The Arlington Archosaur Site: A Model of Citizen-Science in Paleontology

By Chris Noto


Art Sahlstein digging: AAS discoverer and volunteer Art Sahlstein excavating around a fossil bone at the Arlington Archosaur Site in 2016. Photo by Chris Noto.

In the heart of the Dallas-Fort Worth metroplex, paleontologists have partnered with a dedicated team of local volunteers and fossil enthusiasts to excavate a treasure trove of fossils dating from 96 million years ago, during the last period of the Age of Dinosaurs. This prolific fossil area named the Arlington Archosaur Site (AAS) is playing a critical role in expanding our knowledge of a rare, ancient ecosystem largely unknown from North America. Amateur fossil hunters and citizen scientists have played an integral role in the AAS since the beginning. Credit for the discovery of the AAS belongs to local fossil collector Art Sahlstein and University of Texas–Arlington students Phil Kirchoff and Bill Walker, who independently found fossils there in 2003. Organized excavation though was stymied until 2007, when new landowners granted access to the area. This fieldwork was organized and initiated by UTA graduate student Derek Main, who worked with students and amateur groups such as the Dallas Paleontological Society, to methodically excavate what appeared only to be a drab, run-of-the-mill hillside.

A large group of volunteers at a typical dig in 2011. Photo by Derek Main.

As it turns out, that hillside contains one of the most diverse, well-preserved, and numerous fossil accumulations yet discovered in the entire Dallas-Ft. Worth metroplex. The AAS contains the remains of theropod dinosaurs, duck-billed dinosaurs, croc-relatives, turtles, amphibians, snakes, mammals, bony fish, sharks, rays, invertebrates, and plants. The AAS belongs to a body of rock called the Woodbine, which is formed from a series of deltas deposited on a peninsula that jutted out into a shallow seaway during the Cretaceous. Even before discovering the AAS, the Woodbine was considered important because it is one of the few groups of terrestrial rocks known from this place and time, giving us a rare window into what life was like on land in eastern North America, which generally has a poor fossil record. What fossils were previously known from the Woodbine were scattered and incomplete, offering only tantalizing clues as to what organisms existed here. The discovery of the AAS changed all that, acting as a Rosetta Stone paleontologists can use to better interpret and understand the Woodbine.

Volunteers excavating a large, intact turtle shell that may represent a new species. Photo by Derek Main.

The AAS wouldn’t be the success that it is if it weren’t for the small army of dedicated volunteers donating their time, energy, expertise, and resources. Hundreds of people from the community have participated in digs over the years; people from all walks of life and many diverse backgrounds. Many who otherwise may not have come together were it not for their shared interest and passion for fossils. This unique combination of location and interest allowed us to dig nearly year-round, accomplishing much more in this time than many other projects. Conditions aren’t easy, either. During the summers we have to contend with temperatures that top 100˚F and terrible humidity when even the shade tents provide little comfort. In the spring and fall, rains can transform the site into a sticky mud pit teeming with biting insects. There is all manner of wildlife, including spiders, scorpions, centipedes, mosquitos, ants, wasps, velvet ants, snakes, feral pigs, bobcats, and coyotes, to name a few.

To date, three new species discovered at the AAS have been named for the volunteers who found them: the lungfish Ceratodus carteri (Brad Carter), huge predatory crocodyliform Deltasuchus motherali (Austin Motheral), and small, enigmatic croc Scolomastax sahlsteini (Art Sahlstein). There are many more specimens left to describe, many of which will likely also be new species.

Volunteers Ronnie Colvin, Art Sahlstein, and Anissa Camp at an AAS educational outreach booth. Photo by Derek Main.

But volunteer involvement doesn’t stop there. Many volunteers have spent their free time cleaning and repairing the same fossils they discovered—a skill that takes a great deal of time and patience—but is necessary so us scientists can study them properly. More importantly, our volunteers have taken what they learned from working at the site and share it with the wider community. Many of our volunteers are teachers in local schools and have integrated Texas fossils and geologic history into their curricula. A few have even completed research projects related to the AAS, presenting their results at professional scientific conferences. Some take part in educational outreach, traveling to gem & mineral shows, schools, community groups, etc. to educate people about the lost world beneath their feet and communicate the value of these fossil resources to the wider public. Experiences at the AAS have transformed people’s lives, giving them new and unique perspectives, inspiring many to do and learn more. There is no greater outcome that I can think of.

Volunteers Ronnie Colvin and John Beeck with Dr. Chris Noto at eh 2015 Society of Vertebrate Paleontology annual meeting in Dallas. Photo by Chris Noto.

Currently, excavations at the AAS are on hiatus as the research team works on describing the thousands of specimens that have already been discovered, among other projects related to enhancing our understanding of the Woodbine. But public involvement doesn’t end here. Some of our most dedicated and knowledgeable volunteers continue to search the Woodbine for new sites with more fossils that can help us further flesh out this ancient ecosystem. The next AAS could be right around the corner.

The AAS exists because of the hard work of amateurs and fossil enthusiasts who recognize the value of our shared fossil heritage. Every dig they worked hard to get us there with every shovel full of dirt, every trowel-turn of sediment, every single day spent uncovering an ancient Cretaceous coast. The true legacy of the site will be the people: the great numbers of volunteers, scientists, educators, and others who came together to preserve, study, and most importantly educate people about, this unique fossil locality.

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