A Visual Paleontological Inventory of Utah’s National Park Service Areas

Allow me to indulge in a bit of puffery and congratulations...

Let's go back a couple of years ago. We in the NPS Paleontology Program knew that the new edition of the Utah Geological Association's "Geology of Utah's Parks and Monuments" was not going to have an update of the overall park paleontology chapter. (Which is fair enough, since it was 35 pages in the previous update and was not getting shorter. The new volume is still well worth seeing, though, especially if you haven't seen the earlier editions.) We also were working with Tut Tran, then putting the finishing touches on the paleontological inventory report for Bryce Canyon National Park. These touches included some clever biostratigraphic figures of a kind we'd never used before. Thus was an idea born: Tut would prepare a standalone article featuring similar figures for the rest of Utah, with contributions from various luminaries in NPS and Utah paleontology. This article, "A Visual Paleontological Inventory of Utah’s National Park Service Areas", is now available for your edification and reading pleasure. Congrats, everyone!

Utah has 13 National Park Service units: five parks (Arches, Bryce Canyon, Canyonlands, Capitol Reef, and Zion), six monuments (Cedar Breaks, Dinosaur, Hovenweep, Natural Bridges, Rainbow Bridge, and Timpanogos Cave), one national recreation area (Glen Canyon), and one national historical park (Golden Spike). (There are a few other units in the state designated as "National", such as Grand Staircase-Escalante National Monument and Flaming Gorge National Recreation Area, but they are under different agencies.) This is omitting a few NPS trails (California, Mormon Pioneer, Old Spanish, and Pony Express) and the Virgin Wild and Scenic River, which are complicated to deal with because they don't have formal boundaries the same way the other types of units do; one day I'd like to go over rivers and trails thoroughly, but that's for another day. Anyway, the 13 units give Utah one of the best state-wide paleontological records in the NPS, up there with Alaska and California. Each one of them has something, although certainly some have more than others. The five national parks, Dinosaur NM, and Glen Canyon NRA are the most abundantly supplied and feature the longest records.

Figure 2, comparing the stratigraphic records of Utah's NPS units. Click to embiggen. CC BY 3.0 US.

These seven units are fairly similar stratigraphically and in fossil content, with the exceptions of Bryce Canyon (getting started when most of the others are tapering off) and to a certain extent Dinosaur (longer record and some different formations due to distance from the other units). The classic assortment of rocks generally includes the Permian, Triassic (Moenkopi and Chinle), Jurassic (Glen Canyon Group, San Rafael Group, and Morrison Formation), and part of the Cretaceous (Cedar Mountain Formation and Naturita, the old Dakota Sandstone). Arches, Canyonlands, Capitol Reef, and Glen Canyon in particular are geological and paleontological siblings. There are some older and some younger formations, but generally the sweet spot is between about 300 and 100 million years ago.

You might think, based on Dinosaur's reputation, that the Morrison Formation is the big producer, but as it turns out that's not the case. The Lower and Middle Jurassic rocks that make up so much of the scenic vistas, although not big bone producers, are perhaps the most iconic fossil producers with their fossil tracks. (Which is fitting for a park, because just like you can't put a vista in a box and take it somewhere else, fossil tracks are best appreciated where they are found.) The Chinle and Moenkopi are also good but a bit overlooked (Utah's Chinle having the excuse of being in the shadow of Arizona and New Mexico). Another interval that is very productive is the late Quaternary: several units have cave/rock shelter assemblages, usually thanks to packrats, with the assistance of other animals. Glen Canyon in particular is noted for dung caves, including Bechan Cave ("big feces" in Navajo) and its supply of mammoth dung. The Cretaceous is coming into its own with work at Bryce Canyon, Dinosaur, and Glen Canyon; in fact, work on the Cretaceous made our article outdated almost the day it was published, thanks to Pahasapasaurus gillettei from the Tropic Shale of Glen Canyon (Schmeisser McKean 2025). We were able to get October's Athenar bermani in there in the proof stage, but the plesiosaur managed to wait just long enough. (Darn it.)

This article is not a rewrite of the NPS paleontology chapters in the old UGA volumes. It sets out to do different things and is much more visual in focus, rather than textual. (It even has its own nifty cover image, done by artist Benji Paysnoe in the spirit of the great "Vertebrate Paleontology of Utah" volume.) The main things you will find in this that you won't find in the older chapters are Tut's outstanding diagrams and a grand 62-page appendix listing fossil taxa from each park unit by formation, with citations. Between the nine authors, I think we were able to put together a pretty darn comprehensive appendix, although doubtless we missed something. (If you spot something, let us know, so it can be included if we get the opportunity to do an update.) Me, of course, I'm hoping for more Paleozoic invertebrates, but I'm not turning up my nose at anything!

Figure 39, a sample diagram (Rainbow Bridge NM). You should go to the article to see what's been found at the big parks! CC BY 3.0 US.

We're all excited for this to be out, and we hope you find it useful as well, as a unique look at the paleontological riches of Utah's NPS units.

References

Schmeisser McKean, R. L. 2025. A new species of Pahasapasaurus (Plesiosauria: Polycotylidae) from the Upper Cretaceous Tropic Shale (lower Turonian) of southern Utah, U.S.A. Cretaceous Research 106269. doi: https://doi.org/10.1016/j.cretres.2025.106269.

Tran, T., A. R. C. Milner, J. S. Tweet, D. D. DeBlieux, R. Hunt-Foster, A. B. Shaffer, J. I. Kirkland, E. Warner-Cowgill, and V. L. Santucci. 2025. A visual paleontological inventory of Utah’s National Park Service areas. Geology of the Intermountain West 12: 221–292. doi: https://doi.org/10.31711/giw.v12.pp221-292.