July 26, 2013 by TMartin

Last week I surrendered to geekdom peer pressure and went to see the new summer blockbuster Pacific Rim. Living up to my namesake, St. Anthony, I normally don't have a problem resisting such temptations, and just wait to see a movie like this in some other format: DVD, Netflix, or the way movies were originally intended to be seen, on a tiny screen on the back of an airplane seat. But what really pushed me to go was the following image, only glimpsed for a few seconds in one of the trailers:

Ooo, look, a trace made in an intertidal sandflat! Perhaps it's from a ghost crab, moon snail, or shorebird. Hey, wait a minute, something doesn't quite look right. Are those people next to it? (Image from http://www.comicbook.com.)

Yes, that’s right: it's a gigantic footprint, and in what looks like an intertidal coastal environment, between the low tide mark and coastal dunes. That was all the incentive I needed, as I further wondered what other ichnological wonders would be included in the film. I was also encouraged to see where other scientifically inclined bloggers had fun with Pacific Rim by taking a look at its biology (here, here, and most recently, here) and physics (here, here, and most recently, here). So given a $5 afternoon matinee and a spouse (Ruth) willing to indulge my sci-fi inner nerd (OK, so it’s not so “inner”), I had every reason to document the various traces and tracemaking activities in the film. You know, for science and science education.

The verdict? Well, I have to admit some mild disappointment with how the director – Guillermo del Toro - chose to focus on the conflicts between massive amphibious creatures (kaiju) constructed by interdimensional aliens and human-guided fighting machines (jaegers), rather than on their traces. Nonetheless, I managed to find some ichnological gems scattered throughout. For example, the footprint shown in the trailer did indeed look glorious on a big screen, and the human figures associated with it reminded me of Jason Isley’s whimsical underwater photos. But let’s take a closer look at what this footprint tells us about its maker.

Although viewed from an oblique angle, the track seems longer than wide, and has four clearly defined digits, although a probable fifth digit is visible on the side farthest from the viewer. All of the digits are forward-pointing and taper abruptly at their ends. The tracks also has an indentation on the “heel” (proximal) part of the foot, and is more-or less-bilaterally symmetrical. Pits inside of the track may represent additional anatomical traits, such as scales or other bumps on its skin, or could be sediment that underwent liquefaction or other soft-sediment deformation.

Interpreted kaiju track, extrapolated from oblique view. Scale = 10 m (33 ft).

Using the people around the tracks as informal units of measurement, and assuming from the hiragana-katakana in the newscast image that this track - like many items - was made in Japan, we can estimate the dimensions of the track. Average heights for Japanese males and females are 1.71 m and 1.58 m, respectively, and the average of those is 1.64 m. Using one figure (boxed) as a unit that equals 1.64 m (5.4 ft), the footprint had about 18.4 Japanese-Person-Units (JPU) length and 10.1 JPU width, which converts to about 30 m (98 ft) long and 17 m (56 ft) wide. This results in a length:width ratio of about 1.8.

Length and width measurements for kaiju track, including figure used as 1.0 JPU = 1.64 m. Width measurement is assumed on basis of probable fifth digit impression on side of track furthest from the viewer.

Unlike in most articles published in high-impact journals, I'll actually admit potential sources of error in these measurements before I'm forced to retract this blog post under a cloud of scandal, followed by my accepting a high-paying position on Wall Street, where such inaccuracies are rewarded without penalty. For example, the width measurement, because it is being taken from an oblique angle (not so accurate) instead of from directly above (much more accurate) probably underestimates the actual width. So the actual width is probably closer to 20 m (67 ft), which reduces the length:width ratio to about 1.5. The length measurement would also benefit from more of an overhead view, and probably would best be studied using aerial high-resolution LiDAR scanning. So there.

To put this in ichnological perspective, when these dimensions are compared to typical sauropod dinosaur tracks from the Early Cretaceous of Texas - where everything is supposed to be bigger - the sauropod comes out looking pretty puny indeed. In this example, the rear track length is 87 cm (34 in) and width is 59 cm (23"), and although its length:width ratio comes out fairly close to my estimation for the kaiju track (1.47), it is only about 2% of its size. Some "thunder lizard."

Sauropod tracks from the Early Cretaceous (about 120-million-years-old) Glen Rose Formation of central Texas.The larger track is from the left rear foot, and the smaller one in front of it is the left front foot; this sauropod was walking slowly with an "understep" gait, in which its rear foot stayed behind its front. Please read the preceding text for all of that measurement stuff, which ichnologists sometimes call "data." (Photograph taken by Anthony Martin in Dinosaur Valley State Park, near Glen Rose, Texas.)

To-scale comparison between sauropod track (arrow, lower left) and kaiju track (right) to same scale. Looks like some cute little saurischian would be feeling a little inadequate. As Cowboy Curtis once said on Pee Wee's Playhouse, "You know what they say: Big feet, big boots!" Scale = 10 m.

Speaking of high impact, how about track depth and other features of this individual track that might tell us about behavior of the kaiju tracemaker? Oddly enough, the kaiju track looks too shallow to me, measuring only about 1.6 JPU, or about 2.5 m (8 ft) deep. It also lacks pressure-release structures, which are sedimentary structures caused by the tracemaker applying and releasing pressure against the wall of the track. Considering that kaiju were supposed to weigh tens of thousands of tons, this track should have a greater depth, along with major ridges and plates outside of the track outline that would have been imparted by any forward or lateral movement of its foot.

Alternatively, this track may represent more of what I would call a “stamp,” which would have been made by placing a foot directly down onto a soft substrate and pulling it straight up, rather than from moving forward or laterally. Based on this evidence, the kaiju might have been attempting to squish pesky humans, rather thank performing its normal, forward-walking, city-destroying gait. Unfortunately, the preceding and next track are not shown in the photo, which would help to test this hypothesis.

Other than size, how does the form of this track compare to those of other known dinosaur tracks? The length: width ratio comes out close to that of a sauropod dinosaur, yet other qualitative traits of the track, such as thin digits that taper and end with sharp clawmarks, are more like that of a theropod. But I do want to point out a little coincidence. Have you ever seen the front-foot track of a typical raccoon? Hmmm...

I give you you raccoon tracks, and I give you kaiju track. That is all. (Photo of raccoon tracks taken by Anthony Martin on Cumberland Island, Georgia.)

What’s really fun, though, is if you compare the kaiju track to known theropod tracks. Theropod tracks bearing four or more forward-pointing toes are quite rare, and the few identified probably belong to a group of theropods called therizinosaurs, which - by a strictly enforced paleo-nerd law - cannot be mentioned in a sentence without also using the descriptor "bizarre." Late Cretaceous dinosaur tracks recently reported from Alaska with four long, forward-pointing digits have been attributed to therizinosaurs. Were the creators of the kaiju track trying to compare it to that of a really strange theropod dinosaur? Maybe, maybe not.

Artistic rendition of Nothronychus mckinleyi, a therizinosaur from the mid-Cretaceous of North America (left) and a four-toed rear-foot track credited to a therizinosaur from Late Cretaceous rocks of Alaska (right). Therizinosaur artwork by paleoartist Nobu Tamara and available in Wikipedia Commons here; photo of track by David Tomeo and reproduced from Everything Dinosaur.

Although the Pacific Rim kaiju designers used a mix of invertebrate and vertebrate elements for anatomical details appearances of their monsters (detailed splendidly by Darren Naish here), I do wonder how they came up with the track, and which real-life animals - modern or extinct - were supposed to be evoked by this track's brief appearance onscreen. Hopefully the DVD and its Special Features will reveal all once that comes out.

(Incidentally, this attempt to divine the evolutionary relatedness of a science-fictional animal from a single track reminds me of a scene from the classic science-fiction film Forbidden Planet. At some point, an invisible monster comes aboard a spaceship on the aforementioned planet and kills its chief engineer. The ship scientist, Dr. Ostrow, then gave a fine interpretation of the monster based on a plaster cast made from one of its footprints, including how it traits seemed to go against all known evolutionary principles. It's such a fun scene, I've shown it in some of my classes as an example of "extraterrestrial ichnology.")

Other tracemaking in the movie, of course, included wholesale destruction of major population centers by the kaiju, clawmarks left on various city substrates, as well as kaiju scat. Unlike other fans of the movie, I've only seen it once so far, and cannot recall whether the following picture of its droppings was flashed on the movie screen or not.

The banner for this news clip says it all: kaiju excrement, and you can bet this much did indeed contaminate a portion of Manila, Philippines (or the "Phillipines," which may be a gated community just outside of Philadelphia.) On the flip side, I'll bet a certain sick Triceratops in the movie Jurassic Park is now a little less self-conscious about having its wastes piled higher and deeper on the big screen.

One line about their excrement – uttered by kaiju-organ harvester, Hannibal Chau (played by a hilarious Ron Perlman) - alludes to its commercial value based on its phosphorus content. This would accord with the economic importance given to bat or bird guano, which has been mined and sold as fertilizer, and even inspired wars. (I am not making that up.) Still, it would have been beyond awesome to have just one scene showing a deposit of its scat enveloping a large, recognizable monument to a politician in one of those cities.

Hannibal Chau (Ron Perlman), selling kaiju products for whatever might ail you. Alas, their scat is not mentioned in this ad, but he could easily do another one directed at Whole Foods. After all, it would be 100% organic and free-range fertilizer!

What about the jaegers? Their traces are much tougher to discuss, semantically speaking. Ichnologists classify tools themselves as traces of behavior, but most do not count marks made by tools (or machines) as traces. Nonetheless, because the jaegers are being controlled by humans, the marks they leave on the landscape, seascapes, and upside some kaiju’s head, might count as traces, too.

However, in one scene of the movie, in which a kaiju picked up a jaeger and threw it – inflicting much destruction of private and public property – these traces would be those of the kaiju, not the jaeger. I pointed out a similar situation with Jurassic Park. Toward the end of the movie, the poor, misunderstood protagonist of the film - the Tyrannosaurus rex - in an action tinged with self-loathing, hurled a Velociraptor at a mounted T. rex skeleton, no doubt expressing doubt about her place in a post-Mesozoic world. Existentialist angst aside, the destruction of the skeleton was a trace of the tyrannosaur's behavior, not that of the Velociraptor.

So next time you go to a movie featuring multi-ton monsters emerging from the deep sea and massive fighting machines, look for them to make traces, note the traces they make, how these traces may reflect some sort of evolutionary history for the tracemakers, and ask yourself what constitutes a trace. Then no matter how bad the movie, you'll still be guaranteed to enjoy it. Happy movie viewing and tracking!

The Ichnology of Jurassic Park

Posted on April 9, 2013 by TMartin

All paleontologists remember their first time. Mine was in 1993, during a hot, steamy summer in Atlanta, Georgia. I had just spent the previous month camping in wilderness areas of Wyoming, so coming back to a big city with all of its urban temptations meant I was weak and susceptible to seeking out unusual sources of pleasure. Although I was not quite ready to be taken for such an exhilarating ride, it was an experience I’d never forget. Afterwards, once I had recovered enough to be able think about it, I wanted to do it again.

I am, of course, talking about seeing the film Jurassic Park on a movie screen. Sure, this movie has been around long enough (20 years) that nearly every paleontologist has also watched it on a TV, computer, or mobile device. But there is something about seeing dinosaurs – which, let’s face it, are most famous for their size – shown big. The initial glimpse of a Brachiosaurus munching on the tops of tall trees, a herd of Paralophosaurus ringing a glistening lake, an ill Triceratops dwarfing its human caretakers, the grand entrance of the Tyrannosaurus: all of these “actors” were meant to be seen large, and fill us with awe. It worked. Plot, acting, and science aside, Jurassic Park was, and probably still is, the best movie made for conveying what it would feel like for us humans, separated by a minimum of 65 million years, to see real, living dinosaurs.

“It’s, it’s a dinosaur.” That pretty much said it all in 1993, and still does. But what traces were being made by this Brachiosaurus as it strolled through its all-you-can-eat salad bar, known to you and me as a “landscape”? Please read on.

In 1993, though, I did not have an appreciation for some of the smaller details included in this film, and how my research specialty of ichnology – the study of traces, like tracks, burrows, and nests – was reflected throughout it. What dinosaur traces were included in the movie, and how were these traces used to serve or advance the plot? I also wondered how 20 years of field experience and scholarly research in ichnology might have changed my perceptions of it since that first viewing.

So with the re-release of Jurassic Park in 3-D last week, I decided it was time to view it from an ichnological perspective and share these thoughts with others. After all, my next book, Dinosaurs Without Bones (Pegasus Press), is about dinosaur trace fossils, and written for a popular audience. Also, in between the movie’s first release and now, I wrote two editions of a college textbook on dinosaurs (Introduction to the Study of Dinosaurs). Thus I went to the theater well justified in watching Jurassic Park once more, to see for myself how dinosaur traces were portrayed in the most well-loved of all dinosaur movies. And oh yes, for the fun.

For the sake of simplicity, I’ve divided these traces into two categories: those viewers could directly observe in the film, and others that could be inferred from the dinosaurs’ behaviors. Wherever possible, I also connect traces shown in the movie to research done on dinosaur trace fossils during the last 20 years, giving a broad sense of how far dinosaur ichnology has progressed since 1993.

(Ichnologist’s note: Even though all of the live dinosaurs in the movie were set in the 1990s, the study of their modern traces still qualifies as neoichnology. In contrast, any reference I make to actual dinosaur trace fossils is paleoichnology. Just so you know.)

Dinosaur Traces in Jurassic Park

• Velociraptor hatchling traces. Jurassic Park shows two different but complementary examples of hatchling traces for “Velociraptor.” (I will call this dinosaur Velociraptor throughout this post, but as most dino-philes know, the director, Steven Spielberg, scaled up the Late Cretaceous Velociraptor to maximize its frightfulness. Hence it is actually more like the Early Cretaceous Deinonychus or Utahraptor.)

One is an egg-emergence trace, which is the hole left in an eggshell where a dinosaur broke out of its egg. In this scene, a cooing Velociraptor hatchling pokes its cute little nose out of its egg. (This nose, if everything worked out for it, would some day would be warmed by fresh human viscera.) We first witness this tracemaking in the Jurassic Park laboratory toward the start of the film, the same day most of the protagonists arrive on the island (Isla Nublar). As far as I know, such trace fossils have not been interpreted from the fossil record, or if they have, they have not been referred to as trace fossils: which they should be.

The next day, after dinosaur paleontologist Alan Grant and his two companions – Lex and Tim Murphy – were sufficiently terrified (and enthralled) by various dinosaur encounters out in the park, they come across a Velociraptor nest. The nest has about 15-20 broken eggs, and the fracture patterns of the eggshells provide clear evidence of hatching. But these traces also had tiny, two-toed tracks leading away from them. The tracks, with two toes studded by digital pads, were typical for deinonychosaurs. However, unlike nearly every theropod track I’ve seen, these tracks lacked claw marks at their ends. (Tsk, tsk, says this nitpicking ichnologist.)

Aw, look at the cute little Velociraptor tracks and hatched eggs. Don’t these traces just make you want to say, “Who’s the cutest little predator in the world?” Still from Jurassic Park (1993), taken from www.anyclip.com.

Even though these tracks were flashed on the screen for only a few seconds, what’s really cool is how they convey three important pieces of information. One is that the Velociraptor chicks hatched after the torrential rainstorm of the previous night, and thus only mere hours before our wandering heroes saw their traces. Second, the tracks demonstrate that the hatchlings were not altricial, but ready to move and leave the nest immediately, presumably without parental care. Third, Dr. Grant realizes that these successfully fertilized and hatched eggs mean the “female-only” genetic fail-safe plan for the dinosaurs just got disproved. In other words, these traces mattered.

One point about that nest: as far as I could tell from, this Velociraptor mother did not make a rimmed structure to protect the eggs, such as those made by another Late Cretaceous theropod, Troodon, or Late Cretaceous sauropods in Argentina. Instead, the eggs were laid out in the open, like some ground-nesting shorebirds might do. In contrast, the Jurassic Park sequels featured Velociraptor nests that were much more overt as traces, such as a rimmed nest seen in Jurassic Park III.

Partially preserved rimmed nest structure of Troodon, a Late Cretaceous theropod that lived in what we now call Montana. The rim has eroded quite a bit since its discovery in the mid-1990s; the Troodon egg clutch was in the area of the foreground before its extraction. (Photograph by Anthony Martin; scale in centimeters.)

• Triceratops feces. “That is one big pile of sh*t,” observes Dr. Ian Malcolm, the “chaotician” (mathematician) who supplies both pessimism and comic relief throughout the movie. In this scene, where the main protagonists attend to an under-the-weather Triceratops, two impressive piles of fecal material inspire Dr. Ellie Satler, a paleobotanist, to figure out whether or not the ceratopsian had eaten any toxic plants.

Somehow I suspect this scene was meant as a metaphor for what most paleontologists have to do in their day jobs in order to do any paleontology at all.

Still, when added together, this amount of still-moist waste was far too voluminous to have been from one or two depositional events: I mean, this dinosaur was sick, but not that much. As a result, park personnel must have been responsible for making these dung heaps from several days worthy of Triceratops contributions. (Strictly speaking, then, these heaps were composite traces.) If so, this would have been a rather unenviable job, but maybe they were better paid than Dennis Nedry, the disgruntled computer programmer who later provided ample fodder for Dilophosaurus.

Unfortunately, fossil Triceratops feces (coprolites) are thus far unknown from the geologic record. What is exciting, though, is that several excellent studies have been done by Dr. Karen Chin on Late Cretaceous hadrosaur coprolites. These coprolites, like the fictionalized Triceratops feces, contain lots of plant material, telling us much about what these hadrosaurs ate 75 million years ago. They also tell us what ate the feces or grazed on them, which were dung beetles and snails, respectively. (Indeed, I now wonder if Isla Nubar had a severe shortage of dung beetles, which might explain how those Triceratops feces got piled higher and deeper.)

Dinosaur coprolite – probably from a large hadrosaur, such as Maisaura – and filled with wood fragments, accompanied by special bonus trace fossils: dung beetle burrows! Specimen from the Two Medicine Formation (Late Cretaceous, Montana) as part of a Museum of the Rockies traveling exhibit at Fernbank Museum of Natural History. (Photograph by Anthony Martin, taken in 2001 and scanned from a 35-mm slide; scale in centimeters.)

• Tyrannosaurus tracks. Probably the most memorable scene in Jurassic Park is the grand entrance of the Tyrannosaurus, whose approach is first detected by “impact tremors” transmitted in cups of water on the dashboard of a jeep. Following this first bout of terror and the arrival of Ellie Sattler and big-game hunter Robert Muldoon, Malcolm, convalescing in the back of a jeep, looks down at a three-toed Tyrannosaurus track. The track, filled with water from the rain, communicates a warning as it vibrates from the footfalls of the approaching giant theropod. This repeats the previous image of the trembling water in the cup, but is made doubly dreadful by happening in a freshly made footprint of the same animal causing the tremors.

So what was by far the most exciting moment in the movie for me, ichnologically speaking? The Tyrannosaurus making a track, in which mud pushes up and out to the sides of its right foot, observed at 2:38 in the following video clip. Just watch:

This was already a great scene for all of its action, suspense, and lawyer eating. But check out that track-making!

Only a few fossil tracks have been attributed to Tyrannosaurus or other tyrannosaurids, mostly for being the right size (really big) and geologic age (Late Cretaceous). One was discovered in New Mexico in 1983, but wasn’t reported in a scientific journal until the year after Jurassic Park came out. More than a decade passed before another was found in Montana in 2007 and reported in 2008. Tragically, both were isolated tracks, and a Tyrannosaurus trackway, with two or more consecutive steps, has not yet been found. If so, it would make for a pretty darned nice find. So please do let the world know if you find one.

A large and well-preserved three-toed theropod track from the Early Cretaceous Glen Rose Formation of Texas, made about 95 million years ago. Although this track was more likely made by Acrocanthosaurus, rather than Tyrannosaurus rex, you can be assured that this theropod, like all living things, was a distant relative of T. rex. (Photograph taken by Anthony Martin; scale in centimeters.)

• Velociraptor tracks (adults). These tracks, shown only for a few seconds, are outside of the Velociraptor enclosure after the power was shut down. Muldoon, accompanied by Sattler, spots the footprints, and he wordlessly identifies them. (His expression also tells the audience that Sattler and he are going to be in deeper doo-doo than the Triceratops piles.) The twisted and broken bars of the enclosure provide additional traces affirming the conclusion that these ‘raptors are on the loose. All of these traces are shown only minutes before Muldoon utters his meme-inspiring last words, “Clever girl.”

Uh oh: Velociraptor tracks, and these don’t look like they’re from hatchlings. Good thing Muldoon is a big-game hunter, who’s skilled at tracking and predicting Velociraptor behavior based on their tracks. But too bad his hypothesis was falsified in such an unpleasant way, but I suppose he could have picked kinder reviewers. Still from Jurassic Park (1993), taken from www.anyclip.com.

Here’s what a real deinonychosaur track looks like. This one, from the Early Cretaceous of Utah, is a right foot impression, and is just slightly smaller than the adult tracks depicted in Jurassic Park. Notice the digits are thinner and end with sharp clawmarks, too. (Photograph by Anthony Martin; scale in centimeters.)

• Bioerosion of fossil dinosaur bones by modern dinosaurs. Toward the end of the film, the main human heroes – Grant, Sattler, Murphy, and Murphy (which sounds like a law firm, but we know how T. rex feels about those) – are confronted by a Velociraptor pack in the Jurassic Park visitor center. During their attempts to flee the ‘raptors, both species end up disarticulating and breaking some of the mounted dinosaur skeletons in the atrium of the visitor center. Their actions were thus a form of bioerosion, in which the fractured dinosaur bones are traces of their activities. Alternatively, the bones may have been artificial casts, in which case their breakage would have constituted bioerosion of modern substrates.

This bioerosion is made more complicated when the Tyrannosaurus rex (who everyone agrees is the ultimate protangonist of the movie) enters the atrium and, among other antics, smashes a skeleton of itself with a recently crunched Velociraptor. As a result, the jumbled assemblage of bones at the end is attributable to three separate, interacting tracemakers: four humans (two adult, two juvenile), two Velociraptors (both adults), and one Tyrannosaurus (adult). What should be noted, though, is that if the Velociraptor was already dead when flung by the Tyrannosaurus, then the broken skeleton is a trace of the Tyrannosaurus, not the Velociraptor. In other words, the Velociraptor body was just being used as a tool.

Bioerosion in action, as a result of Velociraptor and human interactions. Also, at 2:45: T. rex smash!

Dinosaur Trace-Making Behaviors in Jurassic Park

• Brachiosaurus tracks, browsing traces. When Drs. Grant and Sattler experience their first jaw-dropping glimpse of a Brachiosaurus, they watch it rear up on its hind feet, and come down hard on front feet. Considering that a Brachiosaurus this size might have weighed at least 30 tonnes, it surely would have left deep tracks in both the front and rear from the increased stresses imparted by these actions. Also, its cropping the tops of trees would have caused some easily visible gaps in the canopies of forests on Isla Nubar.

• Theropod toothmarks. Part of the fun of Jurassic Park was indulging in our worst nightmares about these non-avian theropods frequently sampling human flesh. Assuming that the theropod teeth in each instance penetrated skin and muscle and contacted bone, toothmarks would have included the following: (1) Tyrannosaurus toothmarks on goat, human, and Velociraptor bones; and (2) Velociraptor and Dilophosaurus toothmarks on human bones.

• Triceratops resting trace. When the paleontologists and others visit the ailing Triceratops, it was lying on its right side. I couldn’t help but think that if Triceratops or any other large ceratopsian dinosaur ever reclined like that, and in the right type of sediment, it would have left a gorgeous body impression. This scene also reminded me of bison traces I’ve seen in Yellowstone National Park, in which bisons roll onto their sides for a dust bath, leaving outlines of their bodies. Did dinosaurs – especially the feathered ones – ever take dust baths, and leave similar body impressions? We don’t know yet, but such trace fossils are something to look for.

• Dinosaur stampede. One of the most astonishing computer-generated effects of Jurassic Park, and one that was especially effective in 3-D, was of a dinosaur stampede. In this scene, a flock of Gallimus run toward and around Grant, Murphy, and Murphy, just before the ambush-hunting Tyrannosaurus rex slaughters one of them (the Gallimus, that is). I’ve written about this scene before, connecting it to a dinosaur tracksite in Queensland, Australia that has more than 3,000 tracks preserved. Although the site was originally interpreted as the only evidence of a dinosaur stampede, the tracks were recently reinterpreted as swim tracks. I’ll write about this topic at length in my upcoming book, so for now, I ain’t saying nothing more.

Run away, run away!

• Tyrannosaurus drag mark. After the Tyrannosaurus rex decides that a measly goat was just an appetizer and begins seeking out the nearest available mammals for nomming purposes, at some point it overturns and begins pushing an SUV, which still has Lex and Tim Murphy trapped underneath it. Its flipping the SUV with its head certainly would have left a substantial mark on the muddy ground, a trace that then would have been connected to a semi-circular dragmark (clockwise oriented), and with tracks directly adjacent to these traces. Her tracks also may have been deeper in their fronts because of her head being down as she pushed, reflecting a shift in her weight distribution. However, I should again remind everyone that just like with the dead Velociraptor used for bioerosion by this same T. rex later in the film, the SUV is not making the trace. It is only a tool being used by the tyrannosaur, which is the real tracemaker.

• Tyrannosaurus running trackway – This pulse-quickening chase scene, in which the T. rex pursues a jeep driven by Muldoon and with Malcolm and Sattler as passengers, very likely would have caused a wonderful sequence of tracks. These tracks would have shown increasing stride lengths from a standing start to full-speed run, and each successive track would have registered external and internal structures consistent with this acceleration. Even better, the tracks would have cross-cut the jeep tire-tracks at some points, demonstrating to a later observer that the tyrannosaur was very likely following the jeep. (The demolition of a low-hanging tree branch by the T. rex during the chase also counts as some bioerosion along the way.) Some convincing studies have been done since showing that an adult Tyrannosaurus could not have moved as fast as the one in Jurassic Park, but it still could have caught most running humans. And just to repeat what I said earlier, it’d be really nice for someone to find a T. rex trackway, which would give us more direct evidence of how these massive theropods moved.

• Velociraptor scratch marks and other traces. This time, while watching the harrowing and claustrophobic scene in which a pair of Velociraptors hunt the Murphy siblings in a kitchen, I started thinking about the traces they might have left. Did their claws leave scratch marks on the door handles and kitchen counters? Did they indent the steel counters when they jumped up on these surfaces? A broken window is also shown as a trace of their smashing through glass once they became frustrated with a locked door.

OK, enough of the fanciful ichnology. What about other dinosaurs and their traces? Well, it turns out that Jurassic Park saved the real, living dinosaurs for the very end of the movie. These were five brown pelicans (Pelecanus occidentalis), flying in formation as Grant, Sattler, and their companions leave Isla Nubar in a helicopter. For Grant, this is a poignant moment, as he is likely reflecting on how dinosaurs were still with us today as birds. With that thought, I will say “amen,” and add that dinosaur traces – tracks, nests, feces, bite marks, and all – are still here with us, too, and don’t require special glasses to see them in three dimensions. Thanks for that reminder, Jurassic Park.

Want to see some modern dinosaur traces? Here are tracks of a brown pelican, made in wet sand while it was loafing on a beach at low tide on Sapelo Island, Georgia. To see more modern dinosaur traces, just go outside, and you’ll find them wherever birds are found. (Photograph by Anthony Martin; scale in centimeters.)

Further Reading

Chiappe, L.M., Schmitt, J.G., Jackson, F., Dingus, L., and Grellet-Tinner, G. 2004. Nest structure for sauropods: sedimentary criteria for recognition of dinosaur nesting traces. Palaios, 19: 89–95.

Chin, K. 2007. The paleobiological implications of herbivorous dinosaur coprolites from the Upper Cretaceous Two Medicine Formation of Montana: why eat wood? Palaios, 22: 554-566.

Chin, K., and Gill, B.D. 1996. Dinosaurs, dung beetles, and conifers: participants in a Cretaceous food web. Palaios, 11: 280-285.

Elbroch, M., and Marks, E. 2001. Bird Tracks and Sign of North America. Stackpole Books, Mechanicsburg, Pennsylvania.

Erickson, G. M., Van Kirk, S. D., Su, J., Levenston, M. E., Caler, W. E., & Carter, D. R. 1996. Bite force estimation for Tyrannosaurus rex from tooth-marked bones. Nature, 382: 706–708.

Gignac, P.M., Makovicky, P.J., Erickson, G.M., and Walsh, R.P. 2010. A description of Deinonychus antirrhopus bite marks and estimates of bite force using tooth indentation simulations. Journal of Vertebrate Paleontology, 30: 1169-1177.

Hutchinson, J.R., and Garcia, M. 2002. Tyrannosaurus was not a fast runner. Nature, 415: 1018-1021.

Jacobsen, A.R. 1998. Feeding behaviour of carnivorous dinosaurs as determined by tooth marks on dinosaur bones. Historical Biology, 13: 17-26.

Lockley, M.G., and Hunt, A.P. 1994. A track of the giant theropod dinosaur Tyrannosaurus from close to the Cretaceous/Tertiary Boundary, northern New Mexico. Ichnos, 3: 213-218.

Manning, P.L., Ott, C., and Falkingham, P.L. 2008. A probable tyrannosaurid track from the Hell Creek Formation (Upper Cretaceous), Montana, United States. Palaios, 23: 645-647.

Martin, A.J. 2013. Life Traces of the Georgia Coast: Revealing the Unseen Lives of Plants and Animals. Indiana University Press, Bloomington, Indiana: 692 p.

Romilio, A., and Salisbury, S.W. 2011. A reassessment of large theropod dinosaur tracks from the mid-Cretaceous (late Albian–Cenomanian) Winton Formation of Lark Quarry, central-western Queensland, Australia: a case for mistaken identity. Cretaceous Research, 32: 135-142.

Romilio, A., Tucker, R., Salisbury, S. 2013. Reevaluation of the Lake Quarry dinosaur tracksite (late Albian-Cenomanian Winton Formation, central-western Queensland, Australia): no longer a stampede? Journal of Vertebrate Paleontology. 33: 1, 102-120.

Sellers, W.I., and Manning, P.L. (July 2007). Estimating dinosaur maximum running speeds using evolutionary robotics. Proceedings of the Royal Society of London, B, 274: 2711-2716.

Thulborn, R.A., and Wade, M., 1979. Dinosaur stampede in the Cretaceous of Queensland. Lethaia, 12: 275-279.

Varricchio, D.J., Jackson, F. and Trueman, C.N. 1999. A nesting trace with eggs for the Cretaceous theropod dinosaur Troodon formosus. Journal of Vertebrate Paleontology, 19: 91-100.

Tracking Wild Turkeys on the Georgia Coast

Posted on November 20, 2012 by TMartin

Of the many traditions associated with the celebration of Thanksgiving in the U.S., the most commonly mentioned one is the ritual consumption of an avian theropod, Meleagris gallopavo, simply known by most people as “turkey.” The majority of turkeys that people will eat this Thursday, and for much of the week afterwards, are domestically raised. Yet these birds are all descended from wild turkeys native to North America. This is in contrast to chickens (Gallus gallus), which are descended from an Asian species, and various European mammals, such as cattle, pigs, sheep, and goats (Bos taurus, Sus scrofa, Ovis aries, and Capra aegagrus, respectively).

Trackway of a wild turkey (Meleagris gallopavo) crossing a coastal dune on Cumberland Island, Georgia. Notice how this one, which was likely a big male (“tom”), was meandering between clumps of vegetation and staying in slightly lower areas, its behavior influenced by the landscape. Scale = 20 cm (8 in). (Photograph by Anthony Martin.)

American schoolchildren are also sometimes taught that one of the founding fathers of the United States, Benjamin Franklin, even suggested that the wild turkey should be elevated to the status of the national bird, in favor of the bald eagle (Haliaeetus leucocephalus). With an admiring (although I suspect somewhat facetious) tone, he said:

“He [the turkey] is besides, though a little vain & silly, a Bird of Courage, and would not hesitate to attack a Grenadier of the British Guards who should presume to invade his Farm Yard with a red Coat on.”

There are eight of us, and only one of you. Do you really want to mess with us? (Photograph by Anthony Martin, taken on Cumberland Island, Georgia.)

Unfortunately, because I live in the metropolitan Atlanta area, I never see turkeys other than the dead packaged ones in grocery stores. Nonetheless, one of the ways I experience turkeys as wild, living animals is to visit the Georgia barrier islands, and the best way for me to learn about wild turkey behavior is to track them. This is also great fun for me as a paleontologist, as their tracks remind me of those made by small theropod dinosaurs from the Mesozoic Era. And of course, as most schoolchildren can tell you, birds are dinosaurs, which they will state much more confidently than anything they might know about Benjamin Franklin.

Compared to most birds, turkeys are relatively easy to track. Their footprints are about 9.5-13 cm (3.7-5 in) long and slightly wider than long, with three long but thick, padded toes in front and one shorter one in the back, pointing rearward. In between these digits is a roundish impression, imparted by a metatarsal. This is a trait of an incumbent foot, in which a metatarsal registers behind digit III because the rear part of that toe is raised off the ground. The short toe is digit I, equivalent to our big toe, but not so big in this bird. Despite the reduction of this toe, its presence shows that turkeys probably descended from tree-dwelling species, as this toe was used for grasping branches. Clawmarks normally show on the ends of each toe impression, and when a turkey is walking slowly, it drags the claw on its middle toe (digit III), thus making a nicely defined linear groove.

Wild turkey tracks made while it was walking slowly up a gentle dune slope, dragging the claw on the middle digit of its right foot, making a long groove. Also notice the bounding tracks of a southern toad (traveling lower right –> upper left), cross-cutting the turkey tracks. (Photograph by Anthony Martin, taken on Cumberland Island.)

A normal walking pace (right foot –> left foot, left foot –> right foot) for a turkey is anywhere from 15-40 cm (6-16 in), and its stride (right foot –> right foot, left foot –> left foot) is about twice that, or 30-80 cm (12-32 in), depending on the age and size of the turkey. Their trackways show surprisingly narrow straddles for such wide-bodied birds, only 1.5 times more than track widths. This is because they walk almost as if on a tightrope, with angles between each step approaching 180°; so they still make a diagonal pattern, but nearly define a straight line. However, turkeys meander, stop, or change direction often enough to make things interesting when tracking them. Their flocking behavior also means their tracks commonly overlap with one another or cluster, making it tough to pick out the trackways of individual turkeys. However, in such flocks, the dominant male’s tracks are noticeably larger than those of the females or younger turkeys, so these can be picked out and help with sorting who’s who.

Turkey trackway in which it walked across the wind-rippled surface of a coastal dune on Cumberland Island, meandering while moseying. Same photo scale as before. (Photograph by Anthony Martin.)

An abrupt right turn recorded by a turkey’s tracks. Check out that beautiful metatarsal impression in the second track from the right, and how the claw dragmark in the thrid track from the right points in the direction of the next track. (Photograph by Anthony Martin.)

One of the more remarkable points about these Georgia barrier-island turkeys, though, is how their tracks belie their stereotyped image as forest-only birds. Although they do spend much of their time in the forest, I’ve tracked turkeys through broad swaths of coastal dunes, and sometimes they will stop just short of primary dunes at the beach. So however difficult it might be to think about these birds as marginal-marine vertebrates, their tracks overlap the same places with ghost-crab burrows and shorebird tracks. Geologists and paleontologists take note: this exemplifies the considerable overlap between terrestrial and marginal-marine tracemakers that can happen in coastal environments. This also happened with dinosaurs that strolled onto tidal flats or otherwise passed through marginal-marine ecosystems.

Turkey tracks heading toward the beach, with the open ocean visible just beyond. Is this close enough to consider turkeys as marginal-marine tracemakers? (Photograph by Anthony Martin.)

Do these turkeys also have an impact on the dunes themselves? Yes, although these effects vary, from trackways disrupting wind ripples to more overt changes to the landscape. For instance, one of the most interesting effects I’ve seen is where they’ve caused small avalanches of sand downslope on dune faces. Interestingly, this same sort of phenomenon was also documented for Early Jurassic dinosaurs that walked across dry sand dunes, which caused grainflows that cascaded downhill with each step onto the sand.

Grainflow structure (arrow), a small avalanche caused by a turkey walking down a dune face. (Photograph by Anthony Martin.)

Close-up of grainflow structure (right) connected to turkey tracks, which become better defined once the turkey reached a more level surface. (Photograph by Anthony Martin, taken on Cumberland Island.)

What other traces do turkeys make? A lot, although I’ve only seen their tracks. Other traces include dust baths, feces, and nests. Dust baths, in which turkeys douse themselves with dry sediment to suffocate skin parasites, must be awesome structures. These are described as 50 cm (20 in) wide, 5-15 (1-3 in) deep, semi-circular depressions, and feather impressions show up in those made in finer-grained sediments. Although such structures would have poor preservation potential in the fossil record, I hold out hope that if paleontologists start looking more at modern examples, they are more likely to find a fossil dust bath, whether in Mesozoic or Cenozoic rocks.

Turkey feces, like most droppings from birds, have white caps on one end, but are unusual in that these can tell you the gender of their depositor. Male turkeys tend to make curled cylinders that are about 1 cm wide and as much as 8 cm long (0.4 X 3 in), whereas females make more globular (not gobbular) droppings that are about 1 cm (0.4 in) wide. These distinctive shapes are a result of their having different digestive systems. Turkeys are herbivores, so their scat normally includes plant material, but don’t be surprised to see insects parts in them, too. Still think about how exciting it would be to find a grouping of same-diameter cylindrical and rounded coprolites in the same Mesozoic deposit, yet filled with the same digested material, hinting at gender differences (sexual dimorphism) in the same species of dinosaur maker.

Turkeys normally make nests on the ground by scratching out slight depressions with their feet, but evidently this is a flexible behavior. On at least one of the Georgia barrier islands (Ossabaw), these birds have been documented as building nests in trees. Although this practice seems very odd for a large, ground-dwelling bird, it is an effective strategy against feral hogs, which tend to eat turkey eggs, as well as eggs of nearly every other species of bird or reptile, for that matter. Just to extend this idea to the geologic past, ground nests are documented for several species of dinosaurs, but tree nests are unknown, let alone whether species of ground-nesting dinosaurs were also capable of nesting in trees.

As everyone should know from their favorite WKRP episode, domestic turkeys can’t fly. But wild turkeys can, and use this ability to get into the branches of live oaks (arrow), high above their predators, or even curious ichnologists. (Photograph by Anthony Martin, taken on Cumberland Island.)

So whether or not you have tryptophan-fueled dreams while dozing later this week, keep in mind not just the evolutionary heritage of your dinosaurian meal, but also what their traces tell us about this history. Moreover, it is an understanding aided by these magnificent and behaviorally complex birds on the Georgia barrier islands. For this alone, we should be thankful.

Paleontologist Barbie, tracking wild turkeys on the Georgia coast to learn more about how these tracemakers can be used as modern analogs for dinosaur behavior and traces, and once again demonstrating why she is the honey badger of paleontologists. (Yes, photograph by me, and taken on Cumberland Island. P.S. Happy Thanksgiving!)

Further Reading

Dickson,J.G. (editor). 1992. Wild Turkeys: Biology and Management. Stackpole Books, Mechanicsburg, Pennsylvania: 463 p.

Elbroch, M., and Marks, E. 2001. Bird Tracks and Sign of North America. Stackpole Books, Mechanicsburg, Pennsylvania: 456 p.

Fletcher, W.O., and Parker, W.A. 1994. Tree nesting by wild turkeys on Ossabaw Island, Georgia. The Wilson Bulletin, 106: 562.

Loope, D.B. 2006. Dry-season tracks in dinosaur-triggered grainflows. Palaios, 21: 132-142.

Deep in the Dinosaur Tracks of Texas

Posted on August 6, 2012 by TMartin

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.

Public Outreach via Ichnology: Traces for Kids

Posted on July 19, 2012 by TMartin

(This post is the second in a series discussing academic scientists and public outreach of their science, but with a focus on my recent experiences in using ichnology and paleontology for public outreach. The first of the series, introducing science outreach in general and some of its challenges for academic scientists, is here.)

One of the clichés of the environmentalism is to “think globally, act locally,” and the same principle applies well to public outreach done by scientists. For example, here in Atlanta, Georgia, I live near Fernbank Museum of Natural History. And by “near,” I mean I can ride my bicycle to it in 10-15 minutes from either home or my workplace at Emory University. Over my 20+ years in Atlanta, I’ve tried to cultivate a relationship with Fernbank, having done some informal consulting for them on exhibits, given public lectures about my research in ichnology and paleontology, shown some of my science-based artwork there, and otherwise done volunteer work that qualifies as public outreach.

Look, a real paleontologist who somehow escaped from his “ivory tower” (or stone house) and found time to talk with the public! This is a small visual sample of the fun I had this past Saturday at Fernbank Museum of Natural History, talking with children and their parents about dinosaur trace fossils. Why yes, those are Paleontologist Barbies (one of them quite famous) sitting in the box to the right of me. Do you have a problem with that? (Photograph by Ruth Schowalter.)

But one of my acknowledged deficiencies in public outreach with Fernbank and elsewhere has been sharing my science with kids. Full confession: I don’t have children. (As far as I know, that is. If I ever run for political office, I’ll find out for sure.) Moreover, nearly all of the students I teach are 18 to 22 years old, and I normally don’t have children around me through family, friends, or neighbors in everyday life. Thus most of my experience in communicating science at any level is with adults. This leaves me feeling a little handicapped and less confident about my abilities to adapt and use the unique set of skills needed for relating sometimes-complex scientific concepts to children.

Why should I bother getting bothered about this, especially in doing outeach with a local natural history museum? Well, a simple reality of natural history museums today is that their economic survival relies on children visiting them, and preferably (although not necessarily) with their parents in tow. Sure, educating the young has always been a role of natural history museums. But pitching science solely to kids while bypassing adults has become so pronounced in some museums that adults have begun complaining about the “infantilization” of museum exhibits.

Fernbank is not immune to this charge. For example, the traveling exhibit they have there now – The Scoop on Poop – is clearly aimed at viewers 10 years old and younger, and is inspired by a children’s book with the same title. To be fair, though, Fernbank hosting the Darwin exhibit from the American Museum of Natural History last year was a refreshing concession to adults who certainly felt like kids, filled with excitement and awe, while learning about the roots of evolutionary theory.

A study in contrasts of traveling exhibits that have been to Fernbank Museum. Above, here’s part of the sign that greeted visitors to the Darwin exhibit, shown there September-December 2011…

…and here’s the sign welcoming people to the Scoop on Poop exhibit, showing there now. Gee, do you think each was intended for a different audience?

So it was with a mixture of mild trepidation, but also eagerness, that I welcomed an opportunity for outreach with kids and their parents last Saturday, July 14. One of my friends who works at Fernbank asked me several weeks ago if I’d be interested in participating in a museum event they organized for July 14-15, called “The Scoop on Dinosaurs.” In this event, Fernbank put together a range of dinosaur- and other science-related activities and programs for kids, but of course also designed it with the assumption that these kids would be accompanied by parents or other adults. The problem was, all of the planned activities lacked a real, practicing scientist, let alone a paleontologist. And seeing that I’m one of the few paleontologists in the Atlanta area, I live close by, and I enjoy doing public outreach, it made sense for me to participate.

After discussing it with my Fernbank friend, we decided that a simple “meet the paleontologist” format would work best, with me sitting at a table and talking informally with people about one of my research topics – dinosaur trace fossils – as they dropped by. I also thought it would be good to have a few props, and ones that would provoke inquiry-based learning, or what educators used to call “thinking.”

For example, I brought with me two sets of dinosaur bones, one of which was noticeably denser than the other. (And by the way, real bones are essential, so the kids could say and remember when they held real dinosaur bones.) These differences, which engaged a sense other than sight, lent well to the question, “Why is one bone heavier than the other, even though they’re the same size?,” followed by a discussion of the preservation of dinosaur bones.

Whoa, dinosaur bones! The darker dinosaur bone on the left is noticeably heavier than the lighter-colored one on the right, which the kids could feel for themselves right away when they put one in each hand. After they noticed this, I asked them why, and next thing you knew, we were having a scientific discussion.

Of course, because I’m ichnologist, you just knew some traces and trace fossils were somehow going to be involved in this, too. Sure enough, my friends at Fernbank printed out and laminated the following two photographs of mine, which I used to introduce the concept of dinosaur tracks to the kids. But rather than just blabbing on about each track, I showed them the photos and asked “Which one is the dinosaur track, which one is the bird track?” One track was from a modern sandhill crane (Grus canadensis) made on a Georgia barrier island, whereas the other was from a non-avian Cretaceous theropod dinosaur.

Which is the bird track and which is the dinosaur track? It’s kind of a trick question, but one that also introduces the concept that questions can have multiple right answers, and those answers lead to more questions and deeper meaning. And just in case you were wondering, the track on the left is from a theropod dinosaur, preserved in Early Cretaceous rocks that are about 105 million years old, and the one on the right is from a modern sandhill crane. (Both photographs by Anthony Martin, the left one taken in Victoria, Australia, and right one taken on St. Catherines Island, Georgia.)

For the more shy kids, I asked them to just point to the one they thought was the dinosaur track, and assured them that it was OK to be wrong, because being wrong is also part of science. So what was fun about this exercise was how they could be right no matter which they picked. If they pointed to dinosaur track, I would tell them they were right. But if they instead pointed to the modern sandhill crane track, I smiled and said, “You’re right, but it’s from a modern dinosaur, because birds are dinosaurs, too.”

This revelation led to a short explanation of how some dinosaurs are still around as birds, even if all of the other dinosaurs went extinct 65 million years ago. (Most of the kids already knew this, but I’m not so sure all of their parents did.) They also could clearly see that the tracks, which were very similar in size and shape, comprised one piece of evidence showing the relatedness of these two animals, even though they were separated by more than 100 million years. With a few of the older kids, we even talked some about how they were able to distinguish the fossil track from the modern one. (“That looks like a rock, and that looks like sand,” some of them said. Couldn’t have said it better myself.) What was really fun about this approach was to see how much the kids’ parents learned from this ichnologically based exercise, too. In other words, this wasn’t just done with children in mind.

Another simple trace-fossil-oriented quiz came from a photo of a 75-million-year-old dinosaur coprolite. Only I didn’t tell them it was a coprolite; instead, I told them what was in it (bits and pieces of plants), that my hand was in the picture (showing the size of the rock), and that the rock was a type of dinosaur trace fossil.

What’s this? It has bits and pieces of plants in it, it’s big (there’s my hand for scale), and it came from a dinosaur. If you said “paleo-puke,” that’s not bad, but you’re thinking of the wrong end of the dinosaur. It’s a coprolite, probably from a hadrosaur (like Maisaura), and is from the Late Cretaceous Two Medicine Formation of northwestern Montana.

With just those few clues, sometimes aided by my holding my nose, some kids actually figured it out (“DINOSAUR POOP!”), and even those who didn’t immediately get it were delighted with their answer after guiding them with just a few more questions. There’s probably something about their having recently learned proper toilet habits (reinforced daily) that makes feces loom large in a child’s imagination. So linking such traces to dinosaurs makes those feces even bigger, smellier, and hence more memorable.

With regard to other academic paleontologists who do public outreach, several parents mentioned that their kids regularly watch the TV show Dinosaur Train on PBS, and that’s how their children were learning about paleontology (or, more narrowly, just dinosaurs and pterosaurs). Although I’ve only seen a few clips from this show, I knew its host is also a real, academically trained research paleontologist with a Ph.D., Dr. Scott Sampson, sometimes known simply by the kids as “Dr. Scott.” So I made sure to tell these parents how fantastic it was to see an academic paleontologist with such credentials teaching paleontology in a children’s show. In other words, I was trying to counter the “Sagan effect,” while helping to dissuade parents from the notion that academic scientists are all disengaged from the public. (Maybe we paleontologists could call it the “Sampson effect.”)

Dr. Scott Sampson, an academic paleontologist who went on to do something a little different in his career, which was to become a science communicator with a recent focus on teaching paleontology to kids. Yet he still does peer-reviewed research on dinosaurs, meaning the two are not mutually exclusive. And you know what? The rest of us academic paleontologists think that’s cool.

Of course, I had lots of kids say, “I want to be a paleontologist!” Not wanting to crush their dreams with tales of pessimistic woe from academia (see my previous post if you need a big downer on that), I instead saw this as a chance for them to learn science in upcoming years, regardless of whether they become paleontologists or not. So advice I gave to those kids included (in particular order):

Get outside as much as possible. Although I’m not an overly fervent acolyte of Richard Louv and his “get kids in nature” movement, I do agree with the basic premise that kids need to connect more directly with nature by simply getting their little butts outside. From what I understand, “Dr. Scott” preaches the same message, so it’s good for kids to hear this coming from paleontologists, who do lots of their best work outside.
When you’re not outside, read as much as possible. Although, now that I think about it, I should have advised them to read outside.
Take lots of math classes. These kids represent the future, and the future of paleontology means more computer applications and more quantification of our data. So they can’t think about doing paleontology without also thinking about how math will be used in that science. Even though some kids wrinkled their tiny noses at me when I said “lots of math,” they got the message.
Take lots of science classes. And for the science classes, I told them that they’d better take geology, but also biology and chemistry. (I’m not sure if I mentioned physics, but maybe that was my way of getting back at fictional physicist Sheldon Cooper for what he’s said about geology.)

Yes, I know, all of this sounds wonderful, in a self-congratulatory, back-patting sort of way. Yay me! Nonetheless, while doing this outreach, I remained conscious of how I also fulfill a tenacious stereotype in paleontology. This typecasting has been discussed by fellow paleo-bloggers Victoria Arbour (here) and Brian Switek, the latter dubbing it the “male and pale” syndrome. It’s a syndrome exemplified by documentary filmmakers who pretend that the entire paleontological community is composed of middle-aged men of European descent, or, to throw in some diversity, older men of European descent.

Considering I live in an ethnically diverse place – Atlanta is more than 50% African-American, for starters – I’m reminded daily that my face doesn’t match those of most kids around me (and it’s not just the beard). This was certainly true for those kids and parents who stopped by to see me on Saturday: it was a rainbow of ethnicities totally unlike anything I experienced as a kid growing up in Indiana in the 1960s. But for here in Atlanta and many major metropolitan areas in the U.S. and around the world, this is normal. So if paleontologists who look like me plan to do public outreach, they have to be mindful of this reality, get educated about other ethnicities, and adjust accordingly. In this respect, I’ve been enlightened through working some with Emory’s Center for Science Education, which has had great success in implementing a variety of programs working to increase minority participation at all levels in STEM (science, technology, engineering, math) in the Atlanta area.

I’m also sensitive to the gender gap in perceptions of paleontologists, or the expectation that all paleontologists will be male, even as the demographics in our profession start to approach equity (though admittedly, we still have a long ways to go). So I made sure, after showing them the photo I had taken of a dinosaur coprolite from Montana and discussing how feces get fossilized, to tell them that the paleontologist who actually studied those coprolites was Dr. Karen Chin. Plus, I pointed toward the nearby Scoop on Poop exhibit and said they should go in there and watch Dr. Chin speak about her research on coprolites in several videos there. (Karen, if you’re reading this, thanks for your virtual help in being a cool role model!)

Dr. Karen Chin, the acknowledged world expert on dinosaur coprolites, who also doesn’t look like me (and that’s a good thing for both of us.) Here she is holding up one of her research subjects, which fortunately is sufficiently fossilized for her to gesture without getting any of it on her or the person behind the camera. Oh, and sorry if my photo taken from a video in The Scoop on Poop exhibit violates some sort of copyright, but I did it for the children. So there.

So it was with great joy and satisfaction that I’ll note my mere two hours of public outreach filled me with hope for the future. Many kids, accompanied by proud parents, stopped by to meet a “real paleontologist” and chat about, well, paleontology. Although I should have taken data, tabulated results, and analyzed them for significance, of the kids who said, “I want to be a paleontologist,” I recall the gender ratios were about 50:50. Probably my favorite brother-sister pair consisted of the brother who wants to be a paleontologist and the sister wants to be a marine biologist. (Making it even better, their dad was very pleased with the prospect of having two scientists in the family.)

I was also occasionally astonished at how knowledgeable some of the kids were. For example, one 10-year-old girl asked me whether one of the dinosaur bones I had brought was from a hadrosaurine or lambeosaurine dinosaur, which we then discussed (based on the extremely scanty evidence, that is). Her mother wore a face-splitting grin as she watched this exchange between her daughter and me, and other kids stood by in awe: looking at the girl, not me. Now that’s peer teaching!

Her (left): “What? You really think the phylogenetic distinction between the hadrosaur clades is based on THAT plesiomorphy?” Her sister (right): “Yeah, who taught you cladistics anyway?” Me: “Um, uh, OK. Say, have either of you ever watched Dinosaur Train?”

Will I do this kind of public outreach again? Sure, and Fernbank can certainly count on me doing more such programs with them in the future. From this experience I also learned that “dinosaurs and kids” as a frame for science education, whether at natural history museums or elsewhere, is a fountain that apparently never goes dry. But even better, I can still use my academic research specialty – ichnology – to provide a different perspective on dinosaurs specifically and science in general, for children and parents alike.

Public outreach in paleontology with kids can be fun and rewarding, given the right setting, preparation, and attitude. Meanwhile, just behind me, Gigantosaurus is apparently chasing Argentinosaurus, giving a whole new twist to the term “ankle biter.” (Photograph by Ruth Schowalter, taken at Fernbank Museum in Atlanta, Georgia.)

Further Reading

None for now. Go outside instead.

“Worm Burrows” as a Geological Cliché

Posted on November 7, 2011 by TMartin

This past week, I was privileged to have participated in a marvelous three-day field trip to the Triassic and Jurassic sedimentary rocks in and around St. George, Utah. The field trip, organized by paleontologist Andrew Milner and many others in association with the Society of Vertebrate Paleontology meeting in Las Vegas, Nevada, provided our enthusiastic group of nearly forty professional and amateur paleontologists with a grand geological tour of southern Utah and northern Arizona, along with the fantastic dinosaur tracksites in that area.

Foremost among these places where dinosaurs left their marks was one of the most incredible tracksites have seen anywhere, which, like Lark Quarry in Queensland, Australia, is enclosed within a building to protect it. This place, called the St. George Dinosaur Discovery Site at Johnson Farm, has one of the few sitting-dinosaur trace fossils known from the fossil record, along with the world’s best collection of dinosaur swimming tracks, rare examples of dinosaur tail-drag marks, hundreds of other dinosaur tracks, and thousands of invertebrate trace fossils. All were enthralling as detailed records of daily life in the Early Jurassic Period, from about 195 million years ago.

You would think on a field trip like this that Georgia – countering Ray Charles’ memorialized sentiment – would not be on my mind. Yet the modern traces made by living animals of the Georgia barrier islands habitually creep into my thoughts whenever I travel into the geological past. In this instance, the trigger for my thoughts of Georgia traces was through hearing other field-trip participants utter the most recurring of geological clichés connected to invertebrate trace fossils: “worm burrows.”

Invertebrate trace fossils (left) directly associated with theropod dinosaur footprints (right) from the Moenave Formation (Lower Jurassic), southern Utah. These trace fossils are probably the burrows of larval insects made in moist muddy sand, rather than burrows made by earthworms in soils. So don’t be calling them “worm burrows,” or else a baby kitten will get mildly scolded. (Photograph by Anthony Martin.)

Several people spontaneously spoke this ichnological banality as soon as they saw small burrows preserved in the rock, many of which were directly associated with the exquisitely preserved dinosaur tracks. This happened often enough (which is to say, twice) that I just had to call attention to this geological faux pas. “Stop saying ‘worm burrows’!” I said with mock outrage. I quickly followed my joking admonishment with a brief explanation of how most of the burrows were much more likely to be from insects, rather than worms. Traits of the burrows – such as scratchmarks and short, branching, angled tunnels – implied insect tracemakers, such as the larvae of beetles or flies.

Insect traces associated with dinosaur tracks should not be all that surprising to anyone. After all, insects originated in terrestrial environments about 400 million years ago, meaning they were more than halfway through their evolutionary history by the time these Jurassic trace fossils were made. I had seen many similar burrows made by insects on the Georgia barrier islands and elsewhere in Georgia, which gave me enough confidence to propose their more probable identity.

Insect burrows – probably made by “mud-loving” beetles – along the shore of a freshwater pond on Sapelo Island, Georgia. Notice the burrows are relatively younger than (cross-cut) two tail dragmarks made by resident alligators (Alligator mississippiensis). Sandal as scale, which is size 8 1/2 (men’s). (Photograph by Anthony Martin.)

Of course, once you draw attention to a word or phrase among friends that is guaranteed to provoke annoyance, you should expect them to bring it up more frequently later as fodder for their amusement. Indeed, this happened for the remainder of the field trip, and I did not disappoint my audience as I responded with histrionic cringing, flinching, and groaning each time we encountered more of these “worm burrows” in Triassic or Jurassic rocks and they were identified as such.

Look, worm burrows! Ha-ha! The beautiful invertebrate trace fossils, former burrows filled with white sand that contrasts from the surrounding hematite-stained sand, are also in the Moenave Formation (Lower Jurassic) of southern Utah. (Photograph by Anthony Martin.)

All frivolity aside, the point I was trying to make to my field-trip tormenters was this: whenever we look at sedimentary rocks formed in continental environments, and we happen to notice invertebrate trace fossils in those same rocks, we should think before speaking. In other words, we do better as paleontologists, geologists, or naturalists in general when we reexamine our neat, preconceived labels before applying them loudly and confidently to observed phenomena, and particularly with invertebrate trace fossils.

For example, even the word “burrow” can be too glib for interpreting certain invertebrate trace fossils. Many invertebrates do not move underneath a sedimentary surface but along it; traces of such movements are either trackways, which are made with legs and leave impressions of these, or trails, which are made by whole-body movement without legs, such as those formed by worms or snails.

In my experience, trackways and trails are often lumped in with burrows, despite possessing impressions made by legs, furrows, and levees. For example, some of the trace fossils we saw on the field trip were certainly trails, yet I heard these called “burrows” by a few people. Granted, this sort of confusion is actually more understandable than the “worm-burrow” mistake, because trails can segue into shallow horizontal burrows and vice-versa, or some “trails” actually can have tiny leg impressions, meaning they actually are trackways. Thus the distinction between these end members can become blurred quite easily if you don’t pay attention to the details of a given invertebrate trace.

Modern land snail (pulmonate gastropod) making a trail on surface of a coastal dune, Cumberland Island, Georgia; scale in centimeters. (Photo by Anthony Martin.)

Fossil trail, possibly made by a snail, on a former sand dune in the Navajo Formation (Lower Jurassic) of southern Utah. Research funding for scale. (Photograph by Anthony Martin.)

Insect burrow, probably made by a beetle larva, in which it changes from a shallow burrow to a trackway on the surface of a coastal dune, Little St. Simons Island, Georgia. Scale in millimeters. (Photograph by Anthony Martin.)

In the sands and muds of the Georgia barrier islands, insect burrows in particular have often caused me to keep quiet about what I think made them, versus what really made them. Many times I have seen a little lump at the end of a horizontal burrow, scooped up the tracemaker hiding underneath, and been surprised by what was there. Most of these tracemakers have turned out to be small adult beetles or beetle larvae of various species, but I can’t ever predict which life stage or species will be there based just on their traces. (At least, not yet.)

Shallow burrow with short branches in a coastal dune, Cumberland Island, Georgia. Gee, I wonder what worm made it?

Surprise! It was a tiny adult beetle, found at the end of the burrow. Didn’t see that coming, did you? Well, maybe you did after all of the pedantic foreshadowing. (Both photographs by Anthony Martin.)

As a result of these insect-inspired search images, embedded in my consciousness from years of looking at Georgia-coast insect traces, I cannot ever again look at trace fossils made in formerly terrestrial environments and simply say, “worm burrows,” at least with a clear scientific conscience or a straight face. Hence whenever I see similar burrows in sedimentary rocks that were formed in lakes, streams, or soils from the Devonian Period to the recent, my default hypothesis is “insect burrows,” rather than “worm burrows.” Is this always right? No, as some terrestrial trace fossils, such as Edaphichnium and Castrichnus, were almost certainly made by earthworms, and nematode worms may have formed others, like Cochlichnus. (Although Cochlichnus has also been linked with insect tracemakers – but that’s a another story for another day.) Nonetheless, saying “insect burrows” is more likely to be correct than the alternatives, and in science, it’s good practice to learn from your mistakes.

So geologists and paleontologists everywhere, I beseech you not to limit yourselves descriptively when you encounter the millions of lovely and varied invertebrate trace fossils in sedimentary rocks formed in terrestrial environments. The truth will set you free (or at least put you on parole), and these seemingly simple trace fossils will become more intriguing as you realize their full complexity and potential mystery. Call them something other than “worm burrows,” then see what happens.

Invertebrate trace fossils (burrows) in sandstone from the Moeanave Formation (Lower Jurassic) in St. George, Utah. Do they look a little different to you now that you’re ready to give them a different name than mere “worm burrows”? (Photograph by Anthony Martin.)

(Acknowledgements: Many thanks to Andrew Milner, Jim Kirkland, Tyler Birthisel, Martin Lockley, Brent Breithaupt, Neffra Matthews, and many others for their organizing a most excellent three-day field trip to the Triassic-Jurassic rocks of southern Utah and northern Arizona. We all learned heaps from this direct experience, and greatly appreciate the huge amount of time and effort put into preparing for the field trip.)

Further Reading

Milner, A.R.C., Harris, J.D., Lockley, M.G., Kirkland, J.I., and Matthews, N.A. 2009. Bird-like anatomy, posture, and behavior revealed by an Early Jurassic theropod dinosaur resting trace. PLoS One, 4(3): doi:10.1371/journal.pone.0004591.

Rindsberg, A.K., and Kopaska-Merkel, D. 2005. Treptichnus and Arenicolites from the Steven C. Minkin Paleozoic footprint site (Langsettian, Alabama, USA). In Buta, R. J., Rindsberg, A. K., and Kopaska-Merkel, D. C., eds., = Pennsylvanian Footprints in the Black Warrior Basin of Alabama, Alabama Paleontological Society Monograph No. 1: 121-141.

Smith, J.J., Hasiotis, S.T., Kraus, M.J., and Woody, D.T. 2008. Relationship of floodplain ichnocoenoses to paleopedology, paleohydrology, and paleoclimate in the Willwood Formation, Wyoming, during the Paleocene–Eocene thermal maximum. Palaios, 23: 683-699.

Verde, M., Ubilla, M., Jiménez, J.J., and Genise, J.F. 2006. A new earthworm trace fossil from paleosols: aestivation chambers from the Late Pleistocene Sopas Formation of Uruguay. Palaeogeography, Palaeoclimatology, Palaeoecology, 243: 339-347.

Life Traces of the Georgia Coast

Unseen lives of the Georgia barrier islands

Tag Archives: dinosaur tracks

Victorian Dinosaur Tracks of the ’80s

Of Sacred Mules and Sauropod Tracks

The Ichnology of Pacific Rim

The Ichnology of Jurassic Park

Tracking Wild Turkeys on the Georgia Coast

Deep in the Dinosaur Tracks of Texas

Public Outreach via Ichnology: Traces for Kids

“Worm Burrows” as a Geological Cliché

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