Stromatolites in the snow

To close out 2021, here are some stromatolites in the snow.

A big stromatolitic eye; no scale bars today (I couldn't reach this one anyway, but it's a couple of feet across).

At this location there's a large wall of Prairie du Chien Group rocks that was exposed a few years ago during the construction of a bike trail. The bike trail descends from north to south, exposing more of the section as you go until a few dozen feet of the Lower Ordovician are visible. There is a distinct stratigraphic break near the top of the section, and just above this break is a stromatolitic interval with some large colonies, like the eye-shaped example above. I haven't seen any definite fossils below the break, but there might be some (there are numerous small voids, at least some of which could represent dissolved shells). There are some nice sedimentary structures, though, such as cross-bedding and planar bedding (sand grains in the carbonate).

The center of this photo shows a sort of bi-lobed pillow that smooths out into a single mound. It is not far from the eye-like stromatolite in the previous photo. In both cases, the large colony is about a foot above the stratigraphic break.

There are also some blocks that have fallen. In fact, I suspect that the stromatolitic interval is more prone to shedding blocks than the rest of the interval, because the stromatolitic interval has more opportunities for fracturing.

Theory and Application of Hypsibema

The dance of splitting and lumping will go on as long as there are two people and something to classify. On the one hand are the creators of new names. Are they revealing the hidden biological diversity of the past and present, or are they necessary evils at best, scurrilous egotistical rogues who turn taxonomy into tacky monuments to their own questionable genius at worst? On the other hand are the lumpers. Are they providing clarity against confusing multiplicity, or are they cranky reactionary gatekeepers who secretly (or not-so-secretly) flatter themselves as lonely upright crusaders against disorder and incompetence? Well, fellas, you can make questionable decisions splitting or lumping!

Consider, for a moment, the case of Hypsibema:

Late in 1869, Edward Drinker Cope presented a group of bones from North Carolina to the Academy of Natural Sciences of Philadelphia. He proposed to name the assortment Hypsibema crassicauda. The description takes up a grand total of 112 words (no illustrations, of course) and is reprinted below in its entirety:

"He [Cope] exhibited a number of remains of fossil reptiles, from Sampson Co., North Carolina, of cretaceous age, which were intrusive in miocene beds. Among these were humerus, tibia, fibula, metatarsus, caudal vertebra, and perhaps cervical vertebrae and ungueal phalange of a Dinosaur, discovered together by Prof. W. C. Kerr, Director of the Geological Survey of North Carolina. The remains indicated a species having the same general form and size as the Hadrosaurus foulkei. The caudal vertebra was of very different form, and resembled more that of Hylaeosaurus, minus the diapophyses. This vertebra was elongate, depressed and angulate. The animal presented various other points distinguishing it from Hadrosaurus, and was named Hypsibema crassicauda."

Note that Cope had received them second-hand, with no other information about their association other than they were "together". He was young at this time, not yet 30 and just getting started in this dinosaur business, but this was just one example of a worrying tendency that would show up again in his career: despite all of his undoubted paleontological acumen, he never seemed to twig to the idea that perhaps collections of bones found in the same general area did not necessarily belong to the same species or even genus. (See also Monoclonius.)

Because H. crassicauda was thought to have hadrosaurian affinities, Lull and Wright (1942) naturally included it in "Hadrosaurian Dinosaurs of North America". By that point Cope's bounty had been reduced to a caudal vertebra, the distal end of a humerus, a tibial shaft, and a partial metatarsal II, catalogued as USNM 7189 (National Museum of Natural History, Washington, D.C.). Lull and Wright passed the following judgment: "The material is too meager and uncharacteristic to permit a real definition of the genus and species, and the form must therefore be considered a nomen nudum [as mentioned here, basically a nomen dubium as understood today]. It indicates, however, the presence in North Carolina of Cretaceous hadrosaurs of uncertain affinities." Well, hallelujah, and so forth; insert your own uproar as the mood strikes. (One slightly disconcerting note: Lull and Wright thought the caudal resembled the caudal of fellow North Carolina form Hadrosaurus tripos. Hadrosaurus tripos is now regarded as a Pliocene whale.)

In hindsight it is very easy to say that Cope shouldn't have bothered naming Hypsibema crassicauda. The material isn't great and there is no real evidence that any of the bones belong to the same thing. It can be counter-argued that he didn't know any better and was acting within the bounds of mid-19th century vertebrate paleontology, but it still is not his finest hour. (None of the surviving bones can even articulate, for crying out loud. Even if they'd been found in an area the size of a square foot they could still easily be a hydraulic concentration of random fauna, and here he is thinking they're the same thing after getting them second-hand at best?)

So much for the 19th century.

Elsewhere and elsewhen, in 1942 geologists of the Missouri Geological Survey were studying clay units in southeastern Missouri. One of them, Dan Stewart, came into contact with Lulu Chronister, who told him about bones found on the Chronister farm during the digging of a well. One thing led to another, and in early 1945 Stewart and Charles Gilmore (of Thescelosaurus and Alamosaurus fame around here) published a description of 13 caudal centra (neural arches apparently lost around the time of discovery) and two fragments, catalogued as USNM 16735. They used the bones as the basis of new sauropod Neosaurus missouriensis (Gilmore in Gilmore and Stewart 1945). If you've never heard of Neosaurus missouriensis, it's because Neosaurus turned out to be preoccupied, and Gilmore quickly substituted Parrosaurus (Gilmore 1945). Gilmore (in Gilmore and Stewart 1945:25) commented that "[t]he specimen on which the present paper is based consists only of caudal centra that in the ordinary course of events would be considered too meager for generic designation, but in view of the uniqueness of both its geographical and geological occurrence the name Neosaurus missouriensis is proposed for its reception."

Neither Hypsibema crassicauda nor Parrosaurus missouriensis garnered much attention over the next few decades. Then, in 1979 Donald Baird and Jack Horner published a review of Cretaceous North Carolina dinosaurs. Things did not go well for Hypsibema crassicauda at first; Baird and Horner determined that the type material was chimeric. They restricted the type to just the caudal vertebra, because Cope had based the species name ("thick-tailed") on it, and identified it as belonging to a sauropod. They then pulled the tibial and metatarsal fragments as hadrosaurian, and identified the "humerus" as the distal end of a tyrannosaurid femur. So far, this is just another case of the clinical dissection of an obscure questionable name.

Then, though, the authors brought out Parrosaurus missouriensis. Technically speaking, with a publication title of "Cretaceous dinosaurs of North Carolina" they could have ignored P. missouriensis and nobody would have felt shortchanged, but they opted to go the extra mile. In fact, they went farther than the extra mile, sinking Gilmore's species into Cope's species: "Now that Hypsibema has been freed of hadrosaurian encumbrances its genetic identity with Parrosaurus becomes obvious. Every morphological feature cited for the Missouri vertebrae can be matched in those from North Carolina. Indeed, the possibility of specific identity cannot be dismissed..."

The bit about sauropod (mis)identification is a topic for another time and place. For the moment, the critical piece is sinking one poorly known species into a different poorly known genus on the basis of exactly one piece of overlapping material: the caudal of H. crassicauda, with remnants of the neural arch (which you don't even get with P. missouriensis). Even if they are very similar, that's asking a lot out of dinosaurian caudal centra, which are not generally noted for having unusually high concentrations of apomorphies. Implicitly this classification is saying that the rest of the body of the two forms will not differ significantly, a bold statement all around. Whether or not you agree with the synonymization, I suspect you'd probably agree that it's not an ideal situation.

Because for many years there was little interest in the disposition of H. crassicauda and P. missouriensis (although missouriensis became the state dinosaur of Missouri during that time frame), the generic synonymization has persisted. Recent developments in Missouri bode fair to spur a reassessment, though.

[Note: despite the url for this entry, I did not write it in August 2018, I only started working on a post with a couple of the ideas and gave it a custom url because I didn't like the automatic version. (For that matter, the present entry owes much more to another and even older post idea.) Of course, I had long forgotten about the custom link when I dusted it off. Seeing as there's no critical reason to change it, I'll let it stay.]

References

Baird, D., and J. R. Horner. 1979. Cretaceous dinosaurs of North Carolina. Brimleyana: The Journal of the North Carolina State Museum of Natural History 2:1–28.

Cope, E. D. 1869. [Remarks on Hypsibema crassicauda and Hadrosaurus tripos.] Proceedings of the Academy of Natural Sciences of Philadelphia 21:192.

Gilmore, C. W. 1945. Parrosaurus, n. name, replacing Neosaurus Gilmore 1945. Journal of Paleontology 19(5):540.

Gilmore, C. W., and D. R. Stewart. 1945. A new sauropod from the Upper Cretaceous of Missouri. Journal of Paleontology 19(1):23–29.

Lull, R. S., and N. E. Wright. 1942. Hadrosaurian dinosaurs of North America. Geological Society of America Special Paper 40.

A reflection

December 4, 2021:

It's the early afternoon on one of those gray days that Minnesota churns out from about the time the leaf show is over to about the time that snowfall gets serious; it's as if Mother Nature, not quite sure what weather to go with, simply throws the gray blanket over the state until she makes up her mind. I am wandering the Mississippi River gorge in St. Paul and Minneapolis.

The view from the Shadow Falls overlook.

The green rocks of home revisited (now with stromatolites!)

Almost exactly five years ago I posted on a visit to Cottage Grove Ravine Regional Park. I was in the area and thought I'd stop again. There's been a lot of work at the park since then, and I wanted to check that the abandoned stream channel and dry waterfall were still visible. Also, over the past five years I've become much better at finding stromatolites, so I thought I'd try my luck.

Were the landforms still there?

That's a dry waterfall, all right. The lowest interval seems to have some weathered cross-bedding; perhaps a somewhat sandier bed in the Prairie du Chien?

I'd say yes, the old channel is still there.

How about stromatolites?

We have stromatolites!

That's the stuff.

Separation has occurred within a stromatolitic interval here.

At the beginning, I was seeing them in loose blocks, which led to the question "where are they coming from?" This was more complicated. The stromatolitic blocks were much lighter-colored and less weathered, indicating fresh faces. There were no obvious fresh faces on the surrounding walls, though. Had large stromatolitic blocks broken up in the dry stream bed fairly recently? Or were these "plants", Prairie du Chien blocks that had been brought in for landscaping and culvert riprap, then declared surplus and deposited here? The walls were not helping.

Features like the wavy lines give a general biotic impression, but I'd really want to see some light-colored patches indicating fallen blocks to cinch a relationship.

Fine lines are visible behind the dull gray and moss.

Then I saw this enormous fallen block.

Do you see them? They're near center. If not, hold on.

There they were.

How about now?

A proverbial bull's eye.

This block is too large and too well-mossed to have been placed here in the past few years. Clearly at least some of the stromatolites are local. I'm still wondering where the loose "clean" blocks came from, though.

Issi saaneq and Brighstoneus simmondsi

A couple of new non-theropod names have come down the pipe since the beginning of November, and I thought I'd cover them together. Let's tackle the earlier of the two (both geochronologically and publication-wise) first.

Barn Bluff

One of the outstanding geological sites in southeastern Minnesota is Barn Bluff (He Mni Can to the Dakota, La Grange to the early French explorers*) in Red Wing. The bluff is a bedrock island oriented roughly east–west, adjacent to the Mississippi River just above the Lake Pepin section. If you were to have gone back to the early postglacial period, it would have been a literal island thanks to meltwater filling the Mississippi River valley.

*All of the names are kind of prosaic, actually. "He Mni Can" is "hill, water, wood", "La Grange" or "Lagrange" is "the barn" for its general shape, and the English name is just a translation of the French.

The view of the south side of the west end. Observant eyes may notice that the color of the lower outcrops change near the left side of the picture, from orangish on the left to banded green on the right. Read on for why!

The Matagamon Sandstone

I recently had occasion to go to north-central Maine for work. If you've never been there, the geology is the tectonic equivalent of taking a bunch of little leftover bits of colorful modeling clay and smooshing them together: the area was on the margin of the North American craton during the Paleozoic and thus was the recipient of a conveyor belt of crustal fragments. Of course, when this happens, you get all kinds of interesting structural features and metamorphism, which does unfortunately tend to obscure the original geology. Tack on the Pleistocene glaciations and subsequent dumping of drift, followed by the growth of forests, and you can see how things can get complicated and confusing to follow.

One of the geologic units I observed in this region is the Lower Devonian Matagamon Sandstone. The Matagamon has been interpreted as part of a deltaic system that advanced to the northwest during the Acadian Orogeny (Hall et al. 1976; Pollock et al. 1988). We've got a pretty good idea of when its deposition ended because it transitions upward into the Traveler Rhyolite (Rankin 1965), the explosive component of a supervolcano that erupted approximately 407 million years ago (Seaman et al. 2019). Curious about the guts of that volcano? Look no further than Katahdin.

Maine's tallest mountain? The crystallized heart of one of North America's largest volcanoes? Why not both?
(Incidentally, they told us this was the best time of year to do geologic work in north-central Maine. They were right!)

Anyway, the Matagamon is a fossiliferous unit, with an assemblage dominated by brachiopods. Clarke (1909) described a few assemblages from this formation, which was then identified as the Moose River Sandstone (it did not receive its present name until Rankin 1965). The fauna includes plant fragments, corals, brachiopods, monoplacophorans, bivalves, nautiloids, gastropods, tentaculitids, trilobites, crinoids, and invertebrate trace fossils. Brachiopods certainly seemed to be the most abundant fossils in the outcrops I saw.

A fairly large brachiopod with Leptaena-type ridges.

A bulbous shell on the left and a cylindrical object of unknown origin on the right.

A shell bed.

Fossils tended to be abundant in localized areas, mostly preserved as molds, external casts, and steinkerns, with occasional shell material in the brachiopods. (Overall, the rocks, the fossils, and their preservation rather reminded me of the somewhat younger Mahantango Formation from the Delaware River valley.) In some cases, the fossils had been stained bright orange, very appropriate for autumn and Halloween.

Slightly orange small flat ribbed brachiopods, resembling potato chips.

Two strongly orange brachiopods: a small shell with few but heavy ribs on the left, and a much larger brach with many fine ribs in the center.

Some calcitic material remains with these shells.

References

Hall, B. A., S. G. Pollock, and K. M. Dolan. 1976. Lower Devonian Seboomook Formation and Matagamon Sandstone, northern Maine: a flysch basin-margin delta complex. Pages 57–63 in L. R. Page, editor. Contributions to the stratigraphy of New England. Geological Society of America, Boulder, Colorado. Memoir 148.

Pollock, S. G., A. J. Boucot, and B. A. Hall. 1988. Lower Devonian deltaic sedimentary environments and ecology: examples from the Matagamon Sandstone, northern Maine. Pages 81–99 in R. D. Tucker and R. G. Marvinney, editors. Structure and stratigraphy. Maine Geological Survey, Augusta, Maine. Studies in Maine geology: papers to commemorate the 150th anniversary of C. T. Jackson’s reports on the geology of Maine. Volume 1.

Rankin, D. W. 1965. The Matagamon Sandstone–a new Devonian formation in north-central Maine. U.S. Geological Survey, Washington, D.C. Bulletin 1194-F.

Seaman, S. J., R. Hon, M. Whitman, R. A. Wobus, J. P. Hogan, M. Chapman, G. C. Koteas, D. Rankin, A. Piñán-Llamas, and J. C. Hepburn. 2019. Late Paleozoic supervolcano-scale eruptions in Maine, USA. GSA Bulletin 131(11–12):1995–2010.

Compact Thescelosaurus Year Six

The time has come again for the annual review of The Compact Thescelosaurus. This year's new page is on aetosaurs and their close relatives, with the classification diagram page updated. (Don't forget, Wednesday the 13th is also National Fossil Day!)

Aetosaur Desmatosuchus spurensis is one of the subjects of the NPS Prehistoric Life Coloring Book. Coincidentally, an aetosaur also featured in the 2014 National Fossil Day artwork.

Your Friends The Titanosaurs: Menucocelsior arriagadai

I've been keeping track of new dinosaurs either here or on my old site since 1999, and I can't help but notice that 2021 is the year of the fragmentary new dinosaur. Is this a reflection of COVID restrictions at museums and so forth, i.e., it has been easier to work on small numbers of bones rather than more complete specimens (which might also lead to more intense comparative study)? Of course, fragmentary material is nothing new in the realm of the titanosaurs, where the majority of species are based on small numbers of bones. (2021 has been pretty good for titanosaurs.) Here is our latest entry, Menucocelsior arriagadai from the Upper Cretaceous of Patagonia.

Genus and Species: Menucocelsior arriagadai. "Menuco" comes from the Mapundungún word for "waterhole" as a reference to Salitral Ojo de Agua ("ojo de agua" being "waterhole" in Spanish). "Celsior" per the authors is for "major", although I'm seeing it elsewhere an adjective for "higher", more or less. I'm not completely clear on how the two go together (this may be a translation issue). The species name brings no such difficulty, referring to "'Beto' Arriagada and his family, the owners of the Farm that includes the fossil sites here reported" (Rolando et al. 2021).

Citation: Rolando, M. A., J. A. Garcia Marsà, F. L. Agnolín, M. J. Motta, S. Rozadilla, and F. E. Novas. 2021. The sauropod record of Salitral Ojo del Agua: An Upper Cretaceous (Allen Formation) fossiliferous locality from northern Patagonia, Argentina. Cretaceous Research 105029. doi: 10.1016/j.cretres.2021.105029.

Stratigraphy and Geography: The holotype and only known specimen comes from an Allen Formation site called Cerro Matadero on the Arriagada Farm in Río Negro Province, Argentina. The area is known as Salitral Ojo de Agua (Rolando et al. 2021). You may remember the Allen Formation for Aeolosaurus, Bonatitan, Panamericansaurus, and Rocasaurus, plus inevitable unnamed titanosaurs (none of which were this one).

Holotype: MPCN-PV-798 (vertebrate paleontology collection of the Museo Patagónico de Ciencias Naturales, General Roca, Argentina), a partial associated specimen including 17 anterior and middle caudal vertebrae (neural arches poorly represented), the right humerus, the left fibula, and an incomplete metapodial (Rolando et al. 2021).

Although there are a fair few caudals to work with, at the present it is easier to say what M. arriagadai isn't than what it is. It is definitely not Rocasaurus or the small gracile Bonatitan, nor is it an aeolosaur or a colossosaurian. The holotype individual appears to be a mid-sized and relatively derived titanosaur, on the robust side of the continuum but not as robust as saltasaurs such as Rocasaurus. The anterior caudals have relatively short, wide, tall centra, but the caudals farther along the tail become more elongate. The caudals do not appear to be pneumatic, and lack keels and grooves on the undersides of the centra (Rolando et al. 2021). For now, M. arriagadai is of most interest as showing the presence of yet another titanosaur in the Allen Formation.

But that is not where the paper ends, not at all. M. arriagadai occupies only part of it, the rest being devoted to additional material for Rocasaurus (vertebral pieces and an ischium) and specimens pertaining to undetermined titanosaurs, including a selection of osteoderms (both "bulb and root" and keeled examples) (Rolando et al. 2021). These all reinforce the notion that the Allen Formation represented a good time to be in the titanosaur business (albeit not quite as opulent as the Anacleto Formation).

References

Rolando, M. A., J. A. Garcia Marsà, F. L. Agnolín, M. J. Motta, S. Rozadilla, and F. E. Novas. 2021. The sauropod record of Salitral Ojo del Agua: An Upper Cretaceous (Allen Formation) fossiliferous locality from northern Patagonia, Argentina. Cretaceous Research 105029. doi: 10.1016/j.cretres.2021.105029.

Minnesota's state fossil revisited

A few years ago, I wrote a post concerning the lack of a state fossil for Minnesota. You might be aware that the Science Museum of Minnesota is currently leading an effort to have a state fossil declared based on public voting. You can check out the candidates and vote here. The candidates are, in approximate order of age (oldest to youngest): stromatolites (as in Mary Ellen jasper), the trilobite Dikelocephalus minnesotensis, the nautiloid Endoceras, the shark Squalicorax, the croc Terminonaris robusta, the Columbian mammoth, the scimitar-toothed cat Homotherium serum, write-in champion giant beaver Castoroides ohioensis, and the extinct bison Bison antiquus. Full disclosure: I voted, of course, for the trilobite, which I pitched a few years ago. Voting closes September 30, so there's still time to participate.

Bryozoan Overload

Sometimes you look at a slab, and you notice one special thing about it. "That's a nice Isotelus hypostome." "Neat strophs." "Look at that Phycodes!" In this case, it's "Gee, that's a lot of bryozoans!"

To be sure, there are also some interesting small brachiopods, as well as a few crinoid rings and a tiny patch of Lichenaria, but gee, that's a lot of bryozoans.

(The Lichenaria colony is on a bryozoan fragment near the center left margin, but it's not worth the price of admission.)

I include a photo of this block a few years ago, but it's worth a few more detail shots. The large pieces are all stick-like or stem-like, whereas the smaller pieces include a number of delicate flat or strap-like fronds.

Branching straps plus a few different brachiopods.

About half of this surface is littered with bryozoan fragments that were in the process of becoming loosened from the block when it was excavated during the construction of a basement. Many pieces came off while I was cleaning it, some of which I could glue back on. (Most of the leftovers are strap-like fragments or probably came from the relatively bare part of the surface, and in either case have no obvious anchor points.) Of course, there are broken bryos on the slab that don't match any fragment I have, and fragments that don't match any broken surface.

Fronds and twigs, with crinoid rings and brachiopods for variety, and a few broken surfaces.

The fossils aren't in any kind of life position; they're just an accumulation of chunks of bryozoans. Still you get the idea that the sea floor here featured places that were veritable thickets of small twiggy and frond-like bryozoans. To all you time travelers: probably not recommended for bare feet.

It's bryozoans almost all the way through, as well.

Further thoughts on the location of Finn's Glen

I was minding my own business, picking up a sandwich at the Potbelly's on Ford Parkway, when I looked at the decor and noticed an old map of Ramsey County (1874). Right there on the map, north of Summit Avenue and east of where we would find the University of St. Thomas today, is "Wm. Finn". William Finn. Finn of Finn's Glen.

Forgive the flare. It was a dramatic moment.

Bingo. Meaning what, exactly? (Unfortunately, it doesn't identify the glen.) Years ago I wrote about Finn's Glen in conjunction with Shadow Falls. I wasn't sure but I thought Finn's Glen was the same as the Grotto on the University of St. Thomas campus, south of Shadow Falls. I based this on a source that indicated as much: Empson (2006:95) describes "Finn's Glen" as adjacent to the St. Paul Seminary, south of Summit Avenue, and a place of meditation. As a University of St. Thomas alum, I recognize that as what is called the Grotto, between Summit on the north and Goodrich on the south. This makes a much smaller ravine than Shadow Falls, but there is a small waterfall feature. Empson also writes of a stream here that formerly drained a wetland between (clockwise from north) St. Clair, Snelling, Randolph, and Fairview. We can see this in Winchell's "Falls of St. Anthony" map (1877). But...

Finn's Glen is clearly marked...

...Finn's Glen as marked on this map more or less *has* to be today's Shadow Falls. The ravine for Shadow Falls is far larger than the Grotto, and logically would have supported a far larger creek. Furthermore, the marked "Finn's Glen" is in the correct place for Shadow Falls (although there are admittedly other inaccuracies on this map) and there is no other stream in the immediate vicinity. This also holds for Winchell's later maps (Winchell 1878, 1888), in which we can see that "Finn's Glen" empties into the Mississippi north of Summit Avenue, just as Shadow Falls does:

From Winchell (1878).

From Winchell (1888).

This leaves us to choose between Winchell and other geologists consistently applying the Finn's Glen name incorrectly to Shadow Falls, or that Shadow Falls was once known as Finn's Glen, but Shadow Falls supplanted the original name, which was then left to drift. Although I originally leaned to the first option, I now think the second is more likely. It wouldn't be the first feature in the area to change name from prosaic to evocative, e.g., Brown's Falls becoming Minnehaha Falls. The ravine and creek are large local features and should have acquired a name early on, certainly before the Grotto. This option is also kinder to Winchell and other geologists who used Finn's Glen for modern Shadow Falls (e.g., Sardeson and Ulrich). Does it fit with the timeline?

Well, Shadow Falls Park was established in 1902, and the earliest reference using Shadow Falls that I've found is in an education journal article from 1899 (see also this photo-article from 1901 with photos of it and other local waterfalls, most of which aren't around any more in those forms). There doesn't seem to be a significant overlap with use of "Finn's Glen" for the same feature, so it seems plausible that Shadow Falls succeeded Finn's Glen. Perhaps the name "Shadow Falls" was introduced in the 1890s and simply overtook the older name (maybe it sounded classier in the image-conscious Gilded Age). Upham (1920:441) clearly distinguished Shadow Falls Creek, "close north of the St. Paul Seminary," from Finn's Glen "about a mile farther south". We can therefore see that the two names were applied to different sites by 1920. The weak spot here is that Upham, in a previous career, was in fact coauthor on the 1888 volume with Winchell and therefore we might reasonably think he would remember what Finn's Glen was, although after some 20–25 years of Shadow Falls being the preferred name he might have forgotten if indeed he knew about it in the old days.

Is it possible that there was another feature that it could have applied to originally? Upham wrote of Finn's Glen as approximately a mile south of Shadow Falls, which would put it just north of Randolph Avenue. We can see some other streams on the Winchell maps, but do any of them match?

Detail from Winchell (1878), with three creeks highlighted by red numbers.

#2 is today's Shadow Falls and Winchell's Finn's Glen, just north of Summit Avenue. #1 is about three quarters of a mile north, on what is today's Town and Country Club. (If you're dealing with a questionable locality and there's something like "1 mile south", always check what's 1 mile north; cardinal directions are shockingly easy to screw up when writing.) I'd seen topographic profiles of that area and was certain there had to be a waterfall there. Well, there was, but it's been gone a long time. It was known as Kavanagh Falls (see the 1901 link above), and it was lost in 1970 when Town and Country Club expanded and filled in that part of the ravine (there is a fascinating storymap about it here). (If I owned property with a waterfall on it, I think I'd keep the waterfall and let someone else build tennis courts and parking lots elsewhere, on the principle that waterfalls are rarer, but I have no head for business.)

#3 is more of a mystery. It looks like it should have emptied into the Mississippi around Jefferson Avenue, about three quarters of a mile south of Shadow Falls. This is not a mile, but it's not unconscionably off, either. This one is even harder to account for than Kavanagh Falls. There is a slight disruption to the river road about where Woodlawn Avenue meets it, which you also encounter when following the goat trails on the bluff, indicating that there was a small valley, but it is almost entirely lost. Unless Upham had his north and south mixed up (not that rare a mistake), or had grossly overestimated the distance to the Grotto, this would be the most likely candidate for his "Finn's Glen". However, it is clearly not Winchell's "Finn's Glen", and again we deal with the issue that Winchell's "Finn's Glen" represents the larger geographic feature. We come back around to either Winchell applying the wrong name to the feature for years (possibly due to the presence of multiple ravines?), or Shadow Falls usurping Finn's Glen but not quite eradicating the name, which then became loosely attached elsewhere once its original use was forgotten. (Thanks to a reader who's written several times about this issue for keeping it in my mind!)

References

Empson, D. L. 2006. The street where you live: a guide to the place names of St. Paul. University of Minnesota Press, Minneapolis, Minnesota.

Upham, W. 1920. Minnesota geographic names: their origin and historic significance. Collections of the Minnesota Historical Society 17. Minnesota Historical Society, St. Paul, Minnesota.

Winchell, N. H. 1877. The geology of Hennepin County. Minnesota Geological Survey, St. Paul, Minnesota. Annual Report 5:131–201.

Winchell, N. H. 1878. The geology of Ramsey County. Minnesota Geological Survey, St. Paul, Minnesota. Annual Report 6:66–92.

Winchell, N. H. 1888. The geology of Ramsey County. Pages 345–374 in N. H. Winchell and W. Upham. The geology of Minnesota. Minnesota Geological and Natural History Survey, Final Report 2. Johnson, Smith & Harrison, state printers, Minneapolis, Minnesota.

Your Friends The Titanosaurs: Hamititan xinjiangensis

As far as I'm concerned, 2021 has been relatively quiet for new dinosaurs (great year for ophthalmosaurid ichthyosaurs, though; I might even learn to spell "ophthalmosaurid" correctly the first time through). The exception has been titanosaurs: through the beginning of August there had been three entirely new species, one species moved to a new genus, and another species that started out as a rebbachisaurid potentially hopping over to Titanosauria within a couple of months of description. Hamititan xinjiangensis makes another new addition. It was published this week (Wang et al. 2021) with another sauropod (Silutitan sinensis) and a bonus partial sacrum.

Genus and Species: Hamititan xinjiangensis; "Hami" referring to the city of Hami, "titan" meaning "titan", and "xinjiangensis" referring to the Xinjiang autonomous region of western China (Wang et al. 2021). Together they mean something akin to "Hami titan from Xinjiang".

Citation: Wang, X., K. L. N. Bandeira, R. Qiu, S. Jiang, X. Cheng, Y. Ma, and A. W. A. Kellner. 2021. The first dinosaurs from the Early Cretaceous Hami Pterosaur Fauna, China. Scientific Reports 11:14962. doi:10.1038/s41598-021-94273-7.

Stratigraphy and Geography: H. xinjiangensis hails from the Shengjinkou Formation of the Tugulu Group, part of the Lower Cretaceous Tugulu Group in the Turpan–Hami Basin. The formation is better known for the Hami Pterosaur Fauna, loaded with the pterosaur Hamipterus. The holotype and only known specimen of H. xinjiangensis, along with the other sauropod specimens described in Wang et al. (2021), came from lacustrine sandstone. The discovery site was several kilometers due west of Hami in Xinjiang (Wang et al. 2021).

Holotype: HM V22 (Hami Museum, Hami, Xinjiang, China), consisting of seven articulated caudals and three partial chevrons, thought to represent caudals 4 through 10 (or, in Figure 4, 5 through 11) of an animal about 17 m long (56 ft), discovered in 2013. A small theropod shed tooth was found nearby (Wang et al. 2021).

Figure 4 in Wang et al. (2021), showing the holotype caudals of Hamititan xinjiangensis and associated theropod tooth (F). Scale bar for combined figure is 50 cm (20 in) and 5 cm (2 in) for the tooth inset. See here for full caption. CC BY 4.0.

Is H. xinjiangensis indeed a titanosaur? It's a fair question, given both the historical difficulties surrounding Early Cretaceous titanosaurs and the particular difficulties classifying East Asian Early Cretaceous sauropods, which seem to be doing their own thing. First things first: H. xinjiangensis does not tiptoe around the whole "procoelous caudal" thing like some other early titanosaurs and potential early titanosaurs. It is boldly, proudly procoelous. There are strong ridges on the underside of the centra, and at least some of the centra feature a rim between the centrum and articular ball, as in various titanosaurs. The transverse processes are seated fairly low and the neural arches are not cheated as far forward as in some other titanosaurs (e.g., aeolosaurs). The bones do not feature spongy texture (Wang et al. 2021). Despite some quibbles, it's certainly got more going for it than some other putative early titanosaurs (although I certainly would not be surprised if within a few years someone argued it was not a titanosaur, just another East Asian Early Cretaceous sauropod with a titanosaur-like tail).

Is it Silutitan? Well, we can be reasonably certain that the holotype of H. xinjiangensis is not from the same individual as the holotype of S. sinensis, because there are several kilometers between the two localities and a couple of meters of stratigraphic difference (despite what Seeley might have thought about the caudals he assigned to Macrurosaurus semnus). To look at this phylogenetically, Wang et al. (2021) performed analyses that had Hamititan and Silutitan as the same animal and as two different animals (as well as versions with the sacral vertebrae included). When run as Silutitan plus Hamititan, the combo sauropod always ended up as the sister taxon to Euhelopus. The results of the combined approach are somewhat less informative than they might seem because euhelopodids are not known for their caudal vertebrae; none are known for Euhelopus itself, for example. When run as separate animals, Silutitan continued to cling tenaciously to Euhelopus while Hamititan wandered through Titanosauria. Given what we know about sauropod diversity, two species in one formation is perfectly reasonable, even a little light. (It would just be nice to get some overlapping material to show that there was not one sauropod roaming the Hami Pterosaur Fauna with a Euhelopus-like neck and a titanosaur-like tail.)

References

Wang, X., K. L. N. Bandeira, R. Qiu, S. Jiang, X. Cheng, Y. Ma, and A. W. A. Kellner. 2021. The first dinosaurs from the Early Cretaceous Hami Pterosaur Fauna, China. Scientific Reports 11:14962. doi:10.1038/s41598-021-94273-7.

Geranosaurus atavus

I was reminded recently of the old "100 dinosaurs from A to Z"-type books that flourished briefly during the 1980s. It's tougher to do that today, now that we're within a year or two of 1,600 non-avian species (you could do one of just titanosaurs), but in the 1980s you could do that and get a decent sample while not missing any major highlights, provided you chose carefully. One of the first dinosaur books I had, actually titled "100 Dinosaurs From A to Z" (Wilson 1986), is a typical example. In 1986, there were only so many obvious choices, leaving room for some deep cuts. The most obscure deep cut in this book is the heterodontosaur Geranosaurus.

Practical applications of Chesapecten, early 19th century

"Fossil pectens of a large size, some of them ten inches wide, are found abundantly in the lower part of Virginia. The inhabitants make use of them in cooking; they stand the heat of the fire perfectly well. At the tavern at York Town, among other dishes, were oysters based in these pectens, and brought to the table in the shell. I wanted the company of a few scientific friends to enjoy the treat. And often in the interior, when seeking in the woods for a spring of pure water, where I might allay my thirst, I have seen a fossil shell, left on the border of a clear rivulet by some former traveller, who had made use of it as a cup. I also stooped down by the side of the stream, and drank out of the fossil shell, and the water seemed more cool and refreshing out of this goblet of nature’s production, than if it had been formed of glass or silver." (Finch 1833)

Chesapecten madisonius, not quite as famous as C. jeffersonius but still quite nice.

References

Finch, J. 1833. Travels in the United States of America and Canada. Longman, Rees, Orme, Brown, Green, and Longman, London, United Kingdom.

A fossiliferous Prairie du Chien block

The Prairie du Chien Group is great for stromatolites, but not much for other fossils except for localized occurrences of molds and casts of mollusks; see for example the second photo here or the second photo here. You do get lucky occasionally, though. I did not collect the following block myself, nor was it found in situ, but I would be very, very surprised if it did not originate in the Prairie du Chien Group. The most notable aspect about it is this spiral feature:

What is it? A few thoughts:

If you had to pick a second group to find in the Prairie du Chien after stromatolites, it would be snails, and the Prairie du Chien snails do include some large forms that are flat-coiled or coiled in a low spiral, such as Helicotoma and Rhachopea. They're even of comparable size to this.

Some trace fossils spiral, but we can see that the width of the spiral passage increases as it goes out, and animals do not generally increase in girth like that over a short distance unless they handle matter like the Incredible Hulk, so that's not what we have.

Finally, although we usually think of early Paleozoic nautiloids as straight-shelled, there were a few coiled forms, including one known from the Prairie du Chien: Eurystomites. We can see that this spiral seems to separate from the inner coil near the end, and conveniently enough, Eurystomites also gets lax at the end of its coil. However, there's no clear indication of chambers.

What do I think? Without being able to see the entire fossil, you could make an argument that this is an internal cast (steinkern) or external cast of a snail (in which the outer whorl shows separation either because we're looking at the inside or because the plane of exposure isn't low enough to show that the whorl is actually just flaring), or a poor-quality external cast of a Eurystomites or similar nautiloid (can't be internal, because there's no evidence of chambers).

Operating on the principle that where you find one body fossil in the Prairie du Chien, you might find more, I examined the rest of the block, which turned out to have several more easily interpreted molds of much smaller and more obvious snails:

Low-coiled snail, coiling into the block.

A more elongate form; the shell may be slightly sculptured, but relatively coarse mineralization in the mold makes it hard to tell. A similar but less easily photographed example looked much smoother.

A pair of shell molds exposed at an awkward angle.

The Short Life and Unnecessary Death of the Devils Lake Formation

Edward Oscar Ulrich was previously featured here as one of the main players in the brachiopod noir "The Great Brachiopod Caper of 1892", on the side of the "victors". Decades later, though, he seems to have come out on the short end with a formation he named from one of the more geologically notable areas in Wisconsin: Devil's Lake in the Baraboo Range. Devil's Lake itself is more than worthy of a post in its own right, but for the moment I'll just plant that seed for future reference.

A brief bit of exposition is in order, though. The Baraboo Range is an exhumed area of early Paleozoic topography, with a core of Proterozoic Baraboo Quartzite. The range is elliptical and oriented east-west, with a north range and a more complete south range; during the Cambrian and Early Ordovician, before it was buried, the range was oriented north-south instead of east-west. Similar to Taylors Falls, where basalt withstood the advancing seas, the ancient quartzite of the Baraboo Range formed islands in the Cambrian sea. Also like Taylors Falls, there is a conglomeratic sandstone that formed adjacent to the resistant Precambrian rocks, only in this case the conglomerate is composed of material shed from Baraboo Quartzite rather than Midcontinent Rift basalt. It is this flanking sedimentary unit, well-exposed near Devil's Lake, that Ulrich named the Devils Lake Formation.

The Devils Lake Formation first popped up in Ulrich (1920), as a name in a table. It did not get a proper description until Thwaites (1923), where it was described as a "more or less glauconitic sandstone" with quartzite pebble conglomerate. Ulrich (1924) added a little more, emphasizing the well-developed conglomerate found on the flanks of the quartzite ridges and noting its presence in nearby Parfrey's Glen. Never the subject of much discussion, the Devils Lake Formation was laid to rest in the literature following Wanenmacher et al. (1934). The authors regarded the formation as a geological chimera, because it was not coherent in terms of biostratigraphy. (It was also mixed up in Ulrich's doomed effort to establish the Ozarkian and Canadian periods between the Cambrian and Ordovician, which didn't help its reputation.) In light of the push to define formations by their rocks rather than their fossils that came about not long after Wanenmacher et al. (1934), this is a fatally flawed argument: formations live or die on the distinctiveness of their lithology, not because of how many trilobite zones they span. The Devils Lake Formation should have been expected to span multiple zones, because it represents unusual depositional conditions that persisted adjacent to the range beginning with the arrival of the Cambrian seas until the range was buried during the Ordovician. However, going back and resurrecting the Devils Lake Formation was not a high priority for anyone.

The plot thickened when in 1990 Clayton and Attig named a new formation, the Parfreys Glen Formation, for quartzite conglomerate and conglomeratic sandstone found adjacent to the quartzite ridges of the Baraboo Range. The new unit encompasses the same kinds of rocks as the Devils Lake Formation and is present in the same areas. It is hard to avoid the conclusion that the Parfreys Glen Formation is the Devils Lake Formation under a new name. Oddly, even though all of the papers mentioned above are referenced several times in the 1990 publication, nowhere is the term "Devils Lake Formation" used, not even to dismiss it. (This is not the only example of something about Devil's Lake geology going missing; for some reason the Cambrian fossils found near the lake are basically absent from the literature since Resser 1942. For a further "devilish" aspect, no two geologic maps of the area map the Cambrian rocks in exactly the same places around the lake; compare Wanenmacher 1932 [in Raasch 1935], Dalziel and Dott 1970, Clayton and Attig 1990, Baumann and Abrams 2013, and Stewart and Stewart 2021.)

Conglomerate in Parfrey's Glen; is it the Parfreys Glen Formation, or the Devils Lake Formation in disguise? Found on Wikimedia Commons, taken by user Wackybadger. CC BY-SA 3.0.

References

Baumann, S. D. J., and M. J. Abrams. Geologic map of Devils Lake, Sauk County, Wisconsin, United States, T11N R6E and R7E. Midwest Institute of Geosciences and Engineering, Chicago, Illinois. Publication M-072013-1A. Scale 1:12,000.

Clayton, L. and J. W. Attig. 1990. Geology of Sauk County, Wisconsin; with a section about the Precambrian geology by B. A. Brown and an appendix naming the Rountree Formation by J. C. Knox, D. S. Leigh, and T. A. Frolking. Wisconsin Geological and Natural History Survey, Madison, Wisconsin. Information Circular 67. Including geologic map, scale 1:100,000.

Dalziel, I. W. D., and R. H. Dott, Jr. 1970. Geology of the Baraboo District, Wisconsin: a description and field guide incorporating structural analysis of the Precambrian rocks and sedimentologic studies of the Paleozoic strata. Wisconsin Geological and Natural History Survey, Madison, Wisconsin. Information Circular 14. Scale 1:62,500.

Raasch, G. O. 1935. Paleozoic strata of the Baraboo area. Kansas Geological Society, 9th Annual Field Conference Guidebook:405–415.

Resser, C. E. 1942. Fifth contribution to nomenclature of Cambrian fossils. Smithsonian Miscellaneous Collections 101(15).

Stewart, E. K., and E. D. Stewart. 2021. Geologic map of the Baraboo 7.5-minute quadrangle, Sauk County, Wisconsin. Wisconsin Geological and Natural History Survey, Madison, Wisconsin. Open-File Report 2021-02. Scale 1:24,000.

Thwaites, F. T. 1923. The Paleozoic rocks found in deep wells in Wisconsin and northern Illinois. The Journal of Geology 31(7):529–555.

Ulrich, E. O. 1920. Major causes of land and sea oscillations. Journal of the Washington Academy of Sciences 10(3):57–78.

Ulrich, E. O. 1924. Notes on new names in table of formations and on physical evidence of breaks between Paleozoic systems in Wisconsin. Transactions of the Wisconsin Academy of Sciences, Arts and Letters 21:71–107.

Wanenmacher, J. M. 1932. The Paleozoic strata of the Baraboo area, Wisconsin. Dissertation. University of Wisconsin, Madison, Wisconsin.

Wanenmacher, J. M., W. H. Twenhofel, and G. O. Raasch. 1934. The Paleozoic strata of the Baraboo area, Wisconsin. American Journal of Science (5th series) 28(163):1–30.

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.