Sunday, August 19, 2018

Your Friends The Titanosaurs, part 3: Andesaurus, Antarctosaurus, and Argentinosaurus

Plenty of name recognition as far as titanosaurs go in this post of "Your Friends The Titanosaurs", which features Argentinosaurus huinculensis as leading contender for the dinosaur heavyweight crown, Antarctosaurus wichmannianus as one of the most historically important and troublesome titanosaurs, and the somewhat less well-known but supremely steady Andesaurus delgadoi. Three questionable species of Antarctosaurus have been held over for next time.

Sunday, August 12, 2018

Lower Decorah trilobites

Following last week with Strophomena, and having figured out what seems to be a good method of photographing small specimens, I thought I'd try my hand at photo-documenting and identifying some trilobites. The sample set is mostly limited to the lower third to lower half of the Decorah Shale of St. Paul, and the most relevant publications for these trilobites are DeMott (1987) and Rice and Hedbloom (1987); Midwest Paleo also has a fine photo-atlas and list. I'm reasonably satisfied that my identifications at the family or subfamily level are accurate. Genus, I'm not so keen on. Species, I didn't even dare; I would be just parroting.

Sunday, August 5, 2018

Big Ordovician brachiopods: Strophomena and friends

Starting out in the Ordovician rocks of Minnesota and surrounding states, you run into a few kinds of fossils right away. Depending on the rocks you're looking at, these might include nut-like small brachiopods, fragments of branching bryozoans, ring-like or gear-like crinoid columnals, snail shells, conical horn corals and so on. Among the most noticeable of the common fossils are larger D-shaped shells, up to a few cm across. We've encountered these large shells a few times before in the Platteville and Decorah; they are the shells of brachiopods in the Order Strophomenida, one of the most abundant and diverse groups of brachiopods. To avoid any confusion with Strophomenida, Strophomenoidea, Strophomenidae, etc., and because we're all friends here, we'll just call these large shells "strophs". There are also smaller members of Strophomenida, but we'll leave them be for the present.

A good-sized brachial valve of a stroph in exterior view, embedded in a slab. On the left (A) is the valve viewed from the top, while on the right (B) is the profile, showing how steeply convex it is. Because of mud, this was the only fossil I could see on the slab when I picked it up, but the high profile of the shell clued me in.

Sunday, July 29, 2018

Lingwulong shenqi

After our latest titanosaur entry and a week off, here's... another sauropod. This one's different though: it comes from early on in the history of sauropods, and shines a light on the early diversification of the group. I introduce Lingwulong shenqi, debuting as the world's oldest known dicraeosaurid at somewhere around 175 million years old, and the first substantiated dicraeosaurid from Asia. These "oldests" and "firsts" are more important than they might sound.

Sunday, July 15, 2018

Your Friends The Titanosaurs, part 2: Aeolosaurus

Aeolosaurus is one of those dinosaurs that is referenced fairly often in the literature, but has not left a strong impression with non-specialists, kind of like a character actor who's appeared in dozens of movies and TV shows over the years. The name rings a bell, but it's hard to recall much detail. It's easily the least familiar dinosaur to have both a namesake clade (Aeolosauridae/Aeolosaurinae/Aeolosaurini, depending on your taste, with the last being the most commonly used) and three valid species. It's not Aeolosaurus's fault, after all, unless you want to blame it for its habit of bequeathing only bits of tails to posterity. If you saw one amble by, you would definitely remember it.

However, there are good reasons why Aeolosaurus keeps on making cameo appearances: it and its closest relatives have very distinctive caudal vertebrae, and these vertebrae are fairly common in rocks covering the last 15+ million years of Argentina and southern Brazil. Because of my caution regarding titanosaur divisions, I haven't added a formal Aeolosaurini to my own files, but there certainly appears to be a group of South American titanosaurs with distinctive Aeolosaurus-like caudal vertebrae. For the purposes of this post I'm happy to refer to them as aeolosaurinids. I'm not going to get into detailed diagnoses, but I *will* briefly describe these caudals. If nothing else, they're the thing to remember about Aeolosaurus and aeolosaurinids:

In titanosauriformes, the neural arches of the caudal vertebrae have a tendency to creep up on the anterior part of the centra, rather than being centered. Aeolosaurinids take this even farther, with the articulating processes, the prezygapophyses and postzygapophyses, swept forward by the general excitement and the neural spines sometimes directed anteriorly as well. In Aeolosaurus this can be exaggerated to the point that the postzygapophyses are as far forward as the anterior margin of the centrum (Martinelli et al. 2011), which means that the prezygapophyses have to be stretched over nearly the entire preceding centrum to reach their articulations with the postzygapophyses (the exact positions of the processes vary along the tail; Santucci and de Arruda-Campos 2011). You might think of the prezygapophyses as something like stereotypical Frankenstein arms or sleepwalker arms, sticking way out in front of the rest of a vertebra. The figure below probably does a much better job of demonstrating:

Caudals from several aeolosaurinids, from Martinelli et al. (2011), showing how the neural arch and its processes are shifted to the anterior end of the centrum. It also shows the procoelous nature of titanosaurian caudals, a style of ball-and-socket articulation with the socket in front and ball in back. In Aeolosaurus this is not a perfect ball, but skewed dorsally. Anterior is left and posterior is right, in case you need the orientation. "MPMA\without number" is actually part of the holotype of Aeolosaurus maximus, so all three named species are supposedly included, but the specimen labeled here as "MPMA\without number" actually appears to be CPP 248 (supposedly C) per an earlier figure in the publication. Could C and D be mixed up?

Sunday, July 8, 2018

Fun with nautiloids: an essay in futility?

Or: "What good is a seven-foot nautiloid?"

In most reconstructions of marine Paleozoic life, large orthoconic (straight-shelled nautiloids) get two jobs: they are either large menacing objects in the water, usually seizing some unfortunate trilobite; or they are parked on the seafloor, again often engaged with a trilobite. The general takeaway is that a giant nautiloid was a voracious predator. Trilobites presumably are selected as the prey because so few other animals that lived during the heyday of the giant nautiloids both moved under their own power and were bigger than a few inches, making them about the only group worthy of the honor of artistic predation (although we can guess that a not-insignificant part of a giant predatory nautiloid's diet would be smaller nautiloids). Another, less scientific reason for having a nautiloid capture a trilobite is that otherwise Paleozoic marine reconstructions would be a whole lot of small filter-feeding animals not going anywhere, which doesn't make for dramatic art.

Nautiloids and trilobites: natural enemies forever locked in combat. Also pictured: many snails.

Sunday, July 1, 2018

Fossil Bison of the National Park Service

Last year for Fourth of July week I put up a post on dinosaurs of the National Park Service. With the same time of year upon us, I thought I'd try something similar. Now, we haven't had all that much change in NPS dinosaurs over the past year, but there's something else that's even more appropriate: bison. Cue the map!

For this map, parks with paleontological materials of bison are indicated, with two questionable occurrences (18 and 32) represented by gray question marks. See text for caveats. 1. Lava Beds National Monument; 2. Golden Gate National Recreation Area; Santa Monica Mountains NRA; Joshua Tree National Park; 5. Nez Perce National Historical Park; 6. Craters of the Moon National Monument & Preserve; 7. Yellowstone NP; 8. Fossil Butte NP; 9. Timpanogos Cave NM; 10. Arches NP; 11. Glen Canyon NRA; 12. Zion NP; 13. Tule Springs Fossil Beds NM; 14. Lake Mead NRA; 15. Grand Canyon NP; 16. Great Sand Dunes NP & Preserve; 17. Chaco Culture NHP; 18. Gila Cliff Dwellings NM; 19. White Sands NM; 20. Bering Land Bridge National Preserve; 21. Yukon-Charley Rivers National Preserve; 22. Denali NP & Preserve; 23. Theodore Roosevelt NP; 24. Wind Cave NP; 25. Badlands NP; 26. Missouri National Recreational River; 27. Tallgrass Prairie National Preserve; 28. Lake Meredith NRA and possibly Alibates Flint Quarries NM; 29. Waco Mammoth NM; 30. Padre Island National Seashore; 31. Ice Age National Scientific Reserve (affiliated); 32. Valley Forge NHP.

For bison, I'm not quite as confident with my records as I am for, say, mammoths or sloths or dinosaurs. In large part this is because bison are relative latecomers to North America and their record goes to the present. If you've got a random mammoth bone, nobody's going to blink an eye if you call it "Pleistocene", but a random bison bone is not so indicative. There are probably isolated occurrences of fossil material that I don't know about because they've been classified as recent or not classified at all. In addition, some researchers are strict about not considering specimens paleontological if they are more recent than a certain age, whereas I am not so strict about the Holocene. (Of course, then you get into the overlap with archeology.) Therefore, the list I have is subject to change. At this time, perhaps the most notable occurrence from these 32 parks is an early Holocene bison bonebed found in the Wisconsin side of Interstate State Park, one of the units of affiliated Ice Age National Scientific Reserve (I plan to cover it in more detail at another time). Otherwise, the record of NPS fossil bison is mostly isolated, incomplete material, with some bison dung in cave settings.

Distribution is dominated by parks west of the Mississippi, particularly those larger than a few hundred acres. There are some not currently listed, such as Big Bend NP, Death Valley NP, and Glacier NP, that would not surprise me if they eventually are added. East of the Mississippi we don't have as many large parks, and there's a definite tendency for large mammal records to come from caves, so I would expect to add some of the parks with caves over time.

Or maybe I should look at some of the coastal parks. From O. P. Hay's 1923 catalog of eastern North American Pleistocene finds (extant B. bison gets the next map in the volume).

One of the things you will encounter with the genus Bison in North America is the usual complicated taxonomy. The exact timing of the arrival of Bison in North America is not certain, but bison were established by at least 160,000 years ago. Bison arrived as Bison priscus, the widespread Steppe bison, which was not unlike the modern bison. B. priscus evolved into B. latifrons, which can be distinguished by its large size and enormous horns, and B. antiquus, which was not quite so large nor extravagantly equipped with horns.

For B. latifrons, there was never such a thing as having too much horn. Cincinnati Museum of Natural History & Science mount, photo by James St. John via Wikimedia Commons.

B. latifrons went out of the picture during the most recent Ice Age (a unique sense of timing compared to all of the species that went extinct right after), but B. antiquus was still there to carry the bison banner. B. antiquus in turn evolved into the yet smaller B. bison in the early Holocene, about 10,000 years ago. The transitional phase is sometimes described as another species (or subspecies), B. occidentalis. We ran into B. occidentalis way back in early 2014 on I-35E, and this is also the form that has been identified at the Interstate State Park bonebed.

Sunday, June 24, 2018

Regarding forams

Life started out microscopic (at least to humans) and most of it has stayed that way. Of course, many microscopic organisms have poor fossil records, due to factors like lack of hard parts and the whole "microscopic" thing (finding and studying microfossils takes special equipment and expertise that aren't used for collecting, say, brachiopods). However, a subset of microscopic organisms have very significant fossil records. We saw the ostracodes a few years ago, but there are also a number of groups of single-celled organisms that produce hard parts suitable for fossilization. Among the most important are: coccolithophores, phytoplankton which form skeletons of scale-like objects known as coccoliths, micron-scale structures that make up chalk (and which are sometimes called nannofossils because they're so darn small); diatoms, phytoplankton with cell walls made of silica; dinoflagellates, which form organic-walled cysts; radiolarians, protozoans that form body structures of silica; and the subjects of today's entry, the foraminifera, which can be described glibly as "amoebas with shells".

A living foram, the brackish-water benthic calcareous species Ammonia tepida, showing strands of pseudopodia surrounding the coiled test. What do all these terms mean? Read on! (Photo from Wikimedia Commons; unfortunately, no scale, but you'll get an idea of the size of what we're dealing with in the photos to come.)

Sunday, June 17, 2018

Your Friends The Titanosaurs, part 1: Adamantisaurus, Aegyptosaurus, and Ampelosaurus

This is the first in what I plan as a periodic ongoing series. The response from this year's two previous titanosaur posts was better than I expected, especially considering what I thought was some dry subject matter, so if people are liking the big lugs, why not have them around more often? There are certainly plenty of species, and hopefully they don't become overwhelming if they feature once a month or so, when some other topic isn't coming together. The plan is to briefly cover three species in a post, in more or less alphabetical order. For example, in this post we have Adamantisaurus mezzalirai, Aegyptosaurus baharijensis, and Ampelosaurus atacis, taking us from Brazil to Egypt to France. The third species would have been Aeolosaurus colhuehuapensis, but because there are three species of Aeolosaurus I thought it made sense to hold it back and make the next post all Aeolosaurus. The next one would have been Alamosaurus sanjuanensis, but I have other plans for it. Therefore, Ampelosaurus atacis gets the call.

Sunday, June 10, 2018

Postglacial fragments, featuring Hartman's Cave

Although eastern North America contains many things, it is not noted for its terrestrial Cenozoic sedimentary deposits. Conditions just weren't favorable for the long-term preservation of extensive terrestrial sedimentary formations. Therefore, our knowledge of terrestrial life in this region is largely confined to some transitional coastal settings and what we might call "point sources" in comparison to the great formations of the West: sedimentary deposits of caves, fissures, bogs, ponds, and so on. These in turn are strongly biased to just the Pleistocene and Holocene. We've visited a few of these sites before, around Minnesota (Hidden Falls, I-35, Kirchner Marsh, Loring Park, and in general), and in the District of Columbia, Kentucky (Mammoth Cave), and Pennsylvania (Marshalls Creek Mastodon, Port Kennedy Bone Cave). Here is another site in northeastern Pennsylvania, plus some brief commentary on sites nearby.

Sunday, June 3, 2018

Bagualosaurus agudoensis: another sauropodomorph ahead of its time

Our subject today is the newly described Bagualosaurus agudoensis from lower Upper Triassic rocks of southern Brazil. If I'd known back in March 2016 that I'd have the opportunity in a couple of years to write about another "prosauropod" that was "ahead of its time", and that it would include a partial skull justifying a terrible "head" pun, maybe I'd have come up with another title then. Oh, well; spilled milk and all that.

Sunday, May 27, 2018

Midwest Ordovician craters: Decorah and Rock Elm

Life in the Ordovician of the Upper Midwest wasn't all warm tropical seas and all the organic particles you could filter. We've already run into giant volcanic eruptions spreading ash far and wide. There was also a significant glaciation at the end of the Ordovician; the ice itself didn't get to tropical North America, but it did lead into major extinctions. We don't have to go to the poles or volcanoes off the coast of North America for dramatic geologic events, though: we only have to go as far as west-central Wisconsin and northeastern Iowa.

Sunday, May 13, 2018

The secret identity of "Agathaumas"

If you've been at this dinosaur thing for a while, you've probably encountered this piece of Charles Knight artwork, labeled as Agathaumas:

Agathaumas, Charles Knight's work via Wikimedia Commons.

Sunday, May 6, 2018

Titanosaurs in time and space

Nothing too earth-shattering this week, just an adjunct to "Titanosaurs all the way down" featuring these lovingly crafted charts of titanosaur distribution taken from The Compact Thescelosaurus (so you know all mistakes are mine). Given 101 described species to work with, I split the titanosaurs between South America and all of the other landmasses. As with other charts, you'll need to click to embiggen.

Sunday, April 29, 2018

Tracking sloths and people at White Sands National Monument

Earlier this week came some of the biggest news concerning National Park Service paleontology in quite some time: the discovery of tracks, including overlapping tracks, of extinct ground sloths and humans at White Sands National Monument, New Mexico. These finds were published in an article by Bustos et al. (2018), which can be accessed here (don't forget the supplement; less technical summary here). It's a pretty darn substantial way of showing humans and extinct sloths as contemporaries, and new evidence on the early history of humans in the Americas and the twilight of the Pleistocene megafauna. About the only ways you could make the tracks more notable would be to have them continue into the end of a hunt, or to have some dateable material that placed them significantly pre-Clovis.

Part of Figure 2 from Bustos et al. (2018). Part B has some faint sloth tracks (when poorly preserved, it can be difficult to distinguish similarly sized human and sloth tracks). Part C shows a "flailing circle" where a sloth appears to have swung its arms at a human. Part E shows a human track inside a much larger sloth track.

Sunday, April 22, 2018

Foerstediscus splendens, a Minnesotan in Washington

Because I was in northern Virginia, I thought I'd visit the National Museum of Natural History. While nosing around the Ocean Hall, I ran into another Minnesotan: the holotype specimen of the edrioasteroid Foerstediscus splendens (Bassler 1936). I couldn't get right up to due to the glass, so the photos aren't the clearest and there's no scale, but it's still a fine specimen, and somewhat larger than I expected following my experience with the minuscule Pyrgocystis (for reference, it's described as 3 cm across, a little more than an inch).

Points to you if you too noted "Middle Ordovician"; with redefinition and redating of the Ordovician, "Late Ordovician" would be more accurate.

Here's a closer view of the specimen. "S. 4079" is the Smithsonian's number; it was originally a University of Minnesota specimen, UMPC 4742a, but it was donated to the Smithsonian (Rice 1990). From my own experience with the UMPC fossils, I think all of the edrioasteroids they had on hand by approximately the mid-1930s went to the Smithsonian at Bassler's request, with the specimens I photographed coming with Sardeson's collections a few years later.

"Edrioasteroid" means "seated star", which is reasonably self-explanatory.

Edrioasteroids are among the rarest fossils from the Decorah and Platteville formations of Minnesota, with their other competition in that category being other echinoderms such as sea stars and cystoids. Seeing as how these fossils are very rare here except in certain places such as the former Johnson Street Quarry, the obvious scenario is that non-crinoid echinoderms only thrived under certain conditions that are poorly represented in the known outcrops of the Platteville and Decorah. (Alternatively, they *were* more common than we know, but they decomposed so completely to their constituent plates that they've been unrecognizable; be that as it may, though, the Platteville/Decorah echinoderm diversity doesn't seem to be as high as in other formations of similar age in the central US.)

Foerstediscus splendens was collected from the Ford Plant (Bassler 1936). Work on the Ford Plant, Ford Bridge, and Ford Dam (Lock and Dam No. 1) in the 1920s made that area a great place for collecting, as discussed in this post. Clinton R. Stauffer named 56 species of microfossils from collections at the bridge (Stauffer 1933, 1935), and August Foerste named the nautiloid Metaspyroceras perlineatum (Foerste 1932) from the vicinity of the plant and dam. F. splendens was found by Irving G. Reimana from the top of the Rhinidictya bed of the Decorah Shale (Bassler 1936), otherwise known as Bed 4 (Sloan 1987), or, a little more informally, the lower third of the Decorah Shale above the Carimona Member. (One of these days I ought to outline the bed divisions.) In more practical terms, Bed 4 is the Decorah you see at Shadow Falls, so the top of Bed 4 would be somewhere at or a little higher than the highest part of the ravine. Strangely, Stauffer and Thiel (1941) attributed Foerstediscus to the underlying Carimona Member, or Bed 3, despite Stauffer presumably being the one who gave Bassler the stratigraphic information in the first place.

Looking east from Minnehaha Park in June 2013, toward the defunct Ford Plant (across Lock and Dam No. 1, aka the Ford Dam).

The closure and dismantling of the Ford Plant over the past few years provide an unusual opportunity to look at current events in a geological frame of mind. The Ford Plant was a fixture of southwestern St. Paul for decades (and it happened to be there because there was a young river gorge carved by a post-glacial waterfall that could be harnessed for hydroelectric power, and because there was once a pure sandy beach that could be turned into auto glass). Its day is now over, though, and soon its former grounds will be rebuilt into something entirely different. Ten thousand years ago, mammoths and giant beavers roamed its grounds. Seventy million years ago it was probably a coastal plain near a sea filled with ammonites and marine reptiles. 454 million years ago edrioasteroids, nautiloids, and other marine invertebrates lived and died in a shallow tropical sea that had submerged the pure sandy beach. Underneath all of it are volcanic rocks more than a billion years old that fill a scar from Michigan to Kansas. Every part of history is made up of what came before it, and shapes what comes after it.

References

Bassler, R. S. 1936. New species of American Edrioasteroidea. Smithsonian Miscellaneous Collections 95(6).

Foerste, A. F. 1932. Black River and other cephalopods from Minnesota, Wisconsin, Michigan and Ontario (Part 1). Denison University Scientific Laboratories Journal 27:47–137.

Rice, W. F. 1990. Catalog of paleontological type specimens in the Geological Museum, University of Minnesota. Minnesota Geological Survey, St. Paul, Minnesota. Information Circular 33.

Sloan, R. E. 1987. History of study of the Middle and Late Ordovician rocks of the Upper Mississippi Valley. Pages 3–6 in R. E. Sloan, editor. Middle and Late Ordovician lithostratigraphy and biostratigraphy of the Upper Mississippi Valley. Minnesota Geological Survey, St. Paul, Minnesota. Report of Investigations 35.

Stauffer, C. R. 1933. Middle Ordovician Polychaeta from Minnesota. Geological Society of America Bulletin 44(6):1173–1218.

Stauffer, C. R. 1935. The conodont fauna of the Decorah Shale (Ordovician). Journal of Paleontology 9(7):596–620.

Stauffer, C. R., and G. A. Thiel. 1941. The Paleozoic and related rocks of southeastern Minnesota. Minnesota Geological Survey, St. Paul, Minnesota. Bulletin 29.

Sunday, April 8, 2018

Phycodes: bundles of burrows

I'm going out of the office again, so, like last year, I'm tossing up a few pictures of something I find interesting, in this case an invertebrate trace fossil called Phycodes (not to be confused with Phycodes the moth). I touched on Phycodes briefly a few years ago, using the image included below:

That pale gray color is characteristic of the Brickyard in Lilydale, for whatever reason(s).

The whole piece looks like this:

"Licrophycus ottawaensis" in older literature.

I collected it on a Geological Society of Minnesota visit back in 2006 and it has since become one of the pieces I like to take to events because it's a great teaching fossil. I ask people what it is and let them explain their choice if they want to, and then I identify it. I get a lot of plant-based guesses (which of course is what a lot of paleontologists and geologists thought this kind of structure was decades ago). What Phycodes really is is an invertebrate trace fossil recording the behavior of some kind of wormy animal probing in the mud for food and returning to a central point. This resulted in splayed bundles of burrows, giving the trace fossil a characteristic root-like or mop-like appearance. It doesn't have quite the oomph of a dinosaur bone, but it looks interesting, it's good for conversation, and worms are more familiar than, say, crinoids.

When space is an issue, I have a more compact specimen.

Phycodes turns up every so often in the Decorah. It's not as common as Rauffella (which has turned up in a half-dozen posts so far), but it certainly makes a striking fossil.

Suitable for framing: this chunk is almost entirely Phycodes, with little matrix, which also makes it more fragile than the first two specimens (too bad, because it's also the best). The individual tubes are a bit smaller in diameter than those of the first two as well.

The makers of Decorah Phycodes differed from the makers of Rauffella in a couple of notable ways: Phycodes-makers were smaller (a few mm in diameter versus finger thickness for many Rauffella) and apparently smoother (no surficial striations in Phycodes).

This piece is one of the group from the construction site last year. I'm not certain what kind of ichnofossil it is. It resembles Phycodes templus, but it's also kind of poorly preserved and it's not clear if the burrows are bundled, so it might not be Phycodes at all. (Another possibility is poorly preserved "Camarocladia".) Note the brassy ooids.

Saturday, March 31, 2018

"Prorichthofenia": brachiopod horn corals

April Fools' Day not only falls on a weekend this year, but Easter, so I wouldn't be surprised if the typical crop of spoof news articles and blog entries is thinner due to other time commitments. Not that I mind too much; the whole thing gets old, year after year. Still, with April 1 in mind, here are some fossils that aren't what they seem: brachiopods from the Permian of Texas that put a lot of effort into being horn corals.

Sunday, March 25, 2018

Three weeks of ankylosaurs and pterosaurs

March has been busy over at The Compact Thescelosaurus, with ten new entries adding three ankylosaurs, four pterosaurs, and three theropods. There's still a week to go, too. Sometimes people talk about following taxonomy as another kind of stamp collecting. I have a more artistic point of view, with each specimen as more along the lines of tiles in an incomplete mosaic or notes in an unfinished song, each contributing to a greater whole. It just so happens that the currency of the realm is in species and genera. (I also keep track because you can't tell the players without a program!) As usual, I'll leave the theropods to others, except to say that it's nice to see Arkansaurus finally graduate from informal name to the big leagues, thanks to Hunt and Quinn (2018) (the name has figured in print since 1983, after all). A few comments on the ankylosaurs and pterosaurs:

Sunday, March 11, 2018

Marshalls Creek Mastodon

This is something of an apology. I gave a paleontological presentation for the folks at Delaware Water Gap National Recreation Area last September, and after I finished someone brought up the Marshalls Creek Mastodon. I'd been focusing on other topics, so the mastodon hadn't made the cut (for shame on my account!). I am now remedying that omission. For the rest of you who haven't been introduced to the fossil in question, you can also find accounts in Hoff (1969, 2001), which are my primary sources. The Monroe County Historical Association also has a brief online account.

Sunday, March 4, 2018

Jinyunpelta

Ankylosaurs have had a good few weeks, publicity-wise. First we get some actual science done on the long-held belief that they were prone to "bloat and float" (if you don't like to contemplate recently deceased animals, I will simply say yes, it looks pretty good; if you'd like a less-technical summary, go here). We've also now got the oldest record of a true tail club, wielded by the newly minted Jinyunpelta sinensis.

Sunday, February 25, 2018

Rectogloma problematica

What sounds like a kidney disorder, looks kind of like a flattened straight nautiloid possibly with a little curl (or maybe a Devonian Hot Pocket), and remains enigmatic more than a century after its description? It's Rectogloma problematica, which illustrates that even though we're past the Cambrian, the fossil record can still throw some oddballs.

From Van Tuyl and Berckhemer (1914). It's difficult to maintain "natural size" a few generations removed from original illustrations; this is one reason why you should use scale bars instead!

The only reported specimens of Rectogloma problematica were collected by Columbia University students on a field trip to the Delaware Water Gap area. They were found in red shale in the Upper Devonian Catskill Formation in a cut along the Delaware, Lackawanna & Western Railroad near the Henryville station, per Van Tuyl and Berckhemer (1914) ["Henrysville" of their spelling]. The fossils were discovered by Van Tuyl and another student, C. W. Honess, which just goes to show that you should always pay attention on field trips. A couple of the better specimens were collected, and have today made their way into the collections of the American Museum of Natural History (AMNH FI 22377A and B).

The fossils, as illustrated and described by Van Tuyl and Berckhemer (1914) and Conway Morris and Grazhdankin (2005), are a few cm long, roughly rectangular but broader at one end than the other, and have an oval cross-section. They were found oriented vertically, with the wide end pointed up, which as noted by Conway Morris and Grazhdankin (2005) indicates that they are not flattened by compression, but really did have an oval cross-section in life. The broader "sides" are marked with numerous parallel lines 1 to 3 mm apart, each gently arched. Van Tuyl and Berckhemer (1914) described them as "sutures", but they don't go all the way around the fossil. Only one of the two presumed "ends" can be seen in the fossils, so it's not known how the wide end, er, ended. The other end that *can* be seen is also controversial. Van Tuyl and Berckhemer (1914) illustrated a sort of "spit curl" or coil coming off an otherwise rounded termination, but Conway Morris and Grazhdankin (2005) could not confirm this.

Figuring out what Rectogloma problematica is has proven difficult. Van Tuyl and Berckhemer (1914) thought it kind of resembled an abnormal cephalopod, but noted that the incomplete "sutures", lack of a siphuncle, and undivided coil argue against this. (Incidentally, a putative second species, "Rectogloma" zaplensis Turic et al. 1982, did prove to be a nautiloid [Cichowolski 2008].) Knight (1941) noted that it only superficially resembled a gastropod, which is true, but at the same time it's unclear who thought it was a gastropod to start with. Knight instead thought it was more likely a coprolite, which he repeated in 1960 (Knight et al. 1960). While the specimens do indeed appear to be reasonably poop-shaped lumps in basic form, it is rather difficult to produce droppings with smooth sides marked by closely spaced parallel thin features that do not continue all the way around, and a coprolitic identity has been rejected (Häntzschel 1975; Conway Morris and Grazhdankin 2005). Conway Morris and Grazhdankin (2005) did not make any firm classifications; about all they were willing to say was that it may have been "some sort of tube, with a relatively thick wall" of unknown composition. The apparent rarity of Rectogloma fossils and absence of obvious relatives suggest to me that Rectogloma lacked mineralized structures and just lucked out this one time in terms of fossilization. The "sutures" seem more like slits or structural features involved in flexure. Maybe it was some kind of tubular or goblet-like soft-bodied creature, stuck to the sea floor? Or perhaps some kind of fish egg case?

References

Cichowolski, M. 2008. The orthocerid Dawsonoceras? (Nautiloidea) from the Lipeón Formation (Silurian), northwestern Argentina. Ameghiniana 45(4):791–793.

Conway Morris, S., and D. Grazhdankin. 2005. Enigmatic worm-like organisms from the Upper Devonian of New York: an apparent example of Ediacaran-like preservation. Palaeontology 48(2):395–410.

Häntzschel, W. 1975. Treatise on invertebrate paleontology. Part W. Miscellanea. Supplement I. Trace fossils and problematica. Geological Society of America, Boulder, Colorado, and University of Kansas Press, Lawrence, Kansas.

Knight, J. B. 1941. Paleozoic gastropod genotypes. Geological Society of America Special Paper 32.

Knight, J. B., R. L. Batten, E. L. Yochelson, and L. R. Cox. 1960. Supplement. Paleozoic and some Mesozoic caenogastropoda and Opisthobranchia. Pages I310–I331 in R. C. Moore, editor. Treatise on invertebrate paleontology. Part I. Mollusca 1. Geological Society of America, Boulder, Colorado, and University of Kansas Press, Lawrence, Kansas.

Turic, M. A., V. A. Ramos, and J. Oliver Gascón. 1982. "Rectogloma" zaplensis (problemática) de la Formación Lipeón, Provincia de Jujuy, Argentina. Revista del Instituto de Ciencias Geológicas 5.9–14.

Van Tuyl, F. M., and F. Berckhemer. 1914. A problematic fossil from the Catskill Formation. American Journal of Science, 4th series, 38:275–276.

Sunday, February 18, 2018

Identifying invertebrate fossils

Pop quiz! (don't worry, it's not for credit)

Romance *and* brachiopods

Here we have an assortment of fossils, tastefully arranged in a holiday-appropriate setting. They're all the typical local Ordovician stuff, but many Paleozoic shallow marine formations will have a lot of the same general things. What are they, and how can you tell?

Sunday, February 11, 2018

Titanosaurs all the way down

There are a lot of titanosaurs. Over at The Compact Thescelosaurus, there are currently 101 species within Titanosauria, and another 30 non-titanosaurian somphospondyls, which probably include a few things that will be eventually be classified within Titanosauria. (If you're unfamiliar with the term, "somphospondyls" will take some explanation, which I'll get to in a minute; also, "somphospondyl" is a truly unappealing word.) Together they make up a little less than nine percent of the dinosaur chart. Also, as of this weekend, I've removed all of the internal divisions in Titanosauria; it's just titanosaurs all the way down. This is not an admission that all titanosaurs were alike, but rather a recognition that we are still a long way from knowing how they were related to each other.

Sunday, February 4, 2018

The League of Saint Croix

If we can have a "Club Late Ordovician", surely we can have something for those National Park Service units with late Cambrian fossils? Of course it can't just be "Club Late Cambrian". Given that this part of the Cambrian is historically known as the Croixan or St. Croixan (Walcott 1912), it seems fitting to work St. Croix in there somewhere. Therefore, I present the League of Saint Croix. If you're working with a name like "St. Croix", you might as well make it sound like some kind of late Middle Ages/early modern period European military order or alliance.

Sunday, January 28, 2018

Practical guide to St. Croix Valley sedimentary formations

Now that I've seen a fair amount of the Cambrian rocks of St. Croix National Scenic Riverway and the St. Croix Valley, it seems like a good time to set them out as was done for the MNRRA formations. This time around, we'll go to the base of the Cambrian sequence in Minnesota/Wisconsin and work our way up to where the sequence overlaps with the MNRRA rocks. One day I'll have to get into southeastern Minnesota and complete the Paleozoic sequence with the rest of the Ordovician and the Devonian.

As with the MNRRA formations, we're covering a fairly narrow span of time. The Cambrian formations were all deposited between about 500 to 491 million years ago based on biostratigraphic correlations. This includes some unconformities. One other note: I'm working from the Minnesota side of the St. Croix River, and I'm most familiar with the Minnesota names. Mossler (2008) harmonized the stratigraphic nomenclature of Minnesota's Paleozoic rocks with the schemes used in neighboring states, but there is still one difference: the Minnesota Geological Survey uses lithological terms in formation names, while the Wisconsin Geological & Natural History Survey doesn't. The upshot is slightly different names. For example, the units called the Jordan Sandstone and Oneota Dolomite on the Minnesota side of the river are called the Jordan Formation and Oneota Formation on the Wisconsin side. There isn't really a practical difference; the names just look different. In ascending order, the rock units we're most concerned with are the Mount Simon Sandstone, Eau Claire Formation, Wonewoc Sandstone, Tunnel City Group, St. Lawrence Formation, and Jordan Sandstone.

Sunday, January 14, 2018

Diluvicursor

Pride of priority for the first new nonavian dinosaur of 2018 (not counting any of those "available online before 2018 but not in print" guys) goes to Diluvicursor pickeringi, a small ornithopod from Australia. It's the kind of dinosaur that would have been called a hypsilophodont 20 years ago, which means today there's always a chance it ends up outside of Ornithopoda or within Iguanodontia. (Honestly, if your phylogenetic analysis puts all of the old-time hypsilophodonts outside of Ornithopoda, you might as well just abandon the name "Ornithopoda" and go with Iguanodontia for the remainder.)

Sunday, January 7, 2018

Crystal Ball for 2018

For 2018's first post, I once again peer into the mists of futurity and offer dinosaur-centric predictions on the year to come.

Will I once again be called upon to fight a mammoth inside a building? Well, that's always the dream.