Fossil fishes of the "Pain Desert"

Adventures in Petrified Forest National Park

“At day’s end, the light has a beautiful golden quality”

-Jack Stack field notebook, May 2022.

“The sun is my enemy now”

-Jack Stack field notebook, May 2022.

The Petrified Forest is a desolate place. As you walk over the surface, you feel the crunch of eroded shards of rocks beneath your boots. Occasionally you see evidence of the desert denizens, such as a scurrying lizard or a solitary colony of ants. In its own way, the desert is a beautiful, if desolate, ecosystem. As a human, you feel acutely aware that this is an alien world. Moisture is non-existent in the summer except for rare rainfall. A relentless sun beats down on you, unbroken by shade. The Petrified Forest of today is perhaps the last place on Earth you would expect to find a fish. However, this desert tells one of the most important stories in fish history.

The desert is the preferred habitat of the paleontologist because we have direct access to rocks that aren’t covered with soil, plants, houses, or roads. Even though, on our first day, the sign for the “Painted Desert” had lost the “ted”, myself and the crew from Virginia Tech Paleobiology came to appreciate our beloved “Pain Desert”. The rocks of the Petrified Forest preserve an ancient tropical ecosystem teeming with life, including an entire assemblage of fishes and the organisms they lived with. These fishes lived in a mighty river system that cut through North America in the Late Triassic period, approximately 220 million years ago. The logs of fossilized trees that have made the Petrified Forest famous once grew along the banks of this river system. Occasionally, a small section of the river would get cut off, forming a small, isolated lake. These lakes provided quiet waters where deposition of fine mud preserved not only the plants and animals that lived in the lake but anything that died in it as well. Additionally, floods of the river system occasionally dumped the remains of other animals into the lakes, providing a broad sample of the Late Triassic ecosystem. Fast forward 220 million years to the present, we find ourselves back in the beautiful, if hostile, desert of northeast Arizona. The very things that make this desert difficult to traverse make it a perfect place to study the past. The hot, arid conditions prevent all but the most hardy plants from growing. The ground is therefore bare and exposed, leaving its history and the remains of ancient organisms it has entombed for hundreds of millions of years literally within our grasp. People have known about these fossils since the First Nations inhabited these lands 13,000 years ago. Occasional pieces of pottery and tools are evidence of the long history of people in Petrified Forest long before it was a national park (which we paleontologists leave untouched). Later, American soldiers and explorers would find fossils and collect them as natural curiosities or objects of scientific discovery. The nineteenth century was a time of intense exploration coupled with the expansion of the United States across the west, and colonial empires across the globe. Fossils were central in the aim of western nations to expand and control the world. The discovery of such a wealth of fossils prompted US President Theodore Roosevelt to designate the Petrified Forest as a National Monument in 1906. It wasn’t until 1962 that it was elevated to a National Park conserving over 50,000 acres of land for science and nature. This land preserves abundant rocks containing the fossilized remains of ancient organisms that have been studied by National Park scientists and researchers from across the globe for decades. Years of tireless research have recorded dozens of ancient, long extinct species, giving us a window into the natural world of 220 million years ago.

Above: Me enjoying the geology of Petrified Forest National Park during a break from fossil prospecting. Photo by Khanh To.