Compact Thescelosaurus Year Ten

Twelve months have rolled along since our previous check on The Compact Thescelosaurus, now clocking in at a decade of existence. With Triassic and Jurassic pseudosuchians for the previous two years, the obvious addition was Cretaceous pseudosuchians, of which there were more than the previous two additions combined. The Cretaceous section wasn't quite so dominated by one group like the Jurassic was by thalattosuchians, but it was a great time to be a notosuchian.

Like this one, Simosuchus clarki. I took this photo when the traveling exhibit visited the Science Museum 11 years ago; Wikipedia is running a photo of the same mount from another stop on the itinerary.

More odds and ends

At the moment I'm preparing the grand annual update to The Compact Thescelosaurus. If you've been following along over the past couple of years, it doesn't take being Sherlock Holmes to guess what it will be. Actually, it doesn't even take being 1940s Radio Program Watson to guess, but do act surprised. In completely unrelated news, there's a taxon published this week I recommend you see: the little croc Thikarisuchus xenodentes. (What, you were expecting the theropod?) T. xenodentes, from the Cenomanian-age Blackleaf Formation of Montana, had a sharply triangular skull in top view and strongly differentiated teeth, among them the expected bitey teeth at the very front and long, low, narrow teeth at the back. This small croc may have had a taste for plants, or perhaps sliced up insects.

Something we love around here at Equatorial Minnesota is historical content about Minnesota geology. You may be familiar with the Minnesota Geological Survey's publication archive. It turns out that there are a bunch of MGS field notebooks scanned and available via the University of Minnesota libraries. You can find notebooks there from paleontologists such as Frederick Sardeson, Robert Sloan, and Clinton R. Stauffer, all of whom curiously have last names starting with "S". (Also interesting: Sardeson's field notebooks all have the left-hand pages filled out, but right-hand pages are much less frequently used. Was Sardeson a lefty?) There are also materials from the Department of Earth and Environmental Science.

Do you prefer to see your geology in the field? I came across a nice section of the St. Peter through Platteville under the I-94 bridge, on the east bank of the Mississippi. I'd been there years before but don't remember being so impressed with it. Maybe it wasn't as well-exposed then, or maybe I just wasn't experienced enough to appreciate it. The Platteville interval at the top was definitely exposed, but maybe this lower exposure is the result of more recent erosion or something. It definitely bears further photography and investigation, as it has a great view of the Glenwood.

The important part looks like this.

And here's what it looks like if I annotate all over it. I'm not entirely confident with the thickness of the Hidden Falls Member; for some reason the Mifflin is really grungy here. The Glenwood bits are open to interpretation (the Nokomis gets "Glenwood/St. Peter" because it's technically in the Glenwood but can't be distinguished from the St. Peter in well logs or gamma logs). The Tonti Member makes up most of the St. Peter Sandstone, if you're curious. There may be some Carimona at the very top. 

Oh yeah, also saw Bridal Veil Falls nearby, which has, y'know, seen better days, but is still running, after a fashion.

Or maybe you'd like some historical trivia? One of the things I wanted to find more about for the Mammoth Cave National Park paleo inventory was whatever became of the type specimen of Lithodrumus veryi, a Mississippian coral possibly collected from the park. It was described in 1904 by George Greene and the specimen has been lost to science since at least 1944. Greene's collection went first to the American Museum of Natural History and then to the National Museum of Natural History, but Lithodrumus veryi apparently went missing, as Easton (1944) couldn't find it at the AMNH. Just a few days ago I was looking up images of tabulate corals when I came upon a post at Louisville Fossils and Beyond that stated one cabinet had not been sold, and its contents were eventually going to the Indiana State Museum. Hope springs eternal! I've sent a message to the Indiana State Museum to see if perhaps L. veryi's type is there.

It's supposed to look like this (Greene 1904: Plate 49). Have you seen it, by any chance?

So that's what's going on around here. (Oh, that and some unusually intense bot "readership", or the whole of Hong Kong has suddenly discovered a passionate interest in the Ordovician fossils of Minnesota and Elliot Formation prosauropods. Maybe I'm cynical.) Tune in for the next post!

References

Allen, H. J., E. W. Wilberg, A. H. Turner, and D. J. Varricchio. 2025. A new, diminutive, heterodont neosuchian from the Vaughn Member of the Blackleaf Formation (Cenomanian), southwest Montana, and implications for the paleoecology of heterodont neosuchians. Journal of Vertebrate Paleontology e2542185. doi: https://doi.org/10.1080/02724634.2025.2542185

Easton, W. M. 1944. Revision of Campophyllum in North America. Journal of Paleontology 18(2): 119–132.

Greene, G. K. 1904. Contribution to Indiana palæontology 1(17): 168–175.

Compact Thescelosaurus Year Nine

October and National Fossil Day have rolled around again (check out the fall 2024 Park Paleontology News, too!), so it's time to take a look at the previous year's changes to The Compact Thescelosaurus and welcome some new content. First, the new stuff: I'm sure you'll be shocked to find out I've followed up Triassic pseudosuchians with... Jurassic pseudosuchians. I'm rearranging the pseudosuchian content a bit, to have the non-crocodylomorphs on one sheet and the crocodylomorphs on another. This was done to forestall the deployment of an unwieldy number of "subdivision" columns. Provided I get far enough along, something similar might have to happen with the new sheet around Crocodylia or so. Anyway, the main takeaways I got out of Jurassic pseudosuchians are 1) there's been a lot of work on thalattosuchians over the past couple of decades, and 2) I've discovered I'm not very fond of thalattosuchians and certainly don't mind that they conk out midway through the Cretaceous.

Hey, it's the Science Museum "Goniopholis" again! (Most Jurassic pseudosuchians are thalattosuchians, but North America is largely bereft of the darlings, so we make do with crocs like these.)

Compact Thescelosaurus Year Eight

It's that time again, for National Fossil Day (October 11 this year), a new sheet for The Compact Thescelosaurus, and the annual summary of what was added to the spreadsheet in the past 12 months. In addition to National Fossil Day events this month, the latest issue of Park Paleontology News is up for viewing. Also in breaking NPS paleontology news: additional dating of the fossil human tracks at White Sands National Park, and a previously overlooked record of a tyrannosaur tooth at Yellowstone National Park. [Update, 2023/10/10: And a tritylodont bonebed at Glen Canyon National Recreation Area was just announced; goes well with this new paper on a massive track block from the recreation area, too.]

Here at Equatorial Minnesota, we've passed 400 entries this year. Later this year, December 15 will mark 10 years of posting. (Also, anyone know why this nautiloid post would have spiked in interest?) The Compact Thescelosaurus has been around for 8 of those years, and it's traditional to add a new sheet. For this year, first I considered all of Pseudosuchia (except for the aetosaurs, covered already), but decided against it due to the number of species. I then looked at doing just Mesozoic pseudosuchians before being discouraged by whatever it is Thalattosuchia has been doing over the past 200 years. So, for now it's just Triassic forms, with the intent to expand over time.

Prestosuchus threatening an Eoraptor in the "Ultimate Dinosaurs" exhibition at the Science Museum of Minnesota, May 2014.

Musings on Hanyusuchus

Every year a handful of new croc taxa are described. If you're strictly in this business for the dinosaurs, you ought to see what the croc side of Archosauria has been up to from time to time; they were quite versatile in palmier days. Even though they aren't quite as diversified as they used to be, it turns out they had hitherto-unsuspected tricks up their sleeves even as recently as a few hundred years ago. This spring a new genus and species of gavialid was described from the Holocene of south China: Hanyusuchus sinensis. This is fascinating, for many reasons. The obvious is that here we have a species of [insert expletive of choice] 20-foot-long gavial that existed up to perhaps a few hundred years ago in full contact with one of the most thoroughly documented civilizations in history, and it was completely overlooked. It may not have gone extinct until the time of the Ming dynasty. This is something like discovering that bears in Greek and Roman mythology were actually Arctodus, only if Arctodus was the size of a pickup truck. China, of course, is noted for the extant Alligator sinensis, but although the Chinese alligator is many things, not even on its best days has it been a 20-foot-long gavial.

Figure 2(s) from Iijima et al. (2022). Depicted: Hanyusuchus sinensis (composite, scaled to holotype) and 1.8 m (5.9 ft) tall human. Not pictured: Alligator sinensis (to imagine, mentally scale the Hanyusuchus to be about the same size as the human). CC BY 4.0.

Another fascinating aspect is the namesake. Han Yu was a significant writer, philosopher, and politician of the Tang dynasty. At one point in his life, he got in trouble at court and was packed off to Chaozhou in Guangdong, southeastern China to serve as prefect. In this capacity, he issued a proclamation in 819 concerning the crocodilian population. This in itself is not remarkable, except for the audience: he issued it to the crocodiles themselves. A translation of the statement can be found here (well worth a read). The icing on the cake is that the crocodiles reportedly did as instructed and departed, although we can presume that if they *did* indeed vanish from the area, strong hands wielding metal implements (like the Bronze Age weapons that left marks on some specimens) were more important in enforcing the departure. The reader may suppose that Han Yu's action was just a quaint old-time delusion; after all, there is a long history of animals being prosecuted for crimes. However, as the author of the translation notes drily, "Tang prefects did not habitually make formal verbal addresses to the local fauna" (footnote 7, p. 60). One wonders if perhaps Han Yu, who was noted for a sense of humor, had his tongue firmly in cheek.

There's also a melancholic existential aspect to the discussion. H. sinensis was part of the fabric of life in southern China for thousands of years. Descriptions of the species can be identified in historical sources, now that we know what to look for. Dynasties, cultural flowerings and renaissances, wars, conquerors, travelers like Marco Polo and Ibn Battuta, all came and went while 6-m gavials patrolled the southern rivers. They took livestock and killed people. They were apparently very noisy, probably the source of reportedly "thunder-like sounds in the night". Then they were driven into extinction and basically forgotten for hundreds of years.

References

Iijima M, Qiao Y, Lin W, Peng Y, Yoneda M, and Liu J. 2022. An intermediate crocodylian linking two extant gharials from the Bronze Age of China and its human-induced extinction. Proceedings of the Royal Society B: Biological Sciences 289:20220085. doi:10.1098/rspb.2022.0085.

Fossil Crocodylomorphs of the National Park Service

For this year's National Park Service fossil group inventory, I've chosen crocodylomorphs, which for convenience I'm going to refer to as "crocs". Crocodylomorpha encompasses the true crocodilians and their closest extinct relatives, which over the years has been defined to exclude major groups of allied Triassic archosaurs (rauisuchids, poposaurs, prestosuchids, etc.). (Technically speaking, traditional Crocodilia is closer to the clade Crocodyliformes, but I have a soft spot for "sphenosuchians" and it's my blog.) Non-crocodilian crocodylomorphs were big players throughout the Mesozoic but came to peter out in the Cenozoic, with holdouts into the Miocene (Sebecosuchia). Some of these non-crocodilian crocodylomorphs looked basically like modern crocodilians and presumably filled very similar niches, but by definition weren't crocodilians*. Others were quite a bit different; for example, small, long-legged terrestrial crocs had a wide distribution from the Late Triassic through the Jurassic, and there were multiple groups of marine forms.

*I have certain misgivings about crown groups, particularly that future stability of usage relies on groups not going extinct (or there would have to be backdating, like radiocarbon dates are pegged to 1950), although at this point I might as well complain about the decline in use of Etruscan.

The NPS record of croc fossils turns out to be sparser than I expected: there are 17 park units with solid records (albeit two of these being reworked or washed up, making them hard to place stratigraphically), and another couple potential records. Here is the requisite map and its accompanying long caption:

Click to embiggen. The sites mentioned in this post are: 1. John Day Fossil Beds National Monument; 2. Bighorn Canyon National Recreation Area; 3. Fossil Butte NM; 4. Dinosaur NM; 5. Colorado NM; 6. Curecanti NRA; 7. Bryce Canyon National Park; 8. Glen Canyon NRA; 9. Petrified Forest NP; 10. Chaco Culture National Historical Park; 11. Theodore Roosevelt NP; 12. Badlands NP; 13. Agate Fossil Beds NM; 14. Niobrara National Scenic River; 15. Big Bend NP; 16. Waco Mammoth NM; 17. Gateway NRA; 18. Fort Washington Park; 19. Cumberland Island National Seashore.

These 19 units are primarily in the Colorado Plateau and northern Great Plain, and these two areas correlate in large part to temporal distribution: the Colorado Plateau records are mostly Jurassic and Cretaceous, and the Great Plains records are Cenozoic. A couple of compact diagrams will show this:

Part 1 shows the Mesozoic, Paleocene, and Eocene records, which make up the bulk of the reports.

Part 2 shows the few younger records; the two that can't be pinned down are added to keep them company.

You can probably guess a lot of the story if you have some familiarity with the stratigraphy of western North America. As so many other groups of terrestrial vertebrates, the place to go in the NPS for Triassic crocs is Petrified Forest National Park, where "sphenosuchians" have been found in the famous Chinle Formation. (Ignore the phytosaurs; they only look like crocs.) After that, possible early croc tracks have been found in the Navajo Sandstone of Glen Canyon National Recreation Area; with all of the Early Jurassic tracks in the Colorado Plateau parks, there are likely other track records. We have no body fossil records in the parks' rocks yet, though (the facies aren't as forgiving as elsewhere). Four parks have records for the Late Jurassic: Bighorn Canyon National Recreation Area has swim traces attributed to crocs in the Sundance Formation, and no points for guessing what's represented at the other three. (It's the Morrison Formation.) NPS Morrison crocs are best known from Dinosaur National Monument, which primarily has the well-represented Amphicotylus (formerly Goniopholis), but also produced the type specimen of the diminutive Hoplosuchus kayi.

The Cretaceous is more sparsely represented, with nothing confirmed from the Early Cretaceous. Ot the Late Cretaceous records, neither Bryce Canyon NP (Straight Cliffs and Wahweap microvertebrate remains) nor Chaco Culture National Historical Park (Menefee isolated material) have much to speak of. Big Bend NP, on the other hand, has the most impressive croc record in the NPS. Granted, that's an easy call when you can point to the type specimen of the suitably Texas-sized Phobosuchus riograndensis (now a species of Deinosuchus), but the park also has by far the longest record of crocs in the NPS. Five formations are represented: the Aguja Formation and Javelina Formation, both Late Cretaceous; the overlying Black Peaks Formation, which straddles the Cretaceous and Paleocene; the Early Eocene Hannold Hill Formation; and the Middle Eocene Canoe Formation. Recently a second croc species has been named from Big Bend NP fossils: Bottosaurus fustidens, from the Paleocene part of the Black Peaks Formation. Other taxa are present, but have not been studied in as much detail.

Looking elsewhere in the Paleocene, there is a single record of a partial bone from the Aquia Formation at Fort Washington Park, and Theodore Roosevelt NP has crocs in the Bullion Creek and Sentinel Butte Formations, comparable to nearby Wannagan Creek (only not quite so concentrated). The Eocene is fairly good for NPS crocs. Apart from Big Bend, we have croc fossils in: the Wasatch Formation at Fossil Butte NM; the Clarno Formation at John Day Fossil Beds NM; and the Chadron Formation at Badlands NP. The type specimen of Caimanoidea visheri (now considered a synonym of Alligator prenasalis) may have come from Badlands NP.

And that's almost the end. Crocs disappeared from the drying interior of North America during the middle Cenozoic. For the Miocene, we have one *very* sketchy potential record from the early Miocene Anderson Ranch Formation of Agate Fossil Beds NM and better records of crocs from the middle Miocene Valentine Formation of Niobrara National Scenic River (including the type specimen of Nordenosaurus magnus, originally described as a big lizard but now identified as a small crocodilian). At Waco Mammoth NM there is late Pleistocene alligator material, but we are otherwise lacking Pleistocene crocodilian records. Two units have material of uncertain provenance: a scute found in dredge material at Cumberland Island National Seashore and various croc fossils that have washed up at Gateway NRA.

Stegomosuchus longipes, the terrestrial croc relative of Massachusetts

If you're the kind of person who reads this blog regularly, you're probably also the kind of person who's got at least one rock laying around. Maybe you've got dozens. Maybe you've got too many. Who am I to judge? The point is you've got rocks. Odds are, though, there isn't a potential type specimen in your yard.

Fossil Crocs of the Science Museum

Although the dinosaurs get the most press, the Science Museum of Minnesota's paleontology department has a strongly diversified portfolio of ancient reptiles. In particular, champsosaurs and crocodyliforms (modern crocodilians and their closest extinct relatives) are well-represented in the collections and on exhibit. The Science Museum features mounts of four fossil crocs, each one filling different places in their ecosystems: an apex terrestrial/freshwater croc (Borealosuchus formidabilis), a large estuarine croc with elongate jaws living alongside whales (Gavialosuchus carolinensis), a medium-sized terrestrial/freshwater croc from a dinosaur-dominated setting ("Goniopholis"), and a house-pet-sized terrestrial/freshwater generalist (Wannaganosuchus brachymanus). This diversity shouldn't be too surprising. Crocodylomorphs, with around 225 million years of time on their hands, have done quite a bit of experimentation, including truly marine thalattosuchians and small, terrestrial, occasionally dinosaur-like "sphenosuchians".

Meanwhile, over at the Science Museum

Recently, the Science Museum of Minnesota reconfigured the exhibit space for the paleontology in conjunction with changes to other parts of the floorplan. I don't recall if the previous configuration had been stable all the way back to the 2005 Society of Vertebrate Paleontology meeting (I do know a nice Goniopholis was added around 2010), but where once it had looked like this:

January 2013; watch the space on the left of the Stegosaurus.

Now it looks like this:

That Triceratops wasn't there before...

Two major components, the Morrison dinosaurs and the Wannagan Creek fossils, are still where they had been. The major differences are in the section on the east, with the removal of some visible lab space and some more portable specimens, most notably a sort of "circus ring" of small- to medium-sized Cenozoic animals, mostly mammals.

And a tortoise.

 
In their place are a group of mounts from the Oligocene of coastal South Carolina (transferred from the floor above) and the well-known Science Museum Triceratops, relocated from another part of the floor. A Triceratops going mobile is just not a common occurrence these days, so naturally the event received some local coverage. A few other pieces were also rearranged, including the Xiphactinus lurking behind the Stegosaurus in the first picture above, some of the remaining mammals, the Goniopholis, and your friend and mine Thescelosaurus. Green River Formation fossils also get more prominence.

Triceratops (who also answers to "Fafner") plus overhead pterosaur pal in foreground. The South Carolina mounts are visible in the background by the neon; you can see a whale, pseudodontorn,and sea turtle in the air above the hind end of a mostly obscured croc (next photo).

Estuarine croc Gavialosuchus (or Thecachampsa) carolinensis has an honest face. I was glad that space was made for the South Carolina mounts; many places have Morrison dinosaurs, but you can't see Wannagan Creek and South Carolina fossils just anywhere.

On the one hand, the Triceratops no longer has its niche with the backdrop:

On the other hand, you can now walk around the whole mount, if for example you should want to look at the legs and hips:

Like this, perhaps.

I may cover some of these exhibits in a bit more detail in the coming weeks, given the approaching busy holidays. Till then, though, Allosaurus bids you all adieu: