Sunday, August 21, 2016

Champsosaurus: Adventures in 19th century taxonomy

It all started innocently enough with a couple of paragraphs in the 1870 Proceedings of the Academy of Natural Sciences, submitted on behalf of Joseph Leidy. The item notes that Leidy had received a reptilian vertebral centrum (the body of the vertebra, minus all the processes and such) collected by Ferdinand Vandeveer Hayden from the Moreau River, probably from Cretaceous rocks. It reminded Leidy of the vertebrae of marine reptiles, specifically Nothosaurus, so he proposed to name it Nothosaurops, type species N. occiduus. So far, so good. He got around to a longer description in 1873, in which he mostly repeated the 1870 information, but also included some figures of the fossil. Unfortunately, somebody goofed, because the text refers to something called Nothosaurus occiduus, but the plates and captions are using Nothosaurops occiduus. This would not be of much modern interest except for the fact that there is a good chance the specimen is the first described fossil of Champsosaurus.

Sunday, August 14, 2016

Fort Union Trading Post National Historic Site

About a week ago I returned from Fort Union Trading Post National Historic Site, where I'd been dispatched on official business. Fort Union Trading Post NHS, not to be confused with Fort Union National Monument in New Mexico, is located just north of the Missouri River on the North Dakota–Montana border. The reconstructed trading post itself is in North Dakota, but just barely; you can park in Montana and walk to it in less than five minutes (and gain an hour doing so, because you're also crossing time zones. Watch out for time paradoxes!). The fort was established for the American Fur Company in 1828 and lasted until 1867, after the fur boom years had passed. When people talk about forts in the American West, they often conjure images of cavalry, cattle, covered wagons, warfare with Native Americans, and so on. Fort Union, although it has appropriate prickly pears and yucca, was not a military post, although some of its building materials did become part of the Army's Fort Buford just down the river. Instead, as the name makes plain, it was a trading post, where Native Americans from many tribes traded furs for goods. At the time, it was ideally situated right above the Missouri River, but rivers get restless and this one has moved well south on its floodplain. Fort Union itself is not a hotspot for finding fossils, although an occasional inch-scale fragment of petrified wood can be seen, not an unusual thing for North Dakota (and if you do visit the fort and see such a piece, please don't take it!). However, the fort has a place in the historic development of North American paleontology.

Most of Fort Union from just outside the southwest bastion
 
This all goes back to a fortunate convergence of geography and company policy.  The AFC, via the Chouteau family, was noted for its support of artists and scientists, including such notables as John James Audubon, George Catlin, Joseph Nicollet, and Prince Maximilian of Weid, and encouraged their activities (Chaky 2015). Alexander Culbertson, the bourgeois (or manager) of Fort Union from 1837 to 1847, at times traveled from Fort Union to Fort John on the Laramie River, via Fort Pierre in what is now South Dakota. Fort John is better known as Fort Laramie, which incidentally also did not start out as an Army post, but as a fur trading post. It only became an Army post in 1849. The Fort Pierre–Fort John route took him across the Mauvaises Terres (spelled various ways in various sources), today better known as the White River Badlands. On these trips, he would occasionally collect fossils. He is probably the source of the first scientifically reported Badlands fossil, a jaw fragment which became named Paleotherium prouti and which is now known to have belonged to a brontothere (Wischmann 2000). He definitely provided the fossils that Joseph Leidy described as Poebrotherium wilsonii (a camel) and Merycoidodon culbertsonii (an oreodont, in fact "the" oreodont) (Chaky 2015), kick-starting vertebrate paleontology in the Badlands and west of the Mississippi in general. Early press on these finds in the late 1840s attracted other geologists. Among them was David Dale Owen, at that time working on a survey of Iowa, Minnesota, and Wisconsin. He dispatched subordinate John Evans to the Badlands in 1849. Evans returned with another load of vertebrate fossils which was sent to Leidy, whose descriptions of the bones makes up a chapter in Owen's massive 1852 survey publication. The AFC got into the act by sending Alexander's brother Thaddeus with another group in 1850 to make additional collections. In 1853 there was even an early foretaste of the Bone Wars when a government railroad survey crew including Evans butted heads with Ferdinand Vandeveer Hayden and Fielding Bradford Meek (Chaky 2015).

Another lasting trace of the early paleontological work in the area is the name of a rock unit that is commonly exposed in western North Dakota and eastern Montana: the Fort Union Group (North Dakota Geological Survey name) or Fort Union Formation (Montana Bureau of Mines and Geology name). This Paleocene-age sedimentary unit is the source of the Wannagan Creek fossils which can be viewed at the Science Museum of Minnesota, and makes the picturesque badlands of Theodore Roosevelt National Park and Little Missouri National Grassland. It does not appear to be exposed within Fort Union Trading Post NHS, although it is exposed in the uplands just beyond. Hayden used Fort Union as his base of operations in 1854 and early 1855, making collections of nonmarine mollusks from sites around the fort (Hartman 1999; Chaky 2015).

The Fort Union Group in the North Unit of Theodore Roosevelt NP

References:

Chaky, D. 2015. Fossils and the fur trade: the Chouteaus as patrons of paleontology. We Proceeded On 41(2):12–23.

Hartman, J. H. 1999. Western exploration along the Missouri River and the first paleontological studies in the Williston Basin, North Dakota and Montana. Proceedings of the North Dakota Academy of Science 53:158–165.

Owen, D. D. 1852. Report of a geological survey of Wisconsin, Iowa, and Minnesota; and incidentally of a portion of Nebraska Territory. Lippincott, Grambo & Co., Philadelphia, PA. Available at http://archive.org/details/mobot31753000174885 or http://books.google.com/books?id=Y_ZYAAAAYAAJ.

Wischmann, L. 2000. Frontier diplomats: Alexander Culbertson and Natoyist-Siksina' among the Blackfeet. University of Oklahoma Press, Norman, Oklahoma.

Sunday, July 31, 2016

(former) Ash beds in St. Paul

Although many Minnesotans are aware of the great Midcontinent Rift that runs across the state, it's less generally well-known that evidence of some of the largest known volcanic eruptions in the history of the planet can be found in the Twin Cities. In fact, you can easily put your hand on a layer of former volcanic ash by taking a short walk at our old friend Shadow Falls Park, at the end of Summit Avenue.

Sunday, July 24, 2016

Additions

Nothing particularly earth-shattering today. I would just like to direct you to the right-hand sidebar, where I've added a section to make it easier to get to The Compact Thescelosaurus, as well as a page that collects a few dozen sources for downloadable or viewable publications. As long as we're on the latter subject, I'll throw out a plug to Barnum Brown's description of the integument of the AMNH's panel-mounted Corythosaurus, and Henry Fairfield Osborn's description of the same for the "trachodon mummy" (note: 74 mb, but you also get an article on the skulls of Allosaurus and Tyrannosaurus). It also gives me an excuse to use this charmingly old-school restoration of various non-contemporaneous duckbills hanging out, found in Brown's publication.


Sunday, July 17, 2016

Hierosaurus sternbergii

One of the notable quirks of nodosaurids is a predilection for washing out to sea. Nodosaurus textilis and Stegopelta landerensis are a couple of featured examples. We turn now to another species from the Western Interior Seaway: Hierosaurus sternbergii.

Sunday, July 10, 2016

Dystactophycus, the crinoid swirl

A few weeks ago, a friend brought in an odd object to the Science Museum, which he had collected from an excavation in the vicinity. The object is a carbonate rock featuring concentric ridges that seem to be radial around a central depression. On the off-chance that it was some kind of exotic trace or trace-like pseudofossil, and that it had been illustrated, I went across the hall, pulled the volume of the Treatise on Invertebrate Paleontology that covers traces, and was pleasantly rewarded in the pseudofossil section with an illustration of something called Dystactophycus. The illustrated specimen was even from the Cincinnatian, which is practically as good as the Platteville/Decorah, being just a couple of million years younger. Of course, when something comes this quickly I'm honor-bound to be suspicious, but in this case the actual existence of something like Dystactophycus is more interesting than the question of whether or not I was right. (I do get back to the question of identity in the last paragraph.)

Dystactophycus, as currently understood, is one of those things that makes perfect sense once you've heard of it, but otherwise would probably never occur to you. It is composed of concentric markings on a conical structure. The initial describers (Miller and Dyer 1878) interpreted it as a seaweed, because the year was 1878 and the campaign to wrap peoples' minds around invertebrate trace fossils was far from being over. In short order, it was dismissed as an impression of a concentrically ringed bryozoan (Monticulipora by way of Lichenalia concentrica, both then considered corals) (James 1885, 1895–1896). More recently, Dystactophycus has been attributed to crinoids (Osgood 1970; Meyer and Davis 2009). As Osgood described it, the earlier researchers had the thing upside down: instead of an upward-pointing cone, the center was a low depression. The stem was partially buried by mud and the rest of it was spun around by swirling currents, causing its arms to sweep out an area that became the depression and quite naturally leave concentric markings. At some point, the crinoid detached, and the depression filled in the absence of the sweeping action. Although kind of like a trace fossil, these markings are not trace fossils because they are not evidence of biological activity. Think of them more like an Ordovician equivalent to marks left by a log on a river bottom (tool marks, in the parlance). (If you'd like to see a true crinoid trace, check this out!)

The specimen in question (I didn't have a scale handy, so my fingertips will have to do). Although similar in some ways to Dystactophycus, I don't think it's an example.

So, do I think that the specimen in hand is an example of Dystactophycus? Although it is superficially similar to the description, there are a couple of characteristics that lead me to say "no". The major issue is that the specimen is not a simple cone shape. Instead, after rising from the center, it slopes again (so kind of a doughnut shape), and the concentric lines are not confined to the cone but continue on the back side. In addition, the markings are not so much grooves and ridges but concentric terraces. My guess instead is some sort of abiotic sedimentary deformation.

References:

James, J. F. 1885. Fucoids of the Cincinnati Group. Journal of the Cincinnati Museum of Natural History 7(4):151–166.

James, J. F. 1895–1896. Manual of the paleontology of the Cincinnati Group, Part VII. Journal of the Cincinnati Museum of Natural History 18(3–4):115–140.

Meyer, D. L., and R. A. Davis. 2009. A Sea Without Fish. Indiana University Press, Bloomington and Indianapolis.

Miller, S. A., and C. B. Dyer. 1878. Contributions to Paleontology 2.

Osgood, R. G., Jr. 1970. Trace fossils of the Cincinnati area. [regrettably, the plates are not included] Palaeontographica Americana 6(41):280–444.

Sunday, July 3, 2016

A locked dinosaur mystery


So, one of the things you're supposed to do if you have a blog is to talk about your research when a paper you authored comes out. Okay, give me a minute. I mentioned back in the gut contents post that I did my thesis on what was found in the inside of a brachylophosaur. The first part, on the gut contents themselves, was published back in 2008 (Tweet et al. 2008). Finally, after about a decade of gnawing on the manuscript, comes the other part (Tweet et al. 2016).