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.

Speleotherium logani

It would be easy to think that we've got the large Late Pleistocene mammals of North America pretty well locked down. After all, every self-respecting animal of that stripe has a long list of synonyms and pseudonyms, sometimes going well back into the 19th century. (All right, to be fair, horses are a mess if you look closely.) Even here, though, there can be surprises. Recently we had the Pacific mastodon and the re-establishment of the dire wolf in its own genus, and now we have the recognition of an entirely new genus and species of scrubox, Speleotherium logani (White et al. 2025).

If you know a bit of Greek, you'll get the idea that the name indicates we're dealing with a beast ("therium") associated in some way with caves ("speleo"). The holotype and best specimen of Speleotherium logani did indeed come from a cave, and in fact was partially encrusted with cave deposits (which certainly give it an unusual look but haven't made it easy to prepare or interpret). A few years ago the skull was photographed for a photogrammetric model, and you can take it for a spin and see the deposits, particularly on the right side of the face. This specimen and others were discovered in 1976 in what is now called Muskox Cave in its honor, within Carlsbad Caverns National Park, New Mexico. The species name honors the discover, Lloyd Logan. Although the name literally translates to "Logan's cave beast", the authors suggest the common name "Logan's austral scrubox" instead (White et al. 2025).

Figure 31 from Kottkamp et al. (2020), used in several other places as well (including White et al. 2025). You're looking at the back of the skull, going off to the right. Other bones are also visible, as well as the coating of cave mineralization.

The Muskox Cave fossils were long thought to belong to the shrubox Euceratherium (which is the name used for it at the 3D model above). That's how we labeled them in recent inventories of the park's fossils, for example (Kottkamp et al. 2020, 2022). It was not until White et al. began to prepare the specimens that it became apparent that there was something else here. Euceratherium has a narrow "forehead" and complexly twisted horn cores, whereas the Muskox Cave skull has a broad "forehead" and less curvy cores. The metapodials (metacarpals and metatarsals) are also shorter and stockier, which twigged something else; the authors knew of similarly proportioned metapodials of an animal similar to but much smaller than Euceratherium from sites in Mexico and Belize, but had never had a face to go with them. Speleotherium is therefore not a "one-off" but something that had a fairly wide range in North and Central America, and there are probably other examples that are currently listed as Euceratherium (White et al. 2025). The metapodial anatomy is rather similar to the same bones of the takin (White et al. 2025), which is a Himalayan bovid that's kind of in-between things like muskox, sheep, and goats in appearance and habits. That may give an idea of what Speleotherium was doing. The short and stocky metapodials suggest it was active in rugged terrain, but based on fossil distribution it was not limited to higher elevations (White et al. 2025).

The skull in the process of being captured by photogrammetry (producing the 3D model linked above), showing its best side. Figure 36 in Kottkamp et al. (2020).

Given we're dealing with National Park Service fossils, you can imagine it's been on my radar. It showed up in the 2001 inventory of NPS cave fossils as what is now a grainy photo (Santucci et al. 2001), but we've since been able to feature the image in higher resolution glory for Carlsbad-specific inventories (Kottkamp et al. 2020, 2022). There's been a soft spot for it around here; it even got a coloring page, now part of the "Cenozoic Life in the National Parks" coloring book (just mentally substitute Speleotherium for Euceratherium as the label; the coloring page was prepared long before the bones got their new name).

References

Kottkamp, S., V. L. Santucci, J. S. Tweet, R. D. Horrocks, E. Lynch, and G. S. Morgan. 2020. Carlsbad Caverns National Park: Paleontological resource inventory (public version). Natural Resource Report NPS/CAVE/NRR—2020/2148. National Park Service, Fort Collins, Colorado.

Kottkamp, S., V. L. Santucci, J. S. Tweet, R. D. Horrocks, and G. S. Morgan. 2022. Pleistocene vertebrates from Carlsbad Caverns National Park, New Mexico. New Mexico Museum of Natural History and Science Bulletin 88:267–290.

Santucci, V. L., J. Kenworthy, and R. Kerbo. 2001. An inventory of paleontological resources associated with National Park Service caves. NPS Geologic Resources Division, Denver. Technical Report NPS/NRGRD/GRDTR-01/02.

White, R. S., J. I. Mead, and G. S. Morgan. 2025. Logan's austral scrubox, a new ovibovine (Mammalia: Artiodactyla: Bovidae) from Muskox Cave, Eddy County, New Mexico. New Mexico Museum of Natural History and Science Bulletin 101: 473–494.