A reconstruction of Lythronax, a tyrannosaur found in Utah's Grand Staircase-Escalante National Monument.
Read Caption
Photo by Brian Switek.
A reconstruction of Lythronax, a tyrannosaur found in Utah's Grand Staircase-Escalante National Monument.

Digging Into the Grand Staircase

When I tell a new acquaintance that I live in Utah, I ‘m often met with a mild side eye. “Are you a Mormon?” is the question that always follows. No, I’m not, I explain, and I moved to the beehive state for a more unconventional reason. I came here for the dinosaurs.

The most famous of Utah’s fossil sites are Jurassic classics. Localities such as Dinosaur National Monument and the Cleveland-Lloyd Dinosaur Quarry are rich boneyards from the heyday of Late Jurassic giants. But that’s just one relatively narrow slice of history in a state that offers so much undiscovered Mesozoic history. In 2010, the year before I moved to Utah, paleontologists named eight new dinosaur genera from sites in the state. Several more have followed, with a greater number still in preparation.

View Images
At the Top of the Grand Staircase, edited by Alan Titus and Mark Loewen.

The vast majority of the newly-named animals are not from long-known localities, but from Cretaceous sites between 145 and 66 million years old that are only just beginning to be revealed. And of all these places brimming with dinosaur fossils, southern Utah’s Grand Staircase-Escalante National Monument has most forcefully captured the attention and imagination of researchers. Not only are the fossil organisms being found there new to science, but the variety of life – from plants to turtles to mammals to dinosaurs – has raised new puzzles about evolution and what researchers previously expected about Late Cretaceous history. The new technical volume At the Top of the Grand Staircase edited by paleontologists Alan Titus and Mark Loewen synthesizes what has been uncovered so far.

Recognizing the richness of what would become Grand Staircase-Escalante National Monument was a long time coming. Titus documents the slow scientific burn in his introductory chapter. John Wesley Powell and other explorers roughly documented the geology of southern Utah’s badlands in the late 19th century, their work setting the stage for later fossil fuel exploration and geological surveys. The paleontological potential of the vast area didn’t spark much interest until the late 20th century, and even then fieldwork out on the Kaiparowits Plateau was relatively sporadic. Nevertheless, enough new, tantalizing fossils were found that they helped spur the creation of the area as Grand Staircase-Escalante National Monument in 1996, overseen by the Bureau of Land Management.

The fossil rush didn’t take long to start. Within five years, multiple museums were working with the BLM’s paleontology crew – led by Titus – to document the monument’s geology and discover prehistoric creatures never seen before. The badlands are rife with potential,  with, Titus estimates, “hundreds of thousands of hectares of outcrop” that have yet to be explored.

Not all of the monument’s sites are Cretaceous in age. A fine skeleton of the crocodile cousin Poposaurus was found within GSENM’s older Triassic rock, for example. But the monument’s expansive exposures of Cretaceous rock have drawn the most attention and form the backbone of the new volume. A series of formations spanning approximately 93 to 72 million years ago – the Dakota Formation, Tropic Shale, Straight Cliffs Formation, Wahweap Formation, and Kaiparowits Formation – document a time when southern Utah went from being underwater to a lush coastal environment next to a long-vanished seaway. And since everyone loves dinosaurs, the discovery of tyrannosaurs, ceratopsids, hadrosaurs, and other dinosaurs from the Wahweap and Kaiparowits Formations have dominated news from the monument.

But the new volume isn’t all about dinosaurs. In fact, despite Raúl Martín’s lovely Nasutoceratops scene on the thick book’s cover, the contributions relating to dinosaurs make up only a very small part of the book. The first section covers the monument’s geology, from a basic overview to the “implications of the internal plumbing of a Late Cretaceous sand volcano.” Sections on the monument’s prehistoric plants, invertebrates, fish, amphibians, turtles, mammals, lizards, snakes, and crocodylomorphs follow, with the dinosaurs only making their appearance starting on page 445. An assortment of contributions on trace fossils and taphonomy round out the collection.

View Images
The hadrosaur Gryposaurus monumentensis, found in GSENM, at the NHMU. Photo by Brian Switek.

Throughout all these detailed summaries of fossil organisms, there are plenty of references to referred species and yet-to-be-named organisms. Many of the fossils found within the monument are new and yet to be fully described at the time of the book’s publication. In the chapter on horned dinosaurs, for example, the recently-announced Nasutoceratops titusi is called “Kaiparowits centrosuarine A”, so non-expert readers might want to check up to see if some of the animals mentioned in the volume have made their scientific debut. But this also shows the rate at which research into GSENM’s fossils is progressing. Each year new species from the monument are being named, and, according to a recent comment by Titus, there are nearly a dozen that are currently awaiting publication.

Exactly why all this detailed record-keeping is important is hinted at throughout the contributions, but comes into full focus in the very last paper.

Fossils of previously-unknown Cretaceous species are found at sites all over the world, and most prehistoric species from even that one period are still unknown. New species are named all the time.  Yet it’s not simply the novelty of the Grand Staircase-Escalante National Monument fossils that are important, as Scott Sampson and coauthors argue in their closing summary, but their novelty in relation to other organisms that lived elsewhere in North America at the same time. The dinosaurs of southern Utah, in particular, are different at the genus or species level from similar communities that lived at roughly the same time in Cretaceous Canada. This pattern is distinctly different from dinosaur diversity in the following, closing part of the Cretaceous where dinosaurs such as Tyrannosaurus are found over a much wider range.

View Images
Looking into the Kaiparowits Formation from GSENM’s Horse Mountain. Photo by Brian Switek.

Why are the Late Cretaceous species of southern Utah so different? As yet, no one knows. Some sort of physical barrier such as a mountain range or river system could be the answer, or maybe there was some aspect of dinosaur evolution and diversification at play that we don’t yet understand. Perhaps looking to the smaller, less charismatic organisms mentioned in the volume will reveal patterns that then lead us to what was happening to our beloved dinosaurs. All of these fossils present a puzzle to researchers that has yet to be fully worked out. In trying to untangle that mystery, from discovery in the field through description and new understandings of paleobiology, perhaps paleontologists will be able to draw on the monument’s fossils to distill new insights into how evolution works.

The process will take decades of researchers and volunteers working at full tilt. I’m happy to be a very small part of that – I’ve joined crews from the Natural History Museum of Utah for a few outings as they’ve searched for new fossil sites within Grand Staircase-Escalante National Monument. I haven’t found anything noteworthy yet, but, if I do, I’ll anxiously flip through this book to puzzle out what I’ve stumbled across. There’s no better guide to those badlands and the ancient life they contain. And rather than marking an end point, the volume is a foundational manuscript for ongoing research that will be indispensable to anyone researching the monument’s prehistoric life. At the Top of the Grand Staircase  is an essential volume for explorers who are continuing to search through what’s left of Cretaceous Utah.