Catching up with NPS proboscideans

I had occasion recently to review some of the records in the 2020 National Park Service fossil proboscidean inventory (Mead et al. 2020), so I thought it would be useful to produce an update on the roster of parks, National Natural Landmarks, and National Historic Landmarks that we included at that time.

Secrets of "Secrets Of The Dinosaur Mummy", or: How I Got An IMDb Entry

A few days back I did something I hadn't done since 2008: I watched "Secrets of the Dinosaur Mummy". This was mostly because I had a friend over and wanted to show her what the Leonardo thing was all about, along with my minor claim to small-screen fame. Obviously going that road brought out the memories, so I thought maybe it was time to have a look back. Getting the "Truth in Advertising" out of the way up-front: I don't actually have a lot of secrets about "Secrets of the Dinosaur Mummy", but I do know a title when I see one!

It turned out to be unexpectedly difficult to get a good photo of the cover, being moderately glossy and dark, but you get the idea. One of these two blurbs is good for a chuckle, given the prominence of the speaker in the documentary.

Conard Fissure

It's been a while since we've done a good old-fashioned Pleistocene cave fauna, and there's one more wanting to complete the Big Three of Irvingtonian eastern North America. We've already spent some time with Cumberland Bone Cave and Port Kennedy Bone Cave, so now it's the turn of Conard Fissure in northwestern Arkansas.

Rockford, Part 3: Brachiopods

In the previous two posts on the paleontology of Rockford, Iowa, we looked at the site itself and the majority of the fossils, leaving the brachiopods for now. I ended up identifying 13 brachiopod taxa to genus or species. They're written up in alphabetical order below, with a brief description of what I found to be the most important distinguishing characteristics for those of us who know a thing or two about brachiopods but are not conversant with fine anatomical details. I have to admit that the photos are a bit disappointing, which is in part because we're dealing with strongly three-dimensional objects. Pictures are great, but there are things that just don't quite make sense unless you're holding a fossil in your hand. I used Fenton and Fenton (1924) quite a bit, recognizing that the taxonomy is outdated (brachiopod taxonomy does not sit still). I also consulted online galleries of Rockford fossils, e.g., this, this, and this, and had recourse to Ma and Day (2000) for the spiriferids. All in all, I'm happy with the identifications in a broad sense, but inevitably there are a few individual specimens that I'm not sure about.

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.)

Rockford, Part 2: Fossils (exclusive of brachiopods)

Before we get into the festivities, I've recently written an article for the online magazine Agate, about identifying common Paleozoic fossils of Minnesota. It's a compact summary that covers the most abundant groups, so if you're looking for something like that, go have a look!

In our previous post we had a look at the geology of the Fossil & Prairie Park Preserve of Floyd County, Iowa, also known as the Rockford site. For this post I'm going to briefly detail the fossils I collected, with the exception of the brachiopods, which will get a post of their own. For most of the non-brachiopods, I didn't get too far into the weeds on taxonomy, because many of the groups don't lend themselves to simple eye-checks for genera and species. Horn corals and bryozoans, for example, usually require thin sections, and crinoid columnals are generally only diagnostic of the presence of crinoids. I did, though, have recourse to Fenton and Fenton (1924) and other peoples' identifications to get some ideas.

Rockford, Part 1: The Site

A few weeks I was able to join a Geological Society of Minnesota field trip to the Fossil & Prairie Park Preserve of Floyd County, Iowa, which to some of you may be more familiar as the Rockford site. We ended up having a practically ideal day: pleasant temperatures, clear skies, dry conditions, and a light breeze. If you have an itch to collect fossils (an itch that's becoming difficult to legally scratch in Minnesota these days), I highly recommend a visit.

A view into the old quarry directly south of the parking area.

Your Friends The Titanosaurs: Qunkasaura pintiquiniestra

2024 has been a great year for new titanosaurs, as we are now on the fifth to be announced and we're still more than three months from the end of the year. For a change of pace, this time we're heading to Europe. Qunkasaura pintiquiniestra, the first new European titanosaur in more than two and a half years, hails from the Lo Hueco site in Spain.

Fona herzogae

This whole thing started from a website called Thescelosaurus!, so unsurprisingly I'm particularly interested when an old-fashioned "hypsil" metaphorically crosses my desk. Our (belated) guest today is the new genus and species Fona herzogae. Before we get into the meat of the post, I would also like to throw a kind word to the iguanodontian Comptonatus chasei Lockwood et al. (2024), published online the same day. (Yes, it *did* make me think of Camptonotus, which would have been Camptosaurus had somebody not pinned it to a cricket first.)

An unexpected mammoth

While visiting Wisconsin's Interstate Park over the weekend (happy 80th birthday, Smokey Bear!), I was surprised to come across another resident of the Cottage Grove area at the Ice Age Center:

According to the display, this mammoth tooth was discovered on Grey Cloud Island on July 9, 1987, by Arnold Sanford of Frederic, Wisconsin. This is the kind of thing that makes me wish we had an update to Stauffer "1945". (Even if I have to do it myself.) There must be plenty of other post-WWII finds scattered across Minnesota that are only known locally. When I was a little kid, my mother told me that part of a mammoth tooth had been found in Red Wing by a Boy Scout; I've never been able to find anything about it, but it certainly wouldn't surprise me!

Incidentally, the Ice Age Center also has other fossils and cast fossils of Ice Age mammals from the area. (Interstate Park is the western terminus of the Ice Age National Scenic Trail and one of the components of Ice Age National Scientific Reserve.) The most significant are bison bones and a cast skull from the park's bison bonebed, discovered in 1936 during CCC work. The bonebed is in my hopper of topics; until then, here are the specimens on display.

References

Stauffer, C. R. “1945” [at least 1948 based on dates in the article]. Some Pleistocene mammalian inhabitants of Minnesota. Minnesota Academy of Science Proceedings 13:20–43.

Silver Creek Cliff geology

For obvious reasons, this blog has featured plenty of sedimentary rocks, but hardly a crystalline rock (one notable exception being World of Stone, which also allowed me to title a post after an obscure George Harrison song; no particular reason although in hindsight I might have been feeling down at the time). I just got back from a trip to Duluth and the North Shore and discovered my phone had secretly and unexpectedly created this grand panorama of a spectacular roadcut, so I thought I'd mix up the usual topics:

Definitely worth the click to embiggen

This location is the north end of the Highway 61 tunnel at Silver Creek Cliff, where there is a fun roadside pullout with information about the construction of the tunnel (and the former route of Highway 61, which went where the walking path is now and looks like it would have been extremely narrow). What we're looking at is a sequence of events in the old Midcontinent Rift, 1.1 billion years ago. There is an annotated photo showing part of the roadcut here, but most of the different things are easy to spot without too much guidance. On the right, the somewhat pinkish rocks beginning above the road are flows of andesite, a type of volcanic igneous rock. The andesite is cut off by a stark, irregular contact with a dark blue-gray rock; the contact begins near the blue minivan and rises going to the right. The darker rock is diabase, an igneous rock that intrudes into existing rock underground and has a similar composition to basalt. The diabase makes up most of the roadcut, but you may notice a weird "scar" running through it. It begins, from the perspective of the flat image, just right of the right-most metal structure on our side of the road (the one right of the street light pole) and rises to the right until it is lost under vegetation. This "scar" is laced with light-colored rocks. It represents diabase that has been altered by faulting, with new minerals forming in the fault gouge. Thus, the sequence of events is: 1) eruption of andesite; 2) intrusion by diabase; 3) faulting and mineralization within the diabase.

The key part of the panorama, showing the andesite, diabase, and fault.

Fossil Canids of the National Park Service

We've been taking a tour of Mammalia for the past two annual "Fossil [Group] of the National Park Service", and this year we'll make it three in a row with man's best friends, the Canidae. The dog record starts up in the Eocene with the hesperocyonines, who held court through the Oligocene but then petered out in the Miocene. Turning up in the Oligocene are the borophagines, or "bone-crushing dogs," and the canines, which include wolves, foxes, domestic dogs, and close relatives. Borophagines, as the nickname suggests, had robust jaws and teeth, which doesn't mean they should be typecast as slavering hypercarnivorous brutes (canids in general have been pretty flexible about diet over their history). They drop out of the record at about the end of the Pliocene, leaving the field clear for the canines, which had been a fairly minor component of the canid radiation until about the Late Miocene. If you're interested in paleontological nitty-gritty on these two groups, check out Wang et al. (1999) on borophagines and Tedford et al. (2009) on canines. Canids, incidentally, are a North American invention, and unlike some other groups that originated in North America (camels, horses, rhinos), they have never gone extinct on the continent.

Your Friends The Titanosaurs: Tiamat valdecii

I've been remiss in getting to our latest titanosaur, in part because I was busy with other projects and in part because it took a while to get a copy of the paper. A side visit to the University of Michigan library system after conference hours solved the second issue, so without further ado I present Tiamat valdecii.

Campus fossils of the University of Michigan

For the previous week I was attending the North American Paleontological Convention, held this year in Ann Arbor, Michigan by the University of Michigan. While walking and wandering on the campus, it became clear that many of the buildings include fossiliferous rock, so I began to look for interesting examples.

Like that. That's interesting. (coin in all examples with coins is a US quarter)

Diamantinasaurs, and being or not being a titanosaur

It's not all about new taxa with titanosaurs here. There are always publications on other topics; it might be fun to do a roundup feature every so often. Anyway, I thought I'd catch up on the Australian branch of the tree, as well as the eternal question of just what is a titanosaur, after all.

The Lives of the Strophs

As mentioned a few years ago, strophomenid brachiopods must have had a different lifestyle than your typical brachiopod. With no pedicle to attach to anything, they would have been loose on the seafloor. Their strongly concave-convex shell anatomy seem likely to have been inconvenient in several ways. If you place them convex-up, the opening between the valves is liable to be in the sediment, which doesn't help a filter-feeder. If you place them concave-up, the shell is liable to be flipped over if it is not partially sunk into the sediment, and even if it's clear, the narrow gape would make the intake prone to fouling. Clearly, though, they must have been doing something right, at least for a few million years in the Late Ordovician if the rocks in the Twin Cities have anything to say about it.

A stroph in the Magnolia Member of the Platteville. See, I can always find ways to use even more photos from Uŋčí Makhá Park!

A new publication by Dattilo et al. (2024) offers a lifestyle reconstruction of the stroph Rafinesquina that may resolve these issues: in brief, rather than a narrow valve gape, these brachiopods may have lived with their valves wide-open.

Perhaps like this, as restored by Kyle Hartshorn for Figure 15, not unlike some modern brachiopods. CC BY 4.0.

Dattilo et al. present several lines of evidence leading to the conclusions that Rafinesquina had a typical gape around 45 degrees and could potentially open wider. The major area of focus was the anatomy of the hinge, including both the hard structures and the inferred musculature. The assembly, as it turns out, is rather more complex than one might suspect just looking at Stroph #46893 in a random Platteville surface. (It's also rather more complex than can be explained in a couple of sentences, so fortunately there is the paper to refer to.)

Although to be fair, Stroph #46893 has its charms.

The possibility of widely gaped strophs leads to some other potential implications. For instance, once the ability to make a respectable gape is admitted, there is also the possibility for mobility. A stroph buried by sediment could have used valve clapping to escape. (And if we're doing that, why not a bit of clap-swimming, like modern scallops?) Clapping is also a great way to quickly clear sediment from the feeding organs, and we may have evidence of this in the form of "moats" around some stroph fossils. A natural wide gape also helps explain how stroph internal anatomy worked: a stroph with a narrow gape has a cramped area for its lophophore to function in, while a stroph with a wide gape doesn't have to worry about this as much, as long as there's enough space to stow the lophophore when the valves are closed. Finally, a wide gape does not settle the concave-up or convex-up question, as the brachiopod can function in either mode. Dattilo et al. suggest that convex-up is more stable and protective for the stroph's soft parts.

References

Dattilo, B. F., R. L. Freeman, K. Hartshorn, D. Peterman, A. Morse, D. L. Meyer, L. G. Dougan, and J. W. Hagadorn. 2024. Paradox lost: wide gape in the Ordovician brachiopod Rafinesquina explains how unattached filter-feeding strophomenoids thrived on muddy substrates. Palaeontology 67(2): e12697. doi:https://doi.org/10.1111/pala.12697.

Uŋčí Makhá Park 2024: another winter, more echinoderms

Two years after opening, Uŋčí Makhá Park can be considered a paleontological gem in the Twin Cities. With its Magnolia Member bedding planes, side cuts through the Magnolia and Carimona, easy access, and lack of vehicle traffic, it's nigh-on perfect for getting in touch with St. Paul as it was about 454–453 million years ago. It's kind of like our own Carnegie Quarry wall, except it's tiny marine invertebrates rather than dinosaurs, it probably wasn't planned, and you can walk right out over it. It's always fun to get to spend time there for work, and like last year, I got the opportunity to assist with a training session for Mississippi National River & Recreation Area seasonals there. Then, of course, I just had to make a quick return trip later to follow up on some things we'd seen.

Your Friends The Titanosaurs: Titanomachya gimenezi

2024 has been productive for titanosaurs. Not counting other titano-centric publications, there have already been (potentially) three new genera and species. For number 3, we head back to the familiar land of Patagonia in Argentina, although in this case our new guest represents an Upper Cretaceous formation with no previous named titanosaurs (which seems like a real oddity these days). Titanomachya gimenezi is also decidedly non-titanic for a titanosaur, hanging out down in the saltasaur neighborhood.

Your Friends The Titanosaurs: Udelartitan celeste

Today's new entrant is actually a former briefly featured coming attraction coming off the board, the fourth such coming attraction to have arrived. It is also the first classic dinosaur to be named from Uruguay, which is the first new country added since Ecuador with Yamanasaurus lojaensis a few years back. (2020 if you insist on paper, 2019 if you just want to get it over with. Also, of course, that was a titanosaur too!) So, with that introduction, we welcome Udelartitan celeste.

A Brief Digression on the Art of Identifying Fossils

If you let it get around that you have some knowledge of fossils, inevitably somebody is going to ask you to identify something. I'm sure everyone in this position has the usual gripes about "dinosaur eggs" or "dinosaur hearts" or "dinosaur skulls" that are really just regular humble rocks viewed through bifocals of hope and inexperience. The only skills and resources needed here are tact and diplomacy, to work the conversation in such a way that it comes to an expedient close without unnecessarily cheesing off the hopeful inquirer (and recognizing that sometimes it's just not possible to have a productive interaction with somebody who insists they have dinosaur eggs).

Then there's the real thing. I get a few requests for identification every month, sometimes through work, sometimes submitted by blog readers to my email. This can be a challenge, especially for work, since the National Park Service can boast an impressive sweep of geologic time and diversity of fossils. I can be looking at photos of Devonian marine invertebrates one week and Cenozoic plant fossils the next. Then, of course, there's dealing with the fossils I find; I've had several in the past few months that were clearly something of interest but were also outside of my experience. It's been a long, long time since someone could be familiar with every kind of described fossil. What is one to do?

If identifying fossils is something that interests you beyond picking up a few names, you can learn from fossil and rockhound communities (online and in person). You're also going to be in for some self-teaching. Fossil identification has never been a huge field and has dwindled (for one thing, biostratigraphy is no longer as important for industry). Whether identifying fossils for someone else or yourself, the first thing you'll want is references with lots of good pictures. A good field guide to fossils, like the National Audubon Society's version, is a handy starter to at least get you into the correct phylum. Many times, that's all you need or want; for groups that require thin sections to identify, or groups where you get a lot of internal casts, "bryozoan" or "snail" is often enough, maybe with some morphological jargon. Depending on how much attention people have given your local rocks, there may be specialist books (like this one), online guides, or both. A "Roadside Geology"-type book may also be helpful in providing background information on your rock formations, which is useful for figuring out more specialized publications. (Or sometimes not, if people can't agree on what to call the rocks!) Similarly, if you are interested in specific kinds of fossils (e.g., shark teeth), there may be dedicated references available.

A few other observations:

• A lot of things simply aren't identifiable very far: too weathered, too fragmented, too much covered by matrix, weird cross-sectional view, etc. That's just the breaks.
• Photos in field guides and other sources are generally of the best specimens, with museum-quality preparation. The average person is probably not going to be that lucky and probably doesn't have access to those skills. This is something that needs to be taken into account when making identifications. When I work on paleontological resource inventories, I like to include "typical" images of fossils so park staff will have a better idea of what to expect.
• Good photos and illustrations are not available for every species (especially older names in areas where not much work has been done), and what is out there will not generally cover every potential view.
• A further complication when hunting reference images is changes in taxonomy. For some groups (I'm thinking especially of brachiopods at the moment), species have switched genera several times. To further complicate things, not all authors will catch on, and some will simply disagree. Hardcore identification may require becoming familiar with name changes, because the images you need to find may be under an unexpected name. This is, needless to say, very frustrating.
• Unless you've gotten involved in high-stakes fossil identification, there's no shame in revising identifications as you get more experience. When you start off, you'll have a natural bias to identify things in terms of the first things you learned to identify. You may also tend to identify things as more rare or unusual options, or make identifications to genus or species when you'd be better off sticking at a higher level, or have other biases due to inexperience. When I started with Decorah fossils, I had a hard time with trilobites and basically pretended they didn't exist until I got an eye for them. (A little bit of the buried edge of a small ribbed brachiopod shell can look a lot like the margin of a buried pygidium, especially when you don't know what you're doing.) Similarly, despite what this blog might suggest, it took me a long time to get an eye for stromatolites.
• It's good to know about common types of pseudofossils, especially if your area has a particular specialty.

Stromatolites in situ

A few weeks ago, during the elongated-dry-autumn-with-long-nights that has been substituted for winter in these parts this year, I visited a stromatolite patch in the Prairie du Chien Group and took the usual digital heap of photographs. The photos aren't quite as sharp as I would have liked, but they show a variety of aspects of stromatolites both up close and in situ, unlike the usual circumstances of getting only one of those two properties.

First off, here's a general idea of what we're dealing with:

Click to embiggen, as usual; the thing about stromatolites is sometimes they're more apparent at a distance, and sometime they're more apparent when your nose is practically on them. In this photo, there are columns a couple of centimeters across in the lower part, leading to a small shelf with a knobbly surface representing the tops of said columns, followed by an interval of more obscure growth.

The prolific interval was up to about three quarters of a meter thick, with some significant variation, microbial mounds not being big on standardization. Within this interval it was possible to see where a mound's growth had been cut off, or changes between narrow columns and broader stacks.

Here we have a broad mound of numerous coalesced small centers that is cut off starkly about two-thirds of the way up the photo.

Another example where there appears to be discontinuity between the growth lower in the photo and that in the upper part.

This tall mound is fairly broad at the base, then goes into narrower columns, then appears to show column consolidation near the top.

Part of why the photos may have lacked some clarity is the weathering of the surfaces (and the bright light). The stromatolites had a sort of artistic appearance in places, a bit like fingerprints in rock. I could see paintings of these done with heavy strokes to emphasize the tactile appearance of weathering layers.

There's a certain melted quality to this exposure.

I'm not sure what happened here, but this one looks like it's breaking up (and there seems to be a big rounded pebble in the upper left).

Another interesting feature was the occasional exposure of the top surface of a stromatolitic interval. Given the preponderance of smallish columns, it should not come as a surprise that such surfaces are knobbly.

A close look will reveal the more or less concentric layers of individual columns that have been truncated by weathering.

Finally, here's a surface showing columns that apparently grew out laterally. We usually think of the original microbial colonies growing vertically, to reach the light, but again microbial mounds aren't big on standardization, and will grow as conditions influence them. (Or maybe this mound was simply knocked over at some point; unfortunately, we're missing most of it.)

Preservation is different in this one as well, with layers still being evident but expressed less colorfully.

Finding waterfalls

A couple of months back, a friend pointed out a news items covering a slot canyon in Crosby Farm Park, so we decided to see if we could find it. We were successful in locating what's also called Homer's Odyssey (must be a pun based on the proximity to Homer Street), and it turned out to be one of the most unusual natural features of the Twin Cities. It's certainly worth a visit the next time you're in the park, although I can imagine it could be difficult to access during a year when it rains more than once every three months or so.

Approaching the entrance.

Looking back through the slot.

Inside the feature, which is kind of like a tall roughly cylindrical void.

Looking up at the top.

The canyon is almost like someone took a knife and cut straight down. Granted, it's not as if fresh St. Peter Sandstone shows much in the way of resistance to erosion, but I do wonder if there was a pre-existing weakness that focused this erosion so narrowly. Maybe there were voids in the sandstone or something similar?

Active waterfalls, waterfalls reduced to a trickle, and former waterfalls are scattered all over the Twin Cities metro. Some former falls, like the one in Cottage Grove Ravine Park or the abandoned falls northeast of Minnehaha Falls, have been high and dry for a long time due to the loss of their water source in the mists of time, but many have lost their flow due to drainage control measures in the past 150 years or so. Some could be reanimated with different priorities, while others have been buried or destroyed.

And even the best of them sometimes get caught short in droughts, as Minnehaha Falls shows in early October 2022.

Even beyond the named falls, there are many small-scale unnamed or obscure features. If you're looking to find some for yourself, you can often guess general areas to look from topo maps: look for valleys crossing steep contours. That's a telltale sign that a creek once crossed a bluff, or something similar. Or, if you'd rather try immediate adventure, get on one of the gorge trails (e.g., the Winchell Trail in Minneapolis or the unnamed goat path equivalents on the St. Paul side) and just keep your eyes open; they're there.

The falls in the Grotto, exiting the University of St. Thomas.

This is on the Minneapolis side, just across from E 36th Street. I've never heard that this one had a name, so it may well not have been doing more than a trickle when Minneapolis was developed, but it would have been substantial at one time.

Another area is south of Minnehaha Park, in the Coldwater Spring/dog park area. There is a secluded active waterfall southeast of Coldwater that has cut a modest slot in the St. Peter; again I'm not sure if it has a widely circulating name. Novelty Falls on the bluffs north of the dog park is very difficult to notice when the falls aren't falling; observation of the bluffs suggests there are several other places that may get mini-falls if there is a lot of rain or meltwater. Marks of water erosion at the top of the bluffs and water-worn hollows at the base will show you where flow has occurred.

A close view, low and up into the chute of the Coldwater waterfall. It's rather more impressive in person, as it tends to photograph poorly due to the confines of the site and the limited foot space. (Note that this area below the bluff has a tendency to become a respectable swamp following anything stronger than a light rain.)

Novelty Falls itself wasn't running in November, but these bluffs are very interesting!

They are also present on the south side of the Mississippi; for example, the Brickyard trail in Lilydale Regional Park passes right by one:

Here pictured during one of the few days this "winter" when there was snow on the ground.

(And yes, I am well aware that this blog has never covered the Brickyard...)

Your Friends The Titanosaurs: Gandititan cavocaudatus?

Here we are, already through January of 2024, and clearly we are not starting out like 2023, where the entire month had nary a new dinosaur. Today's entrant was the third of five announced in January 2024 (a couple of weeks ago, actually). You may notice the question mark in the post title; although described as a basal titanosaurian, Gandititan cavocaudatus fits a certain "type" of sauropod (mid-Cretaceous East Asian titanosauriform) that delights in phylogenetic instability. This to me is a subtle signal that something is going on we don't understand yet, so I'd best hedge my bets. So, maybe it's a titanosaur, maybe it isn't, but at any rate it's worth an introduction.

Parks Stewardship Forum: National Park Service Paleontology

For the past year, my supervisor Vincent Santucci and I have been assisting the preparation of a group of articles on National Park Service paleontology for Parks Stewardship Forum. We've assembled seventeen articles from various contributors on a variety of topics and parks, covering aspects of inventory, monitoring, research, and curation, from semitechnical to technical (the Florissant and John Day articles are the most technical, if you're concerned about that). Our issue has now gone live, and you can read and download each of the articles here. I hope you find something you like!

The cover comes from one of my pet projects, the paleontology of George Washington Birthplace National Monument (for which I contributed an article).

Cottage Grove cystoid

I recently paid a return visit to the site in Cottage Grove where I'd previously spotted a few blocks with brachiopods/etc. of the typical Platteville persuasion. While there, a few true outcrops were visible under the snow-free conditions of the so-called winter of December 2023, confirming that the Platteville is indeed at the surface and not just present as lag or buried under a bad toupee of soil and glacial debris. More significant was one of the blocks. See if you can spot what drew my attention:

Any ideas?

How about if we go in closer on the area of interest?

If you answered something along the lines of "the thing near the center that looks kind of like a truncated letter K", you've won! I snapped a couple of pictures thinking it might be echinoderm in origin and moved on. Later, upon reviewing the photos, the rectangular bit below it caught my eye; that definitely looked echinoderm. In fact, there is only one kind of thing it could belong to, as proclaimed by the chevron arrangement of slots on it surface. This is a plate from a rhombiferan cystoid bearing a pore rhomb in a pectinirhomb configuration. ("Of course!" you shout.) (Okay, so I looked up the anatomical terminology). Basically, the slots are vents for the animal's water circulation system.

This rock was obviously a good candidate for further study and photography, so I took some more photos with the hope of doing some taxonomy. Further inspection revealed a couple sharply ridged features similar to the "K", but more weathered.

There's a pretty well-developed one in the upper right, and one that is more poorly exposed near the left side.

When I first noticed the "K", I thought it might be ridges on a crinoid plate, but local crinoid plates don't usually have such sharp ridges. Instead, it turns out that there is a Platteville cystoid that does, Coronocystis durandensis. Coincidentally, this particular cystoid also has pore rhombs that are a good match for the pore rhomb plate on this rock (see photos in Kolata 2021).

Here close-up and with a tiny drip of water applied. There is also a gray rectangular ridge visible near the right border that I suspect to be another plate, but it's not as well-exposed.

I hesitate to make a firm identification from the available material, but it certainly appears that we have Coronocystis or something very similar. Coronocystis is interpreted as a stalked rhombiferan cystoid, unlike its free-thrashing cousin Pleurocystities (which does pore rhombs differently and has softer ridges). I interpret the block as from the Mifflin Member of the Platteville, but I suppose it could be higher. Whatever the exact identification at the genus or species level, this is clearly a rhombiferan cystoid, and the first I've ever seen in the field (and I'm pretty sure the first record from Cottage Grove). Plus, the several bits suggest a disarticulated but fairly associated specimen.

References

Kolata, D. R. 2021. Fossils of the Upper Ordovician Platteville Formation in the upper Midwest USA: an overview. Illinois State Geological Survey, Prairie Research Institute, University of Illinois at Urbana-Champaign, Champaign, Illinois. Bulletin 108.