Track Makers in Southern Utah: The St. George Dinosaur Discovery Site | PLOS Paleo Community

Featured image: Megapnosaurus model on display in front of Grallator-type dinosaur tracks at the St. George Dinosaur Discovery Site at Johnson Farm. Photograph by Sarah Gibson.

This is a post that I originally wrote for the PLOS Paleontology Community blog in May of 2016. I am archiving it here on my website, so some of my references to the 2016 SVP meeting in Salt Lake City are a bit outdated. Nevertheless, you’ll get the gist about this awesome site. You can find the original blog post here.

UPDATE August 22, 2016: It is with great sadness that we announce the passing of Dr. Sheldon Johnson last week from leukemia. You may find his obituary here, and please consider donating to the DinosaurAh!Torium Foundation, which helps fund research and preservation of tracks at the St. George Dinosaur Discovery Site at Johnson Farm.

When it comes to absolutely amazing paleontological resources, Utah arguably reigns supreme within the United States (I may be a bit biased). And with the upcoming Society of Vertebrate Paleontology meeting taking place in Salt Lake City, paleontologists and paleo enthusiasts will be flocking to the Beehive State to discuss and share the latest breakthroughs in the field. To those coming to the meeting this October, one thing I cannot stress enough: do not miss what Utah has to offer in terms of spectacular fossil sites and museums. It will be difficult to avoid, as the SVP host committee this year is offering up eleven (eleven!!!) field trips to different parts of the state to see everything from the Triassic-Jurassic transition to Mesozoic dinosaurs to Eocene fishes to Pleistocene shorelines, and more.

If you’d rather go rogue and visit some places on your own, you are greeted with a plethora of options: at least a dozen museums, five national parks and many more national monuments, and some beautiful in situ fossil localities open to visitors. I recently visited one of the more recent additions of paleo places to visit in Utah, and it’s one of my favorites as well because, well, I worked there for two years! Let me make the case for why you should consider a jaunt down to St. George, Utah and view some of the most spectacularly preserved dinosaur tracks in North America.

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Dr. Sheldon Johnson pictured with one of the dinosaur track blocks in 2000. Image courtesy Andrew R. C. Milner.

Located at the southwestern tip of the state, the St. George Dinosaur Discovery Site at Johnson Farm(hereafter called SGDS) was only very recently discovered in 2000, when landowner and retired optometrist Sheldon Johnson was clearing some land for development. Overturning some large sandstone blocks, he observed natural casts of dinosaur footprints that were so detailed, he initially thought he had an actual dinosaur preserved in the rock with its foot hanging out. As he moved and overturned more blocks, he quickly realized he was looking at exquisite dinosaur trackways.

Now, here is where Dr. Johnson did a wonderful thing. Rather than destruction of the tracks in order to develop the land, he called local geologists and paleontologists, who quickly came and assessed the site. They found more of the tracksite in situ, and realized that they were dealing with multiple layers of dinosaur tracks, as well as invertebrate traces, body fossils, stromatolites, plants, and more. The City of St. George hired Andrew R.C. Milner to document and preserve the site, along with help from a dedicated group of volunteers, the Utah Friends of Paleontology, over the next few years. And working with the City of St. George, the Johnsons donated the land to preserve the site, and a museum was built over the bulk of the tracksite in 2005, still in its original location on the Johnson property.

Sixteen years since the initial discovery, the SGDS is operating better than ever, with over 38,000 visitors per year, according to Liz Freedman-Fowler, the Executive Director of the SGDS. The museum is now autonomous and is managed by the non-profit Dinosaur Ah!Torium Foundation. Andrew R.C. Milner continues to research, curate, and preserve the tracksite and associated fossils as the the Site Paleontologist and Curator. And the Utah Friends of Paleontology continue to support the site the site, with 37 active volunteers who have provided over 6600 volunteer hours per year.

The museum has undergone many changes in the past eleven years. When I worked there from 2006–2008, the in situ tracksite was difficult for visitors to view; the sandstone, as resilient as sandstone can be, was still very delicate after being exposed, and thus patrons were not allowed to walk out onto the surface. However, in the years since, the SGDS has blocked out large windows, built a brand-new raised wooden platform over the tracksite, and provided proper illumination to make the dinosaur tracks and other traces visible to every visitor.

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The brand new raised walkway over the track surface allows visitors to view the tracks in place. Image by Sarah Gibson.
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Eubrontes track on display. Image by Sarah Gibson.

So, what will you see when you visit the SGDS? Yes, you will see dinosaur tracks, but this site offers so much more than just tracks. This site represents a 200 million year old snapshot of a ecosystem: an ancient shoreline of a large lake that, during the Early Jurassic, was surrounded by vast desert and dunes. Dinosaurs, early crocodylimorphs, fishes, all came here to drink and thrive. Thus far, the trace fossils have been identified to several ichnogenera: Eubrontes, Grallator, Anomoepus, Kayentapus, and Batrachopus, to name a few examples. By far, Grallator-type tracks are the most abundant, made by a small theropod dinosaur, possibly Megapnosaurus. Larger Eubrontestracks are also prominent, made by a larger theropod, such as Dilophosaurus. Eubrontes tracks are also represented by some of the most well-preserved natural casts at the site, allowing you to see details down to the claws and toe pads.

The tracks can tell us so much about the behavior of organisms: speed has been calculated on several of the trackways, as well as the size of the the organisms. One particular trackway told us a lot about theropod stance, posture, and behavior. The trackway was discussed and published in PLOS ONE in 2009, by Andrew R.C. Milner et al. The trackway preserves a moment where, a theropod dinosaur crouched in the mud as it emerged from the water of the lake, scooted forward a bit (creating two overlapping crouching impressions). The impression of the ischia is visible, as is the tail mark behind the dinosaur. In addition, the “heels” are well-preserved, telling us that this animal crouched in a manner similar to birds. Hand impressions are also visible, showing that the palms of the animal faced inwards.

The crouching dinosaur trace, one of only six in the world.
The crouching dinosaur trace, one of only six in the world. Image by Sarah Gibson.

We can follow the path of this dinosaur as it stood up from crouching in the mud, and began walking across the surface. A beautifully reconstructed Dilophosaurus model is visible in the end of the trackway as it is preserved, allowing visitors to imagine the dinosaur itself, walking out of the lake and through the mud.

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A reconstruction of Dilophosaurus, placed in the trackway of the crouching dinosaur. Image by Sarah Gibson.

With the renovations to the museum, this spectacular crouching trace and subsequent trackway, along with thousands of other tracks and traces, are now easily visible to every visitor of the site, along with hundreds of blocks showcasing some of the SGDS’s finest tracks. Mud cracks, ripple marks, swim tracks, skin impressions, are all visible to the naked eye.

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Can dinosaur tracks be cute? Image by Sarah Gibson.

The site also boasts body fossils, with isolated dinosaur teeth and a vertebra recovered, as well as fossilized remains of sharks and ray-finned fishes, including some articulated fishes likely belonging to the genus Lophionotus (whom yours truly described). In the nearby area, coelacanth and lungfish remains have also been discovered. Numerous plants have also been found at SGDS.

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The largest single block of tracks at the tracksite, featuring several distinguishable Grallator trackways, possibly made by Megapnosaurus. Image by Sarah Gibson.

Overall, it’s pretty hard to find a better moment in time of an ecosystem preserved, and it really is thanks to the Johnsons, who had the foresight to preserve and protect the fossils for future generations. And with the beautiful preservation  of the tracksite, protected within the SGDS museum, this site will continue to provide evidence of a time 200 million years ago, when some thirsty dinosaurs found some solace in a lake among the desert. Its a spectacular locality well worth your time and patronage. If you are interested in more information, Jerry Harris, paleontologist and professor at Dixie State University in St. George, along with Andrew R.C. Milner, have recently published a book chronicling the science and history of the site. See the links below for information!

Restoration of Early Jurassic environment preserved at the SGDS, with the theropod Dilophosaurus wetherilli in bird-like resting pose, demonstrating the manufacture of SGDS.18.T1 resting trace. By Heather Kyoht Luterman.
Restoration of Early Jurassic environment preserved at the SGDS, with the theropod Dilophosaurus in bird-like resting pose. By Heather Kyoht Luterman. From Milner et al. (2009).

And happy tracking!

Read more:
Harris JD, Milner ARC (2015) Tracks in Deep Time: The St. George Dinosaur Discovery Site at Johnson Farm. University of Utah Press.

Milner ARC, Harris JD, Lockley MG, Kirkland JI, Matthews NA (2009) Bird-Like Anatomy, Posture, and Behavior Revealed by an Early Jurassic Theropod Dinosaur Resting Trace. PLoS ONE 4(3): e4591. doi:10.1371/journal.pone.0004591

Published by Sarah Z. Gibson

Dr. Sarah Z. Gibson is a paleontologist and science communicator based in Minnesota. Her research focuses on the evolutionary history of ray-finned fishes from the Early Mesozoic. https://orcid.org/0000-0002-6784-3980

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