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Something we love around here at Equatorial Minnesota is historical content about Minnesota geology.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.

Whatever Happened to Euskelosaurus?

In principle, any dinosaur name considered dubious or a synonym can be brought back into use unless it is an objective junior synonym (based on the same specimen as a previous name) or suppressed by the International Commission on Zoological Nomenclature. In practice, some names are much more likely than others to rise out of the mire. For example, when was the last time you thought about Polyonax? (Is this the first time you've ever had occasion to think about Polyonax?) Then there are historical names based on questionable material that once were widely used but have now fallen completely out of favor. Think Monoclonius, Palaeoscincus, or Trachodon, long-time favorites that have staggered into obsolescence and cheap dinosaur toys.

Pulaosaurus qinglong

We're admittedly getting to Pulaosaurus qinglong a bit after announcement and description, but what's a few weeks after 160 million years? "Hypsil"-type dinosaurs are always going to be welcome here, and this one also has potential gut contents, albeit left for a later date, so let's extend a welcome and have a look after the jump break.

Minnesota Spring Inventory

While working on something else recently, I stumbled on the Minnesota Spring Inventory. More importantly, especially in terms of time consumption, the inventory also has a great interactive map.

See any patterns?

You can zoom and select any point, or if you are interested in a particularly named spring you can type the name in the search bar to find it. Clicking on a point gives a pop-up box with information about the spring, and sometimes there are one or more links to photos.

For example, this is Big Spring at Beaver Creek State Park.

Incidentally, it looks like this. Highly recommended!

If you're curious about what the various data fields are measuring, the rules and guidelines used for documenting Minnesota springs are in this document.

If you're curious about natural or human features, there's a lot of interest to be had playing around with the map. Why human features? Springs that flow reliably and with a significant volume are great places to live, especially in the days before municipal waterworks, and many of these are of archeological and historical interest. For example, fooling around in the Minnesota River Valley area, I stumbled on one called Sacred Heart Geyser with this note: "Water was bottled and shipped to Chicago about 1900."

Obviously springs are significant natural features as well, but not only as just springs. At a glance at the map, for example, it's very easy to pick out the karst terrain of Minnesota. They can also be used as proxies for geological horizons. Springs form where groundwater isn't moving down, but laterally out of a surface. One of the biggest reasons why groundwater isn't moving down is because the flow is interrupted by a change in lithology. Maybe there's porous sandstone over non-porous shale, or limestone with fractures over shale, or pretty much anything over shale. Groundwater hits the non-permeable surface and spreads laterally, and if it runs into open air before it finds a path downward, a spring may form. (Or just a seep, which is more diffuse and less powerful.) As noted in the document, there are several geological contacts that are prone to this in Minnesota, such as glacial drift over the Decorah Shale and the Magnolia Member of the Platteville over the more shaley Hidden Falls Member. Many of the springs in Minneapolis and St. Paul are probably at one of these two contacts. (Less scientifically, springs in some settings will be found with exposed bedrock, and anywhere you've got exposed bedrock and flowing springs has a good chance of interesting geological and scenic viewing...*)

(*as always, land ownership restrictions and common sense about terrain awareness apply) 

Going up (and down!) in section, southeastern Minnesota

I was recently on a trip to southeastern Minnesota for several days. While there, inevitably I ended up with some geological photos. I must confess that I've never spent any time down here outside of passing through, and this was actually the first occasion I'd spent any time above the Cummingsville, so it was nice to see the overlying units I'd only read about before. If you'd like to know what we're up against, I recommend the Minnesota Geological Survey's geologic atlas of Fillmore County (the trip wasn't entirely in Fillmore County, but you'll get the idea).

Fossil Ursids of the National Park Service

Here we are, a little later than usual for the annual "Fossil [Group] of the National Park Service" but present nonetheless. I decided to get in another group of carnivorans, this time the bears (Ursidae). If you've been here for the cats and dogs, you can probably guess the basic shape of things: a few records earlier in the Cenozoic, then a big slug in the Pleistocene into the Holocene, with many of the records representing living species. That is indeed how it goes with the bears as well, with a couple of quirks: the bear record goes back as far as the dog record, into the Chadronian (Late Eocene), but is never as diverse as the records for either cats or dogs. Essentially you get a couple of genera or species in a formation, and that's about it. Bears, it seems, have never felt the need to be profuse about the business of being bears. It's not quite "one-bear-fits-all", but bears favor generalism, and there's only room for so many species of generalists in one place and time.