Paleontology of Scotts Bluff National Monument

Those of us old enough to have attended elementary school circa 1985–1990 may remember the experience of successfully (or less-than-successfully) traversing The Oregon Trail. Although the game certainly included a great deal of content and detail, you can play as long as you like but you'll never find a trace of a fossil in it. The people who actually used the real Oregon Trail and its counterparts did find fossils, though. One such intersection of paleontology and human history is Scotts Bluff National Monument (SCBL), which you can read about in our freshly issued paleontological resource inventory (Shaffer et al. 2026).

A former exhibit at the monument's visitor center highlighted examples of journal records. Figure 2 in Shaffer et al. (2026).

SCBL is part of a small cluster of National Park Service units that document the middle Cenozoic of the northern Great Plains. The most famous of these is Badlands National Park and its White River Group, but of course there is also Agate Fossil Beds National Monument and the younger Arikaree Group. Niobrara National Scenic River we saw last year. Wind Cave National Park also has some White River Group outcrops, and Fort Laramie (another place in The Oregon Trail) of today's Fort Laramie National Historic Site sits among Arikaree Group strata and was used by O.C. Marsh as a base of operations. Another Trail landmark, Chimney Rock, is the focus of NPS-affiliate Chimney Rock National Historic Site as well as the source of type specimens for the bird Phasianus (now Archaeophasianus) mioceanus Shufeldt 1915 and the rodent Eumys brachyodus Wood 1937. SCBL fits quite neatly among this regional crowd, complementing some of them and partially filling the temporal and stratigraphic gap between the Early Oligocene of Badlands and the Early Miocene of Agate Fossil Beds.

Click to expand for the annotations. 120 years can make a difference! Figure 5 in Shaffer et al. (2026).

The new report includes a new stratigraphic column for the monument and a detailed discussion of the mammalian biostratigraphy. Stratigraphically the monument encompasses the Oligocene part of the White River Group (Brule Formation), the mid-Oligocene Gering Formation, and younger undivided strata of the Arikaree Group. The biostratigraphy and lithostratigraphy are not quite nailed down at the top, but there is reasonable (but not conclusive) evidence that it gets into the late Early Miocene (Hemingfordian).

And if you want the technical explanation for the previous image... Figure 7 in Shaffer et al. (2026).

What kinds of fossils have been found at the monument? The great majority with solid location information come from the Brule Formation, so if you're familiar with Badlands, Scotts Bluff won't seem terribly different. There are the inevitable turtles (observed by 19th century travelers), oreodonts, and nimravids, and a whole host of ungulates. (There are only so many ways to say "small, extinct, and deer-like". It's a bit like "hypsilophodont" for any small bipedal ornithischian.) The higher stratigraphic units have not been as profuse with vertebrate body fossils as the Brule, but they do all right with trace fossils. In fact, trace fossils are one of the monument's specialties. There are vertebrate burrows in the Brule about 0.3 meter (1 foot) across and up to 4 meters (13 feet) long. One is associated with a turtle specimen. Cross-sections of animal tracks can be seen in the Gering Formation, some of which may have been made by entelodonts. Root traces and invertebrate burrows are abundant in the undivided Arikaree Group (Shaffer et al. 2026).

A number of tracks can be seen in cross-section just above the pronounced break, and the underside of one is just peeking out a little right of center. Figure 12 in Shaffer et al. (2026).

Although the people traveling by Scotts Bluff did not have time to do much more than note fossils, the site and its geologic exposures attracted geological interest. As a result, there are substantial vintage collections from "Scotts Bluff" (regrettably little other provenance information at hand) at the American Museum of Natural History, Harvard's Museum of Comparative Zoology, the Smithsonian, and especially Yale's Peabody Museum of Natural History, which has probably the longest history. At least seven fossil taxa were named from specimens found at or in the vicinity of the bluff, although only four could still be considered in use. Despite the evident interest, a comprehensive description of the site's paleontology has not been prepared until now. Scotts Bluff National Monument can take its rightful place among the paleontological parks of the Great Plains.

References

Shaffer, A. B., E. Evanoff, E. Welsh, J. S. Tweet, and V. L. Santucci. 2026. Scotts Bluff National Monument: paleontological resource inventory (public version). Science Report NPS/SR—2026/504. National Park Service, Fort Collins, Colorado. https://doi.org/10.36967/2319364.

Shufeldt, R. W. 1915. Fossil birds in the Marsh Collection of Yale University. Transactions of the Connecticut Academy of Arts and Sciences 19: 1–110.

Wood, A. E. 1937. The mammalian fauna of the White River Oligocene. Part II. Rodentia. Transactions of the American Philosophical Society 28(2): 155–269.

Punchbowls and Mixing Bowls

Although amazing scenic geology is not usually considered one of the features of east-central Minnesota and west-central Wisconsin, this area has its surprises. For example, there are a few places that are known as "mixing bowls" or "punchbowls", sometimes with "Devil's" attached. The "bowl" part of the name can be a bit confusing at first if, like me, you think of a bowl or other enclosed depression. Rather, these sites are steep-sided short narrow gorges just off of larger drainage. At one time they were supplied with enough flowing water to carve a gorge, but this has now dwindled to practically nil. If you go above the bowl, you'll find the former streambed. The bowls form wonderful secluded glens. Some are easier to find (and more widely publicized!) than others. Here are three I've come across, all in western Wisconsin.

Seashells in the Salton Trough, 1775

Among the various types of National Park Service units are National Historic Trails. Many of these pass through fossiliferous areas, but stating that fossils are found on a given trail is not always easy. Unlike national parks and national monuments, where the NPS owns and manages parcels of land, the trails are not defined by boundaries, per se. In their absence, I like to look for reports of fossils made by users of the original trails, like the handful of fossils observed by Lewis and Clark, or John Strong Newberry's extensive description of the Santa Fe Trail. That at least shows a historical association.

Juan Bautista de Anza National Historic Trail, located in Arizona and California, recognizes the 1775–1776 expedition led by Juan Bautista de Anza to establish a Spanish presence in San Francisco Bay and an overland route to the area from greater New Spain, as the California coast was otherwise only accessible by water. If you're from the Southwest or have an interest in the Cenozoic paleontology of that area, you may have already recognized that name as part of California's Anza-Borrego Desert State Park, and you may have guessed where I'm going...

Anyway, one of the members of the expedition was Padre Pedro Font, a Franciscan missionary. Font was the expedition's chaplain, was responsible for taking latitudes, and also kept a diary (link to English translation). From this we can see that the expedition was not especially comfortable for him; a significant part of the trip he was ill with various maladies, and there were several bouts of bickering with his commander. (If someone asked you to lug around a psalterio and then never asked you to play it, or didn't give you access to the surveying tool you were supposed to be using, all while you were suffering from malarial fevers, you'd probably be annoyed too.) Also, of course, the reader should not expect that an 18th century missionary's first response to unfamiliar natives is going to be "These people are doing all right and we should certainly not try to change them in any way." That said, Padre Font displayed a canny eye for natural history in his entry for December 9, 1775:

"…On the road about a league after starting there is a salty lagoon without pasturage, and at about four leagues a little well of salty water which Father Garcés called El Rosario... On account of the unfruitfulness of these lands, so level, and of the aspect of the sand dunes, and especially of the abundance of shells of mussels and sea snails which I saw today in piles in some places, and which are so old and ancient that they easily crumble on pressing them with the fingers, I have come to surmise that in the olden time the sea spread over all this land, and that in some of the great recessions which the histories tell us about it left these salty and sandy wastes uncovered... It is not possible that people should have made such mountains of shells by carrying them from the sea so great a distance merely to bury them in piles. All of which, although merely conjecture, has a high degree of probability."

At this point the expedition had just left Laguna de Santo Olella, Site #44 on this map. It's southwest of Yuma in Baja California, west of the Colorado River, and well north of the Gulf of California. We know today that he was completely correct: the Gulf had been this far north, and even farther, thanks to tectonic shenanigans, and had left beds with marine shells. Excellent reasoning by the Padre, without a geologic or paleontologic framework to lean on. One slight catch for the National Historic Trail, though: as noted, this site is in Baja California. Did he observe any fossils in what is now the United States? On December 11, on the part of the trail that crosses the international border, he reported

"One sees along the way many piles of mussels and an infinity of sea snails, very small and spiral shaped, and in places as white as flour. This confirms my opinion that this is a sea beach, and although the sea has reached here sometime, yet no barrancas are found like yesterday."

We're closer, although technically it's possible he saw them entirely on what is now the Mexican side. A few days pass without more shells, then bingo. On December 19:

"...We set out from San Sebastián [Site 49] at one o'clock in the afternoon, and at half past four halted at a flat [Site 50] with some galleta grass but without water, having traveled some four leagues west by north. The road is level, with sandy but firm soil, having some mussel shells and sea snails..."

At this point we are well within California, actually just east of Anza-Borrego Desert State Park in the Ocotillo Wells area. Not only does Font get credit for an astute inference about natural history, but he also cinches Juan Bautista de Anza National Historic Trail as a fossiliferous NPS unit (and one of the few with a report predating the Declaration of Independence).

World of Stone II: The Hinckley Sandstone

While on a brief trip up north recently (Moose Lake Agate Days, naturally enough!), I spent an afternoon around Sandstone and Banning State Park. The name of the town is a good clue as to what I saw there.

Why, yes, sandstone!

Your Friends The Titanosaurs: Mesetasaurus protector (plus news from Antarctica)

The newest titanosaur is the second from Uruguay and the Guichón Formation. Here's the breakdown:

Genus and Species: Mesetasaurus protector. The genus name is a reference to the locality, Meseta de Artigas. The species name is a reference to the Uruguayan national hero José Artigas, (Soto Núñez et al. 2026). His name is also part of the locality, so we end up with a multilayered reference that boils down to "José Artigas's lizard".

Citation: Soto Núñez, M., F. Montenegro, and D. Perea. 2026. A new aeolosaurini (Sauropoda, Titanosauria) from the Upper Cretaceous of Uruguay. Ameghiniana (advance online publication). doi: https://doi.org/10.5710/AMGH.19.06.2026.3689

Geography and Stratigraphy: The type and only known specimen is from Meseta de Artigas, in the northern part of Paysandú Department, Uruguay. We are in the Guichón Formation, previously noted as the source of the titanosaur Udelartitan celeste (Soto et al. 2024). At that time, an age in the first half of the Late Cretaceous was suggested. This time a somewhat younger age is proposed, "perhaps late Santonian-early Campanian" (Soto Núñez et al. 2026).

Holotype: FC-DPV 3740 (Vertebrate Fossil Collection, Facultad de Ciencias, Universidad de la República), two anterior caudals (Soto Núñez et al. 2026). The authors refer to the more anterior caudal as 3740A and the more posterior as 3740B, and suggest A is the third caudal and B is the sixth.

The two caudals are well-preserved, although unfortunately this is not the same as completeness (the processes are truncated). They are distinct from those of U. celeste, being decidedly aeolosaurine/id/inid in anatomy. They are also somewhat smaller, not that U. celeste was an especially titanic titanosaur in the first place. Not surprisingly given its anatomy, M. protector plots among the aeolosaurs, making it the second record of an Uruguayan aeolosaur after the Asencio Formation caudal in Soto et al. (2022).

I don't have a whole lot to say about this species. To make this post a little less perfunctory, I'd like to go a little farther south. Barrett et al. (2026) have reported the second titanosaur from Antarctica, after the caudal reported by Cerda et al. (2011, 2012). The new material is BAS D.8621.25 (British Antarctic Survey, Cambridge, United Kingdom), a partial anterior caudal that coincidentally enough also has a bit of an aeolosaur appearance. It comes from the early Campanian-age Beta Member of the Santa Maria Formation on James Ross Island. (For those of you keeping track, Cerda et al. also described their specimen, a partial middle caudal, from the Santa Maria Formation. The particular strata have since been placed in the overlying Snow Hill Formation as the Gamma Member.) It is not well preserved and is rather small, at only 59 mm (2.3 in) long, 89 mm (3.5 in) if you include the substantial posterior condyle. This puts it in the company of Magyarosaurus dacus. We can't be sure of the exact growth stage, but there's enough of the neural arch to show it wasn't a very young juvenile. Interestingly, although not described until now, BAS D.8621.25 is actually the first classic dinosaur fossil collected from Antarctica, way back in December 1985 (Barrett et al. 2026).

Several views of BAS D.8621.25. Figure 3 in Barrett et al. (2026). CC-BY-4.0.

References

Barrett, P. M., P. D. Mannion, S. L. Beeston, M. C. Lamanna, B. Clark, A. Otero, J. P. O’Gorman, and M. Evans. 2026. A titanosaurian sauropod dinosaur from the Upper Cretaceous of Antarctica. Acta Palaeontologica Polonica 71(2): 349–362. doi: https://doi.org/10.4202/app.01315.2025.

Cerda, I., A. Paulina Carabajal, L. Salgado, R. Coria, and J. J. Moly. 2011. The first record of sauropod dinosaurs from Antarctica. Journal of Vertebrate Paleontology, Program and Abstracts, 2011:86.

Cerda, I. A., A. Paulina Carabajal, L. Salgado, R. A. Coria, M. A. Reguero, C. P. Tambussi, and J. J. Moly. 2012. The first record of a sauropod dinosaur from Antarctica. Naturwissenschaften 99:83–87. 

Soto, M., F. Montenegro, F. Mesa, and D. Perea. 2022. Sauropod (Dinosauria: Saurischia) remains from the Mercedes and Asencio formations (sensu Bossi, 1966), Upper Cretaceous of Uruguay. Cretaceous Research 131:105072. doi: https://doi.org/10.1016/j.cretres.2021.105072. 

Soto, M., J. L. Carballido, M. C. Langer, J. C. G. Silva Junior, F. Montenegro, and D. Perea. 2024. Phylogenetic relationships of a new titanosaur (Dinosauria, Sauropoda) from the Upper Cretaceous of Uruguay. Cretaceous Research 105894. doi: https://doi.org/10.1016/j.cretres.2024.105894.

Soto Núñez, M., F. Montenegro, and D. Perea. 2026. A new aeolosaurini (Sauropoda, Titanosauria) from the Upper Cretaceous of Uruguay. Ameghiniana (advance online publication). doi: https://doi.org/10.5710/AMGH.19.06.2026.3689.

Fossil Marine Mammals of the National Park Service

This year it works out that I'm a little early for the annual "Fossil [Group] of the National Park Service", and we continue our tour of mammal groups with a bit of a grab-bag. As with the marine reptiles, there is not one single group of marine mammals. Rather, several different groups became adapted to the oceans. There are the cetaceans, including whales, dolphins, and porpoises (and yes, dolphins and porpoises are small whales, but you know what I mean). There are the pinnipeds, including animals such as seals, sea lions, and walruses (and yes, there are two distinct groups of pinnipeds called seals, true seals without ears and eared seals that are closer to sea lions; it wouldn't be an Equatorial Minnesota post without mentioning at least a couple of caveats and technicalities, after all). Finally, we also have sirenians (dugongs and manatees) and desmostylians (extinct, kind of hippo-like things), two herbivorous groups that may or may not have been related.

The Arctic Cretaceous revisited

One of the earliest posts here, way back in March 2014, was about an assemblage of high-Arctic Late Cretaceous coprolites that had been part of my graduate work. We did quite a bit with them (Chin et al. 2008), but there's always more that can be discovered. One of the things Chin et al. (2008) noticed was the rarity of body fossils for large potential coprolite producers. They broached the idea that the producers were only around part of the time, living elsewhere during the polar winter and only turning up to feed during the long sunny summer days. Duffy et al. (2026) takes this idea and runs with it.

You may recall that back in 2014 we discussed two major categories of coprolites, those with a dominantly greensand composition and those with a dominantly phosphatic composition. The greensand coprolites had various kinds of inclusions, including crustacean carapaces, bivalves, and squid hard bits* and such (interestingly without evidence of processing by teeth), suggesting consumers that were bottom-feeders, whereas the phosphatic coprolites were loaded with planktonic microfossils, suggesting filter feeding (or feeding on soft-bodied filter feeders) (Chin et al. 2008). The division is nuanced a bit more this time around, with an intermediate group with greensand embedded in phosphate. At the time, we could easily see that the phosphatic coprolites had spiral structures, as in shark excrement. As it turns out, at least some greensand coprolites also have internal tubular structures, although usually not as easy to spot (Duffy et al. 2026). What that means is that most of the coprolite producers therefore had spiral intestinal valves like sharks.

*I had the hardest time figuring out those squid-pen bits when I was working with the fossils. I thought they might be horseshoe crab tails.

There is one group that fits quite well for producing the whole range of coprolites while also not producing abundant body fossils: sturgeons. Sturgeons have spiral valves. The adults don't have teeth to shed, so they aren't leaving hundreds of potential fossils, and they aren't crushing or cutting prey. Rather, they are bottom-feeders that suck in prey items (and sediment). They are also big enough to produce the size range of greensand coprolites. Meanwhile, young sturgeons have small teeth (but they lose them), and they feed on zooplankton. Finally, there are sturgeons today that migrate from marine water to estuaries or shallow marine settings to feed on seasonal food blooms before spawning in freshwater (Duffy et al. 2026). They're about as perfect of "poopetrators"** as we could ask for.

**I still regret nothing! 

It's the migration part that particularly interested Duffy et al. Most behaviors are pretty darn difficult to fossilize clearly; or, if you want to get philosophical about it, all behaviors are reflected somewhere in anatomy, but most of them produce effects that are too subtle to pick out or are swamped by the effects of other behaviors. We can look for evidence for migration in certain large land animals such as mammoths by studying stable isotopes in bones. These animals were big enough to travel long distances (and thus drink water in places with different isotopic signatures, for example) and had nice big bones that allow sampling for time sequences. The Devon Island situation is not quite so convenient, but a few lines of evidence are suggestive (Duffy et al. 2026):

1. The microfossils in the coprolites suggest plankton blooms during long polar summer days, which is a pretty common high-latitude pattern; make hay when the sun shines, after all. Blooms of one kind of organism attracts populations of other organisms to consume them. This is a pretty simple way to establish a migratory pattern. (The flip side is that everything would clear out during the polar winter. Think of an Old West boom town, except for having annual booms and busts.) This is the strongest line of evidence in my mind.
2. There are lots of coprolites and not much skeletal evidence for what made them. This is interpreted as evidence for producers that only lived there part of the time. I think this is a bit weaker, as there are always going to be more turds than bodies, but it's worth noting.
3. Sturgeons, as likely producers for some large percentage of the coprolites, are known to be migratory today, and anatomically haven't changed much since the Late Cretaceous.
4. Finally, many of the vertebrates inhabiting the Western Interior Seaway and neighboring areas have distributions that are pretty darn cosmopolitan in this region, consistent with migratory patterns. Like the second point, I don't think this is as strong as the first, but again it's worth noting.

All in all, I like it, and I think it's great to learn new tricks from old turds. You never know what will turn up once you start looking at these humble fossils!

References

Chin, K., J. Bloch, A. Sweet, J.Tweet, J. Eberle, S. Cumbaa, J. Witkowski, and D. Harwood. 2008. Life in a temperate Polar sea: a unique taphonomic window on the structure of a Late Cretaceous Arctic marine ecosystem. Proceedings of the Royal Society B 275(1652): 2675–2685. doi: 10.1098/rspb.2008.0801.

Duffy, F., K. Chin, S. Cumbaa, and L. Wilson. 2026. Coprolite evidence for marine vertebrate migration in the warm Cretaceous Arctic. Historical Biology. doi: 10.1080/08912963.2026.2670771.