Sunday, December 4, 2016

Parksosaurus

For a small herbivorous dinosaur with no crest, horns, etc., Thescelosaurus has managed to sweep through a respectable number of species. There's the type species (T. neglectus), T. assiniboiensis, T. edmontonensis, T. garbanii, Bugenasaura infernalis, and the subject of today's entry, which entered science as Thescelosaurus warreni but which is better known as Parksosaurus (warreni or warrenae, depending on how you feel about far-after-the-fact emendations).

Saturday, November 26, 2016

Cottage Grove Ravine Regional Park: the green rocks of home

I come from Cottage Grove, Minnesota, and in the southeast part of town there's Cottage Grove Ravine Regional Park. Up until a few weeks ago, I had no idea that there was actually exposed bedrock in the park. The only outcrops I knew of in town were a couple of pockets around the compost site, a couple of spots in Old Cottage Grove, and some outcrops of the St. Peter Sandstone up high on Camel's Hump overlooking Highway 61 (there's a little park up on the crest of the hill now, with a good view across the valley, by the way). Obviously, I had to have a look around.

The rocks, counterintuitively, are the green things in this photo.

Sunday, November 20, 2016

Meanwhile, over at the Science Museum

Recently, the Science Museum of Minnesota reconfigured the exhibit space for the paleontology in conjunction with changes to other parts of the floorplan. I don't recall if the previous configuration had been stable all the way back to the 2005 Society of Vertebrate Paleontology meeting (I do know a nice Goniopholis was added around 2010), but where once it had looked like this:

January 2013; watch the space on the left of the Stegosaurus.

Now it looks like this:

That Triceratops wasn't there before...

Two major components, the Morrison dinosaurs and the Wannagan Creek fossils, are still where they had been. The major differences are in the section on the east, with the removal of some visible lab space and some more portable specimens, most notably a sort of "circus ring" of small- to medium-sized Cenozoic animals, mostly mammals.

And a tortoise.
 
In their place are a group of mounts from the Oligocene of coastal South Carolina (transferred from the floor above) and the well-known Science Museum Triceratops, relocated from another part of the floor. A Triceratops going mobile is just not a common occurrence these days, so naturally the event received some local coverage. A few other pieces were also rearranged, including the Xiphactinus lurking behind the Stegosaurus in the first picture above, some of the remaining mammals, the Goniopholis, and your friend and mine Thescelosaurus. Green River Formation fossils also get more prominence.

Triceratops (who also answers to "Fafner") plus overhead pterosaur pal in foreground. The South Carolina mounts are visible in the background by the neon; you can see a whale, pseudodontorn,and sea turtle in the air above the hind end of a mostly obscured croc (next photo).

Estuarine croc Gavialosuchus (or Thecachampsa) carolinensis has an honest face. I was glad that space was made for the South Carolina mounts; many places have Morrison dinosaurs, but you can't see Wannagan Creek and South Carolina fossils just anywhere.

On the one hand, the Triceratops no longer has its niche with the backdrop:


On the other hand, you can now walk around the whole mount, if for example you should want to look at the legs and hips:

Like this, perhaps.

I may cover some of these exhibits in a bit more detail in the coming weeks, given the approaching busy holidays. Till then, though, Allosaurus bids you all adieu:


Sunday, November 13, 2016

Some thoughts on St. Anthony Falls

If you're familiar with the history of Minneapolis, you probably know that beneath what we now call St. Anthony Falls are the remains of the natural St. Anthony Falls. The real falls went kaput quite a while ago; October 5, 1869, to be precise. The creation of the Hennepin Island tunnel is usually named as the culprit, but after seeing this photo I am beginning to suspect suicide. For various reasons, the presence of a waterfall or a reasonable facsimile thereof was required, so with the aid of the Army Corps of Engineers, the body was embalmed in wood and cement, and propped up in its accustomed place.

Granted, it's a pretty darn good job of embalming.

Sunday, November 6, 2016

Claosaurus

Out of the blue, my supervisor recently asked me if I knew anything about a piece of art depicting a shall-we-say stylized and retro dinosaur labeled "Claosaurus" at the Berlin Aquarium. This was one of those odd coincidences that we are taught to avoid in fiction: I'd been thinking about writing a post on Claosaurus, and now I was being commanded by the gods of serendipity. I've had a soft spot for this modestly publicized duckbill since before I was ten, when I read about it in a magazine and it became my first "hipster" dinosaur. (My second was Epanterias, because this was the late '80s/early '90s, when iconoclasts like Bob Bakker and Greg Paul had just raised the siren song for the splitting of Allosaurus fragilis and the community was not yet hardened by cynicism about mysterious giant theropods not known from enough material to draw a dirty look in the express checkout.)

Sunday, October 30, 2016

Near-dinosaurs

The Triassic was an experimental time for large tetrapods. The Permian–Triassic extinction event had eviscerated the prevailing communities of diverse therapsids (relatives of mammals), various early reptiles, and large temnospondyl amphibians (for more on them, Tetrapod Zoology has made them a cottage industry since 2007). Into that vacuum the survivors seem to have gone with the strategy of "throw everything at the wall and see what sticks". Some lineages stuck quite well. Early turtles and sphenodonts (tuatara) showed up during the Triassic, as well as forerunners of crocodilians and mammals. Lizards are probably in there too somewhere. Frogs may predate the Triassic, but the first good fossils are Triassic. Famously, the dinosaur line, which eventually produced birds, appeared in the Triassic as well. Long-lived but now extinct groups that got their start in the Triassic include the ichthyosaurs, plesiosaurs, pterosaurs, and our friends the choristoderes. There was also a veritable heap of briefly successful groups that for whatever reason went extinct by the close of the Triassic. Among them: aetosaurs (armored herbivores that look vaguely like ankylosaurs), drepanosaurs, nothosaurs and other plesiosaur cousins, placodonts, phytosaurs (crocodiles before there were crocodiles), rauisuchians (carnivores with theropod-like skulls), rhynchosaurs (big beaked herbivores), tanystropheids (necks plus neck delivery systems), thallatosaurs (lanky marine reptiles), and all kinds of other strange one-hit wonders.

Until the 1960s, dinosaurs seemed to have more or less just appeared in the Late Triassic, with theropods and prosauropods (in the sense of "all them sauropodomorphs what ain't sauropods")  recognized as present. What came before those theropods and prosauropods wasn't known, although there were a few guesses and extrapolations. One popular option of the time was that, technically speaking, there weren't really any basal dinosaurs because "dinosaurs" themselves were an artificial group "united" by some coincidental bits of anatomy related to being large land-living animals. This view is practically extinct, although I cannot say completely extinct. One of the great truths of humanity is that there is someone who will believe any proposition. One of the great truths of the Internet is that now you can find that person (or oftentimes, they will find you, if you are holding an opposing position). Other researchers drafted in various poorly known Triassic reptiles. The most enduring may have been Teratosaurus, which people who got into dinosaurs before the late 1980s will probably remember as a sort of megalosaur-like thing stalking the wilds of Late Triassic Europe. It was actually based on jaw material from a rauisuchian, with prosauropod skeletal remains misattributed to it. The misidentification of Teratosaurus, though illustrative, serves mostly as a lesson in the honesty of bonebeds. More recent work with Reveultosaurus, Shuvosaurus, and others shows that it can be darn hard to separate true early dinosaurs from the various wacky archosaurs of the Triassic if you've only got a few remains. The terrestrial Triassic still has more fools to make.

Of all the various bits and pieces put forward as early dinosaurs in the days before the 1960s, the only one that actually is both vaguely useful and does not easily slot into any of the known clades of true dinosaurs is Saltopus elginensis, described in 1910 by von Huene. It got to be in all the best dinosaur books as an archetype, overcoming the significant handicap of being a terrible specimen, which just goes to show that sometimes all you have to do to succeed is show up. The first useful basal dinosaurs to be described, Herrerasaurus and Ischisaurus, were described in 1963, followed by Staurikosaurus in 1970. They were followed by Lagosuchus, Lagerpeton, and Lewisuchus in 1971 and 1972, which were underappreciated at the time but eventually were shown to be dinosaurian cousins once we got that whole "unnatural Dinosauria" thing worked out of the collective scientific system. At the present, there are around 20 species of near-dinosaurs, from Dinosauromorpha to Dinosauria. This doesn't compete with, say, Titanosauria, but it's not bad for about 45 years of serious work. There's a little wiggle room built in depending on how charitable you feel toward Pseudolagosuchus, how you handle "Thecodontosaurus" alophos and borderline cases (e.g. Agnosphitys, Alwalkeria, Teyuwasu), and the occasional analysis that pulls Herrerasauridae or Eoraptor out of Saurischia. Some of them can be grouped as lagerpetids, diminutive bipeds, or as silesaurids, larger animals which could reach roughly the size and shape of Fred Flintstone's pet Dino. At least one of these, the namesake Silesaurus, was equipped with a little can-opener of bone at the tip of its lower jaw, perfect for being confused with the ornithischian predentary. A few others either don't slot comfortably into either group, or are poorly known (and I tend to the conservative when it comes to where I slot, which in this case mostly affects Lewisuchus/Pseudolagosuchus). The chart below lays them out with age and continent denoted. One thing to note is the abundance of species for South America and Africa, which not only suggests a Gondwanan origin but also provides a partial explanation for why these animals have only come to light in the past few decades: there haven't been a lot of paleontologists in those areas until recently.

Click for further enlightenment

Another important thing to keep in mind is to avoid the trap of turning extinction and evolution into a morality play. "Near-dinosaurs" were not merely a sideline, or waiting hopefully to eventually evolve into dinosaurs, or a bunch of saps that got pushed out of the way by their cousins. They were their own creatures, diversifing into several lineages and living alongside their more famous cousins for twenty or so million years, at least. We currently have named examples from four continental landmasses, and it would hardly be surprising to add a few more landmasses, five to ten million years, or additional lineages.

Dromomerom romeri, by Nobu Tamura (from https://commons.wikimedia.org/wiki/File:Dromomeron_BW.jpg). For whatever reason I've always found this restoration charming.

Sunday, October 16, 2016

Year One of The Compact Thescelosaurus (now with extra choristoderes)

Mid-October is the time of National Fossil Day, as well as just past the anniversary date of the late lamented Thescelosaurus! and the introduction of The Compact Thescelosaurus. In honor of the occasion, I've made a couple of additions. One is a new page with a selection of online museum collections databases. The other is a new worksheet on The Compact Thescelosaurus, featuring choristoderes. This sheet is the first of what I hope to be a series covering other fossil groups; choristoderes were selected for the honor this time around because there are only a few. I have a few candidates in mind for the next addition, perhaps a year from now; it depends on how ambitious I'm feeling. I haven't given up on the idea of making a version of the old website's contents available, but I haven't really decided how to do it.

So it's not really surprising that I came up with a post on subtle nuances of the nomenclature of Champsosaurus.