Minnesota's dinosaurs

The stats for Equatorial Minnesota have recently shown visitors looking for "Minnesota dinosaur", no doubt because of the recent announcement of a ~90 million-year-old theropod claw from Hill Annex Mine State Park on the Iron Range. Minnesota, as you might know, is not noted for its dinosaur fossils. (I usually have to add the modifier "non-avian" or "classic" to "dinosaur", but I don't know of any bird fossils, either, unless you want to count refuse bones from archeological sites. Maybe the St. Peter Sandstone holds a buried Pleistocene-age cave in a filled river channel somewhere...) However, there are a handful of reports of Cretaceous dinosaurs from Minnesota.

Algae and not-algae

The last of the fossils to be covered to complete the Upper Ordovician Twin Cities set (barring some microfossils and real rarities) are a nebulous group of oft-times enigmatic organisms that either are algae, or have been classified as algae. "Algae" is a much more problematic a term than you might suspect. To put it simply, "algae" is more of a state of mind than a formal classification. At its broadest, "algae" covers basically anything that does photosynthesis and doesn't have the obvious distinct tissues of derived plants, like leaves and roots. This would include anything from diverse microbes to seaweeds. While this has some utility for back-of-the-envelope things, it is not the most useful term for serious classification. It should not be surprising that untold numbers of fossils have been been classified as algae, and that many of these "algae" belong to disparate groups, some of which still have unsettled classifications. About a half-dozen taxa from the Platteville, Decorah, and basal Cummingsville formations have fallen into the "algae" bin at one time or another. They include the following:

The Compact Thescelosaurus

National Fossil Day is this Wednesday, October 14th. The 16th birthday of Thescelosaurus would have been last Wednesday, October 7th. In honor of both, here is The Compact Thescelosaurus, a sortable spreadsheet of basic information on classic (non-avian) dinosaur species, minus names that have not been formally described. I began working on it shortly after I decided to end the website; I still wanted the information to be available, but I also wanted something that was lower-maintenance, and more flexible to edit. This is what I came up with. The other nice thing about it was that I updated a number of things, which I can now use to clean up my original files and perhaps make them available as pdfs, for people who miss the dry commentary and the nomina nuda. This wouldn't happen for several more months, though. Anyway, here's a short user guide to the spreadsheet below the jump, column by column. If someone wants to use the format for some other group, they are free to do so. Otherwise, have fun!

[A quick note, 2015-10-12: I've received a couple of inquiries about being added as editors. I appreciate the interest, but at this time, I'd prefer to keep this project under one person. Feel free to send corrections and other information, though! (I consider many aspects of taxonomy to be matters of judgement, so we many have to agree to disagree on those matters.)]

Conodonts

A common yet easily overlooked type of fossil is the conodont (or "conodont element", should we choose to be picky and/or technical). They are easy to overlook because they are sub-millimeter-scale fossils, which makes them just barely visible to the naked eye if you look really hard. Most of the time, though, all you can do is to take bulk samples of rock and run them acids to liberate these tiny fossils; conodont fossils are made of calcium phosphate, so they will not be dissolved by some acids that do dissolve calcium carbonate, i.e. limestone. Having dissolved your limestone, you can then inspect the remainder under a microscope. Ideally, you will have some little pointy toothy bits, which are the conodont elements.

Graptolites: gone yesterday, here today?

Graptolites are one of the less-heralded members of the local Ordovician menagerie, probably because they don't seem to be all that common around here. Graptolites were colonial animals (and I use "were" and other past-tense terminology with implied quotation marks, because of the shocking twist yet to come). The colonies, called "rhabdosomes", are made up of branches called "stipes", which support cup-like structures called "theca" that housed the individual animals. (See also here for official terminology.) The overall effect is that stipes often resemble saw blades, with the "teeth" being the theca. Early graptolites were apparently attached to the seafloor and formed densely branching (dendritic) colonies (see for example several of the specimens here and here), whereas later forms were apparently planktonic and attached to floats of their own device or other floating things, such as seaweeds [2020/11/11: no! It appears that there is no evidence for floats or attachments; see Maletz 2015 for the gory details]. The rapid taxonomic turnover of graptolites, coupled with the ease of distribution for planktonic forms, make them excellent index fossils. Planktonic distribution also has the neat side effect of getting graptolites into rock formations that otherwise lack much for fossils, usually because of low oxygen levels in the water column precluding a great deal of life while the formation was being deposited. While low oxygen would limit bottom dwellers, it wouldn't stop things from drifting through higher up the water column. Fossils of graptolites are found from the Cambrian into the Carboniferous. This may not be where the story ends, though: it has been known for a while that graptolites are most similar to pterobranchs, a living group of tube-dwelling often-colonial worm-like hemichordates. There is evidence that pterobranchs are, in fact, living graptolites (e.g. Mitchell et al. 2013; Discovery Magazine ran an article on this topic back in 1993). Should this be the case, it would appear that only the planktonic forms truly disappeared; seafloor forms persisted, albeit in much reduced circumstances (only a handful of pterobranch genera and species are known). All of the species reported from the Twin Cities appear to be of the planktonic persuasion.

As mentioned, graptolites are an uncommon component of the local fauna. They do pop up from time to time, though, and their thin dark saw blade fossils are quite distinctive if you get a large enough chunk. Reports of graptolites in the Twin Cities go back almost to the beginning of local geology, actually. Shumard (1852) reported graptolites from a bluff about a half-mile downstream from Fort Snelling, in what would now be considered the lower Platteville Formation. Winchell and Schuchert (1895) provided illustrations for three species, Climacograptus typicalis, Diplograptus pristis?, and Diplograptus putillus. All of their cited specimens came from outside the metro, and apparently from higher stratigraphically than virtually all metro rocks, with C. typicalis from what would now be the Cummingsville Formation and the other two from what would now be the Dubuque Formation, per the stratigraphic table in Winchell and Ulrich (1897). Stauffer (1930) found abundant black fragments of graptolites in a particularly calcareous layer low in the Decorah Shale in rocks recovered from a heating shaft dug for Northrop Auditorium. Stauffer and Thiel (1941) observed C. typicalis in what would now be the Mifflin Member at Lock and Dam 1, on the Ramsey County side. Their lists reported three following species in the Platteville Formation and Carimona Member (their Spechts Ferry). All three were listed under Hydrozoa, the group that includes relatives of corals and jellyfish, which was a reasonable enough hypothesis at the time (before the discovery of pterobranch affinities, graptolite relationships were a free-for-all):

Climacograptus typicalis (Pl, Ca)
Climacograptus (Mesograptus) putillus (Pl)
Diplograptus amplexicaulis? (Pl)

(More graptolites are known from older rocks a bit farther afield in Minnesota. Ruedemann [1933] described several species from the Upper Cambrian St. Lawrence Formation of Afton.)

From Winchell and Schuchert (1895). This looks kinda like at least one of the examples in the following photo, but you should always be wary of diagnosing your fossils via photos and plates.

A University of Minnesota piece with a few graptolites (look for the things that look like saw blades on sticks. Mouse-sized hacksaws.).

References

Maletz, J. 2015. Graptolite reconstructions and interpretations. Paläontologische Zeitschrift 89:271–286.

Mitchell, C. E., M. J. Melchin, C. B. Cameron, and J. R. Maletz. 2013. Phylogenetic analysis reveals that Rhabdopleura is an extant graptolite. Lethaia 46(1):43–56.

Ruedemann, R. 1933. The Cambrian of the upper Mississippi Valley, part III, Graptolitoidea. Milwaukee Public Museum Bulletin 12(3):307–348.

Shumard, B. F. 1852. Geological report of local, detailed observations, in the valleys of the Minnesota, Mississippi, and Wisconsin rivers, made in the years 1848 and 1849, under the direction of David Dale Owen, United States Geologist, by B. F. Shumard, head of subcorps. Pages 481–531 in Owen, D. D. 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 (plates not included), https://archive.org/details/reportofgeologi00owen (full plates) or http://books.google.com/books?id=Y_ZYAAAAYAAJ.

Stauffer, C. R. 1930. Conodonts from the Decorah Shale. Journal of Paleontology 4(2):121–128.

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

Winchell, N. H., and C. Schuchert. 1895. Sponges, graptolites, and corals from the Lower Silurian in Minnesota. Pages 55–95 in Lesquereux, L., C. Schuchert, A. Woodward, E. Ulrich, B. Thomas, and N. H. Winchell. The geology of Minnesota. Minnesota Geological and Natural History Survey, Final Report 3(1). Johnson, Smith & Harrison, state printers, Minneapolis, MN.

Winchell, N. H. and E. O. Ulrich. 1897. The lower Silurian deposits of the Upper Mississippi Province: a correlation of the strata with those in the Cincinnati, Tennessee, New York and Canadian provinces, and the stratigraphic and geographic distribution of the fossils. Pages lxxxiii–cxxix in L. Lesquereux, C. Schuchert, A. Woodward, E. Ulrich, B. Thomas, and N. H. Winchell. The geology of Minnesota. Minnesota Geological and Natural History Survey, Final Report 3(2). Johnson, Smith & Harrison, state printers, Minneapolis, Minnesota.

Coming Attractions in Dinosauria?

One more trip to the well... In the spirit of Addendum II, here is my own compilation of undescribed dinosaurs. I am deliberately avoiding repeating entries from the 1982 list (sorry, "Thotobolosaurus" [2020/04/19: now Kholumolumo], Archbishop, Cleveland-Lloyd ankylosaur, and Monoclonius recurvicornis). In the spirit of that list, I full expect some of these to be named next week and some to be still hanging around, say, thirty-three years from now, like some from 1982 are still waiting in 2015. This is not an exhaustive list, but more of a "greatest hits". It is biased to reports with some history behind them, and also biased to reports that I think will eventually be substantiated, so there's none of the "[random place] [random dinosaur represented by a single bone]". Let me know if they ever get around to "Ngexisaurus".

Where are they now: 1980s dinosaur rumors, ornithischians

We now reach the final section, the part dealing with ornithischians (links to theropods and sauropodomorphs). The ornithischian portion of Glut (1982)'s Addendum II is a real mixed bag. It's not just because people seem to forget about ornithischians, especially when the ornithischians come without bearing horns or plates. There's some really scrappy stuff listed and some really vague entries, as well as two genera that had been named and had entries in the rest of the book, and a third that had been named but hadn't made the book.