Discovering Shonisaurus popularis, Nevada’s State Fossil

By Paige dePolo

Our state has adopted many symbols to honor and give a sense of the character of its high deserts, mountains, and valleys and of the pioneering spirits of the folks who live here. Of the state symbols, our state fossil, Shonisaurus popularis, the ichthyosaur, stands out at almost mythical proportions. These animals were approximately the length of a school bus (~11-15 m) and dominated the warm, shallow seas that covered Nevada ~215 million years ago during the Triassic period.

Artist's reconstruction of Shonisaurus popularis, Nevada's state fossil. Image courtesy of Dmitry Bogdanov, CC by 3.0.

Shonisaurus popularis, was actually named for Nevada with Shonisaurus referencing the Shoshone Mountains of central Nevada (Nye County) where its fossils were originally found and popularis (‘of the people’) paying tribute to the immense amount of local effort spent in excavating these massive animals.

Although ichthyosaur bones from a variety of smaller species like Mixosaurus and Cymbospondylus have been known from Nevada since the mid-1800s, the bones of Shonisaurus were brought to the attention of researchers at the University of California Museum of Paleontology (UCMP) at Berkeley in the early 1950s by Margaret Wheat, a noted ethnographer and archaeologist from Fallon. Her persistence resulted in the director of the UCMP, Charles Camp, arranging an expedition to central Nevada in 1953 and ultimately kicked off several decades of exploration and excavation in the foothills of the Shoshone Mountains overlooking Ione Valley near the small ghost town of Berlin (once part of the Union Mining District).

Camp immediately realized the paleontological potential of the area and, even in the earliest days of his work, envisioned the creation of an ichthyosaur park where the public could view the spectacular remains of these ancient animals. On July 2, 1954, after a day of work on excavating a quarry with “a great jumble of bones” he wrote in his field notes, “This is a thing that should be preserved in situ for all to see. It will probably not be duplicated again in this world.”

Eventually, the canyon where the ichthyosaurs were found and the land on which the ghost town, Berlin, stood was made an official State Park in 1957.

Several ichthyosaur rib fragments found while prospecting in the hills near Berlin-Ichthyosaur State Park in 2017. The area is so fossiliferous that hundreds of Shonisaurus fossils have been found over the last half-century of research. Image courtesy of Paige dePolo

Despite the long history of research, culminating in the creation of the State Park and the publication of scientific descriptions of Shonisaurus in 1976 and 1980, many mysteries about these central Nevadan ichthyosaurs remain. On the local scale, the question of why so many adult ichthyosaur skeletons were concentrated in such a limited geographical area has inspired many creative hypotheses from Camp’s original theory that the creatures had suffered a mass beaching (since disproven) to the animals falling victim to an algal bloom to the massive concentration of individuals at the site resulting from generations of ichthyosaurs using the area as a birthing ground. On a more global scale, questions about what may have driven the group of large-bodied ichthyosaurs to which S. popularis belonged (Shastasauria) to attain their gigantic proportions also remain.

The bones of Shonisaurus popularis are critical to answering these big questions. Now, almost 70 years after Camp’s initial visit to the area and excavation of the type specimens, a team of researchers from the University of Nevada, Reno, the University of Utah, Vanderbilt University, the Smithsonian Institution, and the University of Edinburgh are working to understand the paleobiology and life history of these iconic giants. We are tackling these questions using a variety of approaches including: digitizing the Visitor’s Quarry at the park so that we can carefully investigate the ichthyosaur skeletons still in the ground, revisiting and documenting the historical fossils and papers at the UCMP and the Nevada State Museum, Las Vegas, and prospecting for and excavating new specimens from the area around the park. Looking at these old bones with new eyes is already yielding interesting early results. We are very excited to start sharing a more detailed story of our state fossil with folks over the next few years.

Paige dePolo is a visiting researcher at the Nevada State Museum, Las Vegas, studying Shonisaurus popularis. Her interests include ichthyosaurs and dinosaur footprints. Paige’s PhD. studies at the University of Edinburgh will begin this fall.